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Stainless steel seamless tube features
2021-11-18 10:50:33

First, the thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the higher the processing cost will be. Secondly, the process of the product determines its limited performance. The seamless steel tube has low precision: uneven wall thickness, low brightness inside and outside the tube, high fixed-length cost, and pitting and black spots on the inner and outer surfaces are not easy to remove; thirdly, its detection and shaping must be processed offline. Therefore, it embodies its superiority in high-pressure, high-strength, mechanical structural materials.

Types of stainless steel tubes:

The rolling method is divided into hot rolling, hot extrusion and cold drawing (rolling) stainless steel tubes.

According to the stainless steel metallographic structure, it is divided into semi-ferritic semi-Martensitic stainless steel pipes, martensitic stainless steel pipes, austenitic stainless steel pipes, austenitic-ferritic iron stainless steel pipes.

Stainless steel tube specifications and appearance quality:

A. According to GB14975-94 "Stainless Steel Seamless Steel Pipe", the normal length of steel pipe (indefinite) hot-rolled steel pipe is 1.5~10m, and the hot-extruded steel pipe is equal to or greater than 1m. Cold drawn (rolled) steel pipe wall thickness of 0.5 ~ 1.0mm, 1.0 ~ 7m; wall thickness greater than 1.0mm, 1.5 ~ 8m.

B. There are 45 kinds of hot-rolled (hot-extruded) steel pipes with a diameter of 54-480 mm; a total of 36 kinds of wall thicknesses of 4.5-45 mm. There are 65 kinds of cold drawn (rolled) steel pipes with a diameter of 6 to 200 mm, and 39 kinds of wall thicknesses of 0.5 to 21 mm.

C. There shall be no cracks, folds, cracks, cracks, rolling, separation and crusting defects on the inner and outer surfaces of the steel pipe. These defects shall be completely removed (except for mechanical processing pipes), and the wall thickness and outer wall shall not be removed after removal. The diameter exceeds the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation may not be removed.

D. Straight road allows depth. Hot-rolled and hot-extruded steel pipes, not less than or equal to 140mm in diameter and not more than 5% of the nominal wall thickness, the maximum depth is not more than 0.5mm; cold-drawn (rolled) steel pipes are not more than 4% of the nominal wall thickness, and the maximum depth is not more than 0.3 Mm.

E. Both ends of the steel pipe should be cut at right angles and the burrs should be removed. Stainless steel seamless pipe manufacturing process:

1. Hot rolling (extrusion seamless steel pipe): round billet → heating → perforation → three-roll cross-rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing diameter) → cooling → straightening → hydraulic test (or flaw detection) → mark → warehousing

The raw material for rolling the seamless pipe is a round tube blank, and the round tube blank is cut into a blank having a length of about 1 m by a cutting machine, and sent to a furnace for heating via a conveyor belt. The billet is fed into a furnace and heated to a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. Furnace temperature control is a key issue. After the round billet is released, it is subjected to a through-hole punching machine. The more common perforating machine is a conical roller punching machine. This perforating machine has high production efficiency, good product quality, large diameter of perforation and can wear a variety of steel types. After perforation, the round billet is successively rolled, rolled or extruded by three rolls. After extrusion, the tube should be sizing. The sizing machine is rotated at a high speed by a conical drill bit into a steel core to form a steel pipe. The inner diameter of the steel pipe is determined by the outer diameter of the sizing machine drill bit. After the steel pipe has been sized, it enters the cooling tower and is cooled by water spray. After the steel pipe is cooled, it is straightened.

2. Cold drawn (rolled) seamless steel pipe: round tube billet → heating → perforation → head → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening →Hydraulic pressure test (inspection)→marking→into the warehouse.

The rolling method of cold drawn (rolled) seamless steel pipe is more complicated than hot rolling (extrusion seamless steel pipe). The first three steps of their production process are basically the same. The difference begins with the fourth step. After the round billet is hollowed out, it is required to start and anneal. After annealing, it is acid washed with a special acidic liquid. After pickling, apply oil. This is followed by a multi-pass cold drawing (cold rolling) of the blank tube, followed by a special heat treatment. After heat treatment, it is straightened. After the steel pipe is straightened, it is sent to a metal flaw detector (or water pressure test) by a conveyor belt for internal flaw detection. If there are cracks inside the steel pipe, bubbles and other problems will be detected. After the quality inspection of the steel pipe, it must be carefully selected by hand. After the quality inspection of the steel pipe, the paint is sprayed with the number, specification, production batch number, etc. It is hoisted into the warehouse by a crane.