Stainless steel seamless steel pipe is a long steel material with a hollow section and no seams around it. stainless steel seamless pipe

Features of stainless steel seamless pipes:

First, the thicker the wall thickness of the product, the more economical and practical it is. The thinner the wall thickness, the processing cost will increase significantly. Secondly, the process of the product determines its limited performance. Generally, Seamless steel pipes have low precision: uneven wall thickness, low brightness on the inside and outside of the pipe, high cost of sizing, and pitting and black spots on the inside and outside that are difficult to remove; thirdly, its detection and shaping must be processed offline. Therefore, it reflects its superiority in terms of high pressure, high strength, and mechanical structural materials.

Types of stainless steel pipes:

The rolling methods are divided into hot rolling, hot extrusion and cold drawn (rolled) stainless steel pipes.

According to the different metallographic structures of stainless steel, it can be divided into semi-ferritic and semi-martensitic stainless steel pipes, martensitic stainless steel pipes, austenitic stainless steel pipes, austenitic-ferritic stainless steel pipes, etc.

Stainless steel pipe specifications and appearance quality:

A. According to the provisions of GB14975-94 "Stainless Steel Seamless Steel Pipe", the usual length of steel pipes (indeterminate length) is 1.5 to 10m for hot-rolled steel pipes and equal to or greater than 1m for hot-extruded steel pipes. Cold drawn (rolled) steel pipes with a wall thickness of 0.5 to 1.0mm, 1.0 to 7m; those with a wall thickness greater than 1.0mm, 1.5 to 8m.

B. There are 45 types of hot-rolled (hot extruded) steel pipes with diameters ranging from 54 to 480mm; and 36 types with wall thicknesses ranging from 4.5 to 45mm. There are 65 types of cold-drawn (rolled) steel pipes with diameters ranging from 6 to 200mm; and 39 types of wall thickness ranging from 0.5 to 21mm.

C. There must be no cracks, folds, cracks, cracks, folds, separation layers and scarring defects on the inner and outer surfaces of the steel pipe. These defects should be completely removed (except for pipes for mechanical processing). After removal, the wall thickness and appearance must not be changed. diameter exceeds the negative deviation. Other minor surface defects that do not exceed the allowable negative deviation do not need to be removed.

D. Allowable depth of straight track. Hot-rolled and hot-extruded steel pipes with a diameter less than and equal to 140mm shall not exceed 5% of the nominal wall thickness, and the maximum depth shall not exceed 0.5mm; cold-drawn (rolled) steel pipes shall not exceed 4% of the nominal wall thickness, and the maximum depth shall not exceed 0.3 mm.

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

1. Hot rolling (extruded seamless steel pipe): round tube blank → heating → perforation → three-roll cross rolling, continuous rolling or extrusion → detubing → sizing (or diameter reduction) → cooling → straightening → hydraulic test (or flaw detection) → Mark → Warehouse

The raw material for rolling seamless pipes is round tube billet. The round tube billet must be cut by a cutting machine into a billet with a length of about 1 meter and sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated to a temperature of approximately 1,200 degrees Celsius. The fuel is hydrogen or acetylene. Temperature control in the furnace is a key issue. After the round tube comes out of the furnace, it must be pierced through a pressure punching machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can penetrate a variety of steel types. After perforation, the round tube blank is successively cross-rolled, continuous rolled or extruded by three rollers. After extrusion, the pipe should be removed and calibrated. The sizing machine rotates a tapered drill bit at high speed into the steel blank to drill holes to form a steel pipe. The inner diameter of the steel pipe is determined by the outer diameter length of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened.

2. Cold drawn (rolled) seamless steel pipe: round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet tube → heat treatment → straightening →Hydraulic test (flaw detection)→Marking→Storage.

The rolling method of cold-drawn (rolled) seamless steel pipe is more complicated than hot-rolled (extruded seamless steel pipe). The first three steps of their production process are basically the same. The difference starts from the fourth step. After the round tube blank is hollowed out, it needs to be headed and annealed. After annealing, special acidic liquid should be used for pickling. After pickling, apply oil. Then it is followed by multiple passes of cold drawing (cold rolling) and then special heat treatment. After heat treatment, it is straightened.

After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by a conveyor belt for internal flaw detection. If there are cracks, bubbles and other problems inside the steel pipe, they will be detected.

After quality inspection, steel pipes must undergo strict manual selection. After the quality inspection of the steel pipe, spray the serial number, specification, production batch number, etc. with paint. And it is hoisted into the warehouse by a crane.