RU2386496C2 - Method for rolling of pipes in installation with automatic mill - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention is related to method for production of seamless pipes and may be used in production of pipes in pipe-rolling installations with automatic mills. Method for rolling of pipes in installation with automatic mill includes heating of billet, broaching of cartridge, its rolling in mandrel of automatic mill, rolling in rolling mill and calibration, at the same time front end of cartridge prior to rolling in automatic mill is expanded at the cone mounted on stopper for rolling interruption.

EFFECT: usage of this method of rolling in installation with automatic mill will make it possible to increase resistance of mandrels and to improve quality of inner pipe surface.

Description

The invention relates to pipe production, and in particular to a method for the production of seamless pipes, and can be used in the production of pipes in pipe rolling plants with automatic mills.

In pipe production, there is a known method of rolling pipes in an automatic mill, which consists in periodically turning the mandrel after the pipe leaves the caliber (B21B 17/08, AS No. 239905, application. 50966, publ. 21.12.73).

This solution reduces the wear of the mandrel, but does not solve the problem. When flashing, the front end of the sleeve is uneven, i.e. there is no perpendicularity to the axis, and therefore, when the sleeve is set into the mill, the more advanced part of the end face will somehow get on the mandrel, i.e. mandrel rotation is ineffective.

The closest technical solution is the method of rolling pipes, in which the front end of the sleeve before rolling on an automatic mill is heated to a temperature 10-50 ° higher than the temperature of the body of the sleeve, while the heating time is carried out according to (B21B 17/08, A.S. No. 2271885, published March 20, 2006)

where t is the duration of heating, s;

S is the wall thickness of the sleeve, mm;

D is the diameter of the sleeve, mm;

a - thermal diffusivity, m ³ / h;

T ₃ = T + (0-50 °) - the temperature of the end face of the sleeve after heating, ° C;

T is the body temperature of the sleeve, ° C;

T _t - temperature of the end face of the sleeve before heating, ° C;

T _f - flame temperature, ° C.

The disadvantage of this method is the inability to withstand the temperature of the front end of the sleeve according to this relationship. As a result of heating, moments of temperature increase occur, which leads to crushing of the front end of the liner and its sticking in the mill.

The objective of the proposed method is to increase the durability of the mandrels, i.e. elimination of tearing and sagging on the surface of the mandrels and, accordingly, reducing or completely eliminating defects on the inner surface of the pipes.

The technical result is achieved by the fact that the front end of the sleeves before rolling on an automatic mill is expanded on a cone mounted on a stop to stop rolling.

The main reason for the quick failure of the mandrels is the lowered temperature of the front end of the sleeve, namely the sharp edges of the end from the inner surface of the sleeve. When the sleeve is set by a pusher in an automatic mill, an impact occurs on the work rolls, which is softened by rotation of the rolls, then the edges of the end of the sleeve are bent, and the sharp edge of the front end with a low temperature strikes the conical part of the mandrel, tearing metal out of it, and in the process of subsequent sleeves deformation in places of breakouts, sagging on the working surface of the mandrel is formed, leading to the formation of marks on the inner surface of the pipes and the quick exit of the mandrel.

Comparative analysis with the prototype shows that the proposed method of rolling in a plant with an automatic mill is characterized in that the front end of the sleeve before rolling in an automatic mill is expanded on a cone mounted on a stop to stop rolling, i.e. remove the sharp edge of the end from the inner surface of the sleeve. These differences allow us to conclude that the criterion of "inventive step".

Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed solution from the prototype, which corresponds to the patentability "inventive step".

The method was tested on a pipe-rolling installation with an automatic mill 140 of ChTPZ OJSC in the production of cold-resistant pipes of 159 × 5 mm in size from 13KhFA steel.

In the line of axial delivery of the sleeve from the piercing mill, before the rack of the automatic mill, on a swinging stop, a removable device was mounted having a conical protrusion (steel 15X5M) with a base diameter of 160 mm and a height of 80 mm. As tests have shown, after the axial delivery of the sleeve, upon impact while the pipe is on the cone, the sharp edge is crushed (flaring of the front end of the sleeve). When this sleeve is placed in the mill, it strikes the conical part of the mandrel not with a sharp edge of the end from the inner surface of the sleeve, but with a flat, flared part, which excludes tearing of metal from the mandrel, which leads to an increase in the resistance of the mandrels by 1.6-1.9 times.

Thus, the use of the inventive rolling method in a plant with an automatic mill will increase the resistance of the mandrels and improve the quality of the inner surface of the pipes.

Claims (1)

A method of rolling pipes in a plant with an automatic mill, including heating the billet, flashing the sleeve, rolling it on the automatic mill, running on the rolling mill and calibrating, characterized in that the front end of the sleeve before rolling on the automatic mill is expanded on a conical protrusion mounted on a stop for rental stops.