SU1082590A1 - Method of removal of weld deformations and strains - Google Patents

Abstract

A METHOD FOR ELIMINATING WELDING DEFORMATIONS AND STRESSES OF WELDED JOINTS BY ROLLING A ROLLER-AND-WELD SEAM, DIFFERENT. In order to improve the quality and endurance of the joint, rolling is performed with heating to a temperature not lower than the polymorphic transformation temperature, and the roller is given a reciprocating movement along the weld axis by an amount equal to 40-50 thicknesses of the weld metal, and rolling pressure in the opposite direction, it is set equal to 0.2-0.3 rolling pressures in the forward direction.

Description

The invention relates to mechanical engineering, in particular, to the production of welded structures of aviation, chemical, shipbuilding, and other industries of the national economy. Various methods are known to eliminate welding deformations and stresses; creating nodules in the weld zone; heat treatment} shot blasting; rolling along the weld, which has found wide application in the industry. However, creating nubs is not always applicable in structures, especially from thin-sheet material, but if it is possible to create a structure, this leads to an increase in the product sama and lowering of the CIM. Heat treatment can increase the strength of only a limited range of materials, but it can cause additional deformation. Shot blasting cannot also be applied on thin-sheet materials, as it causes deformations and requires special conditions from the point of view of industrial sanitation. The most effective way to reduce strain and stress is rolling. Methods are known for eliminating stresses and strains by rolling 2. However, in these methods, internal weld defects are not eliminated, and deformation in the transverse direction is also not eliminated. The closest in technical essence to the proposed is. The method of elimination of welding deformations and stresses of welded joints by rolling the weld rollers, which reduces welding deformations and peak stresses by rolling along the weld with nonepe4HbnvjH vibrations of a roller in a cold h. However, the quality of welded joints and the fatigue limit are not sufficiently high, because with this method, internal defects are drawn out and external defects are thickened. The purpose of the invention is to increase the quality and endurance of the compound. This goal is achieved by the fact that, according to the method of eliminating welding deformations and stresses of welded joints by rolling weld rollers, rolling is performed with heating to a temperature not lower than the polymorphic transformation temperature, and the roller is given reciprocating movement along the weld axis by an amount -50 thicknesses of the weld metal, the rolling pressure in the opposite direction being set to 0.2-0.3 rolling pressure in the forward direction. The method is carried out by cyclic loading. The first stage of rolling is carried out in the forward direction at a nominal pressure P, which is determined by the formula p,, 1 Oi P - G, where P is the rolling force, kgf; b is the width of the rollers, mm; d is the diameter of the rollers, cm; 5 - the thickness of the metal in the rolling zone, cm; elastic model of rolled metal, kgf / cm; yield strength of the metal in the rolling zone at temperature, re superplasticity, kgf / cm. The second stage of rolling, called training, is carried out in the opposite direction at a pressure of PJ 0.2-0.3 P 200 - 300 kgf, i.e. little additional deformation is created for the occurrence of compressive stresses in the surface layers. It is known that compressive stresses increase the efficiency of welded joints. During the first rolling stage, thermomechanical metal treatment (TMT) is performed, at which the tensile welding stresses are removed and the weld metal is strengthened. A decrease in pressure to 0, 1 P 100 kgf does not increase the quality and endurance of the compound, and an increase in pressure to 0.4 P 400 kgf also does not give a positive effect, since the surface stresses increase. After passing the step with rollers equal to 40-50 metal thicknesses in the forward and reverse directions, let i

until the end of this step, the rollers are idled, after which a new step with a nominal pressure begins.

With a metal thickness of 1.2 mm, the pitch is 48-60 mm. When reducing the pitch to 40 mm, defects are not eliminated, with an increase in it, the deformations from the rolling itself remain.

In the contact zone with the roller, which creates pressure P 1000 kgf, the welded joint is heated, for example by passing an electric current, to a temperature not lower than the polymorphic transformation temperature of the metal, t; e creates an interval of onset of superplasticity of the material. Such a temperature, for example, for titanium anew CTA alloy, is a temperature in the range of 880-900 ° C, for VT6 900 ° C, for VT20 960-980 ° C.

when the temperature reaches above the polymorphic transformation temperature of the material, for example, for titanium, it occurs at oi-j transformation, splicing of porosity, cavities and other internal defects occurs, as well as complete smoothing of the outer surface of the weld metal and elimination of external stress concentrators. Rolling with heating effectively corrects the deformations of thin-sheet structures, as a mismatch of the edges (reduction) of local warping and protrusion. ; Seams, etc. Especially efficiently, hot rolling fixes welded assemblies in the form of shells, shells, pipes and bottoms.

After rolling with heating, the endurance limit increases significantly, as can be seen from the table. Experiments were conducted on titanium alloys OT4-1, PT7-M and al. 40, material thickness 1.2 mm. Samples in the amount of 3 pieces of each variant were welded by automatic argon-arc welding, subjected to X-ray translucency. Welding was performed according to the following mode: O 70A, and 8-10V, welding speed 12 m / h. After X-ray transmission, defects were found in the form of pores, undercuts of an underestimation to a depth of 0.3 mm. The samples were laminated according to the basic coolant variant and according to the proposed hot rolling at the superplasticity temperature. Modes of rolling: width of rollers 10 mm, diameter of rollers 150 mm, PA about. 1500 kgf during cold rolling and 1000 kgf during hot rolling 908 After rolling, the properties of welded joints, endurance, and the number of defects were examined (table). Analysis of the results showed that the strength of the compounds during hot rolling is higher, the endurance also, for example, for the OTA-1 alloy increased by 8 kgf / iz:., Which is very important. Defects in the form of undercuts and porosity and deformation were absent. Welding stresses in the weld metal are relieved. Thus, it can be seen that the proposed method is effective and useful for production and will find wide application in rolling titanium pipelines. The introduction of the proposed method will increase the service life of pipelines 1.5-2 times. Only at one enterprise, for example, in the manufacture of product Ш1-62, the economic effect will be 210 thousand rubles.

Claims (1)

METHOD FOR REMOVING WELDING DEFORMATIONS AND STRESSES of welded joints by rolling with a roller of a weld, characterized in that the fact that, in order to improve the quality and endurance of the joint, rolling is carried out with heating to a temperature not lower than the temperature of the polymorphic transformation, and the roller is informed of reciprocating movement along the axis of the seam by an amount equal to 40-50 thicknesses of the metal of the welded joint, and the rolling pressure the reverse direction is set equal to 0.2-0.3 rolling pressure in the forward direction. $