阅读说明：本技术 一种用于降低汽车焊接件的焊接热影响区强度衰减比例的焊接方法 (Welding method for reducing intensity attenuation proportion of welding heat affected zone of automobile welding part ) 是由 罗世兵 李文通 糜罕峰 姚清涛 张传宾 张兴状 万光强 周卫林 蔡翱 刘宇 于 2021-06-18 设计创作，主要内容包括：本发明提供了一种用于降低汽车焊接件的焊接热影响区强度衰减比例的焊接方法,所述汽车焊接件由若干零件焊接构成,包括步骤：步骤S1：对零件进行自然时效；步骤S2：对经过自然时效后的所述零件进行焊接,得到汽车焊接件；步骤S3：对汽车焊接件的整体进行人工时效。采用上述技术方案后,能够使焊接件的焊接热影响区的强度衰减比例降低约一半,强度衰减比例减少至20％左右,大大的提升了焊接件的强度,且焊缝质量好,无气孔等不良缺陷。能够广泛应用于汽车的副车架、保险杠、仪表盘支架等,甚至适用于在有焊接工艺要求的零件中全面推广。(The invention provides a welding method for reducing the strength attenuation proportion of a welding heat affected zone of an automobile welding part, wherein the automobile welding part is formed by welding a plurality of parts, and the welding method comprises the following steps: step S1: naturally aging the part; step S2: welding the parts subjected to natural aging to obtain an automobile welding part; step S3: and carrying out artificial aging on the whole automobile welding part. After the technical scheme is adopted, the strength attenuation proportion of a welding heat affected zone of the welding part can be reduced by about half, the strength attenuation proportion is reduced to about 20%, the strength of the welding part is greatly improved, and the welding seam has good quality and has no bad defects of air holes and the like. The welding method can be widely applied to auxiliary frames, bumpers, instrument panel supports and the like of automobiles, and is even suitable for comprehensive popularization in parts with welding process requirements.)

1. A welding method for reducing the strength attenuation proportion of a welding heat affected zone of an automobile welding part, wherein the automobile welding part is formed by welding a plurality of parts, is characterized by comprising the following steps of:

step S1: naturally aging the part;

step S2: welding the parts subjected to natural aging to obtain an automobile welding part;

step S3: and carrying out artificial aging on the whole automobile welding part.

2. A welding method for reducing the rate of weld heat affected zone strength decay in automotive weldments as claimed in claim 1, characterized in that in step S1, the temperature of natural aging is 40 ℃ or less and the time is more than 24H.

3. A welding method for reducing the attenuation ratio of the strength of the weld heat affected zone of an automotive weldment as claimed in claim 1, wherein the weld zone temperature at the time of welding is 550 ℃ to 650 ℃ and the heat affected zone temperature is 300 ℃ to 400 ℃ in step S2.

4. The welding method for reducing the strength attenuation ratio of the welding heat affected zone of the automobile weldment as defined in claim 1, wherein in step S3, the temperature of the artificial aging is 170-180 ℃ and the time is 6H-12H.

5. A welding method for reducing the rate of strength decay in the weld heat affected zone of an automotive weldment as described in any one of claims 1 to 4, wherein said parts that make up said automotive weldment are aluminum alloys.

6. A welding method for reducing the rate of weld heat affected zone attenuation of automotive weldments as claimed in claim 5, wherein said automotive weldments are sub-frames, bumpers, instrument panel braces, rocker beams, or battery frames.

7. A welding method for reducing the weld heat affected zone strength attenuation ratio of an automotive weldment as in claim 5 wherein the aluminum alloys comprise all types of 6-series aluminum alloys.

Technical Field

The invention relates to a welding method for reducing the strength attenuation proportion of a welding heat affected zone of an automobile welding part.

Background

The aluminum alloy strengthening principle is that at a certain temperature, along with the extension of the heat preservation time, a strengthening phase is continuously separated out and exists in a coherent structure (shown as A in figure 1) with an aluminum matrix, and further the strength of a product is improved. When the phenomenon reaches the maximum density and the alloy strength is highest, as the holding time is prolonged, a part of hard phases begin to aggregate and grow, and form stable beta phases to be separated from an aluminum matrix, so that the reinforcing phase and the aluminum matrix present a semi-coherent structure (see B in figure 1), and the product strength is reduced. When the holding time is further extended, the stable β phase mostly aggregates and separates from the matrix, and forms a non-coherent structure with the matrix (see C in fig. 1), and the product strength drops to the bottom of the valley.

The traditional welding process method is that before welding, each single piece is subjected to artificial aging treatment, and after the strength of the single piece reaches a peak value, welding is carried out; in the welding process, which is a high-temperature process, the strengthening phase in the alloy is continuously converted into a beta phase, so that the strength is reduced; the temperature in the welding process is high, the temperature of a welding line area and a fusion area can reach 550-; the heat affected zone is not hot enough to dissolve the hard phase into the aluminum matrix, which exacerbates the precipitation transformation in this region; this is also the main factor that the strength of the heat affected zone after welding is the lowest position. Based on the above, there are two main ways to improve the strength attenuation ratio of the welding heat affected zone: (1) increase the cooling strength after welding, and (2) improve the influence of welding on the degree of precipitation transformation of the strengthening phase.

For the first approach, i.e. increasing the cooling strength after welding, the prior art is mainly divided into the following: (1) indirect heat conduction (such as arranging a heat-dissipation water pipe in a welding area) has poor heat conduction and dissipation effects, and the attenuation proportion of the tensile strength of a welding heat affected area to the base material is about 50%; (2) the direct air-blowing cooling effect is poor, and the attenuation ratio of the tensile strength of the welding heat affected zone to the parent metal is about 40 percent; (3) the direct water spraying effect after welding is relatively good, the attenuation proportion of the tensile strength of a welding heat affected zone relative to the base metal is about 27%, but the welding progress and the welding seam quality are affected, and bad defects such as air holes and the like are easy to occur; (4) and a direct increase in cooling strength is currently not preferable.

For the second approach, i.e., to improve the effect of welding on the degree of strengthening phase precipitation transformation, the related art does not disclose a process that can significantly reduce the rate of strength decay in the weld heat affected zone.

In summary, the conventional welding process has a large attenuation ratio of the heat affected zone performance, and the attenuation amount reaches 50%, which obviously reduces the overall strength of the part. Therefore, it is necessary to develop a process method that can reduce the strength degradation ratio of the heat affected zone after welding.

Disclosure of Invention

In order to overcome the technical defect that the strength attenuation proportion of a welding heat affected zone of a welding part is larger in the traditional welding process, the invention aims to provide a welding method for reducing the strength attenuation proportion of the welding heat affected zone of an automobile welding part, wherein the automobile welding part is formed by welding a plurality of parts, and the welding method comprises the following steps:

step S1: naturally aging the part;

step S2: welding the parts subjected to natural aging to obtain an automobile welding part;

step S3: and carrying out artificial aging on the whole automobile welding part.

Further, in step S1, the temperature of natural aging is 40 ℃ or lower and the time is more than 24H.

Further, in step S2, the weld zone temperature during welding is 550 ℃ to 650 ℃, and the heat affected zone temperature is 300 ℃ to 400 ℃.

Further, in step S3, the temperature of the artificial aging is 170-180 ℃ and the time is 6H-12H.

Further, the parts constituting the automobile weldment are aluminum alloys. Preferably, the aluminum alloy is a 6-series aluminum alloy.

Further, the welding method for reducing the strength attenuation ratio of the weld heat affected zone of an automotive weldment, which includes all types of 6-series aluminum alloys, in other words, the present application, is applicable to all 6-series aluminum alloys.

Further, the automotive weldment includes, but is not limited to, an automotive subframe, a bumper, a rocker beam, a battery frame, or an instrument panel bracket, etc.

After the technical scheme is adopted, compared with the prior art, the method has the following beneficial effects:

the welding method has the advantages that the influence of welding on the precipitation transformation degree of the strengthening phase is improved, so that the intensity attenuation proportion of the welding heat affected zone is improved, specifically, the intensity attenuation proportion of the welding heat affected zone of the welding part can be reduced by about half by adopting the welding method, the intensity attenuation proportion is reduced to about 20%, the intensity of the welding part is greatly improved, the quality of a welding seam is good, and no bad defects such as air holes exist. The welding method is suitable for being widely applied to auxiliary frames, bumpers, instrument panel supports and the like of automobiles, and even suitable for being comprehensively popularized in parts with welding process requirements.

Drawings

In fig. 1, a is a schematic diagram of a coherent structure, B is a schematic diagram of a semi-coherent structure, and C is a schematic diagram of a non-coherent structure.

Detailed Description

The advantages of the invention are further illustrated below with reference to specific examples. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Examples

1. Test materials: 6-series aluminum alloy part with instrument panel bracket as base material

2. The test method comprises the following steps:

(1) respectively adopting a traditional welding method and the welding method of the application to prepare the instrument panel bracket (i.e. a welding part) of the 6-series aluminum alloy

1) The instrument panel bracket is welded and prepared by adopting a traditional welding method and comprises the following steps:

step S1: carrying out artificial aging treatment on each part at 180 ℃ for 6H until the strength of the part reaches the peak value of 267.49 MPa;

step S2: and welding the parts subjected to artificial aging to obtain the instrument panel bracket.

2) The welding method for preparing the instrument panel support comprises the following steps:

step S1: placing the part for more than 24H in a natural environment, and performing natural aging;

step S2: welding the parts subjected to natural aging to obtain an automobile welding part, namely an instrument panel bracket;

step S3: the whole of the automobile welding part (namely the instrument panel bracket) is artificially aged for 6H at 180 ℃.

(2) And a detecting instrument for testing the tensile strength of the welding heat affected zone of the base metal and the welding part and calculating the tensile strength attenuation proportion: universal tensile testing machine.

The calculation formula of the tensile strength attenuation ratio is as follows: the tensile strength attenuation ratio (base material tensile strength-weld zone tensile strength)/base material tensile strength × 100%.

3. Test conclusion and analysis: the results of the intensity decay ratios for the different welding methods are compared in table 1.

TABLE 1 intensity decay ratios for different welding methods

As can be seen from Table 1, the welding method of the application enables the intensity attenuation ratio of the heat affected zone to be close to half of the original intensity attenuation ratio, and the intensity of the welded part is greatly improved by reducing the intensity attenuation ratio to about 20%. The specific principle is as follows: under natural conditions, the reinforced particles of the 6-series aluminum alloy are difficult to generate aggregation and growth transformation due to low temperature of the parts, and Mg atoms and Si atoms are aggregated to generate solute atom enrichment (namely beta' phase). Subsequently, during the welding process of the aluminum alloy, the strengthening phase in the aluminum alloy is sequentially changed from a beta ' phase to a beta ' phase (namely, an unstable precipitated phase) and then from the beta ' phase to the beta phase (namely, Mg of a stable phase)₂Si), the relation between the strength of the alloy and the aging temperature and the holding time is a trend close to a parabola, if the aging temperature is too high or too low, or the aging holding time is too long or too short, the strength of the aluminum alloy is not favorably improved, and the strengthening phases beta 'and beta' can coexist only at proper aging temperature and aging holding time, and the strength of the aluminum alloy can reach a peak value at the moment. Specifically, (1) when the beta ' phase begins to be transformed into the beta ' phase, Mg atoms and Si atoms begin to be combined to form an unstable precipitated phase beta ', and the strength of the aluminum alloy is in a positive correlation with the aging temperature and the aging time; (2) when the beta 'phase and the beta' phase coexist, the strength of the alloy is highest; (3) as the β' phase gradually transitions to the β phase, the intensity begins to gradually decrease until the strengthening phase has all transitioned to the stable β phase, with the intensity being minimized.

According to the welding method, firstly, the parts in the natural aging state are welded, and then the welded parts are subjected to integral aging. This method can reduce the intensity attenuation ratio of the heat affected zone to the maximum extent, mainly because: under the natural condition of the part, because the temperature is lower, the strengthening particles are difficult to generate aggregation and growth conversion, and Mg atoms and Si atoms are aggregated to generate solute atom enrichment; in the welding process, a welding seam area and a fusion area are subjected to solid solution transformation again, a certain amount of hard phase particles existing in a heat affected zone are firstly aggregated and grown, and are separated out in advance and transformed into a beta' phase and a stable beta phase; during subsequent overall aging, all strengthening phases are transformed according to the aging transformation mechanism, and atoms which are not enriched can still be strengthened through subsequent aging. Because only a small part of the strengthening phase in the heat affected zone is precipitated and converted into the stable beta phase in advance, the strength loss of the heat affected zone is low, and the strength loss of the heat affected zone is greatly reduced compared with the strength loss of the heat affected zone in the traditional welding method.

It should be noted that the embodiments of the present invention have been described in terms of preferred embodiments, and not by way of limitation, and that those skilled in the art can make modifications and variations of the embodiments described above without departing from the spirit of the invention.