how is seamless stainless steel pipe made

Manufacturing Process of SS Steel Pipe

Seamless stainless steel pipe is made from solid stainless steel bar which is called billet. By using different processing techniques such as extruding, gun drilling or piercing, the steel bars are produced to be steel tubes.

• 1. Firstly, the billets would be inspected exactly.
• 2. Then put the billets into the heat to raise the temperature.
• 3. The hot billets would then be pierced through the center with a mandrel. Through this procedure, the bar shape billet becomes hollow shape billet.  
• 4. The next step is rolling and stretching the hollow billet. The billet is precisely rolled and stretched until it meets all the specifications with length, diameter and wall thickness as specified by the customer order.

With the above basic process, the billets become pipes, then according to different requirements, the pipes would then receive heat treatment, cooling, straightening and other tests. Generally, the common manufacturing process of seamless stainless steel tube is as follows:

 

Comparison of Hot Rolled & Cold Rolled SS Steel Pipe

While seamless steel pipes can be formed into hot and cold rolled technique. How to distinguish hot and cold rolled seamless stainless steel pipe?

Hot rolled	Cold rolled
Larger diameter	Smaller diameter
Lower accuracy	Higher accuracy
Cheaper	More expensive
Technique process: 1. heating 2. perforation 3. extrusion 4. sizing block 5. hot rolling 6. cooling 7. heat straightening 8. Hydraulic test (or flaw detection) 9. marking 10. storage	Technique process: 1. heating 2. perforation 3. annealing 4. pickling→oil coating 5. cold rolling 6. heat treatment 7. straightening 8. Hydraulic test (or flaw detection) 9. marking 10. storage

1.Advantages of hot rolled process

Hot rolled seamless steel pipe can damage the casting structure of the steel ingot, refine the crystal grains of the steel, and eliminate the defects of the microstructure. In this way, the steel organization is compacting and the mechanical properties would be improved.
This improvement is reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; bubbles, cracks and looseness formed during casting can also be welded under high temperature and pressure.

2.Advantages of cold rolled process

Forming fast, high output and no damage to the coating, cold rolled seamless stainless steel tubes can be made into a variety of cross sectional forms to meet the needs of the use of conditions.
In addition, cold rolled process can cause great plastic deformation, so as to improve the yield of the steel point.