CN113427111A

CN113427111A - Alleviate fixture of pipe-stopper structure piezoresistance welding head surface transition unsmooth

Info

Publication number: CN113427111A
Application number: CN202110759452.8A
Authority: CN
Inventors: 林健; 冯刚; 雷永平; 符寒光; 季顺成; 崔泰然; 杨乐
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2021-07-05
Filing date: 2021-07-05
Publication date: 2021-09-24
Anticipated expiration: 2041-07-05
Also published as: CN113427111B

Abstract

A fixture for relieving the unsmooth transition of the outer surface of a pressure resistance welding head of a pipe-plug structure belongs to the technical field of fixtures. The problem that transition of the outer surface of a joint is not smooth in the pressure resistance welding process is solved. The fixture is of a centrosymmetric structure and comprises two parts, wherein the first part is a base which can be matched with a positioning fixture of welding equipment to play a positioning role; the second part is a hollow clamping apparatus cylinder, the front end face of the cylinder is parallel and level with the end face to be welded of the pipe, and the inner wall of the cylinder comprises a straight section hole wall and an inclined section hole wall. The straight section hole wall is matched with the outer diameter of a pipe to be welded, the oblique section hole wall can limit free flow of extruded metal under the action of high temperature and pressure in the welding process, and finally the extruded metal flows radially along a certain angle and forms interface combination with the end plug, so that the problem of unsmooth transition of the outer surface of the joint is greatly relieved, the fusion area of pressure resistance welding can be increased, and the mechanical property of the joint is improved.

Description

Alleviate fixture of pipe-stopper structure piezoresistance welding head surface transition unsmooth

Technical Field

The invention belongs to the technical field of clamps, and particularly relates to a clamp for relieving unsmooth transition of the outer surface of a pressure resistance welding head of a pipe-plug structure.

Background

In pressure resistance welding, the pipe and the end plugs are clamped in two pairs of clamping devices with similar sizes, and the end face of the pipe is generally parallel to the end faces of the clamping devices, namely the pipe does not extend out of the clamping devices. After the welding process begins, the welding current and the resistance of the tube-plug interface act together to generate a large heat source, and under the upsetting of the welding pressure, the tube extrudes part of the metal towards the inside and the outside. In the service process of metal extruded into the pipe, the risk of crack initiation and expansion exists, however, the metal extruded into the pipe is not easy to be improved by clamping, and the welding process is usually adjusted to avoid the occurrence of the metal extruded into the pipe; the metal extruded outside the pipe can affect the smooth transition of the joint, so that the stress concentration and other problems exist at the joint, the performance of the joint is reduced, the metal extruded outside is required to be polished smoothly by a mechanical method after welding, and the pipe at other parts is easily damaged in the polishing process. External extruded metals are difficult to modify by tuning the process and it is generally considered to alleviate the problem of transition unevenness by modifying the fixture. The problem of unsmooth transition of a pipe-plug structure pressure resistance welding joint is solved by changing the geometric dimension of the end face of a clamp for clamping a pipe.

Disclosure of Invention

The invention aims to overcome the defects, provides a design scheme of a clamp for clamping a pipe in the pressure resistance welding process, relieves the problem of unsmooth transition outside a joint, increases the fusion area of a resistance welding joint of a pipe-plug structure, reduces post-welding mechanical treatment work and improves the manufacturing efficiency.

The fixture designed by the invention is made of industrial pure copper, and the raw materials are machined to finally form a group of centrosymmetric fixtures.

The fixture is a hollow cylinder with a base and mainly comprises two parts: the first part is a circular ring base (1) formed by splicing two independent semicircular rings, and the base (1) can be matched with a positioning fixture of welding equipment so as to play a positioning role; the second part is two independent semi-hollow cylinders (2), the two semi-hollow cylinders (2) are spliced into a complete hollow cylinder, and a pipe needs to be placed in a hole of the hollow cylinder before welding; each semi-circular ring and one semi-hollow cylinder (2) form an integrated structure, the central axis of the circular ring base (1) and the central axis of the hollow cylinder coaxially extend, and the diameter of the central hole of the circular ring base (1) is the same as that of the hole of the hollow cavity cylinder; the inner hole wall of the front end hole corresponding to the front end surface (5) of each semi-hollow cylinder (2) is provided with a right-angled triangle chamfer.

A circle of chamfer with a right-angled triangle-shaped axial section, namely a right-angled triangle groove, is processed on the inner hole wall at the front end of the hollow cylinder (2), the side wall of the chamfer is a bevel segment hole wall (4), and the bevel segment hole wall (4) corresponds to the bevel edge of the right-angled triangle; two right-angle sides of the right-angle triangular groove are respectively along the axial direction and the radial direction; the inclined line segment hole wall (4) of the hollow cylinder (2) extends backwards along the axial direction and is a straight section hole wall (3); the front end surface (5) of the hollow cylinder corresponds to one vertex of the right-angled triangle groove.

The length of the chamfer in the axial direction, namely the length of a right-angle side of the chamfer in the axial direction, is 0.8-3 mm, the length of the right-angle side of the chamfer in the radial direction is 0.08-2 mm, and the specific size depends on the wall thickness of the pipe.

The copper is made of industrial pure copper, so that the high-efficiency heat-conducting property and electric conductivity of the copper are ensured.

The base (1) plays a role in positioning, and a pipe is placed in the inner hole; the hollow cylinder plays a role in clamping and conducting current for the pipe, the oblique line segment hole wall (4) limits metal flow in the welding process, and unsmooth transition of the joint is relieved.

Clamping a pipe (7) in a fixture before welding, wherein the end face (6) to be welded of the pipe is flush with the front end face (5) of the hollow cylinder, welding is started after a butt joint is formed with an end plug, a small part of metal extruded to the outside of the pipe is extruded in a chamfer in the hot metal compression process, most of the metal flows to the side of the end plug along a bevel segment hole wall (4), and is gradually limited by a wall surface in the flowing process, so that the metal is closer to the surface of a workpiece; however, part of metal is extruded out of the front end face (5) of the hollow cylinder, but due to the slope effect of the inclined line segment hole wall (4), the part of metal is not directly extruded along the axial direction, but is extruded along a certain angle towards the radial direction, so that most of the extruded metal is smoothly combined with the interface of the end plug along the inclined line segment hole wall (4), and the problem that the transition is not smooth enough is solved. In addition, because the axial and radial dimensions of the inclined line segment hole wall are smaller, the heat dissipation efficiency of the pipe to the fixture is not influenced.

The invention has the following beneficial effects:

by adopting the pipe clamp with the oblique hole wall on the front end face, metal extruded under pressure can be better combined with the end plug to form an interface in the pressure resistance welding process, the fusion area is increased, and the heat dissipation efficiency of the pipe is ensured while the problem of unsmooth transition of the outer surface of the pipe-plug structure welding joint is solved. The invention avoids the process of removing extruded metal by using a mechanical method and can realize high-efficiency manufacturing efficiency of the pipe-plug welding joint.

Drawings

FIG. 1 is a schematic view of a fixture used in the present invention;

FIG. 2 is a longitudinal sectional view of a jig used in the present invention;

the fixture comprises a fixture base, a fixture hollow cylinder, a flat section hole wall, a diagonal section hole wall and a hollow cylinder front end face (5).

FIG. 3 is an assembly view of the clamping apparatus with a diagonal hole wall clamping the pipe in the invention;

wherein, (6) -the surface to be welded of the pipe, (7) -the pipe, and (8) -the fixture with the inclined line segment hole wall.

FIG. 4 is an assembly view of a clamp holding a pipe without a diagonal hole wall;

FIG. 5 is a weld joint obtained using a fixture with a diagonal segment bore wall;

wherein (9) -end plug.

FIG. 6 is a weld joint obtained using a fixture without a diagonal segment bore wall;

FIG. 7 is a tube-plug configuration pressure resistance weld joint.

Wherein (10) -the end plug is a straight section.

Detailed Description

The invention is further described below with reference to the accompanying drawings. However, the present invention is not limited to the following examples.

Example 1

In the embodiment, the Zr-4 end plugs and the CZ pipe are subjected to pressure resistance welding on a Gleeble thermal simulator, and the method specifically comprises the following steps:

firstly, before pressure resistance welding, the welding end face (6) of the cladding tube is slightly polished by #1500 abrasive paper, so that the cladding tube can be ensured to be fully contacted with the end plug, and the burning loss of the joint caused by poor contact can be avoided. Degreasing cotton is dipped in acetone solution to wipe oil stains and impurities on the surface of the workpiece.

And secondly, respectively clamping the end plugs and the pipes in corresponding clamps, wherein the pipes are clamped by the clamps (8) with inclined line segment hole walls, and the clamping schematic diagram is shown in figure 3. After the clamping is finished, a hydraulic device is used for pushing the clamping tool on the side of the end plug, so that the end plug and the pipe form a butt joint, and finally, the vacuum pumping treatment is carried out.

And thirdly, setting pressure resistance welding process parameters and welding.

And fourthly, after welding, cutting the welded part along the axial direction by using a linear cutting machine, and observing the macro morphology of the joint after grinding and polishing.

The macroscopic morphology of the joint obtained in this example is shown in FIG. 5.

Comparative example 1

The comparative example, which used a fixture without a diagonal hole wall (only a straight section) to clamp a pipe for pressure resistance welding, was carried out according to the following steps:

And secondly, respectively clamping the end plugs and the pipe in corresponding clamps, wherein the pipe is clamped by the clamps without inclined line segment hole walls, and the clamping schematic diagram is shown in fig. 4. After the clamping is finished, a hydraulic device is used for pushing the clamping tool on the side of the end plug, so that the end plug and the pipe form a butt joint, and finally, the vacuum pumping treatment is carried out.

And thirdly, setting the same pressure resistance welding process parameters for welding.

The joint macro-topography obtained in this comparative example is shown in fig. 6.

The length value h and the angle value theta are used in the experiment to represent the smooth transition degree of the outer joint, as shown in fig. 7. Wherein the length value h is the distance from the outermost edge of the outer extruded metal to the flat section (10) of the end plug, a smaller value of h indicating a smoother transition of the joint; the angle value theta is the transition arc angle of the straight part and the extrusion part of the pipe, and the smaller the arc angle is, the smoother the transition of the joint is. The h value of the joint obtained by using the fixture with the inclined line segment hole wall is 0.31mm, and the theta value is 7 degrees through measurement; whereas the joint obtained with the conventional jig had an h value of 0.60mm and a theta value of 27 deg.. The joint transition obtained by the fixture with the inclined line segment hole wall is smoother. In addition, the joint fusion area obtained by the fixture with the chamfer is larger, and the performance of the joint can be improved.

The clamp with the oblique hole wall is adopted for pressure resistance welding of the pipe-plug structure, so that the problem of unsmooth transition of the joint can be effectively solved, the fusion area can be increased, and the performance of the joint is improved.

Claims

1. The utility model provides a alleviate unsmooth fixture of pipe-stopper structure piezo-resistance welding head surface transition which characterized in that, for centrosymmetric fixture, be a hollow cylinder who takes the base, mainly constitute by two parts: the first part is a circular ring base (1) formed by splicing two independent semicircular rings, and the base (1) can be matched with a positioning fixture of welding equipment so as to play a positioning role; the second part is two independent semi-hollow cylinders (2), the two semi-hollow cylinders (2) are spliced into a complete hollow cylinder, and a pipe needs to be placed in a hole of the hollow cylinder before welding; each semi-circular ring and one semi-hollow cylinder (2) form an integrated structure, the central axis of the circular ring base (1) and the central axis of the hollow cylinder coaxially extend, and the diameter of the central hole of the circular ring base (1) is the same as that of the hole of the hollow cavity cylinder; the inner hole wall of the front end hole corresponding to the front end surface (5) of each semi-hollow cylinder (2) is provided with a right-angled triangle chamfer.

2. A fixture for relieving the transition unevenness of the outer surface of a pressure resistance welding joint of a pipe-plug structure as defined in claim 1, wherein the length of the chamfer in the axial direction, i.e., the length of the right-angle side of the chamfer in the axial direction, is 0.8mm to 3mm, and the length of the right-angle side of the chamfer in the radial direction is 0.08mm to 2mm, depending on the wall thickness of the pipe.

3. The clamp for relieving the unevenness of the outer surface transition of the pipe-plug structure pressure resistance welding head as recited in claim 1, wherein the clamp is made of industrial pure copper, so that the high heat conductivity and the high electric conductivity of the clamp are ensured.

4. A fixture for relieving the unevenness of the outer surface transition of a pressure resistance welding joint of a pipe-plug structure according to claim 1, wherein the base (1) is used for positioning and placing a pipe in the inner hole; the hollow cylinder plays a role in clamping and conducting current for the pipe, the oblique line segment hole wall (4) limits metal flow in the welding process, and unsmooth transition of the joint is relieved.

5. A method of using a fixture for relieving the unevenness of the outer surface transition of a pressure resistance welded joint of a pipe-plug structure according to claim 1, characterized in that a pipe (7) is held in the fixture before welding, the end face (6) to be welded of the pipe is flush with the front end face (5) of the hollow cylinder, after the butt joint with the end plug is formed, welding is started, a small part of the metal extruded to the outside of the pipe during the hot metal compression process is extruded in the chamfer, and most of the metal flows to the end plug side along the wall (4) of the chamfer section and is gradually limited by the wall during the flow process, and the metal is closer to the surface of the workpiece; however, part of metal is extruded out of the front end face (5) of the hollow cylinder, but due to the slope effect of the inclined line segment hole wall (4), the part of metal is not directly extruded along the axial direction, but is extruded along a certain angle towards the radial direction, so that most of the extruded metal is smoothly combined with the interface of the end plug along the inclined line segment hole wall (4), and the problem that the transition is not smooth enough is solved.