CN111360406B

CN111360406B - Laser welding method for plate consisting of steel substrate and precoating

Info

Publication number: CN111360406B
Application number: CN201811496005.2A
Authority: CN
Inventors: 杨上陆; 王艳俊
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2018-12-07
Filing date: 2018-12-07
Publication date: 2022-03-08
Anticipated expiration: 2038-12-07
Also published as: CN111360406A

Abstract

The invention discloses a laser welding method for a plate consisting of a steel base body and a pre-plating layer.

Description

Laser welding method for plate consisting of steel substrate and precoating

Technical Field

The invention relates to a laser welding method for a plate consisting of a steel substrate and a precoating, in particular to a method for using a coated steel plate for laser welding in the fields of automobiles, aerospace, ships and the like.

Background

In the fields of automobiles, aerospace and the like, plates for manufacturing parts are generally required to have high corrosion resistance, and the corrosion resistance of the plates can be improved by coating zinc, aluminum and other coatings on the surfaces of the plates, so that more and more plates with coatings on the surfaces are applied. Because the steel material with the surface coated with the aluminum or the aluminum alloy manufactured by the cold rolling or hot rolling method not only has better corrosion resistance, but also has high temperature resistance, the steel plate with the surface coated with the aluminum alloy is often applied to the manufacturing of automobile bodies, such as door reinforcements, B-pillar structural parts, roof reinforcements and other parts, particularly to hot stamping plates with ultrahigh strength, thereby achieving the purposes of higher corrosion resistance of automobile body parts, reduction of the weight of the automobile bodies and improvement of collision absorption energy.

In the automobile manufacturing industry, in order to reduce the vehicle weight and achieve the aim of light weight, more and more plates with equal thickness, unequal thickness, homogeneity and heterogeneity are firstly welded and then stamped to manufacture welded pieces, so that better weight reduction effect and cost reduction can be achieved. The laser welding method is the preferred method of this approach, with higher quality, higher efficiency and better flexibility, known as "laser tailor welded blanks".

However, when laser welding a plate coated with aluminum or an aluminum alloy on the surface, the coating layer on the surface of the plate enters into the melting area, especially into the heat affected zone of the weld, the coating layer entering into the heat affected zone is in the dendritic space of the steel substrate, during the subsequent austenitizing process of the heated substrate, aluminum and iron or other components diffuse into each other to form an alloy, and intermetallic compounds remain in the heat affected zone, and because the strength of the heat affected zone of the weld is weak, the weld failure zone of the welded part is often in the heat affected zone under the subsequent mechanical load, and the intermetallic compounds become the initial position of the failure crack, which seriously weakens the bearing capacity of the welded joint, so it is necessary to remove or reduce the coating layer entering into the heat affected zone of the weld.

At present, the method for eliminating the above influence mainly removes the coating on the surface by a mechanical method, a laser method or other methods in advance to prevent the coating from entering the weld joint, but the method has the problems of high cost, complex process and the like, so a better method is needed for realizing high-efficiency laser welding of the surface coating plate.

Disclosure of Invention

In order to solve the problems, the invention provides a method for preheating two sides of a welding seam by using a preheating heat source before laser welding, guiding a coating layer on the surface of the welding seam to flow away from the welding seam, and further reducing the influence of the coating layer entering the welding seam, particularly a heat affected zone, in the subsequent laser welding process so as to weaken the influence of the coating layer on the mechanical property of the welding seam, thereby improving the strength of the welding seam.

In order to solve the above problems, the present invention adopts a technical solution that: a laser welding method for a plate consisting of a steel substrate and a precoating layer is provided, which comprises the following steps:

(a) providing two or more plates consisting of a steel substrate and a pre-plating layer, and butting the end faces of the plates;

(b) two preheating heat sources are adopted to preheat two sides of the butt joint of two adjacent plates, so that a precoating layer on the surfaces of the plates is melted and evaporated;

(c) and irradiating the joint of the two adjacent plates by using a laser welding light source to weld the two adjacent plates together.

In another preferred example, the precoating layer is an aluminum alloy or an aluminum base.

In another preferred embodiment, the pre-plating layer comprises the following components by weight: 6-12% of silicon, 1-5% of iron, and the balance of aluminum or inevitable impurities.

In another preferred embodiment, the temperature of the preheating is 1000 ℃ to 1500 ℃.

In another preferred example, the two preheating heat sources are symmetrically arranged by taking the butt joint of two adjacent plates as a symmetry center.

In another preferred example, the preheating heat source is a TIG welding heat source or a laser light source.

In another preferred example, the distance from the center of the preheating heat source to the joint of the two adjacent plates is 0.1-2.5 mm.

In another preferred embodiment, the thickness of the plate is 0.5-3 mm.

In another preferred example, the distance between the center of the preheating heat source and the center of the laser welding light source in the welding direction is 0.5-10 mm.

It is to be understood that within the scope of the present invention, the above-described features of the present invention and those specifically described below (e.g., in the examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.

The technical principle of the invention is as follows: the method comprises the steps of firstly heating areas on two sides of the butt joint of adjacent plates by adopting a preheating heat source to the extent that a plating layer is melted and evaporated, melting and flowing the plating layer on the surface of a welding seam area of the adjacent plates to the vicinity of the edge of a hot melting area, and then welding the plates by adopting a laser welding light source, so that the plating amount on the surface of the finally formed welding seam is reduced, the finally formed welding seam is far away from the welding seam, particularly a heat affected zone, intermetallic compounds of the welding seam area are reduced, and the strength of the welding seam is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other alternative embodiments can be obtained according to the drawings without creative efforts.

Fig. 1 shows a schematic diagram of an embodiment of the present invention.

Fig. 2 shows a top view of two butt-jointed sheets of fig. 1.

Fig. 3(a), 3(b), and 3(c) show the welding step in example 1 of the present invention.

Fig. 4 is a sectional view showing a pre-heated TIG heat source for welding a pre-coated steel sheet by the welding method of example 2 according to the present invention.

Reference numerals, 1 and 2, denote a plate material composed of a steel substrate and a pre-plating layer, 3, a pre-plating layer on the surface of the steel substrate, 4, a thermal melting zone formed after preheating by using a preheating heat source, 5, a first preheating heat source, 6, a second preheating heat source, 7, a laser welding light source, and 8, a welding seam.

Detailed Description

The present inventors have made extensive and intensive studies and, as a result, have found, through a large number of experiments, that it is possible to suppress the problem of poor welding quality caused by a precoat material by preheating both sides of a weld using a symmetrical heat source before laser welding.

Term(s) for

The term "precoat" as used herein refers to an aluminum alloy or aluminum substrate that is plated on the surface of a steel substrate by an electroplating or hot-dipping process, an intermetallic compound layer formed by diffusion of the aluminum element with iron or other components in the steel.

Referring to fig. 1, which is a schematic view showing an embodiment of the present invention, and fig. 2, which is a plan view showing two butt-jointed plates in fig. 1, wherein the plates are made of a steel substrate and a pre-plating layer, as shown in fig. 1 and 2, the method of the present invention includes the steps of, first, butt-jointing the end surfaces of two equal-thickness plates; then, two preheating heat sources are adopted to heat the areas on the two sides of the butt joint of the two plates so as to melt and evaporate the coating of the heat affected zone of the plates; and finally, welding the butt joint of the two plates by adopting a laser welding light source to form a welding seam. The welding laser light source is positioned at the rear sides of the two preheating heat sources and right above the butt joint of the two steel plates, the welding rear side refers to the direction opposite to the welding direction in the figure 2, the heat affected zone refers to the zone where the two sides of the final welding seam are not melted but affected by heat, and the heat melted zone refers to the preheating heat source acting zone 4.

Preferably, the two preheating heat sources are symmetrically arranged with the joint of the two plates as a symmetrical center, as shown in fig. 2, d2 is the distance between the centers of the two preheating heat sources, i.e. the range of the heat affected zone, and the distance d2 is 0.2-5mm, preferably 0.4-3 mm; in the figure, d1 is the distance between the preheating heat source and the center of the laser welding light source in the welding direction, and the distance d1 is 0.5-10mm, preferably 1-10 mm. In actual welding, the numerical values of d1 and d2 are adjusted according to the thickness of the steel plate, the thickness of the coating and the type of the coating.

Preferably, the precoating is an aluminum alloy or an aluminum base, the thickness is 3-40 μm, and the precoating comprises the following components in parts by weight: 6-12% silicon, 1-5% iron, with the remainder being aluminium or inevitable impurities.

It should be noted that the number of the plates welded by the welding method of the present invention is not necessarily two, and includes a case where a plurality of welded steel plates are welded in a butt joint manner in order. The two preheating heat sources and the laser welding light source can be arranged on the same heat source device as a whole or can be arranged on different heat source devices separately.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the drawings are schematic and, thus, the apparatus and devices of the present invention are not limited by the size or scale of the schematic.

It is to be noted that in the claims and the description of the present patent, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, the use of the verb "comprise a" to define an element does not exclude the presence of another, same element in a process, method, article, or apparatus that comprises the element.

Example 1

FIG. 3(a), FIG. 3(b), FIG. 3(c) show the welding step of this embodiment, first, the end faces of two steel base plates 1 and 2 with a thickness of 1.2mm and a pre-plating layer thickness of 40um are butted against each other, as shown in FIG. 3 (a); then, heating the areas on the two sides of the butt joint of the two plates 1 and 2 by using a first laser light source 5 and a second laser light source 6, as shown in fig. 3 (b); and finally, welding the butt joint of the plates 1 and 2 by using a welding laser light source 7 to form a welding seam 8, wherein the pre-plating layer is made of aluminum alloy.

The laser light sources 5 and 6 are symmetrically arranged by taking the butt joint of the two plates as a symmetrical center, the welding laser light source 7 is positioned at the rear side of the laser light sources 5 and 6 and right above the butt joint of the plates 1 and 2, and the welding rear side refers to the direction opposite to the welding direction in fig. 2; the temperature for heating the areas on the two sides of the joint of the two plates by the first laser light source and the second laser light source is 1000 ℃; the distance between the center of the laser light source 5 and the center of the laser welding light source 7 in the welding direction is 10mm, and the distance between the center of the laser light source 5 and the butt joint of the two plates is 0.1-2.5 mm.

The first laser light source 5, the second laser light source 6 and the laser welding light source 7 are arranged on the same device as a whole, and all advance along the welding direction at the speed of 0.5-10 m/min.

When welding, the symmetrically distributed laser light sources 5 and 6 are adopted to melt the coating 3 on the two sides of the butt joint of the plates 1 and 2, the molten coating 3 flows to the position near the edge of a hot melting area 4 formed after the preheating of the preheating light source, and then the butt joint of the adjacent plates is welded by the laser welding light source 7, so that the coating amount of the upper surface and the lower surface of a finally formed welding seam 8 is reduced, the coating is far away from the welding seam, particularly a heat affected area, intermetallic compounds of the welding seam in the welding seam area are reduced, and the strength of the welding seam 8 is improved.

Example 2

This example is similar to example 1, except that the two preheating heat sources of this example are TIG torches.

The welding result of this embodiment is shown in fig. 4, and it can be seen from the figure that the preplating layer 3 in the heat affected zone flows to the preheating heat source melting zone under the action of the preheating source TIG welding torch, and the influence of the preplating layer on the heat affected zone is greatly reduced when the laser welding light source is used for welding two plates.

Claims

1. A laser welding method for a plate consisting of a steel substrate and a precoating layer is characterized by comprising the following steps:

(a) providing two or more plates consisting of a steel substrate and a precoating, and butting the end faces of the plates with no gap, wherein the thickness of the precoating is 3-40 mu m;

(b) two preheating heat sources are adopted to preheat two sides of the joint of two adjacent plates, so that a precoat of a plate heat affected zone is melted and evaporated, and the plate heat affected zone refers to an area where the two sides of a final welding seam are not melted but affected by heat;

(c) irradiating the butt joint of two adjacent plates by using a laser welding light source to weld the two adjacent plates together,

the distance between the center of the preheating heat source and the butt joint of the two adjacent plates is 0.1-2.5mm, the two preheating heat sources are symmetrically arranged by taking the butt joint of the two adjacent plates as a symmetrical center, d2 is the distance between the centers of the two preheating heat sources or the range of a plate heat affected zone, the preheating temperature is 1000-1500 ℃, the two preheating heat sources melt the plating layers (3) on the two sides of the butt joint of the two plates, the melted plating layers (3) flow to the position near the edge of a hot melting zone (4) formed after the preheating light source is preheated, and then the butt joint of the two adjacent plates is welded by a laser welding light source (7), so that the plating layer amount of the upper surface and the lower surface of a finally formed welding line (8) is reduced.

2. A process for laser welding of sheets consisting of a steel substrate and a precoating according to claim 1, characterized in that the precoating is an aluminium alloy or an aluminium base.

3. A process for the laser welding of sheets consisting of a steel substrate and a precoating according to claim 2, characterized in that the precoating comprises, by weight: 6-12% of silicon, 1-5% of iron, and the balance of aluminum or inevitable impurities.

4. A process for laser welding of sheets consisting of a base body made of steel and a precoat according to claim 1, characterized in that the laser welding light source is located behind the two preheating heat sources and directly above the butt joint of the two sheets.

5. A method for laser welding of sheets consisting of a steel substrate and a precoat according to claim 1, characterized in that the preheating heat source is a TIG welding heat source or a laser light source.

6. Laser welding process for sheets consisting of a base body made of steel and a precoat according to claim 1, characterized in that the thickness of the sheet is between 0.5 and 3 mm.

7. A process for laser welding of sheets consisting of a steel base body and a precoat according to claim 1, characterized in that the two preheating heat sources and the laser welding light source can be either one unit arranged on the same heat source device or separate units arranged on different heat source devices.

8. A laser welding method for sheets consisting of a steel base body and a precoat according to claim 1, wherein the distance between the center of the preheating heat source and the center of the laser welding light source in the welding direction is 0.5 to 10 mm.