Steel Pipes & Tubes

What is a steel pipe?

Steel pipes are tubular objects made of steel, usually used to transport liquids, gases, or other substances.

Classification of steel pipes

Steel pipe is a widely used building material and mechanical component. According to its purpose, production method, and shape, steel pipes can be divided into the following categories:

Classification by production method of steel pipes

Steel pipes can be divided into two categories according to production methods: seamless steel pipes and welded steel pipes. Welded steel pipes are abbreviated as welded pipes.

1. Seamless steel pipes can be divided into hot rolled seamless pipes, cold drawn pipes, precision steel pipes, hot expanded pipes, cold spun pipes, and extruded pipes according to production methods.

Seamless steel pipes are made of high-quality carbon or alloy steel, which can be hot-rolled or cold-rolled (drawn).
2. Due to their different welding processes, Welded steel pipes are divided into furnace-welded pipes, electric welding (resistance welding) pipes, and automatic arc-welded pipes. Due to their different welding forms, they are divided into straight-seam and spiral-welded pipes. Due to their end shapes, they are divided into circular welded pipes and special-shaped (square, flat, etc.) welded pipes.
Welded steel pipes are rolled steel plates welded with butt or spiral seams. In terms of manufacturing methods, they are further divided into welded steel pipes for low-pressure fluid transportation, spiral welded steel pipes, directly rolled welded steel pipes, welded pipes, etc. Seamless steel pipes can be used in various industries, such as liquid pressure pipelines and gas pipelines. Welded pipelines can be used for water, gas, heating, and electrical pipelines.

Classified by the material of steel pipes

Steel pipes can be divided into carbon pipes, alloy pipes, stainless steel pipes, etc., according to their material (i.e., steel grade).
Carbon pipes can also be divided into ordinary and high-quality carbon structural steel.
Alloy pipes can also be divided into low alloy pipes, alloy structural pipes, high alloy pipes, nickel-based alloy pipes, molybdenum-based alloy pipes, aluminum alloy pipes, copper alloy pipes, bearing pipes, titanium alloy pipes, high-temperature alloy pipes, and precision alloy pipes.

Classified by the connection method of steel pipes

Steel pipes can be divided into smooth pipes (without threads at the pipe end) and threaded pipes (with threads at the pipe end) according to the pipe end connection method.
The threading steel pipe is further divided into ordinary threading pipe and thickened threading pipe at the end of the pipe.
Thickened thread pipes can also be divided into externally thickened (with external threads), internally thickened (with internal threads), and internally thickened (with internal and external threads).
Threading pipes can also be divided into ordinary cylindrical or conical threads and special threads according to the thread type.
In addition, according to user needs, wire pipes are generally delivered with pipe joints.

Classification by coating characteristics

Steel pipes can be divided into black (non-coated) and coated pipes according to their surface coating characteristics.
Coated pipes include galvanized, aluminum, chrome, aluminized, and other alloy-coated steel pipes.
Coated pipes include outer-coated pipes, inner-coated pipes, and inner and outer-coated pipes. Common coatings include plastic, epoxy resin, coal tar epoxy resin, and various glass-type anti-corrosion coating materials.
Galvanized pipes are divided into KBG, JDG, threaded pipes, etc.

According to the classification and use of steel pipes

• Pipes for pipelines. For example, seamless pipes for water, gas, and steam pipelines, oil transmission pipes, and pipes for oil and natural gas pipelines. Agricultural irrigation faucets with pipes and sprinkler irrigation pipes, etc.
• Pipes for thermal equipment. For example, boiling water and superheated steam pipes are used in general boilers, and superheated pipes, large smoke pipes, small smoke pipes, arch brick pipes, and high-temperature and high-pressure boiler pipes are used in locomotive boilers.
• Mechanical industry pipes. For example, aviation structural pipes (round pipes, elliptical pipes, flat elliptical pipes), automotive half axle pipes, axle pipes, automotive tractor structural pipes, oil cooler pipes for tractors, square and rectangular pipes for agricultural machinery, transformer pipes and bearing pipes.
• Pipes for petroleum geological drilling. For example, petroleum drilling pipes, petroleum drill pipes (square and hexagonal drill pipes), drilling rods, petroleum oil pipes, petroleum casings, various pipe joints, geological drilling pipes (core pipes, casings, active drill pipes, drilling rods, clamps, and pin joints, etc.).
• Chemical industry pipes. For example, petroleum cracking pipes, pipes for chemical equipment heat exchangers and pipelines, stainless acid-resistant pipes, high-pressure pipes for fertilizers, and pipes for transporting chemical media.
• Management for other departments. For example, container pipes (high-pressure gas cylinder pipes and general container pipes), instrument pipes, watch case pipes, injection needles, medical device pipes, etc.

Classification based on the cross-sectional shape of steel pipes

The steel types and specifications of steel pipe products are extremely diverse, and their performance requirements are also various. All of these should be distinguished according to changes in user requirements or working conditions. Usually, steel pipe products are classified based on cross-sectional shape, production method, pipe material, connection method, coating characteristics, and usage.
Steel pipes can be divided into round steel pipes and irregular steel pipes according to their cross-sectional shape.
Deformed steel pipes refer to various noncircular cross-section steel pipes.

The main ones are: square pipe, rectangular pipe, elliptical pipe, flat elliptical pipe, semicircular pipe, hexagonal pipe, hexagonal inner circular pipe, unequal hexagonal pipe, equilateral triangular pipe, pentagonal plum blossom pipe, octagonal pipe, convex pipe, double convex pipe, double concave pipe, multiple concave pipe, melon shaped pipe, flat pipe, rhombic pipe, star shaped pipe, parallelogram pipe, ribbed pipe, drop-shaped pipe, inner finned pipe, twisted pipe, b-pipe, d-shaped pipes and multi-layer pipes, etc.

Steel pipes are divided into equal-section steel pipes and variable-section steel pipes according to their longitudinal shape. Variable cross-section (or variable cross-section) steel pipes refer to steel pipes that undergo periodic or nonperiodic changes in the shape, inner and outer diameters, and wall thickness of the cross-section along the rectangular direction of the pipe. It mainly includes outer conical pipe, inner conical pipe, outer stepped pipe, inner stepped pipe, periodic section pipe, corrugated pipe, spiral pipe, steel pipe with heat dissipation fins, and gun barrel with double lines.

Steel pipe connectors

The connection of steel pipes can usually be carried out in the following ways:

• Welding connection: This is the most common connection method to ensure the strength of the connection between steel pipes. Common welding methods include arc welding, gas-shielded, laser, ultrasonic, etc.
• Thread connection: By machining threads at the end of the steel pipe and then using threaded joints or flanges for connection. This connection method is suitable for small and medium-sized diameter steel pipes.
• Flange connection: By welding a flange at the end of the steel pipe and then connecting the two flanges using bolts and gaskets. This connection method suits large-diameter steel pipes or situations requiring frequent disassembly.
• Ferrule connection: A sealed connection is formed by using a special ferrule to fix the end of the steel pipe on the joint. This connection method is suitable for conveying high pressure, high temperature, or special media.
• Bonding: Use special adhesive to bond the steel pipe and joint together. This connection method is suitable for situations that do not withstand high voltage.
• Crimping: Using a crimping machine to crimp steel pipes and joints together, forming a sealed connection. This connection method is suitable for small and medium-sized diameter steel pipes.

The choice of connection method depends on factors such as the steel pipe’s purpose, diameter, working pressure, and working temperature. In practical applications, the above connection methods may be combined as needed.

Standard for steel pipes

Steel pipes are manufactured and used based on various standards that specify their dimensions, mechanical properties, chemical composition, testing methods, and other technical requirements. These standards are developed by various organizations and are used globally to ensure the quality, safety, and compatibility of steel pipes for different applications.
Here are some of the most common standards for steel pipes:
ASTM (American Society for Testing and Materials) Standards:

• ASTM A53: Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded, and Seamless.
• ASTM A106: Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service.
• ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes.

API (American Petroleum Institute) Standards:

API 5L: Specification for Line Pipe. This standard specifies requirements for manufacturing two product specification levels (PSL 1 and PSL 2) of seamless and welded steel pipes for use in pipeline transportation systems in the petroleum and natural gas industries.

EN (European Standard) Standards:

• EN 10216: Seamless steel tubes for pressure purposes.
• EN 10217: Welded steel tubes for pressure purposes.

ISO (International Organization for Standardization) Standards:

ISO 3183: Petroleum and natural gas industries — Steel pipe for pipeline transportation systems.

JIS (Japanese Industrial Standards) Standards:

• JIS G3454: Carbon steel pipes for pressure service.
• JIS G3455: Carbon steel pipes for high-pressure service.
• JIS G3456: Carbon and alloy steel pipes for high-temperature service.

BS (British Standards) Standards:

BS 1387: Specification for screwed and socketed steel tubes and tubulars and for plain end steel tubes suitable for welding or for screwing to BS 21 pipe threads.
DIN (Deutsches Institut für Normung – German Institute for Standardization) Standards:

• DIN 2440: Steel tubes – Dimensions and weights of threaded tubes.
• DIN 2441: Steel tubes – Dimensions and weights of medium-weight tubes.

These are just a few of the many standards available for steel pipes. The appropriate standard depends on the application, region, and industry. If you have a specific application or requirement in mind, please provide more details, and I can assist you further.

Material of steel pipe

Steel pipes are typically made from steel, an alloy primarily composed of iron and carbon. The carbon content in steel generally ranges from 0.12% to 2.0%. Adding carbon strengthens the iron, making it harder and more durable.

In addition to carbon, steel can contain other alloying elements to achieve specific properties. Some common alloying elements include:

• Manganese: Enhances strength and hardness.
• Chromium: Increases durability, hardness, and resistance to wear and corrosion.
• Nickel: Improves toughness and resistance to corrosion.
• Molybdenum: Increases strength and resistance to heat.
• Vanadium: Enhances hardness and wear resistance.

The specific composition of steel used for pipes can vary based on the intended application. For instance:

• Carbon Steel Pipes: Made primarily from iron and carbon. They are cost-effective but can corrode more easily than other steel pipes.
• Stainless Steel Pipes: Contains a significant amount of chromium, which provides excellent resistance to corrosion.
• Alloy Steel Pipes: Contain various alloying elements to achieve desired properties, such as improved strength or corrosion resistance.
• Galvanized Steel Pipes: Carbon steel pipes that have been coated with a layer of zinc to improve corrosion resistance.

Chemical composition comparison table for martensite, ferrite, austenite, and duplex stainless steel

Chemical composition list of nickel-based alloys

Performance requirements for steel pipes

Physical performance requirements

1). Thermal conductivity

Thermal conductivity refers to the ability of an object to conduct heat, which measures the heat transfer ability of a steel pipe. In general, thermal conductivity is related to the composition and temperature of the steel. Steel pipes with good thermal conductivity are widely used in the industrial field. For example, steel pipes with excellent thermal conductivity can be used as heat transfer materials.

2). Thermal expansion coefficient

The coefficient of thermal expansion refers to the proportion of changes in the length or volume of a material during temperature changes. Materials with high thermal expansion coefficients are prone to temperature deformation and deformation, reducing their service life and range of use. Therefore, it is very important to choose steel pipes with small thermal expansion coefficients in engineering practice.

3). Conductivity

Conductivity refers to the electrical conductivity of a material per unit length or area at a unit voltage. High-conductivity steel pipes can be used in the field of power transmission, while low-conductivity steel pipes can avoid various safety issues caused by high conductivity. Therefore, steel pipes with different conductivity can be selected according to specific needs in different application scenarios.

Chemical Property Requirements

1). Chemical composition

Chemical composition is one of the important indicators of steel pipe quality. The chemical composition of steel pipes directly determines their service life and performance indicators. Generally speaking, ordinary carbon steel pipes with low alloying element content have lower costs, but their mechanical properties and corrosion resistance are relatively poor. Alloy steel pipes containing many alloying elements have higher costs but better mechanical properties and corrosion resistance.

2). Corrosion resistance

Steel pipes need good corrosion resistance when used in fields such as marine, chemical, and environmental protection. Corrosion resistance is one of the important evaluation indicators for the quality of steel pipes. Generally, methods such as galvanizing are used to improve its corrosion resistance.

Mechanical performance requirements

1). Strength

Strength is an indicator of a material’s ability to resist external forces. High-strength steel pipes are mainly used in mechanical manufacturing, construction, shipbuilding, and automobiles.

2). Hardness

In fields such as mechanical manufacturing, mining, and construction, the hardness of steel pipes is an important performance indicator. Steel pipes with high hardness can better resist external damage, thereby improving their service life.

3). Resilience

Toughness refers to the ability of steel pipes to undergo plastic deformation and dissipate energy under external forces. On the premise of ensuring strength and hardness, toughness is also an important indicator. Good toughness can ensure that steel pipes are not easily broken or deformed during use.

Steel pipes are important industrial and civil building materials, and their quality assurance involves many performance indicators. This article provides a detailed analysis of the performance requirements in terms of physical, chemical, and mechanical properties, hoping to help readers better understand the quality standards of steel pipes. When selecting steel pipes, choosing high-quality products that meet corresponding standards based on the specific application field is necessary.

Pressure rating of steel pipes

Definition and classification of pressure levels for steel pipes

The pressure level of a steel pipe refers to the maximum pressure that the steel pipe can withstand, usually expressed in Mpa. According to different pressure levels, steel pipes can be widely used in various fields, such as petrochemicals, water conservancies, construction engineering, etc. The pressure levels of steel pipes are mainly classified into four levels: low pressure, medium pressure, high pressure, and ultra-high pressure. The specific introduction is as follows:

• Low-pressure steel pipe: The commonly used low-pressure steel pipe has a pressure rating of 0.1Mpa to 1.6Mpa, mainly suitable for water supply, gas transportation, and other fields.
• Medium-pressure steel pipe: The commonly used medium-pressure steel pipe has a pressure rating of 2.5Mpa to 6.4Mpa, mainly suitable for chemical engineering and thermal pipelines.
• High pressure steel pipe: The commonly used high-pressure steel pipe has a pressure rating of 10Mpa to 32Mpa, mainly suitable for petrochemical and water conservancy fields.
• Ultra high pressure steel pipe: The commonly used ultra high pressure steel pipe has a pressure rating of 32Mpa to 100Mpa, mainly suitable for marine development, nuclear power plants, and other fields.

Marking and application precautions for pressure rating of steel pipes

For the convenience of use and management, the pressure rating of steel pipes is generally marked on the pipes. The marking method is to cover the surface or port of the pipe with a signboard and indicate information such as name, specification, material, and pressure level on the signboard. In addition, the following points should be noted when using steel pipes:

• The pressure rating of the steel pipe should meet the requirements of the construction specifications.
• The appearance of the steel pipe should be free of defects such as cracks, defects, waves, bends, and deformations.
• During the transportation, storage, and construction of steel pipes, avoiding damage such as collision, compression, and bending is necessary.
• Steel pipes should avoid overloading during use, exceeding the pressure level that the pipes can withstand.
• Steel pipes should be inspected and tested before use to ensure their safety.

In summary, the pressure level of steel pipes is an important performance indicator. When using them, attention must be paid to selecting the appropriate pressure level and using and managing them according to the signs and precautions.

Dimensions of steel pipes

The size of a steel pipe usually includes its outer diameter, wall thickness, and length. Different applications and standards may have different size requirements. For example, the construction, oil, natural gas, and water treatment industries may use steel pipes of different sizes.

In China, the size of steel pipes is usually classified according to GB (national standard). For example, GB/T 8162 is a standard for seamless steel pipes used in structures, while GB/T 8163 is a standard for seamless steel pipes used in fluid transportation.

Each standard will list a series of steel pipe sizes, including outer diameter, wall thickness, etc. For example, common outer diameter dimensions may include: 3/4 “steel pipe, 1 1/4” steel pipe, 1 1/2 “steel pipe, 2 inch steel pipe, 3 inch steel pipe, 4 inch steel pipe, 6 inch steel pipe, 8 inch steel pipe, 10 inch steel pipe, 12 inch steel pipe, etc., while wall thickness may include: schedule 80 steel pipe, schedule 40 steel pipe, etc.

Comparison Table of Nominal Wall Thickness, Diameter, and Unit Weight of American Standard (ASTM) Steel Pipe

Calculate weight of steel pipe

The calculation formula for steel pipe weight:

(outer diameter wall thickness) × Wall thickness mm × 0.02466 × Length m

• Example: Steel pipe 114mm (outer diameter) × 4mm (wall thickness) × 6m (length)
• Calculation: (114-4) × 4 × 0.02466 × 6 = 65.102kg

Extension materials

The formula for calculating the weight of threaded steel:

Diameter mm × Diameter mm × 0.006one 7× Length m

• Example: threaded steel Φ 20mm diameter × 12m (length)
• Calculation: 20 × twenty × 0.006one 7× 12 = 29.616kg

The formula for calculating the weight of round steel:

Diameter mm × Diameter mm × 0.006one 7× Length m

• Example: Round steel Φ 20mm diameter × 6m (length)
• Calculation: 20 × twenty × 0.006one 7× 6 = 14.808kg

The formula for calculating the weight of square steel:

Edge width (mm) × Edge width (mm) × Length (m) × 0.00785

• Example: 50mm square steel (edge width) × 6m (length)
• Calculation: 50 × 50 × 6 × 0.00785 = 117.75 (kg)

The formula for calculating the weight of flat steel:

Edge width (mm) × Thickness (mm) × Length (m) × 0.00785

• Example: Flat steel 50mm (edge width) × 5.0mm thick × 6m (length)
• Calculation: 50 × 5 × 6 × 0.00785 = 11.775 (kg)

The formula for calculating the weight of hexagonal steel:

Opposite diameter × Opposite diameter × Length (m) × 0.00068

• Example: hexagonal steel 50mm (diameter) × 6m (length)
• Calculation: 50 × 50 × 6 × 0.0068 = 102 (kg)

The formula for calculating the weight of steel plates:

7.85 × Length (m) × Width (m) × Thickness (mm)

• Example: Steel plate 6m long × 1.51m (width) × 9.75mm thick
• Calculation: 7.85 × 6 × one .5 one × 9.75 = 693.43kg

The formula for calculating the weight of equilateral angle steel:

(Edge width + edge width) × thick × 0.0076 × Length m (rough calculation)

• Example: Angle steel 100mm × 80mm × 8 THK × 6m long
• Calculation: (100+80) × 8× 0.0076 × 6 = 65.67kg

The formula for calculating the weight of unequal-angle steel:

Edge width mm × thick × 0.0one 5 × Length m (rough calculation)

• Example: Angle steel 50mm × 50mm × 5 thick × 6m long
• Calculation: 50 × 5 × 0.0one 5 × 6 = 22.5kg

The formula for calculating the weight of brass tubes:

(Outer diameter wall thickness) × thick × 0.0267× Length m

• Example: Brass tube 20mm × 1.5mm thick × 6m long
• Calculation: (20-1.5) × one .5 × 0.0267× 6 = 4.446kg

The formula for calculating the weight of copper tubes:

(Outer diameter wall thickness) × thick × 0.02796 × Length m

• Example: Copper tube 20mm × 1.5mm thick × 6m long
• Calculation: (20-1.5) × one .5 × 0.02796 × 6 = 4.655kg

The formula for calculating the weight of aluminum flower board:

Length m × Width m × Thickness mm × 2.96

• Example: Aluminum flower board 1m wide × 3m long × 2.5mm thick
• Calculation: 1 × three × 2.5 × 2.96 = 22.2kg

Brass plate: specific gravity 8.5; Copper plate: specific gravity 8.9; Zinc plate: specific gravity 7.2; Lead plate: specific gravity 11.37

Calculation method: Specific gravity × Thickness = Weight per square meter

What does SCH40 mean for pipeline wall thickness?

SCH40 is a type of pipeline specification that represents the pipeline’s wall thickness and pressure bearing capacity. SCH is the abbreviation for Schedule, representing the pressure bearing capacity level of pipelines. 40 represents the pipeline’s wall thickness in units of 1/1000 inch. So, the wall thickness of the SCH40 pipeline is 40 × 1/1000=0.040 inches=1.016 millimeters. According to the American pipeline standard ANSI/ASME B36.10M, the specific specifications of SCH40 steel pipes are:

• Outer diameter: 1/8-30 inches, with a wide range covering various pipeline applications.
• Wall thickness: 0.040 inches, approximately 1.016 millimeters.
• Nominal diameter ratio: 0.85 (D/t).
• The minimum yield strength specified by the standard is 35000PSI or 240Mpa.
• Standard work pressure rating (schedule 40 steel pipe pressure rating): up to 700PSI, approximately 48.3 bar.

So, the SCH40 pipeline specification represents:

• The pipeline’s wall thickness is 0.040 inches, which is relatively moderate and has a certain strength without being too heavy.
• This pipeline has a high-pressure bearing capacity, with a maximum working pressure of up to 700PSI, which can meet the pressure requirements of general industrial pipeline systems.
• The strength of the pipeline also meets a certain standard, with a minimum yield strength of 35000PSI, which can ensure the firmness of the pipeline.
• The outer diameter range is wide, from 1/8 inch to 30 inches, which can meet the needs of different pipeline diameters.

In summary, SCH40 is a commonly used and universal pipeline specification, representing pipelines with medium wall thickness, high pressure bearing capacity and strength, and a wide selection of outer diameters, which can meet the requirements of most industrial pipeline systems. This is also the reason for its widespread application.

The manufacturing process of steel pipes

Steel pipes are divided into seamless steel pipes and welded steel pipes. How is steel pipe made? The production process of seamless steel pipes involves threading solid billets or ingots into hollow tubes and then rolling them into the required size of steel pipes. The different perforation and rolling methods constitute different methods for producing seamless steel pipes. The production process of welded steel pipes involves bending the pipe blank (steel plate or strip) into a tubular shape and then welding the gaps to form the steel pipe. Due to the different forming and welding methods used, different methods for producing welded steel pipes are formed. 

How is seamless steel pipe made? Seamless steel pipes are mainly produced by the hot rolling method. The extrusion method is mainly used to produce low plasticity high alloy steel pipes or special-shaped steel pipes and composite metal pipes that are difficult to pierce. Cold rolling and cold drawing methods can continue to process hot-rolled pipes into small diameter and thin-walled steel pipes. The welding process of steel pipes is simple, with high production efficiency, low cost, and an increasing variety of products.

The production method of seamless steel pipes

Hot rolling and cold drawing are the two main manufacturing methods for seamless steel pipes.

Process flow chart of hot rolled seamless steel pipe: Round tube billet → Heating → Piercing → Three roll oblique rolling, continuous rolling or extrusion → Tube detachment → Sizing (or reducing) → Cooling → Straightening → Hydrostatic testing (or flaw detection) → Marking → Warehousing

The raw material for rolling seamless pipes is round tube blanks, which need to be cut and processed by a cutting machine to form a billet of about 1 meter in length and then sent to the furnace for heating through a conveyor belt. The billet is fed into the furnace for heating, with a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. Temperature control in the furnace is a crucial issue. After the round tube billet is discharged from the furnace, it needs to be pierced through by a pressure piercing machine.

The commonly used piercing machine is a conical roller piercing machine with high production efficiency, good product quality, large perforation, and expansion capacity, and can pierce various steel grades. After perforation, the round tube blank is sequentially rolled, continuously rolled or extruded by three rollers. After squeezing, the pipe needs to be detached and sized. The sizing machine uses a conical drill bit to rotate at high speed into the steel billet for drilling, forming a steel pipe. The outer diameter of the sizing machine drill bit determines the inner diameter of the steel pipe. After the steel pipe is sized, it enters the cooling tower and is cooled by water spray. After cooling, the steel pipe needs to be straightened.

After straightening, the steel pipe is transported by a conveyor belt to a metal inspection machine (or hydraulic test) for internal inspection. If there are cracks, bubbles, and other issues inside the steel pipe, they will be detected. Strict manual selection is also required after the quality inspection of steel pipes. After the quality inspection of the steel pipe, the number, specification, production batch number, etc., are sprayed with paint and lifted into the warehouse by a crane.

Process flow chart of cold drawn seamless steel pipe: round tube blank → heating → perforation → heading → annealing → acid washing → oil coating (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → hydraulic test (flaw detection) → marking → warehousing.

The rolling method of cold-drawn (rolled) seamless steel pipes is more complex than that of hot-rolled (extruded seamless steel pipes). The first three steps of their production process are the same. The difference starts from the fourth step; after the round tube blank is punched, it must be heated and annealed. After annealing, a special acidic liquid should be used for pickling.

After pickling, apply oil. Then, it is followed by multiple passes of cold drawing (cold rolling) and specialized heat treatment for the billet. After heat treatment, it needs to be straightened. After straightening, the steel pipe is transported by a conveyor belt to a metal inspection machine (or hydraulic test) for internal inspection. If there are cracks, bubbles, and other issues inside the steel pipe, they will be detected. Strict manual selection is also required after the quality inspection of steel pipes.

After the quality inspection of steel pipes, the standard classification of seamless steel pipes is quoted using painted steel pipes. The production and manufacturing methods of thick wall pipes can be divided into hot rolled pipes, cold rolled pipes, cold drawn pipes, extruded pipes, etc., according to different production methods. Hot-rolled seamless pipes are generally produced on automatic rolling mills, and the solid pipe blank is inspected and removed from surface defects to cut into the required length. Centering is carried out on the end face of the piercing end of the pipe blank and then sent to the heating furnace for heating. The piercing is carried out on the machine while continuously rotating and advancing. Under the action of the rolling roller and head, a cavity is gradually formed inside the pipe blank, which is called a capillary. It is then sent to the automatic pipe-rolling machine for further rolling. Finally, the entire machine is evenly adjusted for wall thickness, and the sizing machine determines the diameter to meet the specification requirements.

Continuous rolling mills to produce hot-rolled seamless steel pipes is a more advanced method. To obtain smaller and better quality seamless pipes, cold rolling and cold drawing or a combination of both methods must be used. Cold rolling is usually carried out on a two-roll mill, where the steel pipe is rolled in a circular pass composed of a variable cross-section circular groove and a fixed conical head; cold drawing is usually carried out on a single chain or double chain drawing machine by extrusion method. The heated tube blank is placed in a closed extrusion cylinder, and the perforated rod and extrusion rod move together to extrude the extruded part from the smaller mold hole. This method can produce steel pipes with smaller diameters.

Production method of welded steel pipes

With the widespread application of steel pipes, the production process of welded steel pipes has gradually become a focus of attention. The production process of welded steel pipes is an important link in steel pipe production, and its quality and efficiency are directly related to the quality and production cost of steel pipes.

Production method of straight seam submerged arc welded steel pipes

The production process of straight seam submerged arc welded pipes is flexible. It can produce any specification and wall thickness within the production range, with lower production efficiency than high-frequency straight seam welded steel pipes and spiral welded steel pipes. The biggest advantage of straight seam submerged arc welded pipes is that they can produce specifications and models that cannot be produced for high-frequency steel pipes, spiral steel pipes, or even seamless steel pipes. The production cost of straight seam submerged arc welded pipes is higher than that of high-frequency steel pipes and spiral steel pipes, but there is much room for price discounts compared to seamless steel pipes. Straight seam submerged arc welded pipes can produce high-frequency steel pipes, and materials that spiral steel pipes cannot produce.

1) Pre-forming process and main equipment

Steel plate → Vacuum lifting → Ultrasonic testing of steel plate → Milling → Pre bending.

Pre-bending machine: The pre-bending of steel plates is divided into roller pre-bending and mold pressing pre-bending, as shown in the following figure.

Figure. Structural schematic diagram of roller pre-bending machine and mold pressing pre-bending machine

2) JCO molding process and equipment

J forming → C forming → O forming.

After the conveyor roller transports the steel plate to the oil pressure bed for positioning, the first time, 1/3 of the width of the plate is formed by the upper and lower molds, called “J forming.” The other end of the second molding is 1/3 of the board width, known as “C-molding”; Finally, the remaining 1/3 of the board width is formed from the center of the board, resulting in a circular tube shape called “O forming”.

Figure. JCO Forming Process Diagram

a) “O” stamping forming b) “C” stamping forming c) “J” stamping forming

3) Post-forming process

Pre-welding (CO₂ shielded welding) → welding of arc plate → internal welding → external welding → de-welding (extinguishing) Arc plate → slag suction → rounding → X-ray testing → ultrasonic testing → front water flushing → mechanical expansion of the entire pipe body → rear water flushing → straightening → hydraulic testing → ultrasonic testing → pipe end weld grinding → mechanical end repair → X-ray testing → pipe end X-ray testing → pipe end ultrasonic testing → pipe end magnetic particle testing → weighing and measurement → finished product inspection → external anti-corrosion → internal anti-corrosion → spray labeling → packaging and warehousing.

Pre-welding equipment: Pre-welding equipment includes feeding and sealing devices, welding operators, welding systems, and electrical control systems. The formed steel pipe is sent to the joint device and welding system for welding through the feeding device.

Welding equipment for the inner surface of steel pipes: After the steel pipes are hoisted into the welding machine for positioning, a straight rod with a guide wheel installed at the front end is used to guide the welding at the weld bead and maintain a straight line. A welding rod escort machine is installed at the front end of the straight rod to escort the welding wire and welding machine to the conveyor box so that the welding flux falls by its weight. The straight rod is then slowly backed off by the platform vehicle according to the welding speed.

Welding equipment outside the steel pipe: After the steel pipe is hoisted into the welding machine for positioning, a vehicle-mounted welding wire transport machine and welding machine transport plate are used, and the welding flux is lowered by its weight to protect the welding area. The trolley moves slowly according to the welding speed.

Rounding, expanding, and straightening machine: The rounding is driven by the rolling force from the upper and lower rollers, forcing the compressed steel pipe to pass through the rounding machine and causing permanent steel pipe deformation at the yield point.

The expanding machine belongs to the straight seam metal welded pipe shaping equipment. It uses a conical expanding head to expand inside the steel pipe, eliminating the forming pressure and welding stress of the steel pipe and ensuring that the true diameter of the entire length of the straight seam welded steel pipe is consistent. The equipment consists of a small car, an expander, a working sleeve, a fixed seat, an oil cylinder, a lubrication station, a bench, a hydraulic station, and an electric control system. The expander is set on the small car, and the expander is connected to the oil cylinder by the working sleeve; the expander is composed of an expander head, an expander block, a guide plate, a pull rod, etc. Large-scale equipment that ensures the shape sizing of straight seam metal welded pipes and eliminates stress through a segmented mechanical extrusion process. Straightening machines use pressure or straightening rollers to compress bars and other materials to change their straightness.

Ultrasonic inspection equipment: Ultrasonic inspection of the weld bead is required before and after the water pressure test.

The production method of straight seam high-frequency resistance welded steel pipes.

It was uncoiling → Leveling → Shear Butt Welding → Looper Storage → Plate Exploring → Trimming → Roller Forming → High-Frequency Welding → Removing Inner and Outer Burrs → Online Ultrasonic Testing → Intermediate Frequency Annealing → Air Cooling → Water Cooling → Sizing → Straightening → Cutting → Initial Inspection of Dimensions and Appearance → End Repair → Hydrostatic Testing → Full Pipe Ultrasonic Testing → Offline Weld Ultrasonic Testing → Pipe End Ultrasonic Testing → Final Inspection of Dimensions and Appearance → Application of Anti-rust Paint → Spray Marking → Pipe End Protection → Comprehensive Inspection And warehousing.

The uncoiler, leveling machine, shear welding machine, and storage bin is essential for the uninterrupted supply of steel strips to the forming machine and for improving production efficiency.

Cutting and butt-welding machine: Cut and butt the tail of the previous steel coil with the head of the subsequent steel coil.

Loop storage device: The loop is indispensable and important equipment to ensure the automatic production of high-frequency straight seam welded pipes, playing a role in ensuring the storage, supply, and continuous operation of the main rolling mill. As shown in the following figure.

Figure. High-frequency welding loop material storage device

Forming process (rolling tube): The deformation of the plate in the process of forming the tube is mainly manifested in two aspects: continuous transverse and longitudinal, and the constraint force applied on it is implemented through two aspects: the roll pass and the arrangement of the rolling mill. The roll pass causes transverse deformation of the steel plate, and the rolling mill arrangement causes longitudinal deformation. The following figure shows the forming process of welded pipes.

Figure. Schematic diagram of welding pipe forming process

High-frequency welding: By utilizing the skin effect of high-frequency current, high-frequency electrical energy can be concentrated on the surface of the welding piece, and by utilizing the proximity effect, the position and range of the high-frequency current flow path can be controlled. When high-frequency current is required to be concentrated in a certain part of the weldment, this requirement can be achieved by forming a current circuit between the conductor and the weldment and making the conductor close to this part of the weldment so that they form adjacent conductors with each other. High-frequency welding is based on the specific form and special requirements of the weldment structure, mainly using the skin effect and proximity effect to quickly heat the surface metal of the weldment to be welded and achieve welding. As shown in the following figure.

Figure. Schematic diagram of high-frequency welding

HF high-frequency power supply; T-tube blank movement direction

1. Welding parts; 2. Extrusion roller; 3. Impedance device; 4. Contact position of the contact

Comparison between Longitudinal High-Frequency Resistance Welded Steel Pipe (ERW) and Longitudinal Submerged Arc Welded Steel Pipe (UOE)

1) Differences in raw materials and production capacity

The raw material of ERW steel pipe is hot-rolled steel coil, while the raw material of UOE steel pipe is cold-rolled steel plate. Therefore, ERW steel pipes can achieve continuous assembly line operations with high production efficiency and low production costs; UOE steel pipes are processed using steel plates, which cannot achieve continuous assembly line operations, resulting in low production efficiency and high production costs.

2) Welding differences

ERW steel pipe welding does not require the addition of welding wires; UOE steel pipes require the addition of welding wires.

3) Product differentiation

ERW steel pipes are limited by the thickness of the steel coil, with a maximum thickness of 25mm and a maximum diameter of 660mm that can be produced. The maximum thickness that UOE steel pipes can produce is 40mm, and the maximum diameter that can be produced is only limited by the width of the steel plate. Currently, the maximum diameter that can be produced is 1422mm.

4) Application differences

ERW steel pipes are mainly used in long-distance land pipelines such as natural gas, refined oil, crude oil, and mineral slurry. UOE steel pipes are mainly used in high-pressure subsea long-distance pipelines, high-altitude cold areas, etc.

Production method of spiral seam submerged arc welded steel pipes

Spiral welded pipes are made by rolling low-carbon or low-alloy structural steel strips into pipe billets at a certain helix angle (called forming angle) and then welding the pipe seams together. It can produce large-diameter steel pipes using narrower strip steel. The specifications are represented by outer diameter * wall thickness, and the welded pipe should ensure that the weld seam’s hydraulic test, tensile strength, and cold bending performance meet the regulations. They are mainly used for oil and natural gas transmission pipelines.

I am unwinding → Leveling → Shearing and butt welding → Milling edge → Plate edge pre-bending → Forming → Internal and External welding → Cutting → Ultrasonic testing → X-ray testing → Pipe end welding seam grinding → Pipe end expansion → Hydrostatic testing → Ultrasonic testing → End repair → X-ray testing → Finished product inspection → Spray marking → Warehousing.

• Unwinding: Unfold the rolled steel plate.
• Leveling: Straighten the unfolded steel plate to ensure its flatness.
• Shear butt welding: Cut the steel plate to the required size and perform butt welding.
• Milling: Milling the edges of the steel plate to prepare for subsequent welding.
• Plate edge pre-bending: Pre-bending the edges of the steel plate to ensure that it fits tightly during forming.
• Forming: The steel plate is shaped in a spiral through specific equipment.
• Internal and external welding: Conduct internal and external welding on the formed steel pipe to ensure its sealing performance.
• Cutting: Cut the welded steel pipe to the required length.
• Ultrasonic testing: Use ultrasonic waves to inspect steel pipes to ensure they are defect-free.
• X-ray inspection: Use X-ray to inspect steel pipes to ensure the quality of welds.
• Pipe end welding seam grinding: Grind the end welding seam of the steel pipe to ensure its flatness.
• Pipe end expansion: Expanding the end of the steel pipe to meet the needs of the connection.
• Water pressure test: Conduct a water pressure test on the steel pipe to ensure its sealing and strength.
• Ultrasonic testing: Reuse ultrasonic testing on steel pipes.
• End repair: Repair the end of the steel pipe to ensure its flatness.
• X-ray testing: Use X-ray again to test the steel pipe.
• Finished product inspection: Conduct final quality inspection on the completed steel pipe.
• Spray marking: Spray markings on steel pipes, such as production date, specifications, and other information.
• Warehousing: Warehousing the steel pipes that have passed the inspection.

This series of production steps ensures the quality and performance of spiral seam submerged arc welded steel pipes, enabling them to work stably under various working conditions.

Key points of the process

In the production process of spiral seam submerged arc welded steel pipes, several key points need special attention:

The pre-treatment of steel plates is very important. It is necessary to ensure that the surface of the steel plate is free of impurities and oxides and that the smoothness meets the requirements. Otherwise, it will affect the welding quality and the service life of the pipe body.

The welding process should be reasonably selected. The welding process of spiral submerged arc welded steel pipes needs to consider welding efficiency and weld quality. The parameter settings for bottom arc welding and filling arc welding should be reasonable, and parameters such as welding speed and current should be controlled to ensure the quality of the weld seam.

Weld treatment should be meticulous.

The internal and external treatment of the weld seam directly impacts the welding quality and the anti-corrosion performance of the pipe body. Attention should be paid to avoiding excessive grinding during the treatment of internal welds to avoid affecting the thickness and strength of the steel plate. The treatment of external welds should be uniform and consistent, removing welding slag and oxides.

Nondestructive testing should be strictly carried out. Nondestructive testing is an important means to ensure welding quality and the pipe body’s integrity. Specified requirements must be carried out, and the test results must be recorded.

The production process of spiral seam submerged arc welded steel pipes is complex and rigorous work that requires strict control of each link’s quality and process requirements. Only by ensuring that each step meets the standards can reliable quality spiral seam submerged arc welded steel pipes be produced.

Quality requirements for steel pipes

The requirements for using seamless steel pipes in the construction industry are very high, and their quality may affect the quality of buildings. Therefore, the quality of seamless steel pipes is very important. So, how can the quality of seamless steel pipes be guaranteed? Today, we will discuss the quality requirements for seamless steel pipes.

(1) Chemical composition of steel pipes:

The chemical composition of steel is one of the most important factors affecting the performance of seamless steel pipes and is also the main basis for formulating rolling process parameters and steel pipe heat treatment process parameters.

• Alloy element: intentionally added, depending on the purpose
• Residual elements: brought in by steelmaking, appropriately controlled
• Harmful elements: Strictly control (As, Sn, Sb, Bi, Pb), gases (N, H, O)

Off-furnace refining or electroslag remelting: improve the uniformity of chemical composition and purity of steel, reduce non-metallic inclusions in tube billets, and improve their distribution morphology.

(2) Geometric dimensional accuracy and appearance of steel pipes

The accuracy of the outer diameter of steel pipes depends on the sizing (reduction) method, equipment operation, process system, etc.

Allowable deviation of outer diameter δ = (D-D_i)/D_i × 100%

In the formula:

• D: Maximum or minimum outer diameter mm;
• D_i: nominal outer diameter mm.

Steel pipe wall thickness accuracy: related to the heating quality of the pipe blank, process design, and adjustment parameters of each deformation process, tool quality and lubrication quality, etc.

Allowable deviation of wall thickness: ρ = (S-Si)/Si × 100%

In the formula:

• S: The maximum or minimum wall thickness on the cross-section;
• Si: nominal wall thickness mm.

Ovality of steel pipe: indicates the degree of noncircularity of the steel pipe.

Steel pipe length: normal length, fixed (multiple) length, and allowable deviation in length.

Steel pipe bending degree: represents the bending degree of the steel pipe (bending degree per meter of steel pipe length, bending degree of the entire length of the steel pipe).

Cutting slope of steel pipe end face: represents the degree of inclination between the steel pipe’s end face and the steel pipe’s cross-section.

The angle and blunt edge of the steel pipe end face groove.

(3) Surface quality of steel pipes: surface smoothness requirements

• Dangerous defects: cracks, internal folds, external folds, crushing, delamination, scarring, concavities, protrusions, etc.
• General defects: pits, green lines, scratches, bumps, minor inner and outer straight lines, roller marks, etc.

Cause of occurrence:

• ① Caused by surface or internal defects in the tube blank.
• ② During the production process, issues include the incorrect design of rolling process parameters, the unsmooth surface of the mold, poor lubrication conditions, and unreasonable design and adjustment of the pass.

The precision and high requirements of these processes determine the quality of steel pipes, and strict quality control is required at every step to ensure the quality of seamless steel pipes is qualified.

(4) Physical and chemical properties

The mechanical properties at room temperature, as well as the mechanical properties (thermal strength and low-temperature performance) and corrosion resistance (such as oxidation resistance, water corrosion resistance, acid, and alkali resistance) at a certain temperature, generally depend on the chemical composition, structural properties, purity of the steel, and the heat treatment method of the steel. In some cases, steel pipes’ rolling temperature and degree of deformation can also impact their performance.

(5) Process performance

Including the expansion, flattening, curling, bending, ring pulling, and welding performance of steel pipes.

(6) Metallographic structure

Including the macrostructure and macrostructure of steel pipes.

(7) Special requirements

Requirements beyond the standards proposed by users when using steel pipes.

Applications of steel pipes

• Structure: Steel pipes are often used in building bridges, buildings, and tunnels. They provide strength and stability for the structure.
• Fluid transportation: Steel pipes are commonly used to transport water, oil, natural gas, and other fluids.
• Low and medium-pressure boilers and high-pressure boilers: Steel pipes are used in manufacturing boilers because they can withstand high temperatures and pressures.
• Fertilizer equipment: During the fertilizer production process, steel pipes are used to transport and store chemical substances.
• Petroleum cracking: Steel pipes transport crude oil and other chemical substances in petroleum cracking.
• Geological drilling and diamond core drilling: Steel pipes are used for geological exploration to help scientists and engineers obtain underground samples.
• Oil drilling: In oil extraction, steel pipes are used for drilling and extracting crude oil.
• Ship: Steel pipes are used for structural and fluid transportation in ship manufacturing.
• Car half axle sleeve: Steel pipes are used to manufacture parts of cars, such as half axle sleeves, to provide car strength and stability.
• Diesel engine: Diesel engines use steel pipes to transport fuel and coolant.

One of the benefits of using steel pipes is that they can effectively prevent leakage, thereby ensuring the safe transportation of fluids. In addition, the strength and durability of steel pipes make them an ideal choice for many applications, thereby improving material utilization.

How to weld steel pipe?

Welding steel pipes is a technical process that requires professional welding equipment and skills. The following are the basic steps for welding steel pipes:

1) Inspection: Steel pipes must be inspected before use, and the material, specifications, pressure rating, and processing quality of the pipe joints must comply with the design regulations. Visual appearance inspection shall be conducted under sufficient lighting conditions, and the inner and outer surfaces shall be free of defects such as cracks, folds, folds, delamination, hairlines, scars, etc.

2) Cutting: Before cutting pipelines, different cutting methods should be selected based on different materials and diameter sizes, such as manual cutting, mechanical cutting, flame cutting, etc. However, electric welding should not be used as a substitute for cutting. The cut pipe mouth should be flat, and the burrs on the inner wall should be removed promptly. The quality of the incision should comply with the following regulations: the surface of the incision should be flat, without cracks, double skin, burrs, bumps, shrinkage, slag, iron oxide, and iron filings; The inclination deviation of the end face of the incision should not exceed 1% of the outer diameter of the pipe.

3) Bevel: Before welding the pipeline, the groove should be made according to the requirements of the design documents and welding process. Mechanical methods should be used for pipeline groove processing, and thermal processing methods such as plasma arc and oxygen acetylene can also be used. After using the hot processing method to process the groove, the oxide skin, slag, and surface layers that affect the quality of the joint should be removed from the groove surface, and the uneven areas should be polished flat.

4) Assembly: Clean the inner and outer surfaces manually or mechanically before welding the joint. There should be no paint, rust, oxide skin, burrs, or other harmful substances to the welding within the 20mm range of the groove. The pipeline group shall be equipped with dedicated assembly tooling to ensure the flatness of the pipes. A level or ruler shall be used to measure the pipe at a distance of 200mm from the center of the interface, with an allowable deviation of 1mm. The deviation of the entire length shall not exceed 10mm. The assembly of pipeline butt welding joints should be flush with the inner wall, and the misalignment of the inner wall of the steel pipe should not exceed 10% of the wall thickness and should not exceed 2mm. When the inner wall misalignment exceeds the specified value or the outer wall misalignment exceeds 3mm, correction should be made, as shown in the left figure. The alignment gap should meet the requirements and not be aligned with a strong force to avoid causing additional stress.

5) Spot welding: Welders who weld the same pipe should carry out pipeline assembly and spot welding. The welding rods or wires used for spot welding should be the same as those used for formal welding, and the spot welding process conditions must be the same as the formal welding process conditions and be fully welded. The length of spot welding for spot welding is 10-15mm, the height is 2-4mm, and should not exceed 2/3 of the pipe wall thickness.

6) Welding: Pipeline welding should be based on the selected pipeline material, specifications, process requirements, design pressure, and working temperature to determine the construction process. Welders participating in welding must hold a welder certificate. The position of pipeline welds should comply with the following regulations:

• The distance between the center planes of two butt welded joints on a straight pipe section should not be less than 150mm when the nominal diameter is greater than or equal to 150mm; When the nominal diameter is less than 150mm, it should not be less than the outer diameter of the pipe.
• The distance between the weld seam and the bending point of the bend (excluding the pressed bend) shall not be less than 100 mm and shall not be less than the outer diameter of the pipe.
• It is not advisable to open holes on pipeline welds and their edges.

7) Post weld treatment:

• Clean the weld seam to remove welding slag and oxides.
• Check the weld seam’s quality to ensure no defects such as cracks and pores.
• If necessary, subsequent heat treatment or surface treatment can be carried out.

8) Inspection: A visual inspection of the weld seam must be carried out after welding the pipeline. Before inspecting the weld seam, spatter and welding slag should be removed thoroughly. The appearance of the weld seam should be well-formed, and the width should be 2mm from the edge of the cover groove on each side. The surface of the weld and heat affected zone should not have defects such as cracks, pores, incomplete fusion of slag, etc. The depth of the pipeline undercut should be at most 0.5mm, the length of the connection undercut should be at most 100mm, and the total length of undercut on both sides of the weld should be at most 10% of the total length of the weld. The surface of the weld shall not be lower than the surface of the pipeline.

Can you weld steel pipes through the above learning?

How to buy the correct steel pipe?

The following aspects need to be considered when buying the correct steel pipe:

• Purpose: First, determine what you want to do with steel pipes. For example, they are used in building structures, conveying liquids, manufacturing mechanical components, etc.
• Material: Select the appropriate steel material according to the purpose. For example, stainless steel pipes are suitable for corrosive environments, while carbon steel pipes are more suitable for general industrial purposes.
• Specification: Determine the required steel pipe diameter, wall thickness, and length. This usually depends on design requirements and practical applications.
• Standard: Check if the steel pipe meets relevant national or international standards, such as GB, ASTM, DIN, etc.
• Manufacturer: Choose a manufacturer with a good reputation and quality assurance. You can view their production license, quality certification, and other information.
• Surface treatment: As required, steel pipes may require surface treatment such as rust prevention, galvanizing, and painting.
• Price: To meet all the above requirements, compare the steel pipe prices of different suppliers and choose the one with higher cost-effectiveness.
• Inspection report: When buying steel pipes, it is required to provide a quality inspection report to ensure that their performance meets the requirements.
• Consulting experts: If you need help choosing, you can consult experts or engineers in the relevant field.
• Storage and transportation: Ensure that steel pipes are not damaged during transportation and storage.
• Contract: At the time of purchase, ensure to sign a detailed contract with the supplier, specifying specifications, quantity, price, delivery date, etc.
• Subsequent service: Consider whether the supplier provides after-sales service.

Finally, it is recommended to conduct on-site inspections before purchasing, personally inspect the quality of the steel pipes, and have in-depth communication with suppliers to ensure that suitable products are purchased.

How to find a suitable steel pipe manufacturer?

Finding a suitable steel pipe manufacturer requires considering the following steps:

Determine requirements: Firstly, you need to clarify your own needs. This includes the required type, specification, quantity, and budget of steel pipes.

Research and collection of information:

• Online search: Use search engines to search for relevant steel pipe manufacturers and view their official websites and product catalogs.
• Industry exhibitions: Participate in relevant exhibitions, communicate directly with manufacturers, and learn about their products and services.
• Industry associations: Contact relevant industry associations, usually with a list of recommended manufacturers.

Verify qualifications: Ensure the manufacturer has relevant production licenses and quality certifications, such as ISO certification.

Sample requirements: Before placing an order, the manufacturer can be requested to provide samples to verify their quality.

Reference customer feedback: Review other customer evaluations and feedback to understand the manufacturer’s reputation and service quality.

Price negotiation: Conduct price negotiations with manufacturers to obtain the most favorable prices.

Consider logistics and delivery time: Ensure manufacturers can deliver on time and consider logistics costs.

Sign a contract: After confirming the cooperation, sign a formal contract with the manufacturer to clarify the rights and obligations of both parties.

Continuous supervision: During the cooperation process, continuously monitor the manufacturer’s production progress and quality to meet their needs.

Establishing long-term cooperative relationships: Establishing long-term cooperative relationships with high-quality manufacturers can ensure stable future supply and potentially better prices and services.

Finally, when choosing a steel pipe manufacturer, one should consider the price and multiple aspects, such as quality, service, and reputation, to ensure that the most suitable partner is selected.

Why did the customer choose Guanxin’s steel pipe?

The reason why customers choose our steel pipes is because Guanxin’s products and services have the following potential advantages:

• Quality assurance: Guanxin’s steel pipes have undergone strict quality testing and certification, and high-quality products can ensure long-term durability and safety.
• Price competitiveness: Guanxin’s prices are more competitive than other suppliers.
• Diversified product selection: Guanxin provides steel pipes of various specifications, models, and uses to meet the needs of different customers.
• Good customer service: Guanxin’s sales team provides timely, professional, and friendly service, as well as providing customers with reassuring after-sales service.
• Fast delivery time: Guanxin can deliver a large number of orders in a short period.
• Technical support and consulting: Guanxin provides technical support and consulting services to help customers choose the product that best suits their needs.
• Environmentally friendly: Guanxin’s production process is environmentally friendly and has environmental certification.
• Innovation capability: Guanxin frequently updates its products and introduces new technologies and materials to maintain its leading position in the industry.
• Good reputation and customer reviews: Guanxin has many satisfied repeat customers and positive customer reviews.
• Geographic location: Guanxin’s production and warehousing facilities are located in a convenient location for logistics and delivery.

Of course, every enterprise and market has uniqueness, so the most important thing is to understand your target customer group and their needs and highlight your advantages based on these needs.