RU2025241C1 - Method of welding by pressure - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: prior to pressing the parts, composition of protective activating medium is introduced into chamber, thus increasing the duration and intersifying activation of surfaces being welded together. EFFECT: enhanced reliability of protection against oxidation and connection as a whole. 3 cl

Description

 The invention relates to pressure welding with heating and can be used in various fields of engineering.

 There is a known method of welding in vacuum (ed. St. N 1463415, class B 23 K 20/14, 1989), in which blind cylindrical holes are made on one of the surfaces to be welded, an intermediate gasket is placed and diffusion bonding is carried out.

 The disadvantage of this method is the complexity of manufacturing perforated holes, evacuation of the welded parts, which leads to an increase in the duration of the process.

 A known method of pressure welding (ed. St. N 975284, class B 23 K 20/14, 1982), including high-speed heating of the connection zone during the pyrolysis of a protective activating medium under pressure and subsequent isothermal exposure.

 The disadvantage of this method is the insufficient degree of activation of the welded surfaces and the possibility of edge discontinuities, which reduces the quality of the connection and leads to the need for additional machining and additional consumption of metal.

 A known method of diffusion welding [1], which is taken as a prototype, in which a cavity is made on the surface to be welded to at least one of the parts to be joined, the parts are compressed and the joint zone is heated to the welding temperature, followed by isothermal exposure.

 The disadvantage of this method is the need for evacuation of parts or the connection of an inert atmosphere, which leads to an increase in the duration of the process, as well as a low degree of activation of the surfaces to be welded, which reduces the quality of the connection and leads to the need for additional deformation of the surfaces to be welded and, as a result, to an additional increase in the volume of subsequent machining .

 The purpose of the invention is the intensification of the process and improving the quality of the connection.

 This is achieved by the fact that in the known welding method, in which a cavity is made on at least one of the surfaces to be welded, parts are compressed and the connection zone is heated, it is proposed to introduce a protective-activating medium (ZAC) into the cavity. In the particular case, it is advisable to introduce organic compounds based on hydrocarbons or an exothermic mixture into the cavity.

 The introduction of ZAS into the cavity allows an additional sharp increase in the volume of ZAS in the joint, which leads to an increase in the duration of activation of the surfaces to be welded, to an increase in the quality of their protection against oxidation, due to which intensification of the welding process is achieved, and the quality of the joint is improved, which leads to a reduction in metal overall volume of subsequent machining.

 The method is as follows.

 A cavity is made on the surface to be welded to at least one of the parts to be welded and filled with a protective activating medium (ZAC) (in the particular case, the cavity is filled with organic compounds based on hydrocarbons or an exothermic mixture). The surfaces of the parts to be welded are coated with a ZAC composition, which provides local protection of the surfaces to be welded from oxidation when the joint is heated in air.

 The parts prepared for welding are compressed, heated to a welding temperature at a high speed, isothermal exposure is carried out, and after the formation of the joint, the parts are cooled.

 In the process of heating a compound at a high speed to a welding temperature, ZAC pyrolysis initially occurs on surfaces, which prevents them from oxidation when the compound is heated in air.

 Under the influence of temperature and pressure, the ZAC is displaced from the cavity and its additional supply to the welded surfaces warmed up to the welding temperature, which leads to a sharp increase in the pressure of vapor-gas ZAS pyrolysis products in microvolumes, to the intensive removal of pyrolysis products and oxide film residues under constantly increasing excess ZAS pressure from cavities and, as a result, to intensive facilitated crushing of micro roughness, accompanied by migration of the interface and the formation of high-quality compounds the entire welded surface without the formation of edge discontinuities.

Introduction into the cavity exothermic mixture facilitates momentary increase in temperature in flash time to 2500 ^{° C,} resulting in overheating ASDs in micro junction and a sharp abrupt increase in vapor pressure, until the mode "shock boiling" which further intensifies the welding process, thereby reducing the residual strain amount and reducing the volume of subsequent machining and metal saving.

 The solid products of the exothermic reaction remain in the cavity without compromising the quality of the compound as a whole.

 PRI me R. Welded St45 + P18 cylindrical in shape with a diameter of 10 mm, a length of 60 mm.

On one of the samples to be welded, the most refractory in its central part, a cavity was made in the form of a blind cylindrical hole with a diameter of 1.5-2 mm and a depth of 3-4 mm. An ED20 epoxy was introduced into the cavity. Weldable surface coated ED20, parts confining pressure of 1.5 kgf / mm ^2, the joint was heated at a rate ^of 200-250 C / s to welding temperature 1150 ^{° C} and isothermal exposure was performed for 40 seconds.

 For comparison, the same samples were welded in the same modes without a cavity.

 The nature of the compounds was determined by edge defects.

 When comparing it, it turned out that when welding with a cavity, there are no boundary discontinuities, while welding without a cavity - 5% -10% of the total area of the surface being welded.

Welded St45 + VK8 alloys through a 0.1 mm thick Ni spacer applied to the hard alloy in a galvanic manner. The welded area is 60 mm ² .

A cavity was filled in the central part of the steel part, which was filled with an exothermic mixture of Ti - C elements taken in a stoichiometric ratio. Squeezed by a force of 1.5 kgf / mm ² and heated at a speed of 100 ^about C / s to a temperature of 1100 ^about C and isothermal exposure for 120-180 s. The connection is high-quality.

Claims (3)

 1. PRESSURE WELDING, in which a cavity is made on the surface to be welded to at least one of the parts to be joined, parts are compressed and the connection zone is heated, characterized in that, in order to improve the quality of the connection and intensify the process, a protective-activating medium is introduced into the cavity .  2. The method according to claim 1, characterized in that as a protective activating medium take hydrocarbon-containing organic compounds.  3. The method according to claim 1, characterized in that the exothermic mixture is taken as a protective activating medium.