CN114515938A

CN114515938A - Preparation method of composite intermediate layer suitable for lap joint of titanium alloy and stainless steel heterogeneous material

Info

Publication number: CN114515938A
Application number: CN202011328890.0A
Authority: CN
Inventors: 张岩; 周建平; 高一迪; 于得水; 曾浩源
Original assignee: Xinjiang University
Current assignee: Xinjiang University
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2022-05-20

Abstract

The invention relates to the technical field of welding (connecting) of titanium/steel heterogeneous materials, in particular to a preparation method of a composite intermediate layer suitable for a lap joint of a titanium alloy and a stainless steel heterogeneous material, which can completely avoid the formation of brittle metal compounds in the titanium/steel joint; the titanium/steel dissimilar material welding is converted into the same material welding by adding the composite intermediate layer, so that the problem of poor weldability of dissimilar materials is fundamentally solved, and a larger process parameter interval is provided for the welding process; the TA2-304 composite intermediate layer is prepared by an explosion welding method, the microstructure of the titanium/steel joint is greatly improved, meanwhile, laser is used as a welding heat source, and the effective connection of the titanium alloy-TA 2-304 composite intermediate layer-stainless steel is realized by combining a transition section double-pass welding process, so that the mixing and mutual diffusion of Ti and Fe elements are avoided, no Ti-Fe intermetallic compound is generated in the joint, and the brittleness of the joint is reduced.

Description

Preparation method of composite intermediate layer suitable for lap joint of titanium alloy and stainless steel heterogeneous material

Technical Field

The invention relates to the technical field of dissimilar alloy welding (connection), in particular to a preparation method of a composite middle layer suitable for a titanium alloy and stainless steel dissimilar material lap joint.

Background

The welding metallurgy and the weldability of the heterogeneous materials are main contents of welding theory research and are also the foundation of welding technology research and development. Therefore, the research of preparing the explosive composite intermediate layer and connecting the heterogeneous materials by combining the transition section welding process is developed, so that the basic theory of welding the heterogeneous materials can be enriched, the advantages of explosive welding and laser welding are combined and complemented, and the development of the welding technology, the light weight technology and the major equipment manufacturing technology is facilitated. Titanium alloy and stainless steel are important engineering materials and are widely applied to various industrial fields, in particular to high and new technical fields such as aerospace and the like. With the development of science and technology, the requirements on the service performance of product parts are increasingly strict, a single material (stainless steel or titanium alloy) cannot meet the requirements on the service performance, and a titanium alloy/stainless steel composite structure is an effective way for solving the problem. Due to the obvious difference of chemical components and physical properties of stainless steel and titanium alloy, the weldability of titanium alloy and stainless steel and the mechanical properties of titanium/steel joints are seriously deteriorated, which also becomes one of the key scientific and technical problems which hinder the practicability of the titanium/steel composite structure; therefore, welding (connecting) of titanium alloy/stainless steel dissimilar materials is a problem to be solved.

Disclosure of Invention

The invention aims to provide a preparation method of a composite intermediate layer suitable for a lap joint of a titanium alloy and a stainless steel heterogeneous material, and aims to solve the problems that the weldability of the titanium alloy and the stainless steel and the mechanical property of a titanium/steel joint are seriously deteriorated due to the obvious difference of chemical components and physical properties of the stainless steel and the titanium alloy in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of a composite intermediate layer suitable for a titanium alloy and stainless steel heterogeneous material lap joint comprises the following steps:

step 1: preparing a composite intermediate layer: adopting 304 and TA2 as preparation materials of the composite intermediate layer, and preparing a TA2-304 composite board by an explosive welding method;

step 2: cutting the prepared TA2-304 composite board by using linear cutting equipment to process a TA2-304 composite intermediate layer with the required size;

and step 3: the joint is in an I-shaped groove butt joint mode, and the TA2-304 composite middle layer adopts an overlapping structure of 1+1 mm;

and 4, step 4: the TA2-304 composite intermediate layer is fixed by the plate group clamp, and the pre-tightening force of the stainless steel contact surface can be adjusted by the plate group clamp;

and 5: welding by adopting CW laser welding equipment, wherein the laser power is 400-1000W; the defocusing amount is-5 to +5 mm; the welding speed is 500-700 mm/min; the flow rate of the protective gas is 20-30L/min;

step 6: during the first welding, the laser offset is 0, namely, a laser spot irradiates on the contact surface of the titanium alloy-TA 2, and part of the titanium alloy and TA2 are melted to form a titanium alloy-TA 2 welding seam; during the second welding, the laser offset is 0, namely, the laser spot irradiates on the contact surface of the 304-stainless steel, and the part 304 and the stainless steel are melted to form a 304-stainless steel welding seam.

Preferably, in the step (5), welding is performed by using a CW laser welding device, and the laser power is 700W; the defocusing amount is 0 mm; the welding speed is 600 mm/min; the flow rate of the protective gas is 25L/min.

Preferably, in the step (6), when the TA2-304 composite intermediate layer is applied to weld the titanium/steel dissimilar metal plates, the laser beam is focused on the contact surfaces of the titanium-TA 2 and 304-stainless steel respectively to weld. After welding, 0.5mm-1mm of unmelted TA2-304 composite intermediate layer is reserved between the welding seams at two sides and the explosive welding bonding surface of the composite intermediate layer.

The invention has the beneficial effects that:

(1) the laser welding process is stable, the weld joint is attractive in appearance, welding defects such as cracks, air holes, undercut, incomplete penetration and incomplete fusion are avoided, and the welding process performance is good.

(2) TA2 and 304 are selected as the component materials of the composite intermediate layer, so that the microstructure of the welding seams at two sides is controlled, the joint with good weldability is obtained, the Ti-Fe intermetallic compound and other intermetallic compounds are inhibited from being formed in the welding seams at two sides, and the brittleness of the joint is greatly reduced.

(3) The titanium alloy-composite intermediate layer-stainless steel is subjected to double-pass laser welding to obtain a high-quality and high-efficiency welded joint of dissimilar metal materials comprising a titanium alloy-TA 2 welding seam, an unmelted TA2, a TA2-304 explosive welding interface, an unmelted 304 and a 304-stainless steel welding seam; in the tensile strength test, when the length of the explosion welding interface is 1-4mm, the tensile strength of the composite intermediate layer is 400-750MPa and the fracture occurs at the interface, and when the length of the explosion welding interface is 6mm, the tensile strength of the composite intermediate layer is 916MPa and the fracture occurs on the 304 stainless steel side.

Drawings

FIG. 1 is a schematic illustration of a titanium/steel explosion welded composite panel;

FIG. 2TA2-304 explosion welded composite plate interface morphology;

FIG. 3 is a schematic view of an additive composite interlayer weld;

FIG. 4 shows the change of the length of the explosion-welded interface of the composite intermediate layer is 1mm-3 mm;

FIG. 5 is a cross-sectional view of a joint with a change in length of the explosion-welded interface of 1mm to 3 mm.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

example 1

A preparation method of a composite intermediate layer suitable for a titanium alloy and stainless steel heterogeneous material lap joint comprises the following process steps:

step 6: during the first welding, the laser offset is 0, namely, a laser spot irradiates on the contact surface of the titanium alloy-TA 2, and part of the titanium alloy and TA2 are melted to form a titanium alloy-TA 2 welding seam; during the second welding, the laser offset is 0, namely, the laser spot irradiates on the 304-stainless steel contact surface, and the part 304 and the stainless steel are melted to form a 304-stainless steel welding seam.

And in the welding process, high-purity argon is adopted to protect a welding area, CW laser welding equipment is adopted to respectively butt-weld the two sides of the composite intermediate layer and the parent metal at the two sides together, the composite intermediate layer is prevented from being completely melted in the welding process, and two laser welding seams are formed at the interfaces at the two sides after welding. The laser power is 400-1000W; the defocusing amount is-5 to +5 mm; the welding speed is 500-700 mm/min; the flow rate of the protective gas is 20-30L/min; the welding parameters are adjusted to control the melting amount of the TA 2-titanium alloy and the 304-stainless steel, so that the microstructure distribution in the welding seam is controlled, and the brittleness of the joint is reduced. In the titanium-composite intermediate layer-stainless steel joint, the titanium alloy-TA 2 weld joint structure is acicular alpha' martensite, the 304-stainless steel weld joint structure is gamma-Fe austenite and a small amount of alpha-Fe ferrite, the brittleness of the joint is greatly reduced, and the mechanical property of the joint is improved.

In this embodiment, in the step (5), CW laser welding equipment is used for welding, and the laser power is 700W; the defocusing amount is 0 mm; the welding speed is 600 mm/min; the flow rate of the protective gas is 25L/min.

In addition, in the step (6), when the TA2-304 composite intermediate layer is applied to weld the titanium/steel dissimilar metal plates, the laser beams are respectively focused on the contact surfaces of the titanium-TA 2 and 304-stainless steel to weld. After welding, 0.5mm-1mm of unmelted TA2-304 composite intermediate layer is reserved between the welding seams at two sides and the explosive welding bonding surface of the composite intermediate layer respectively, and the function of the composite intermediate layer is to avoid liquid mixing of parent metal at two sides and prevent mixing and mutual diffusion of Ti and Fe elements, thereby avoiding forming brittle Ti-Fe intermetallic compounds in the welding process; in the steps (1) and (2), in order to compare and verify the influence of the length of the explosion welding bonding surface on the mechanical property of the joint, the TA2-304 composite plate is subjected to linear cutting processing, the explosion welding interfaces are respectively kept to be 1mm, 2mm and 3mm, and then the TA2-304 composite intermediate layer is used for welding (connecting) titanium and stainless steel; the mechanical property of the welded joint is tested in a tensile sample testing machine, and the strength of the composite intermediate layer is increased along with the extension of the explosive welding interface, so that the mechanical property of the titanium/steel joint is improved; and the explosive welding interface is prolonged according to actual requirements, and a joint with higher strength can be obtained.

The scheme provides a design scheme for preparing the explosive cladding middle layer and connecting the titanium alloy and the stainless steel by combining a transition section welding process. The unique composite intermediate layer is prepared by an explosive welding method, and the microstructure and the mechanical property of the titanium/steel joint are improved by utilizing a transition section welding process. Due to the high interface strength of the explosion-welded composite plate and the advantages of accurate control and high flexibility of laser welding, the unmelted composite intermediate layer serves as a transition section in the welding process to avoid the formation of any intermetallic compound and ensure the strength of the titanium/steel joint. The composite interlayer is prepared to combine the advantages of explosive welding and laser welding, and simultaneously solves the problem that the explosive welding structure is difficult to popularize and apply due to the influence of the geometric shape to a certain extent.

The lapped composite intermediate layer is processed on the prepared titanium/steel explosive welding composite plate by utilizing wire cutting, then the effective connection of the titanium alloy and the stainless steel is realized by laser double-pass welding, and the titanium/steel is respectively welded with two sides of the composite intermediate layer TA2-304 in the welding process. By adjusting welding parameters and controlling the laser incidence position, the explosion welding interface of the composite intermediate layer is prevented from melting in the welding process, the unmelted composite intermediate layer serves as a transition section to prevent the titanium alloy and the stainless steel from generating liquid mixing, and therefore the formation of Ti-Fe intermetallic compounds and other brittle intermetallic compounds is avoided in the welding process. The strength of the welded titanium/steel joint is mainly determined by the unmelted explosive composite intermediate layer, the strength of the composite intermediate layer can be improved by prolonging the length of an explosive welding interface, and when the strength of the composite intermediate layer is higher than that of the parent metal, laser welding seams at two sides become weak areas of the joint. According to the previous test, taking TA2-304 composite intermediate layer as an example, when the explosive welding interface length is 1-4mm, the tensile strength of the composite intermediate layer is 400-750MPa and the fracture occurs at the interface, and when the explosive welding interface length is 6mm, the tensile strength of the composite intermediate layer is 916MPa and the fracture occurs at the side 304, the welding requirement is fully satisfied.

By adopting double welding and accurately controlling welding process parameters, the titanium alloy-stainless steel welding joint comprising a titanium alloy-TA 2 welding line, an unmelted composite intermediate layer and a 304-stainless steel welding line is obtained, and no Ti-Fe intermetallic compound is formed in the welding process. Meanwhile, by accurately controlling the laser incidence point, during the first welding, laser spots irradiate on the interface of the titanium alloy-TA 2, so that the titanium alloy and TA2 part of metal are melted to form a titanium alloy-TA 2 fusion welding seam; in the second weld, a laser spot is directed at the 304-stainless steel to melt portion 304 and the stainless steel to form a 304-stainless steel weld. The unmelted composite intermediate layer serves as a transition section, liquid mixing of the titanium alloy and the stainless steel is avoided, and Ti-Fe intermetallic compounds and any other intermetallic compounds are not formed in the welding seams on the two sides.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A preparation method of a composite intermediate layer suitable for a titanium alloy and stainless steel heterogeneous material lap joint is characterized by comprising the following steps:

step 1: adopting 304 and TA2 as preparation materials of the composite intermediate layer, and preparing a TA2-304 composite board by an explosive welding method;

and 2, step: cutting the prepared TA2-3044 composite board by using linear cutting equipment to process a TA2-304 composite intermediate layer with a required size;

and 5: welding by adopting CW laser welding equipment, wherein the welding parameter is laser power of 400-1000W; the defocusing amount is-5 to +5 mm; the welding speed is 500-700 mm/min; the flow rate of the protective gas is 20-30L/min;

2. The method for preparing the composite middle layer suitable for the lap joint of the titanium alloy and the stainless steel heterogeneous material according to the claim 1, wherein in the step (5), welding is carried out by using CW laser welding equipment, and the laser power is 700W; the defocusing amount is 0 mm; the welding speed is 600 mm/min; the flow rate of the protective gas is 25L/min.

3. The method for preparing a composite interlayer suitable for a lap joint of a titanium alloy and a stainless steel dissimilar material according to claim 3, wherein in the step (6), when the TA2-304 composite interlayer is applied to weld titanium/steel dissimilar metal plates, laser beams are respectively focused on contact surfaces of titanium-TA 2 and 304-stainless steel for welding, and after the welding is completed, 0.5mm-1mm of unmelted TA2-304 composite interlayer is reserved between the welding seams at two sides and the explosive welding joint surface of the composite interlayer respectively.