Definition

Stainless steel seamless pipe is a kind of long strip steel with hollow section and without joints.

Types of seamless stainless steel tubes:

Hot rolling, hot extrusion and cold drawing (rolling) stainless steel tubes according to rolling method.

Stainless steel seamless tubes, martensitic stainless steel seamless tubes, austenitic stainless steel seamless tubes, austenitic ferritic stainless steel seamless pipes, etc., are classified according to the stainless steel metallographic structure.

Specification and appearance quality

A, according to GB14975-2002 "stainless steel seamless steel tube" stipulates, steel pipe length (variable length) hot-rolled steel pipe 1.5 ~ 10m, hot extrusion steel pipe is equal to or greater than 1m. The thickness of cold drawn (rolled) steel pipe is 0.5 ~ 1.0mm, 1 ~ 7m; the wall thickness is greater than 1.0mm, 1.5 ~ 8m.

The diameters of B and hot rolled (hot extruded) steel tubes are 54 to 480mm, 45 to 36, and 4.5 to 45mm in thickness. The diameter of cold drawn (rolled) steel pipe is 6 to 200mm in total, 0.5 to 21mm in thickness, and 39 to 65 in thickness.

C, both inside and outside the pipe surface shall not have cracks, folding, cracking, crack, rolling reduction, separation and scarring and defects, these defects should be completely removed (except for machining tube), after the removal of the outer wall thickness and shall not exceed the negative deviation. Other minor surface defects which are not allowed to exceed the allowable deviation can not be removed.

Allowable depth of D and straight line. Hot rolled, hot extruded steel pipe, diameter less than and equal to 140mm is not greater than the nominal wall thickness of 5%, the maximum depth is not greater than 0.5mm; cold drawn (rolled) steel pipe is not greater than the nominal wall thickness of 4%, the maximum depth is not greater than 0.3mm.

E, the ends of the steel pipe should be cut into right angle, and the burr can be removed.

Manufacturing process of seamless stainless steel tube

1. hot rolling (extruded seamless steel tube): round billet, heating, piercing, three roll cross rolling, continuous rolling or extrusion, stripping, sizing (or reducing diameter), cooling, straightening, water pressure test (or flaw detection), marking and warehousing

The raw material of rolling seamless tube is round tube billet, and the billet of the round tube is cut by cutting machine, and the billet is about 1 meters in height, and then sent to the furnace by conveyor belt. The billet is heated into a furnace and the temperature is about 1200 degrees centigrade. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key problem. After the billet is out of the furnace, the piercing mill must pass through the pressure piercing machine. The most common piercer is cone roll piercer, which has high production efficiency, good product quality, large perforation and large diameter, and can be used in various steel grades. After piercing, the round billet is successively rolled, rolled or pressed by three rollers. After extrusion to remove pipe sizing. The sizing machine passes through the cone bit and rotates into the steel embryo at high speed to form a steel pipe. The inner diameter of the steel pipe is determined by the outer diameter length of the sizing machine. After the steel tube is fixed, it enters the cooling tower and is cooled by water spraying. The steel pipe is straightened after cooling. After straightening, the steel pipe is sent to the metal flaw detector (or water pressure experiment) by the conveyor belt for internal flaw detection. If there are cracks in the steel pipe, bubbles and other problems will be detected. Quality inspection of steel pipe must be carried out through strict manual selection. After the quality inspection of the steel pipe, spray the paint with the number, specification, production batch number and so on. It is hoisted into the warehouse by crane.

2. cold drawing (rolling): seamless steel billet, heating, perforation, head, annealing, pickling, oil pipe (copper), multi pass drawing (Leng Zha), the blank pipe, heat treatment, straightening, pressure test (testing), marking and warehousing.

The rolling method of cold drawn seamless steel tube is more complicated than that of hot rolling (extruded seamless steel tube). Their production process is basically the same as the first three steps. The difference starts from the fourth step. After the billet is empty, it should start the heading and anneal. After annealing, special acid liquid is used for pickling. After pickling, oil. Then followed by a multi pass cold drawing (Leng Zha) re cast tube, dedicated heat treatment. After heat treatment, it must be straightened.