CN115319235B - A welding method for aluminum alloy medium and thick plates - Google Patents

Abstract

The application discloses a welding method of an aluminum alloy medium plate, and belongs to the field of material processing. The welding test plate groove adopts the combination of double V shapes and U shapes, and the blunt edge is 2 mm-4 mm. Wherein: the angles of the front double V-shaped grooves are 140 degrees and 60 degrees respectively, the angle of the back U-shaped groove is 60 degrees, the round angle is R5, and the groove gap is less than or equal to 1mm. The welding method is suitable for welding the 7A52 high-strength aluminum alloy with the thickness of 20-40 mm, the porosity of a welding joint is less than 1%, the tensile strength of the joint is more than or equal to 320MPa, and the strength coefficient of the joint is more than or equal to 0.75. The groove shape and the groove size are flexibly designed aiming at the problems in the welding process of the aluminum alloy medium plate, the air hole escape distance is reduced, the air hole escape time is increased, the number of air holes in a welding line is effectively reduced by combining a cold metal transition and pulse welding technology, the softening size of a heat affected zone is reduced, welding line grains are thinned, and a welding line joint with higher strength is obtained. The tensile strength of the welding joint is more than or equal to 322MPa, the strength coefficient of the welding joint is more than or equal to 0.75, and the welding method has great potential in the welding of the medium-thickness plate aluminum alloy.

Description

A kind of welding method of aluminum alloy medium and thick plate

Technical Field

The invention relates to the technical field of material processing, and in particular to a welding method for aluminum alloy medium and thick plates.

Background technique

Aluminum alloys are widely used in aircraft fuselage structures, special vehicles, railway transportation, and cryogenic pressure vessels due to their low density, high strength, good corrosion resistance, and excellent fracture toughness. Welding, as an important manufacturing technology, is a process of "melting and resolidification". In this process, due to the low melting point and high thermal conductivity of aluminum alloys, defects such as pores, cracks, and unfused welds are very likely to appear in the welds; at the same time, the welds have coarse grains and the heat-affected zone softens severely, resulting in reduced mechanical properties of the welded joints. Especially for the welding of medium and thick aluminum alloy plates (20-40 mm), the molten pool cools faster, and the pore problem and heat-affected zone softening problem become more serious and have never been solved.

Summary of the invention

The purpose of the present invention is to provide a welding method for aluminum alloy medium and thick plates, so as to solve the problems in the background technology existing in the welding of conventional aluminum alloy medium and thick plates.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

The present invention provides a method for welding aluminum alloy medium and thick plates, comprising the following steps:

1) Select aluminum alloy plate with a thickness of 20 to 40 mm;

2) Groove processing: The groove of the welding test plate adopts a combination of double "V" shape and "U" shape, and its blunt edge is 2mm~4mm; the front side is a double "V" groove, and its angles are 130°-150° and 50°-70° respectively; the back side is a "U" groove, and its angle is 50°-70°, and its fillet is R5; the groove gap is ≤1mm;

3) The base weld adopts pulse (P) welding mode, welding current 210A ~ 280A, welding voltage 22.3V ~ 24.5V, wire feeding speed 12.7m/min ~ 18m/min;

4) The filling weld adopts cold metal transfer technology (CMT) + pulse (P) welding mode, the welding current is 210A~240A, the welding voltage is 21.7V~22.5V, the wire feeding speed is 11.8m/min~13.0m/min, and the welding speed is 0.3m/min~0.48m/min.

In this embodiment, in step 2), the groove size and shape are designed, wherein the larger the groove angle, the smaller the pore escape distance. For the test plate with a larger groove angle, the height of the weld is smaller, and the pore escape distance is also smaller, so the probability of pore escape is also increased, and the fewer pores remain in the weld, so the number of pores can be effectively reduced; wherein the pore escape distance is reduced and the pore escape time is increased, so as to reduce the number of pores in the weld joint.

In this embodiment, the base weld in step 3) adopts a pulse (P) welding mode, wherein the pulse current is composed of a base current and a peak current. The use of a larger current can not only ensure penetration, but also reduce incomplete fusion and incomplete penetration defects.

Among them, cold metal transfer technology (CMT) + pulse (P) can effectively reduce welding heat input, reduce the deformation of aluminum alloy plates, and has a good stirring effect on the molten pool, which can reduce the generation of porosity defects, thereby achieving the effect of refining weld grains and improving weld strength.

In this embodiment, it is further preferred that the groove is polished before welding to remove the surface oxide film, and acetone is used to remove oil stains. During the welding process, the interpass temperature is controlled to be ≤80°C to reduce the deformation.

In this embodiment, it is further preferred that during welding, the shielding gas used is 50% He + 50% Ar, the gas flow rate is 16-22 L/min, and the interpass temperature is ≤80°C.

In this embodiment, it is further preferred that the aluminum alloy plate is 7A52 high-strength aluminum alloy, and the porosity of the welded joint after welding is less than 1%, the tensile strength of the joint is ≥320MPa, and the strength coefficient of the joint is ≥0.75.

In the present embodiment, it is further preferred that when the groove is processed, the front side is a double "V"-shaped groove, and the angles thereof are 130°-150° and 50°-70° respectively, and the "V"-shaped groove of 130°-150° is at the bottom, and the "V"-shaped groove of 50°-70° is at the top.

In the present embodiment, it is further preferred that, when the groove is processed, the front side thereof is a double "V"-shaped groove, and the angles thereof are 140° and 60° respectively.

In this embodiment, it is further preferred that during groove processing, the back side is a "U"-shaped groove, the bottom side is a rounded structure, and the side wall angle is 60°.

Compared with the prior art, the present invention has the following beneficial technical effects: in the present application, the size and shape of the groove are designed to reduce the pore escape distance, increase the pore escape time, and thus reduce the number of pores in the welded joint; the base weld adopts the pulse (P) welding mode, and the pulse current is composed of the base current + the peak current. The use of a larger current can not only ensure full penetration, but also reduce the defects of incomplete fusion and incomplete penetration; the cold metal transition technology (CMT) + pulse (P) can effectively reduce the welding heat input, reduce the deformation, and have a good stirring effect on the molten pool, which can reduce the generation of pore defects, refine the weld grains, and improve the weld strength; in view of the phenomenon that the mechanical properties of the joint are relatively low due to the problems of pores, cracks, incomplete fusion, and softening of the heat-affected zone that occur during the welding of conventional aluminum alloy medium and thick plates, the present invention obtains a welded joint with excellent mechanical properties by reasonably designing the shape and size of the groove and adopting a suitable welding mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings.

FIG1 is a schematic diagram of a thick plate aluminum alloy welding test plate groove of a welding method for a medium and thick aluminum alloy plate of the present invention;

FIG2 is a diagram showing the pore distribution in the weld zone of the welded joint of the welding method for the aluminum alloy medium and thick plate of the present invention;

FIG3 is a diagram showing the pore proportion and size distribution of the weld zone of the welded joint of the welding method for the aluminum alloy medium and thick plate of the present invention;

FIG. 4 is an EBSD diagram of the microstructure of the weld zone of the welded joint of the welding method for the aluminum alloy medium and thick plate of the present invention.

Detailed ways

This embodiment discloses a welding method for aluminum alloy medium and thick plates, wherein ER5087 wire is selected to perform a 40 mm thick 7A52 aluminum alloy welding experiment. The technical solution of the present invention is described in detail below in conjunction with specific embodiments.

Example 1

In this embodiment, a 40 mm thick 7A52 aluminum alloy welding experiment was carried out using the groove designed by the present invention, wherein the groove features are shown in FIG. 1 , and the blunt edge is 2 mm.

Before welding, the groove is polished to remove the surface oxide film, and acetone is used to remove oil stains. During welding, the interpass temperature is controlled to ≤60℃ to reduce deformation.

The welding process parameters are shown in Table 1. The pulse welding mode is used for base welding and the CMT+P welding mode is used for filling.

The distribution of pores in the weld area is shown in Figure 2. The number of pores in the weld area is small, the size is small, and no macroscopic pores or cracks are generated. Twenty areas are randomly selected in the weld area for pore statistics. The results are shown in Figure 3. The porosity of the weld area is 0.85%, and the pore size is mainly concentrated below 20μm.

The weld zone microstructure grows equiaxed (as shown in Figure 4), with an average grain size of about 32μm. Since ER5087 contains rare earth element Zr, nano-scale Al ₃ Zr is precipitated in the weld zone during solidification. The particles are completely coherent with the matrix, which can refine the grains and improve the joint strength. The tensile strength of the welded joint is 325MPa, and the joint strength coefficient is 0.79.

Table 1 7A52 aluminum alloy welding process parameters

Example 2

In this embodiment, the groove designed by the present invention is used to carry out a 40mm thick 7A52 aluminum alloy welding experiment. The groove is shown in Figure 1, and the blunt edge is 2mm. Before the experiment, the groove is polished to remove the surface oxide film, and the surface oil is removed with acetone. The interpass temperature is controlled to be ≤70°C during welding. The welding process parameters are shown in Table 2. The pulse (P) mode is used for primer and the CMT+P mode is used for filling. 20 areas are randomly selected in the weld area for pore statistics. The porosity is 0.72%, and the pore size is mainly concentrated in 10-15μm; the weld area organization is equiaxed, and a large number of nano-scale Al ₃ Zr phases appear, which refines the weld grains. The average grain size is about 26μm, which significantly improves the joint strength. In this embodiment, the tensile strength of the joint is 336MPa, and the joint strength coefficient is 0.82.

Table 2 7A52 aluminum alloy welding process parameters

Example 3

In this embodiment, the groove designed by the present invention is used to carry out a 40mm thick 7A52 aluminum alloy welding experiment. The groove is shown in Figure 1, and the blunt edge is 3mm. Before the experiment, the groove is polished to remove the surface oxide film, and the surface oil is removed with acetone. The interpass temperature is controlled to be ≤70°C during welding. The welding process parameters are shown in Table 3. The pulse welding mode is used for base laying and the CMT+P welding mode is used for filling. Twenty areas are randomly selected in the weld area for pore statistics. The porosity is 0.67%, and the pore particle size is mainly concentrated in 15-20μm. The average grain size in the weld area is about 28μm. The welded joint has excellent tensile properties, a tensile strength of 327MPa, and a joint strength coefficient of 0.80.

Table 3 7A52 aluminum alloy welding process parameters

Example 4

In this embodiment, the groove designed by the present invention is used to carry out a 40mm thick 7A52 aluminum alloy welding experiment. The groove is shown in Figure 1, and the blunt edge is 4mm. Before welding, the groove is polished to remove the surface oxide film, and the surface oil is cleaned with acetone. The interpass temperature is controlled to be ≤80°C during welding. The welding process parameters are shown in Table 4. The pulse welding mode is used for base laying and the CMT+P welding mode is used for filling. After welding, 20 areas are randomly selected in the weld area for pore statistics. The porosity is 0.98%, and the pore size is small, mainly concentrated below 15μm. Due to the increase in welding current, the grains in the weld area grow, the average grain size is about 35μm, and the Al ₃ Zr phase in the organization coarsens and increases in size. The tensile strength of the weld joint is 322MPa, and the joint strength coefficient is reduced to 0.78.

Table 4 7A52 aluminum alloy welding process parameters

In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

The above embodiments are only descriptions of the preferred methods of the invention, and are not intended to limit the scope of the invention. Without departing from the design spirit of the invention, various modifications and improvements made to the technical solutions of the invention by ordinary technicians in this field should fall within the protection scope of the claims of the invention.

Claims (6)

1. A welding method of an aluminum alloy medium plate is characterized by comprising the following steps: the method comprises the following steps:

1) Selecting an aluminum alloy plate, wherein the thickness of the aluminum alloy plate is 20-40 mm;

2) Groove processing: the welding test plate groove is formed by combining a double V shape and a U shape, and the blunt edge of the welding test plate groove is 2 mm-4 mm; wherein the front surface is provided with double V-shaped grooves, the angles of the double V-shaped grooves are 130-150 degrees and 50-70 degrees respectively, the V-shaped groove of 130-150 degrees is arranged below, and the V-shaped groove of 50-70 degrees is arranged above; the back surface is a U-shaped groove, the angle of the groove is 50-70 degrees, and the round angle of the groove is R5; the gap of the groove is less than or equal to 1mm;

3) The priming welding bead adopts a pulse (P) welding mode, welding current 210A-280A, welding voltage 22.3V-24.5V and wire feeding speed 12.7 m/min-18 m/min;

the filling weld bead adopts a cold metal transition technology (CMT) +pulse (P) welding mode, welding current 210A-240A, welding voltage 21.7V-22.5V, wire feeding speed 11.8 m/min-13.0 m/min and welding speed 0.3 m/min-0.48 m/min.

2. The welding method of an aluminum alloy medium plate according to claim 1, wherein: polishing the groove before welding to remove the surface oxide film, removing oil stains by using acetone, and controlling the temperature between the grooves to be less than or equal to 80 ℃ in the welding process so as to reduce the deformation.

3. The welding method of an aluminum alloy medium plate according to claim 1, wherein: during welding, the shielding gas is 50% He+50% Ar, the gas flow is 16-22L/min, and the inter-channel temperature is less than or equal to 80 ℃.

4. The welding method of an aluminum alloy medium plate according to claim 1, wherein: the aluminum alloy plate is 7A52 high-strength aluminum alloy, the porosity of a welded joint is less than 1%, the tensile strength of the joint is more than or equal to 320MPa, and the strength coefficient of the joint is more than or equal to 0.75.

5. The welding method of an aluminum alloy medium plate according to claim 1, wherein: when the groove is processed, the front surface of the groove is a double V-shaped groove, and the angles of the groove are 140 degrees and 60 degrees respectively.

6. The welding method of an aluminum alloy medium plate according to claim 1, wherein: in groove processing, the back surface of the groove is a U-shaped groove, the bottom of the groove is of a round corner structure, and the side wall angle of the groove is 60 degrees.