Production process of welded steel pipe

The development of steel pipe production technology began with the rise of bicycle manufacturing, the development of petroleum in the early 19th century, the manufacture of ships, boilers, and aircraft during the two world wars, the manufacture of thermal power boilers after the Second World War, the development of the chemical industry, and The drilling and transportation of oil and natural gas have strongly promoted the development of the steel pipe industry in terms of variety, output and quality.
Generally, steel pipes are divided into two types: seamless steel pipes and welded steel pipes according to the production method. This time I will mainly introduce welded steel pipes.

    Welded steel pipes are seam steel pipes, which are produced by bending the tube billet (steel plate and steel strip) into a tube of the required cross-sectional shape and size by various forming methods, and then welding the welds by different welding methods. The process of obtaining steel pipes.
Compared with seamless steel pipe welded pipe, it has high product accuracy, especially wall thickness accuracy, simple main equipment, small footprint, continuous operation in production, flexible production, and wide product range of the unit.

1. The production process of spiral steel pipe is roughly as follows:
1. Raw materials for spiral steel pipes are strip coils, welding wires, and fluxes.
       2. Before forming, the strip undergoes leveling, trimming, planing, surface cleaning and conveying, and pre-curving.
3. The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are strictly controlled.
4. After cutting into single steel pipes, the first three of each batch of steel pipes shall undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, the surface quality of the steel pipes and pass non-destructive inspections to ensure that the pipe manufacturing process is qualified Later, it can be officially put into production.
2. LSAW pipe:
     The longitudinal submerged arc welded pipe (LSAW) is generally made of steel plate as the raw material. After different forming processes, the welded pipe is formed by double-sided submerged arc welding and post-weld diameter expansion.
The main equipment includes milling machine, pre-bending machine, forming machine, pre-welding machine, expanding machine, etc. At the same time, there are many types of forming methods for LSAW pipes: UO (UOE), RB (RBE), JCO (JCOE), etc.
The steel plate is first pressed into a U shape in the forming die, and then pressed into an O shape, and then the internal and external submerged arc welding is carried out. After welding, the diameter (Expanding) is usually called UOE welded pipe at the end or the full length. It is UO welded pipe.
Roll Bending the steel plate, and then carry out internal and external submerged arc welding. After welding, the diameter is expanded to RBE welded pipe or not to RB welded pipe. The steel plate is formed in the order of J type-C type-O type, and the diameter is expanded to JCOE welded pipe or not to JCO welded pipe after welding
UOE LSAW pipe forming process:
The three main forming processes of UOE LSAW steel pipe forming process include: steel plate pre-bending, U forming and O forming. Each process uses a dedicated forming press to complete the three processes of pre-bending the edge of the steel plate, U forming and O forming in sequence to deform the steel plate into a circular tube. As shown:
JCOE LSAW pipe forming process:
Forming: After several steps of stamping on the JC0 forming machine, first press half of the steel plate into a "J,, shape, then press the other half of the steel plate into a "J" shape to form a C" shape, and finally press from the middle to form An open "0"-shaped tube blank is formed. As shown:
Comparison of JCO and UO molding methods:
JCO forming is progressive pressure forming, which changes the forming process of steel pipe from two steps of UO forming to multiple steps. During the forming process, the steel plate deforms uniformly, the residual stress is small, and the surface does not produce scratches.
The processed steel pipe has greater flexibility in the size and specification range of diameter and wall thickness. It can produce both large-volume products and small-batch products; it can produce large-diameter, high-strength, thick-walled steel pipes or Small diameter and large wall thickness steel pipes; especially in the production of high steel grade thick wall pipes, especially small and medium diameter thick wall pipes, it has the unmatched advantages of other processes.
It can meet more requirements of users in terms of steel pipe specifications. The investment is small, but the production efficiency is low, and the annual output is generally 100,000 to 250,000 tons.
UO molding adopts U and O twice pressure molding. It is characterized by large capacity and high output. Generally, the annual output can reach 300 to 1 million tons, which is suitable for mass production of a single specification. The investment is huge, and it is difficult for developing countries to bear.
3. Straight seam high frequency welded pipe:
Straight seam high-frequency welded pipe (ERW) is formed by forming a hot-rolled coil through a forming machine. The skin effect and proximity effect of the high-frequency current are used to heat and melt the edge of the pipe blank, and pressure welding is carried out under the action of a squeeze roller To achieve production.
     Welded steel pipes, also called welded pipes, are steel pipes made by welding steel or strip steel after crimping. Welded steel pipes have simple production process, high production efficiency, many varieties and specifications, and less equipment, but their general strength is lower than seamless steel pipes.
     Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the variety and specifications of welded steel pipes have increased, and they have replaced non-products in more and more fields. Seam the steel pipe. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of welds.
Classification by production method: Process classification-arc welded pipe, resistance welded pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe.
Longitudinal welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. A narrower blank can be used to produce welded pipes with larger pipe diameters, and a billet with the same width can also be used to produce welded pipes with different pipe diameters.
However, compared with the straight seam pipe of the same length, the weld length is increased by 30-100%, and the production speed is lower.
Product Standards
     The commonly used materials of welded pipe are: Q235A, Q235C, Q235B, 16Mn, 20#, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.
The blanks used for welded steel pipes are steel plates or strip steels, which are divided into furnace welded pipes, electric welded (resistance welded) pipes and automatic arc welded pipes due to their different welding processes. Because of its different welding forms, it is divided into two types: straight seam welded pipe and spiral welded pipe. Because of its end shape, it is divided into round welded pipe and special-shaped (square, flat, etc.) welded pipe. Welded pipes are divided into the following varieties due to their different materials and uses:
GB/T3091-2001 (Galvanized for low pressure fluid transportation)