Abstract:Generally, steel pipes are divided into seamless steel pipes and welded steel pipes according to the production method. This time I will mainly introd
Generally, steel pipes are divided into 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 formed by the following methods: the tube blank (steel plate and steel strip) is bent into a tube with the required cross-sectional shape and size through various forming methods, and then the welds are welded by different welding methods . The process of obtaining steel pipes. Compared with seamless steel pipes, welded steel pipes have higher product accuracy, especially wall thickness accuracy, simple main equipment, small footprint, continuous operation in production, flexible production, and a wide range of unit products.
Welded pipes should be divided into three categories from the production process: spiral submerged arc welded pipes; straight seam double-sided submerged arc welded pipes; resistance welded pipes.
1. The production process of spiral steel pipe is roughly as follows
The raw materials of spiral steel pipe are strip coil, welding wire and flux.
Before forming, the steel strip is leveled, trimmed, surface cleaned and conveyed, and pre-bent.
The welding seam control device is used to ensure that the welding seam meets the welding requirements, and strictly control the pipe diameter, the amount of misalignment and the welding seam.
After cutting into a single steel pipe, each batch of three steel pipes must go through a strict first inspection system to check the mechanical properties, chemical composition, weld fusion condition, and surface quality of the steel pipe, and pass non-destructive inspections to ensure that the pipe manufacturing process is qualified. It can be officially put into production.
2. LSAW pipe
The longitudinal submerged arc welded pipe is generally made of steel plate. After different forming processes, the welded pipe is formed by double-sided submerged arc welding and diameter expansion after welding.
The main equipment includes milling machines, pre-bending machines, forming machines, pre-welding machines, tube expanders, etc. At the same time, there are various methods of forming LSAW pipes such as UO (UOE), RB (RBE), JCO (JCOE), etc. First, the steel plate is pressed into a U shape in the forming die, and then pressed into an O shape, and then internal and external submerged arc welding is performed. After welding, the diameter (expansion) is usually called the end or full length of the UOE welded pipe. It is UO welded pipe. The steel plate is rolled and bent, and then internal and external submerged arc welding is carried out. 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 after welding, the diameter is expanded to JCOE welded pipe or not to JCO welded steel pipe.
UOE longitudinal submerged arc welded pipe forming process
The three main forming processes of UOE LSAW pipe forming process include: steel plate pre-bending, U-shaped forming and O-shaped forming. Each process uses a dedicated forming press to complete the following three processes: sequentially bending the edges of the steel plate, and then performing U and O forming to deform the steel plate into a round tube.
JCOE LSAW Pipe Forming Process
Forming: After multiple stepping and stamping on the JC0 forming machine, the upper half of the steel plate is pressed into a "J" shape, and then the other half of the plate is pressed into a "J" shape to form a C shape, and finally pressed from the middle to an open "0" shaped tube.
Comparison of JCO and UOE molding methods
JCO forming is progressive pressure forming, changing the forming process of steel pipe from two steps of UU forming to multiple steps. During the forming process, the steel plate is uniformly deformed, 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 a large number of products and small batches; it can produce large-diameter high-strength thick-walled steel pipes, as well as small-diameter and large-wall thickness steel pipes. Especially in the production of high-grade steel-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes, it has advantages that other processes cannot match. As far as steel pipe specifications are concerned, it can meet more requirements of users. The investment is small, but the production efficiency is low, and the annual output is generally 100,000 to 250,000 tons.
UOE molding adopts U and O double pressure molding. It is characterized by large capacity and high output. It is suitable for mass production of a single specification.
3. Straight seam high frequency welded pipe
Straight seam high-frequency welded pipes are formed by forming hot rolled coils through a forming machine. The skin effect and proximity effect of high-frequency current are used to heat and melt the edge of the tube blank, and pressure welding is performed under the action of the squeeze roller to achieve production.