CN110814499A - Method for reducing grinding frequency of aluminum alloy spot welding electrode - Google Patents
Method for reducing grinding frequency of aluminum alloy spot welding electrode Download PDFInfo
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- CN110814499A CN110814499A CN201910918383.3A CN201910918383A CN110814499A CN 110814499 A CN110814499 A CN 110814499A CN 201910918383 A CN201910918383 A CN 201910918383A CN 110814499 A CN110814499 A CN 110814499A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/30—Features relating to electrodes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/30—Features relating to electrodes
- B23K11/3063—Electrode maintenance, e.g. cleaning, grinding
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Abstract
The invention discloses a method for reducing grinding frequency of an aluminum alloy spot welding electrode, which comprises the following steps: and (3) selecting the type of the electrode cap: selecting a frustum-shaped chromium-zirconium-copper electrode cap, wherein the front end surface of the frustum-shaped chromium-zirconium-copper electrode cap is in arc transition; and a welding parameter selection step: a multi-section welding mode is adopted, wherein the number of selected sections is 4-6, the interval cooling time of multi-section welding is 3-5 ms, and the welding time of each section is 20-30 ms. The invention starts from the angle of improving the welding process, restrains or inhibits factors of electrode burning loss and reduces the grinding frequency caused by the electrode burning loss. By the method, the aluminum alloy spot welding and grinding frequency can be greatly reduced, complex process steps or additional equipment are not needed, and the production takt and the welding quality are ensured.
Description
Technical Field
The invention relates to an aluminum alloy resistance spot welding process, in particular to a method for reducing the grinding frequency of an aluminum alloy spot welding electrode.
Background
Aluminum alloy resistance spot welding (hereinafter referred to as aluminum spot welding) is a common connection process in automobile body-in-white manufacturing, and compared with cold connection processes such as riveting and the like, the aluminum alloy resistance spot welding has a series of advantages of simple system, low cost, high beat, low failure rate and the like. However, the aluminum alloy has strong activity, and easily forms a low-melting eutectic with the copper alloy in the electrode material during welding, and adheres to the surface of the electrode. During continuous spot welding, the electrode surface gradually becomes uneven, the diameter and the shape of the electrode end face also change, the current density and the application of electrode pressure are directly influenced, and the welding quality is sharply reduced.
Before the electrode state is deteriorated, the electrode is polished to restore the electrode end face shape to eliminate the influence, compared with the frequency of polishing 100-200 welding points once for steel welding, the aluminum welding electrode needs 20-30 welding points once on average, the polishing frequency is high, firstly, the production beat is reduced, secondly, the service life of the electrode serving as an easily-consumed product is greatly shortened, and the electrode consumption per year in a factory with ten thousand vehicles can reach thousands. This also becomes a technical bottleneck that hinders the widespread application of the aluminum spot welding process in the automotive industry.
At present, aiming at the problem of high grinding frequency of an aluminum alloy spot welding electrode, the solution mainly comprises the following steps:
firstly, surface pretreatment and coating of a specific coating are carried out on an aluminum alloy workpiece to be welded, so that the copper-aluminum alloying of the surfaces of a copper electrode and the aluminum alloy workpiece during spot welding is reduced, and the service life of the electrode is prolonged.
And secondly, carrying out coating treatment on the surface of the electrode or using the electrode made of special materials, wherein the purpose of the coating or the special electrode materials is also to reduce copper-aluminum alloying, and the purpose of the coating or the special electrode materials also comprises the step of enhancing the plastic deformation resistance of the electrode so as to slow down welding spatter and aluminum adhesion caused by electrode compression and prolong the service life of the electrode.
The scheme can effectively reduce the grinding frequency of the aluminum alloy electrode, but the workpiece coating formula or the special material is extremely complex in process and high in cost, and the effect is difficult to guarantee in practice. In addition, a process gasket is added to block the contact between the copper electrode and the aluminum workpiece, so that the generation of copper-aluminum alloy is avoided, but the method is not suitable for automatic batch production.
Disclosure of Invention
The invention aims to provide a method for reducing the grinding frequency of aluminum alloy spot welding, which aims to solve the problems of low production takt and high electrode consumption caused by high electrode loss and high grinding frequency in aluminum alloy welding.
Therefore, the invention provides a method for reducing the grinding frequency of an aluminum alloy spot welding electrode, which comprises the following steps: and (3) selecting the type of the electrode cap: selecting a frustum-shaped chromium-zirconium-copper electrode cap, wherein the front end surface of the frustum-shaped chromium-zirconium-copper electrode cap is in arc transition; and a welding parameter selection step: a multi-section welding mode is adopted, wherein the number of selected sections is 4-6, the interval cooling time of multi-section welding is 3-5 ms, and the welding time of each section is 20-30 ms.
Further, the diameter of the rear end of the motor cap is 20mm, and the diameter of the front end of the motor cap is
Or
The taper angle is 120 degrees, and the diameter of the arc of the front end surface is R100.
Further, the pressure of the multi-stage welding was 4KN, the welding current was 26KA, the welding time was 24ms x 6, and the inter-stage cooling time was 3 ms.
Further, before spot welding, the contact part of the aluminum alloy plate to be welded and the electrode is ground and graphite-engine oil paint is sprayed on the chromium-zirconium-copper electrode cap.
Further, the method also comprises the step of performing coating after the coating on the chromium-zirconium-copper electrode cap is worn out through multiple spot welding.
The invention starts from the angle of improving the welding process, restrains or inhibits factors of electrode burning loss and reduces the grinding frequency caused by the electrode burning loss. By the method, the aluminum alloy spot welding and grinding frequency can be greatly reduced, complex process steps or additional equipment are not needed, and the production takt and the welding quality are ensured.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows a schematic diagram of a resistance spot welding process for aluminum alloys;
FIG. 2 is a schematic structural view of an electrode cap used in the method for reducing the frequency of spot welding coping of aluminum alloy according to the present invention; and
fig. 3 is a sectional view a-a of the electrode cap shown in fig. 2.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention aims to solve the problems of low production takt and high electrode consumption caused by high electrode loss and high grinding frequency in aluminum alloy welding. The method is suitable for the resistance spot welding process of the aluminum alloy, and the principle and the improvement means of the method are discussed below.
Research shows that the burning loss of the aluminum alloy spot welding electrode is mainly caused by that in the whole welding period, the surfaces of the copper electrode and the aluminum alloy workpiece are subjected to aluminum-copper alloy reaction due to electrifying and heating to generate adhesion, the end face of the electrode becomes uneven and even has a corrosion pit, and meanwhile, along with the continuous welding, the state of the end face of the electrode is accelerated to deteriorate, the welding quality is rapidly reduced, and the grinding requirement is high.
The reason for this is that the low resistivity and high thermal conductivity of aluminum alloy lead to the need of high current and short time for welding, aluminum and copper are prone to generate intermetallic compounds with low melting point and high resistivity, and the conductivity of the intermetallic compounds is only 1/5 of copper, so that the resistance of the contact surface of an electrode and a plate is increased, heat generated at the beginning of welding is prone to generate more heat on the contact surface of the electrode and a workpiece, and the electrode and the workpiece surface are molten and adhered, and the electrode burning loss is increased.
As shown in fig. 1, in fig. 1: 1-contact resistance between the upper electrode and the workpiece; 2-contact resistance between the lower electrode and the workpiece; 3-upper workpiece bulk resistance; 4-lower workpiece bulk resistance; 5-contact resistance between upper and lower workpieces.
In contrast to steel welding, the contact resistances 1 and 2 described above in aluminum welding dominate at the beginning of the weld, rather than the desired contact resistance 5.
Aiming at the situation, the improvement is made by reducing the contact resistance between the copper electrode and the surface of the aluminum alloy workpiece, reducing heat production, increasing the heat dissipation between copper and aluminum contact surfaces, reducing the temperature and slowing down the copper and aluminum alloying.
1. Selection of electrode caps
As shown in FIGS. 2 and 3, a frustum-shaped chromium zirconium copper electrode tip with a diameter of 20mm, a taper angle of 120 degrees and an end surface diameter of 20mm was usedWith arc transition, the diameter of the arc is R100.
The reason for adopting this kind of electrode cap is as follows: 6 terminal surfaces of this electrode front end are less, do benefit to the electrode cap and closely laminate with the work piece, reduce contact resistance, reduce the heat production of contact surface, and current density is even, and circular arc transition molding can provide more stable moulding ring in welding process, prevents inside splash, causes defects such as the nugget diameter is not enough or the gas pocket.
The diameter of the rear end 7 of the electrode is large, the contact area of cooling water and the electrode is increased, a good loop is provided for cooling water circulation, heat dissipation between the electrode and a workpiece is facilitated, and copper-aluminum alloying is effectively inhibited. Meanwhile, good heat dissipation can prevent the hardness of the electrode from being reduced due to overhigh repeated welding temperature and accelerate the adhesion of the aluminum-copper alloy on the end face of the electrode due to softening.
2. Welding parameter selection
According to research, the minimum amount of heat required for nugget formation is substantially constant under the same conditions of material, thickness, manner of overlap, and the like. When the nugget grows to a certain size, the size of the nugget is basically not increased even if the current is increased or the welding time is prolonged, and the electrode is heated continuously to cause overheating between the electrode and the plate, so that the electrode burning loss is accelerated. Suitable welding parameters are particularly important.
Tests prove that under the conditions that the total welding heat is basically the same and the diameters of welding nuggets meet the standard, the service life of the electrode can be effectively prolonged by adopting multi-section welding parameters compared with single-section welding parameters.
The reason for this is that by inserting a plurality of reasonable cooling times in the welding process, the heat dissipation between the electrode and the plate can be increased, and since the nugget formation position is between the plate and the plate, which is far from the cooling water circuit than the contact position of the electrode and the plate, the heat dissipation is far smaller than that between the electrode and the plate, and the nucleation is not affected. Thus, the purposes of reducing heat generation between the electrode and the plate and reducing electrode adhesion are achieved.
The interval cooling time of the multi-section welding is 3-5 ms, and the effect is optimal when the number of sections is 4-6; the longer the time, the more stages lead to excessive cooling, resulting in insufficient heat required for final nucleation; the time is too short, the number of sections is too small, and the purpose of reducing the heat dissipation between the electrode and the workpiece cannot be achieved.
Examples of applications are:
the automobile aluminum front cover is welded, and different welding parameters are compared as follows:
the material and lap joint is 5182-0.9 mm + 5182-0.9 mm;
adopting single-section welding: the welding time is 120ms when the welding current is 26KA and the pressure is 4 KN;
adopting multi-section welding: the welding time of the welding is 24ms x 6 under the pressure of 4KN and the welding current is 26KA, and the cooling time between sections is 3 ms;
the number of weldable points before grinding is 27 by adopting single-section welding;
the number of weldable points before polishing is 41 by adopting multi-section welding, which is increased by 51 percent compared with the prior art.
The invention starts from the electrode burning loss mechanism, reduces the contact resistance and heat generation between the electrode and the plate by designing a proper electrode cap structure and welding parameters, and increases the heat dissipation to effectively inhibit the problems of influence on welding quality and frequent grinding caused by aluminum-copper alloying between the copper electrode and the aluminum plate due to the reasons.
The means for reducing the frequency of the aluminum alloy spot welding grinding can be combined with other means for use.
In one embodiment, before spot welding, graphite-engine oil paint is sprayed on the chromium-zirconium-copper electrode cap, and the aluminum alloy plate to be welded can be ground on the part to be contacted with the electrode. The graphite-engine oil coating is disclosed in patent document CN 102441731A, and is not described herein.
Compared with the method of reducing the grinding frequency by singly using one method, the method has the advantages that different methods are combined for use, and the technical effect is better. In addition, compared with the prior scheme of directly coating the coating on the aluminum alloy plate, the coating is coated on the electrode cap, so that one-time coating can be repeatedly used for multiple spot welding, the graphite-engine oil coating is not required to be coated during each spot welding, and the coating times are reduced.
The coating on the chromium-zirconium-copper electrode cap is subjected to complementary coating after being worn out by multiple spot welding, for example, the coating is subjected to complementary coating at intervals of set spot welding times, for example, at intervals of 10 times, so that the service life of the electrode cap can be prolonged.
In one embodiment, the electrode cap can be pressed on the sponge block stained with the coating to realize dip coating and/or coating supplement, and the coating mode has the advantages of coating saving, uniform coating and convenient operation.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A method for reducing the grinding frequency of an aluminum alloy spot welding electrode is characterized by comprising the following steps:
and (3) selecting the type of the electrode cap: selecting a frustum-shaped chromium-zirconium-copper electrode cap, wherein the front end surface of the frustum-shaped chromium-zirconium-copper electrode cap is in arc transition; and
selecting welding parameters: a multi-section welding mode is adopted, wherein the number of selected sections is 4-6, the interval cooling time of multi-section welding is 3-5 ms, and the welding time of each section is 20-30 ms.
2. According to the rightThe method for reducing the grinding frequency of the aluminum alloy spot welding electrode according to claim 1, wherein the diameter of the rear end of the motor cap is 20mm, and the diameter of the front end of the motor cap is 20mm
Or
The taper angle is 120 degrees, and the diameter of the arc of the front end surface is R100.
3. The method for reducing frequency of thinning of aluminum alloy spot welding electrodes according to claim 1, characterized in that the multi-stage welding pressure is 4KN, the welding current is 26KA, the welding time is 24ms x 6, and the inter-stage cooling time is 3 ms.
4. The method for reducing frequency of aluminum alloy spot welding electrode thinning according to claim 1, further comprising the step of spraying graphite-engine oil paint on the chromium zirconium copper electrode cap.
5. The method for reducing the frequency of thinning of aluminum alloy spot welding electrodes according to claim 4, further comprising the step of applying a make-up coat after the coating on the chromium zirconium copper electrode cap has been worn through multiple spot welds.
6. The method for reducing the frequency of thinning the aluminum alloy spot welding electrode according to claim 4 or 5, characterized by the step of grinding a portion of the aluminum alloy plate to be welded, which is to be in contact with the electrode, before spot welding.
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| CN201910918383.3A CN110814499A (en) | 2019-09-26 | 2019-09-26 | Method for reducing grinding frequency of aluminum alloy spot welding electrode |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112548295A (en) * | 2020-12-05 | 2021-03-26 | 钟丽慧 | Resistance spot welding method for automobile aluminum alloy |
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| CN104084686A (en) * | 2014-06-12 | 2014-10-08 | 上海交通大学 | Electrode for restraining generation of aluminum alloy resistance spot welding crack |
| CN104668756A (en) * | 2013-08-23 | 2015-06-03 | 通用汽车环球科技运作有限责任公司 | Multi-step Direct Welding Of An Aluminum-based Workpiece To A Steel Workpiece |
| CN109014535A (en) * | 2018-10-10 | 2018-12-18 | 安徽巨自动化装备有限公司 | A kind of spot welding method for not uniform thickness aluminium sheet |
| CN109079304A (en) * | 2018-10-10 | 2018-12-25 | 鞍钢股份有限公司 | A kind of spot-welding technology method of carbon equivalent high cold-rolled biphase steel |
| CN110153546A (en) * | 2019-06-05 | 2019-08-23 | 安徽巨一自动化装备有限公司 | A kind of aluminium alloy sheet spot welding method |
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2019
- 2019-09-26 CN CN201910918383.3A patent/CN110814499A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102950373A (en) * | 2011-08-25 | 2013-03-06 | 通用汽车环球科技运作有限责任公司 | Weld schedule for resistance spot welding of alouminum alloy workpieces |
| CN102441731A (en) * | 2011-11-14 | 2012-05-09 | 江苏大学 | Method for increasing service life of aluminium alloy spot-welding electrode |
| CN104668756A (en) * | 2013-08-23 | 2015-06-03 | 通用汽车环球科技运作有限责任公司 | Multi-step Direct Welding Of An Aluminum-based Workpiece To A Steel Workpiece |
| CN104084686A (en) * | 2014-06-12 | 2014-10-08 | 上海交通大学 | Electrode for restraining generation of aluminum alloy resistance spot welding crack |
| CN109014535A (en) * | 2018-10-10 | 2018-12-18 | 安徽巨自动化装备有限公司 | A kind of spot welding method for not uniform thickness aluminium sheet |
| CN109079304A (en) * | 2018-10-10 | 2018-12-25 | 鞍钢股份有限公司 | A kind of spot-welding technology method of carbon equivalent high cold-rolled biphase steel |
| CN110153546A (en) * | 2019-06-05 | 2019-08-23 | 安徽巨一自动化装备有限公司 | A kind of aluminium alloy sheet spot welding method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112548295A (en) * | 2020-12-05 | 2021-03-26 | 钟丽慧 | Resistance spot welding method for automobile aluminum alloy |
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Address after: No.5821, Fanfu Avenue, Baohe District, Hefei City, Anhui Province Applicant after: Anhui Juyi Technology Co., Ltd Address before: 230051 Baohe District, Hefei City, Anhui Province, Shanghai Road East Dalian Road North Applicant before: ANHUI JEE AUTOMATION EQUIPMENT Co.,Ltd. |
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Application publication date: 20200221 |