Forming Process of LSAW Steel Pipe (UOE vs JCOE)

Longitudinal submerged arc welded pipe (LSAW) is generally made of steel plate as raw material. After different forming processes, double-sided submerged arc welding and post-weld diameter expansion are adopted to form welded pipe.

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 steel 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 internally and externally submerged arc welding is performed. After welding, it is usually called UOE welded pipe at the end or the full length range (Expanding). 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 after welding, or it is not expanded to JCO welded pipe.

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 adopts 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.

JCOE LSAW pipe forming process:
Forming: After several steps of stamping on the JC0 forming machine, first half of the steel plate is pressed into a "J" shape, then the other half of the steel plate is pressed into a "J" to form a "C" shape, and finally pressurized from the middle to form An open "0"-shaped tube blank is formed.

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 advantages that other processes cannot match. 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 300,000 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 afford it.

Tips: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW Pipe) and submerged arc welded straight seam steel pipes (LSAW) according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.

In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam of A53 ERW pipe shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.
In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.