Seamless steel pipe hot extrusion

Posted by zora li on November 29th, 2022

Seamless steel pipe hot extrusion

The hot extrusion process of seamless pipe is a pressure forming method, which is to place the tube blank in a pressure-resistant container, and apply an external force to make the tube blank plastically deform under a three-dimensional compressive stress state. During the extrusion process, the tube blank is in a state of three-dimensional compressive stress, so it can obtain a larger plastic deformation than rolling and forging. Depending on the material and extrusion method, the extrusion elongation coefficient can reach 5-500, or even higher. Due to the characteristics of high dimensional accuracy, compact metal structure and stable mechanical properties, hot-extruded seamless steel pipes are widely used in nuclear power, thermal power, petrochemical, aviation, aerospace, transportation and other fields.

hot extrusion process

Blank preparation→ring furnace preheating→vertical induction furnace heating→glass powder lubrication→vertical press punching (expansion)→phosphorus removal→vertical induction furnace reheating→glass powder lubrication→extrusion→cutting and pressing→cooling

When using hot extrusion technology to produce seamless steel pipes, the broken pipe must be a hollow billet. One is a hollow billet for forging or casting billet piercing, and the other is a hollow billet for centrifugal casting. There are 3 different piercing methods for forging or billet piercing depending on steel grade and specification:
①The solid tube blank is pierced on the vertical piercer;
② Drill a small hole (also called pilot hole) in the center of the broken pipe in advance, and use a pressure perforator to perforate;
③ Drill a large hole with a diameter slightly larger than the extruded mandrel in the center of the broken tube, and directly send it to the extruder for extrusion.

During the extrusion process, the glass mat between the tube and the extrusion die melts and acts as a lubricant. The outer diameter of the extruded seamless steel pipe depends on the inner diameter of the die hole, and the gap between the mandrel and the die hole determines the thickness of the steel pipe. After the extrusion is completed, the steel pipes are cooled and collected for heat treatment and finishing

Technical Difficulties in Hot Extrusion Process of Seamless Steel Tube
1. Billet pentoxide heating
2. The service life of the mold
3. Lubrication problem

Read more :  seamless carbon steel pipe