Production equipment introduction of stainless steel seamless steel pipe

Generally, the production of sanitary seamless stainless steel pipes starts with cold drawing. This article will talk about several important equipment in production.

The first is the cold-drawing machine. The perforation of stainless steel round steel is called waste pipe. Usually the waste pipe is Ф655mm or Ф1007mm. The sanitary grade stainless steel pipes for general industrial use range from Ф141mm to Ф2003mm, so it is necessary to expand the pipe and draw the small pipe, which is done by cold drawing machine. And sometimes it is necessary to expand the tube or pull the small tube several times, in which the heat treatment and pickling should be cycled.

There are many advantages of cold-drawn pipe machining, which are reflected in high production efficiency, convenient change of product specifications during production, greater flexibility, and easier equipment manufacturing and maintenance of tools.
However, cold drawing processing also has disadvantages. For example, small deformation in each pass leads to many processing passes and a long production cycle; high metal consumption. The surface finish of the inner and outer surfaces of the tube is relatively poor.
Let’s talk about the multi-roller cold-rolled pipe machine, which is the key equipment used in China to manufacture sanitary seamless stainless steel pipes. Cold-drawn stainless steel tubes are used as blanks. After cold-rolling, the inner and outer diameters and wall thickness of the tubes are less than 0.02-0.05mm in plus or minus, and the inner and outer surface roughness of the tubes is Ra≤0.8μm. The internal and external surface smoothness of the tube is then polished to Ra≤0.2-0.4μm.
However, the biggest disadvantage of the multi-roll cold-rolled pipe after cold-rolling is the hard state, that is, the large yield coefficient, not easy to flaring and bending, and strictly speaking, it is not up to the national standard, so it needs to be heat-cured. Melting treatment (annealing).
Usually, after the stainless steel pipe is treated in a common heat solidification treatment furnace, the inner and outer surfaces of the stainless steel pipe will be pickled, but this will destroy the original inner and outer surface finish of the cold-rolled pipe, resulting in tiny unevenness. , which does not meet the surface finish standards of sanitary pipes. Therefore, it is necessary to choose a gas-protected bright annealing furnace.
The third one is the gas shielded bright annealing furnace, which consists of two parts, including the bright annealing furnace body and the ammonia decomposition complete device.
The main structure of the bright annealing furnace body is a muffle tank with a circular cross-section, using a heating method with high-temperature heating wires arranged on both sides and the bottom, and the ammonia decomposition gas is used as a protective gas and a circulating cooling gas. Among them, the structure is compact, the operation is safe, the control is very reliable and the maintenance is convenient, the furnace temperature is uniform, the temperature can be as high as 1150 ℃, the power loss is low, the shielding gas can be fully utilized, the cooling speed is fast, and the re-precipitation of chromium carbide can be avoided. Let all chromium carbide be completely dissolved into the austenite matrix, changing the hard state and metallographic structure of the original cold-rolled pipe, and truly achieving the purpose of solid solution treatment.
In addition, the complete set of ammonia decomposition device uses pure liquid chlorine to decompose into 70% hydrogen and 30% ammonia, which are filled into the furnace body to drive away air (oxygen) and reduce the air content as much as possible.