The hot rolled, hot extruded and cold drawn (rolled) stainless steel pipes are divided according to the rolling method.

According to the metallographic structure of stainless steel, the stainless steel seamless pipes, martensitic stainless steel seamless pipes, austenitic stainless steel seamless pipes, austenitic ferritic stainless steel seamless pipes and so on are divided into half ferrite half martensitic system, stainless steel seamless pipe, martensitic stainless steel seamless pipe, austenitic stainless steel seamless pipe and austenitic ferrite stainless steel seamless pipe.

Specification and appearance quality

A, according to GB14975-2002 "stainless steel seamless steel pipe", the steel pipe is usually 1.5 ~ 10m hot rolled steel tube, and the hot extruded steel pipe is equal to and greater than 1m. The wall thickness of the cold drawn (rolled) steel tube is 0.5 to 1.0mm, 1 to 7m, and the wall thickness is more than 1.0mm, and 1.5 to 8m.

The diameter of B and hot rolled (hot extruded) steel tubes is 54 to 480mm in diameter, and 36 kinds of wall thickness are from 4.5 to 45mm. The diameter of the cold drawn (rolled) steel pipe is 6 to 200mm in total, and the thickness of the wall is from 0.5 to 21mm, with a total of 39 kinds.

C, inside and outside surfaces of steel pipes must not be cracked, folded, cracked, cracked, rolled, separated and scarred. These defects should be completely removed (except for mechanical processing pipes). After cleaning, wall thickness and outer diameter should not exceed the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation can not be removed.

D and straight channel allow depth. Hot rolled and hot extruded steel tubes, with diameters less than or equal to 140mm, are not larger than 5% of the nominal wall thickness, the maximum depth is not greater than 0.5mm, and the cold drawn (rolled) steel pipe is no more than 4% of the nominal wall thickness, and the maximum depth is not greater than 0.3mm.

E, the end of the steel pipe should be cut into right angle, and clear the burr.

Manufacturing process of stainless steel seamless tube

1., hot rolling (extruded seamless steel pipe): round tube billet, heating, piercing, three roll skew rolling, continuous rolling or extrusion, tube drawing, sizing and reducing, cooling to straightening, water pressure test (or flaw detection), marking, storage.

The raw material for rolling seamless pipe is round tube billet, and the round tube embryo should be cut by cutting machine to grow billets with a height of about 1 meters, and transported to the furnace by conveyor belt. The billet was heated in the furnace, with a temperature of about 1200 degrees centigrade. Fuel is hydrogen or acetylene. The temperature control in the furnace is a key problem. The circular tube must be piercing through the pressure piercer after the furnace is discharged. Generally more common perforator is a cone roll piercer. This piercer has high production efficiency, good product quality, large perforation and large diameter, and can wear a variety of steel. After the perforation, the round tube billet was rolled, rolled or extruded by three rolls. After extrusion to remove pipe sizing. The sizing machine rotates into the steel embryo through the cone bit at high speed and forms the steel tube. The inner diameter of the steel pipe is determined by the diameter of the diameter of the drill bit. After the steel pipe is fixed, it enters the cooling tower and cooling through the water. After cooling the steel pipe, it will be straightened. The steel pipe is straightened and sent from the conveyor belt to the metal flaw detector (or water pressure test) for internal flaw detection. If there are cracks and bubbles inside the steel pipe, it will be detected. After the steel pipe quality inspection, it must be carefully selected by hand. After the quality inspection of the steel pipe, the number, specification and batch number of the paint are sprayed with paint. And the crane is hoisted into the warehouse.

2., cold drawn (rolled) seamless steel tube: round tube billet, heating, piercing, heading to annealing, acid washing, oil painting (copper plating), multi pass cold drawing (Leng Zha), tube to heat treatment, straightening, water pressure test, inspection, marking, storage.

The rolling method of cold drawn (rolling) seamless steel pipe is more complicated than that of hot rolling (extruded seamless steel pipe). The first three steps of their production process are basically the same. The difference is started from fourth steps, and the round tube blank will be hit and annealed. After annealing, a special acid liquid should be used for pickling. After pickling, oil. Then it was followed by a multipass cold - drawing (Leng Zha) re tube, a special heat treatment. After heat treatment, it is to be straightened.