What is hot extrusion of seamless steel pipe?

What is hot extrusion of seamless steel pipe?

The hot extrusion process of seamless pipe is a pressure forming method, that is, the pipe blank is placed in a pressure-resistant container, and an external force is applied to cause the pipe blank to undergo plastic deformation under a three-dimensional compressive stress state. During the extrusion process, the tube blank is in a three-dimensional compressive stress state, 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, dense 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 making→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 pipe blank. 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 the steel grade and gauge:
①The solid tube blank is pierced on a vertical piercer;
② Drill a small hole (also called pilot hole) in the center of the broken pipe in advance, and use a pressure piercer to perforate;
③ Drill a large hole with a diameter slightly larger than the extrusion mandrel in the center of the broken pipe, and send it directly to the extrusion machine for extrusion.

During extrusion, the glass mat between the tube and 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 extrusion is complete, the steel pipes are cooled and collected for heat treatment and finishing

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

Article source: https://article-realm.com/article/Business/49523-What-is-hot-extrusion-of-seamless-steel-pipe.html