JPS60248814A - Mechanical stress improvement - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mechanical method for relieving residual welding stresses in hot-formed j-zones and adjacent pace metals of shells, pipes and machine parts by weld metal.

BACKGROUND OF THE INVENTION Welding pipes, shells and mechanical parts creates residual tensile stresses. These tensile stresses enhance stress corrosion cracking, fatigue, and creep crack propagation.

Therefore, it is highly advantageous to eliminate these residual welding stresses.

Seven methods currently used to improve residual weld stress are induction heating stress improvement methods. This induction heating stress remediation process has been used for /4' Eves and Shells, but fails to induce a net compressive force in either the axial or circumferential direction. The equilibrium of the axial compressive stress by the induction heating stress remediation process induces an axial tensile stress such that the net axial force on any cross section is zero.

In fact, during the induction heating stress remediation process, large bending stresses are caused to the housing body. Therefore, weld defects such as inclusions, porosity, insufficient melting, hot cracks, stress corrosion, fatigue cracks, etc. are subjected to high tensile stress during this one-leading heating stress remediation process. As a result, high stress corrosion cracks, fatigue damage, and creep crack propagation reduce the strength and durability of the walls, making them susceptible to leakage.

The mechanical stress remediation process of the present invention is an improved method that does not induce high tensile stresses in the tube or shell during this process, thus eliminating the potential negative effects of these tensile stresses.

SUMMARY OF THE INVENTION The present invention provides a method for heating a welded metal zone and shell;
Weld metal using a method consisting of mechanically applying a compressive stress to the adjacent pace metals of Tsukuino and mechanical parts that is higher than their individual yield strength and does not exceed their individual ultimate shrinkage strength. Residual stresses in the heating affected zone and adjacent pace metal can be improved. After applying compressive stress, there is no need to apply further compressive stress;
Therefore, it can be finished immediately. In this method, the compressive stress, when added to the original residual stress, exceeds the material yield strength of the heating affected zone by the weld metal and the adjacent pace metal. As a result, materials whose compressive stress exceeds their yield strength undergo permanent plastic flow. Subsequent removal of the compressive stress reduces the original residual tensile stress.

The mechanical device used to achieve the desired effect described above is not critical. For example, in a preferred embodiment used for glossy blades and shells, this mechanical device has an inner surface of 74 mm.
It consists of a split ring corresponding to the outer surface of the ino or shell, and a device 1f for applying a constant compressive deformation to the outer surface of the /4' eve or shell via the split ring. A device for controlling compressive deformation in the circumferential direction along the length of the pipe or shell may be used in one of the raised rings. This is achieved by providing aligned openings at the abutting ends and placing these openings in a vertical position. The size of the '0J gap between adjacent ends of the split ring can be determined by introducing a shim between the ends. A device for controlling the desired axial compression deformation is obtained by using a pair of split rings. Adjacent ends of each of the paired rings have aligned openings, and each of these openings has a ? place the root.

It is obvious that variations and modifications of the invention as described above may be made without departing from the spirit of the invention, and therefore only such limitations as are indicated in the claims are to be imposed. .

Claims (1)

[Claims] l Compressive stress in the heating affected zone by the weld metal and in the adjacent pace metal of shells, pipes and machine parts higher than their individual yield strength and not exceeding their individual ultimate compressive strength. A method for improving residual stresses in a heat-affected zone and adjacent pace metal due to weld metal, comprising mechanically applying . 2. The method of claim 1, wherein the compressive stress is then terminated.