阅读说明：本技术 提高减振钢板焊接质量的焊接工艺 (Welding process for improving welding quality of vibration reduction steel plate ) 是由 陆国欢 徐天添 饶鹏 黄洪浪 王静秋 于 2019-12-05 设计创作，主要内容包括：本发明公开了一种提高减振钢板焊接质量的焊接工艺,属于焊接工艺技术领域。它包括对减振钢板待焊接部位施加外力,逐渐加压至压力为F,保持在压力F一段时间后继续在外力作用下采用小电流对待焊接部位预热使中间阻尼层的树脂融化并流向待焊接部位周边区域,再增大电流进行常规焊接；待焊接完成后,撤除外力；其中,减振钢板的中间阻尼层中添有导电粒子。本发明设计的焊接工艺通过降低钢板上焊接区域的电阻,再按照常规低碳钢板电阻焊标准推荐的焊接电流和时长进行焊接,将电流主体导入到电极所对应的钢板区域,防止较大电流从电极周围的导电粒子处通过,进而降低树脂膨胀爆裂形成孔洞的概率。(The invention discloses a welding process for improving the welding quality of a vibration reduction steel plate, and belongs to the technical field of welding processes. Applying external force to the to-be-welded part of the vibration reduction steel plate, gradually pressurizing to the pressure F, keeping the pressure F for a period of time, then continuously preheating the to-be-welded part by adopting small current under the action of the external force to melt the resin of the middle damping layer and flow to the peripheral area of the to-be-welded part, and then increasing the current to carry out conventional welding; after the welding is finished, removing the external force; wherein, conductive particles are added in the middle damping layer of the vibration damping steel plate. According to the welding process designed by the invention, the resistance of the welding area on the steel plate is reduced, and welding is carried out according to the welding current and time recommended by the conventional low-carbon steel plate resistance welding standard, so that the current main body is led into the steel plate area corresponding to the electrode, larger current is prevented from passing through the conductive particles around the electrode, and the probability of forming holes by resin expansion and explosion is further reduced.)

1. A welding process for improving the welding quality of a vibration damping steel plate comprises an upper steel plate, a lower steel plate and a middle damping layer positioned between the upper steel plate and the lower steel plate, wherein conductive particles are filled in the middle damping layer; the method is characterized in that: applying external force to the to-be-welded part of the vibration reduction steel plate, gradually pressurizing to the pressure F, keeping the pressure F for a period of time, then continuously preheating the to-be-welded part by adopting small current under the action of the external force to melt the resin of the middle damping layer and flow to the peripheral area of the to-be-welded part, and then increasing the current to carry out conventional welding; and after the welding is finished, removing the external force.

2. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1, wherein the welding process comprises the following steps: the pressure F applied to the vibration-damping steel plate meets the low-carbon steel resistance spot welding standard ISO-14373-2015.

3. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1 or 2, wherein: the welding current for carrying out conventional welding on the vibration reduction steel plate is I_WWelding time t₄And the values all meet the low-carbon steel resistance spot welding standard ISO-14373-2015.

4. The welding process for improving the welding quality of the vibration damping steel plates according to claim 3, wherein the welding process comprises the following steps: small current I for preheating the vibration damping steel plate_HAnd a preheating period t_HThe following mathematical relationship is satisfied:

I_H＝(1/3～1/2)I_W，t_H＝(1/4～1/2)t₄。

5. the welding process for improving the welding quality of the vibration damping steel plates according to claim 1, 2 or 4, wherein: before current is applied, the part to be welded of the damping steel plateThe dwell time under the action of the pressure F is t_2,And t is₂Greater than 300 ms.

6. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1, 2 or 4, wherein: the welding process also comprises cutting off the current and continuing to maintain the pressure F after the conventional welding is finished, wherein the maintaining time is t₅Said t is₅Is 200 to 300 ms.

7. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1, 2 or 4, wherein: the conductive particles comprise nickel, copper, aluminum or alloy particles.

8. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1, 2 or 4, wherein: the small preheating current comprises one of a rectangular type, a slope type or a pulse type.

9. The welding process for improving the welding quality of the vibration damping steel plates according to claim 1, 2 or 4, wherein: the welding process is carried out in a power frequency alternating current resistance welding machine or a medium frequency inverse resistance welding machine.

Technical Field

The invention relates to welding of steel plates, belongs to the technical field of welding processes, and particularly relates to a welding process for improving the welding quality of a vibration reduction steel plate.

Background

The laminated vibration damping steel plate is a sandwich metal plate formed by two layers of steel plates and a layer of organic polymer, and is a lightweight material which not only meets certain strength requirements, but also has sound damping characteristics and is developed by steel manufacturers. As a structural material, the composite material is applied to the fields of automobiles and aerospace more importantly and widely at present, and helps to solve the pain points of weight reduction and noise reduction of products.

In the automotive field, laminated vibration damping steel sheets are mainly applied to vehicle body structures and engine oil pan structures. The production of car body and oil sump involves a lot of resistance welding, the weldability of the damping steel plate is very poor because of the electric insulation of the damping layer of organic polymer, in order to realize welding, the organic polymer at the welding position needs to be removed first, so that the welding current forms a loop, but it needs to rely on an auxiliary loop, and the welding equipment and procedure are relatively complicated.

Later, the raw material manufacturers add conductive particles, such as nickel, copper, aluminum or stainless steel particles, in the damping layer to solve the problem of conductivity, so that the damping steel plate can be directly subjected to resistance welding like a common low-carbon steel plate, but the resistance welding process of the damping steel plate is not completely the same as that of the traditional plate welding. At present, the known mature electric resistance welding process related to the vibration reduction steel plate in the welding field is not disclosed. The manufacturers of products related to resistance spot welding of damping steel plates generally apply the traditional spot welding method directly. Suppliers lack knowledge of weld defects in vibration damping steel sheet products and control and evaluation capabilities for weld quality.

The technical personnel in the field study the vibration damping steel plate which appears under the welding process recommended by the material suppliers, and the result shows that the defect rate of the vibration damping steel plate is as high as 70% -80%, and further study the internal structure of the vibration damping steel plate, as shown in figure 1 of the attached drawings of the specification, the upper part and the lower part of the vibration damping steel plate 3 are common steel plates 1, the middle part of the vibration damping steel plate comprises a damping layer 6, conductive particles 2 are filled in the damping layer 6, further, the situation that a plurality of holes, non-through holes 4 and through holes 5 appear around an internal nugget 7 of the vibration damping steel plate 3 is found, and the hole forming mechanism is completely different from that of the resistance welding shrinkage cavity of the common steel plate through study, and the hole forming mechanism is probably caused by the. As can be further seen from fig. 2, the longitudinal resistance distribution in the vibration damping steel plate before the welding current is applied by pressurizing the electrode is as shown in the above figure, and the local contact resistance is low due to the pressing of the pressure below the electrode. The vibration damping steel sheet is electrically conductive through the conductive particles in the middle, and because of the uniformity of particle size, there are always large particles around the electrode to form a local resistance low region, so that the distribution of resistance Ri before welding shown in the figure appears. After the welding current is switched on, the local resistance is low, so that the current is gathered, and then the local resistance is further reduced when the damping layer melts, so that the current gathering is more obvious, and the current I distribution in the graph is shown. The current build-up causes an increase in heat build-up, under which the sheet material under the electrode melts, because of the presence of the electrode pressure, no spattering occurs, and a nugget is eventually formed. And the local heat around the electrode is suddenly increased to melt the resin, further melt the plate, and finally melt the steel plate to splash to form holes.

The holes appear inside, and besides affecting the strength of the welded structure, the holes are difficult to find in a general welding test. Vehicle body parts have high structural strength requirements and this weld quality can present a potential risk. Through voids can also lead to seal failure. For example, the oil drain screw seat of the oil pan is connected to the damping steel plate by resistance welding, and the penetrating hole can cause oil leakage, thereby directly limiting the application of the damping steel plate. Therefore, it is necessary to provide a welding process capable of making up for the technical defects of the common steel plate resistance welding process.

Disclosure of Invention

In order to solve the technical problem, the invention provides a welding process for improving the welding quality of a vibration reduction steel plate. The process reduces the current collection effect in the area around the electrode by increasing the difference in resistance between the resistance under the electrode and the resistance depression at the periphery. Specifically, the resistance of a welding area on a steel plate is reduced, welding is carried out according to the welding current and time recommended by the conventional low-carbon steel plate resistance welding standard, a current main body is led into the steel plate area corresponding to the electrode, larger current is prevented from passing through conductive particles around the electrode, and the probability of forming holes through resin expansion and explosion is further reduced.

In order to achieve the aim, the invention discloses a welding process for improving the welding quality of a vibration-damping steel plate, wherein the vibration-damping steel plate comprises an upper steel plate, a lower steel plate and a middle damping layer positioned between the upper steel plate and the lower steel plate, and conductive particles are filled in the middle damping layer; applying external force to the to-be-welded part of the vibration reduction steel plate, gradually pressurizing to the pressure F, keeping the pressure F for a period of time, then continuously preheating the to-be-welded part by adopting small current under the action of the external force to melt the resin of the middle damping layer and flow to the peripheral area of the to-be-welded part, and then increasing the current to carry out conventional welding; and after the welding is finished, removing the external force.

Further, the resin of the middle damping layer of the part to be welded of the vibration reduction steel plate is subjected to low current I_HThe molten alloy melts and flows under pressure F, so that the difference in resistance between the portion to be welded and the peripheral area of the portion to be welded is increased. The reason is that the small current is used for preheating before welding, when the preheating is carried out, because the total current is small, the main body of the part of the current is totally gathered below the electrode, namely the area to be welded, so that the resin at the local part of the electrode is melted, and because of the action of pressure, the part of the resin flows to the periphery, so that the contact resistance below the electrode is greatly reduced; in the resistance depression around the electrode, the resin cannot be melted due to insufficient heat, and the resistance does not change much, whereby the difference in resistance between the lower side of the electrode and the periphery is further increased.

Further, when conventional welding is performed, welding current is concentrated at the welding site. When the conventional welding is carried out, because the resistance of the area to be welded is small, the welding current is gathered to the electrode area, the phenomenon that the peripheral area is shunted to form local hot spots is avoided, and the phenomenon that large conductive particles splash to form holes due to the heated melting is avoided.

Further, the pressure F applied to the vibration-damping steel sheet satisfies the low-carbon steel resistance spot welding standard ISO-14373-2015.

Further, the vibration damping steel plate is subjected to conventional weldingThe welding current is I_WWelding time t₄And the values all meet the low-carbon steel resistance spot welding standard ISO-14373-2015.

Further, a small current I for preheating the vibration damping steel plate_HAnd a preheating period t_HThe following mathematical relationship is satisfied:

I_H＝(1/3～1/2)I_W，t_H＝(1/4～1/2)t₄。

further, before current is applied, the pressure maintaining time of the part to be welded of the vibration reduction steel plate under the action of pressure F is t_2,And t is₂Greater than 300 ms.

Further, the welding process also comprises cutting off the current and continuously maintaining the pressure F after the conventional welding is finished, wherein the maintaining time is t₅Said t is₅Is 200 to 300 ms.

Further, the conductive particles include nickel, copper, aluminum, or alloy particles.

Further, the small preheating current comprises one of a rectangular type, a slope type or a pulse type.

Further, the welding process is carried out in a power frequency alternating current resistance welding machine or a medium frequency inverter resistance welding machine. The beneficial effects of the invention are mainly embodied as follows:

the welding process designed by the invention has the advantages that through the pre-pressing and preheating process operation before welding, the resistance difference between the resistance of the area to be welded below the electrode and the resistance depression of the periphery is increased, when the electrode is welded conventionally, the welding current is concentrated to the electrode area, the hole probability caused by metal particle melting and splashing due to the fact that the periphery area is shunted to form local hot spots is reduced, and therefore the welding quality is improved.

Drawings

FIG. 1 is a schematic diagram of typical defects of a vibration damping steel plate by direct resistance welding;

FIG. 2 shows the distribution of internal resistance and current when the damping steel sheet is subjected to direct resistance welding;

FIG. 3 is a schematic view of a process for directly welding a common low-carbon steel plate;

FIG. 4 is a schematic view of a welding process for a vibration damping steel plate using the design of the present invention;

FIG. 5 is a schematic view of the principle of the welding process for the vibration damping steel plate adopting the design of the present invention;

FIG. 6 is a schematic view of the internal microstructure of a conventional low-carbon steel plate after welding and a vibration damping steel plate according to the process of the present invention;

wherein the numbering in the above figures is:

the welding method comprises the following steps of a common low-carbon steel plate 1, conductive particles 2, a vibration reduction steel plate 3, a non-through hole 4, a through hole 5, a damping layer 6, a nugget 7, an electrode 8, a current distribution direction 9 and a part to be welded 10.

Detailed Description

The invention discloses a welding process for improving the welding quality of a vibration reduction steel plate, which is different from the common low-carbon steel plate welding process shown in figure 3, and comprises the step of welding a steel plate at t shown in figure 4₁Applying pressure to the to-be-welded part of the vibration-damping steel plate in a time period, gradually pressurizing to a pressure F, and keeping the pressure F for a period of time, specifically t shown in FIG. 4₂Time period, said t₂Greater than 300 ms. Preheating the welding position by adopting one current form of rectangular, slope or pulse, wherein the preheating current is I_HPreheating duration is t_HThe middle damping layer of the vibration reduction steel plate is heated and melted and is extruded out of the welding area under the action of the pressure F, so that the resistance of the welding area is further greatly reduced. Then increasing the current to the welding current I_WWelding time t₄And completing the conventional welding process, wherein the welding current is introduced into the part to be welded 10 corresponding to the electrode 8 according to the current distribution direction 9 shown in fig. 5, so as to prevent a larger current from passing through the conductive particles 2 around the electrode 8, which causes the local temperature of the steel plate around the electrode 8 to be too high, and further causes the resin in the damping layer 6 to expand and burst to form holes.

Cutting off the current and continuing to maintain the pressure F after the conventional welding is finished, wherein the maintaining time is t₅Said t is₅And (4) withdrawing the pressure F for 200-300 ms to complete the welding of one welding point, and repeating the operation process until the whole welding is completed.

Wherein, the I_HHas a value of I_H＝(1/3～1/2)I_WSaid t is_HSatisfies the value of t_H＝(1/4～1/2)t₄. And the value of the pressure F, the welding current I_WValue of (d) and welding time t₄The values of (A) are all referred to the low-carbon steel resistance spot welding standard ISO-14373-2015.

In order to better explain the invention, the following further illustrate the main content of the invention in connection with specific examples, but the content of the invention is not limited to the following examples.