The development of steel pipe production technology began with the rise of the bicycle manufacturing industry, the development of oil 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, production and transportation of oil and natural gas have effectively promoted the development of variety, output and quality of the steel pipe industry..

According to the production method, steel pipes are generally divided into seamless steel pipes and welded steel pipes. This time, we mainly introduce welded steel pipes.

Welded steel pipe is a seam steel pipe. Its production is to bend the tube blank (steel plate and steel strip) into the tube of the required cross-sectional shape and size by various forming methods, and then use different welding methods to weld the weld seam. The process of obtaining steel pipes.

Compared with seamless steel pipe welded pipe, it has the characteristics of 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. The raw materials of spiral steel pipe are strip coil, welding wire and flux.

2. Before forming, the strip steel is leveled, trimmed, planed, surface cleaned and conveyed, and pre-bent.

3. A welding gap control device is adopted to ensure that the welding gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the welding gap are strictly controlled.

4. After cutting into a single steel pipe, a strict first inspection system is required for each batch of three steel pipe heads to check the mechanical properties, chemical composition, fusion state, surface quality of the steel pipe and non-destructive flaw detection inspection to ensure that the pipe making process is qualified Only then can it be officially put into production.

2. Straight seam submerged arc welded pipe:

Straight seam submerged arc welded pipe (LSAW) generally uses steel plate as raw material, undergoes different forming processes, and uses double-sided submerged arc welding and post-weld expansion to form a welded pipe.

The main equipment includes edge milling machine, pre-bending machine, forming machine, pre-welding machine, expanding machine, etc. At the same time, the forming methods of straight-seam submerged arc welded pipes include UO (UOE), RB (RBE), JCO (JCOE) and so on.

The steel plate is first pressed into a U shape in the forming mold, and then pressed into an O shape, and then the internal and external submerged arc welding is performed. After welding, the expansion (Expanding) is usually called UOE welded pipe at the end or the full length range, which is not called For UO welded pipe.

Roll bending the steel plate (Roll Bending), and then perform internal and external submerged arc welding, after welding, the diameter is expanded to RBE welded pipe or the diameter is not expanded to RB welded pipe. The steel plate is formed in the order of J-C-O-type, after welding, the diameter is expanded to JCOE welded pipe or the diameter is not expanded to JCO welded pipe

UOE Straight Submerged Arc Welded Pipe Forming Process:

The three main forming processes of the UOE straight seam submerged arc welded steel pipe forming process include: steel plate pre-flanging, U forming and O forming. Each process uses a special forming press to complete the three steps of pre-bending the steel plate, U forming and O forming in order to deform the steel plate into a round tube. As shown:

JCOE straight seam submerged arc welding pipe forming process:

Forming: After multiple step punching on the JC0 forming machine, first half of the steel plate is pressed into a "J" shape, and then the other half of the steel plate is pressed into a "J" shape to form a C "shape, and finally pressurized from the middle An open "0" shaped tube blank is formed. As shown:

Comparison of JCO and UO molding methods:

JCO forming is a progressive pressure forming, which changes the forming process of steel pipes 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 is not scratched.

The processed steel pipes have greater flexibility in the range of diameters and wall thicknesses. They can produce large-volume products and small-batch products; they can also produce large-diameter high-strength thick-walled steel pipes, as well Small-caliber large-wall thick steel pipe; especially in the production of high-steel grade thick-walled pipes, especially medium- and small-caliber thick-walled pipes, it has advantages that are unmatched by other processes.

It can meet more requirements of users in terms of steel pipe specifications. The investment is low, but the production efficiency is low, and the general annual output is 100,000 to 250,000 tons.

UO molding, which uses U and O pressure molding twice, is characterized by large capacity and high output. Generally, the annual output can reach 300,000 to 1 million tons, which is suitable for single-spec mass production. The investment is large, which is generally unaffordable for developing countries.

3. Straight seam high frequency welded pipe:

Straight seam high frequency welded pipe (ERW) is the hot rolled coil formed by the forming machine, using the skin effect and proximity effect of high frequency current to heat and melt the edge of the tube blank, and pressure welding under the action of the squeeze roller To achieve production.

Welded steel pipe, also known as welded pipe, is a steel pipe made by welding a steel plate or strip after crimping. Welded steel pipe production process is simple, high production efficiency, many varieties and specifications, less equipment, but the general strength is lower than seamless steel pipe.

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, the variety and specifications of welded steel pipes are increasing, and they have replaced Seam steel pipe. Welded steel pipes are divided into straight welded pipes and spiral welded pipes according to the form of welds.

Classified by production method: process classification-arc welded pipe, resistance welded pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe.

Straight seam welded pipe production process is simple, high production efficiency, low cost and rapid development. The strength of spiral welded pipe is generally higher than that of straight seam welded pipe. It is possible to use narrow blanks to produce welded pipes with larger diameters. It is also possible to use the same width of blanks to produce welded pipes with different pipe diameters.

But compared with the straight pipe of the same length, the length of the weld is increased by 30-100%, and the production speed is lower.

Product Standards

Common materials for welded pipes are: Q235A, Q235C, Q235B, 16Mn, 20 #, Q345, L245, L290, X42, X46, X60, X80, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, etc.

The blank used for welded steel pipe is steel plate or strip steel, which is divided into furnace welded pipe, electric welding (resistance welding) pipe and automatic arc welded pipe due to 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)