New technique for manufacturing high alloy steel seamless pipe with heavy calibre by adopting pilger mill

Abstract

The invention discloses a technique for manufacturing a high alloy steel seamless pipe with heavy calibre by adopting a pilger mill, comprising: a hollow shell is made by centrifugal casting; the outside surface of the front end of the hollow shell is processed to be a 'gripping head' with conicity, and machining and quality inspection are carried out on the inside and the outside surfaces aswell as the 'gripping head' of the hollow shell; the tail end of the hollow shell is welded with a plain carbon steel ring-shaped part; heating and dephosphorization are carried out on the hollow shell; a mandril is inserted into the heated and dephosphorized hollow shell and the hollow shell is located, and then the hollow shell is sent into the pilger mill for alternate rolling, so that the pipefittings in accordance with the requirements can be produced; the mandril of the pipe fittings is removed, and the head and the tail are cut off; finally, the qualified finished pipes can be obtainedafter heating, sizing and finishing operation. As the steps of punching and hole expanding are omitted, the process flow is shortened, and the running cost is reduced; the step of reheating is reduced, so that the energy can be saved; the hollow shell is obtained by centrifugal casting and is machined, so that the quality of the product can be improved; as the plain carbon steel ring-shaped partis welded at the tail of the hollow shell, the material consumption of precious metal is reduced, and the yield is greatly improved; furthermore, a section of 'gripping head' with small conicity is processed at the front end in advance, thus facilitating the gripping of rolling and improving the operation efficiency and the stability of rolling.

Description

Technical field: [0001] The invention relates to the manufacturing technology of seamless steel pipes, in particular to the manufacturing technology of high-end seamless steel pipes with large diameter, medium-thick wall and high alloy steel. Background technique: [0002] Steel has good comprehensive performance, can bear the required load and have the required service life cycle under different working conditions, and has good process performance. It is an indispensable and important basic material for national economic construction. Generally speaking, carbon-iron alloys with a carbon content of 0.02%-2% are called steel, and carbon-iron alloys with a carbon content greater than 2% are called cast iron. According to different classification standards, steel can be divided into different categories. According to the chemical composition of steel, it can be divided into carbon steel and alloy steel: [0003] In addition to iron and carbon, the components in carbon steel a...

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Problems solved by technology

[0011] 3. Although the reciprocating rolling on the periodic pipe rolling mill with strong deformation ability (the elongation coefficient can reach more than 10) has the deformation characteristics of forging, it is beneficial to the coarse grain structure of the broken pipe, but it still cannot overcome the hollow pipe. Defects such as dimensional accuracy and poor surface quality of the billet

Although this method can produce special steel pipes containing Cr, Ni, Mo, N and other elements, it needs multiple cycles of cold drawing, and softening treatment, pickling treatment and lubrication treatment are also carried out after each cold drawing, and the process is long. The efficiency is lower, the cost is more expensive, and it is more suitable for the production of precision pipes with small batches and small and medium diameters.

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