Patent Application
20200030914
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-139421, filed on Jul. 25, 2018; the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a welding method, a method for manufacturing a welded product, and a welded product.
In welding, two or more members are melted and integrated to one member. It is desirable that there are few defects in a welded portion where the members are welded together.
According to an embodiment, a welding method comprises pretreatment of melting a part of the first member formed by die casting and solidifying the part of the first member. The method may comprise welding the first member and the second member by melting the solidified part of the first member and the second member in contact with each other.
According to the embodiment, a method for manufacturing a welded product including a first member formed by die casting and a second member comprises pretreatment of melting a part of the first member formed by die casting and solidifying the part of the first member. The method may comprise welding the first member and the second member by melting the solidified part of the first member and the second member in contact with each other.
According to the embodiment, a welded product comprises a first portion including a metal and a second portion connected to the first portion via a welded portion. The first portion includes a first region apart from the welded portion and a second region provided between the first region and the welded portion. A density of voids in the second region is lower than a density of voids in the first region.
Embodiments of the invention will now be described with reference to the drawings.
The drawings are schematic or conceptual; and the relationships between the thicknesses and widths of portions, the proportions of sizes between portions, etc., are not necessarily the same as the actual values thereof. The dimensions and/or the proportions may be illustrated differently between the drawings, even in the case where the same portion is illustrated.
In the drawings and the specification of the application, components similar to those described thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.
As an example, a first member 10 and a second member 20 shown in
The first member 10 is formed by die casting. In die casting, molten metal is pressed into a metal mold. Thereafter, the metal solidifies ; and a member to which the shape of the mold is transferred is formed. The first member 10 includes, for example, aluminum, magnesium, zinc, copper, or iron. As long as the first member 10 and the second member 20 can be welded, the shape, material, manufacturing method, and the like of the second member 20 can be appropriately changed. For example, a metal included in the second member 20 is the same as a metal included in the first member 10.
As shown in
In the pretreatment step, as shown in
For example, when the first member 10 includes aluminum, the part of the first member 10 is heated to 660 degrees Celsius or higher. When the first member 10 includes iron, the part of the first member 10 is heated to 1540 degrees Celsius or higher. When the first member 10 is made of an alloy, the part of the first member 10 is heated above the melting point of the alloy.
A large number of voids V are present inside the first member 10 formed by die casting. The void V is a cavity formed during die casting. The void V is generated as the gas in the welded metal is not released into the atmosphere but is confined in the metal. When the part of the first member 10 melts and the gas in the void V expands by heating, the molten metal is blown off and the gas is released from the first member 10.
When the gas is released, the molten metal flows into the void V, and the void V is buried. Thereafter, when the molten portion is cooled and solidified, a portion having a low density of voids V is formed as shown in
A depression 14 may be formed on the surface of the re-solidified layer 13. The depression 14 is formed by the molten metal being blown off by the expanded gas in the void V. In the present specification, “void” refers to a cavity provided inside the first member 10. “Void” does not include the depression 14 formed on the surface of the re-solidified layer 13. When calculating the density of the voids, the depression 14 is not taken into account.
When welding the first member 10 and the second member 20, and sealing the space inside these members, the laser light L is sequentially irradiated on the surface of the convex portion 12 along the circumferential direction. Thereby, the re-solidified layer 13 having less voids V is formed over the entire circumference of the convex portion 12.
In the cutting step, as shown in
In the welding step, as shown in
The melted re-solidified layer 13 and the melted second member 20 mix and solidify to form a welded portion 15 as shown in
When sealing the space S inside the first member 10 and the second member 20, in the welding step, similarly to the pretreatment step, the laser light L is irradiated to the re-solidified layer 13 and the second member 20 along the circumferential direction. As a result, the convex portion 12 of the first member 10 and the outer periphery of the second member 20 are welded, and the space S is sealed.
The effects of the embodiment will be described.
As described above, the first member 10 formed by die casting includes a large number of voids V. The gas in these voids V expands and blows off the molten metal when the first member 10 is heated. When this phenomenon occurs at the time of welding the first member 10 and the second member 20, a defect (gap) is generated in the welded portion. If a defect occurs in the welded portion, there is a possibility that the first member 10 and the second member 20 are not properly welded together. When the space surrounded by the first member 10 and the second member 20 is sealed by welding, if there is a defect in the welded portion, the airtightness of the space decreases. Therefore, when welding the first member 10 and the second member 20, it is desirable that defects do not easily occur.
In the welding method according to the embodiment, the pretreatment step is performed before the welding step. By the pretreatment step, the re-solidified layer 13 is formed in the first member 10. In the re-solidified layer 13, as described above, the number of the voids V is smaller than that of other portions of the first member 10. By welding the re-solidified layer 13 and the second member 20, occurrence of defects in the welded portion 15 can be suppressed. For example, when the space surrounded by the first member 10 and the second member 20 is sealed by welding, airtightness of this space can be improved.
When there is no need to process the shape of the first member 10, the welding method according to the embodiment may not include the cutting step. When the cutting step is performed, the order of the cutting step and the pretreatment step can be appropriately changed. Preferably, the cutting step is performed after the pretreatment step. In the pretreatment step, a part of the first member 10 is melted. Therefore, the shape of the first member 10 may change. By performing the cutting step after the pretreatment step, it is possible to prevent the shape of the first member 10 obtained by the cutting step from changing. As a result, the first member 10 having a desired shape can be welded to the second member 20.
When the part of the first member 10 is melted in the welding step, as shown in
In the welding step, it is desirable that the heating temperature for melting the re-solidified layer 13 is set lower than the heating temperature for melting the part of the first member 10 in the pretreatment step. According to this condition, the depth a can be made shallower than the thickness b more surely. When laser light is used for heating in the pretreatment step and welding step, for example, the power of the laser light in the welding step is set to be lower than the power of the laser light in the pretreatment step. Or the irradiation time per unit area of the laser light in the welding step is set shorter than the irradiation time per unit area of the laser light in the pretreatment step.
Even if a defect occurs in the welded portion 15, there is a possibility that the first member 10 and the second member 20 are sufficiently bonded. Welding of the first member 10 and the second member 20 may be achieved. However, when sealing the space inside the first member 10 and the second member 20, if there is a defect in the welded portion 15, the space can not be sealed. Therefore, the welding method according to the embodiment is particularly suitable for manufacturing the sealing housing by welding the first member 10 and the second member 20 and sealing the space surrounded by these members.
The welding method and the method for manufacturing a welded product according to the embodiment described above are, for example, applied to a device such as a secondary battery, a heat exchanger such as a heat sink, a gas generator used for an air bag or the like, a rotor for an air conditioner. In the manufacturing process of these devices, two or more members are welded, and the space inside these members is sealed, so that the sealing housing is manufactured.
With reference to
The welded product 30 shown in
As shown in
The first portion 31 includes a first region 31a and a second region 31b. The first region 31a is apart from the welded portion 33. The second region 31b is located between the first region 31a and the welded portion 33. The density of the voids V in the second region 31b is lower than the density of the voids V in the first region 31a. The second region 31b corresponds to a part of the re-solidified layer 13 that has not melted in the welding step. As shown in
The second region 31b with few voids V is provided at a position adjacent to the welded portion 33. This structure can improve the strength in the vicinity of the welded portion 33 of the welded product 30. For example, when the inner space of the welded product 30 is sealed, the strength in the vicinity of the welded portion 33 is improved. Even if an impact is applied to the welded product 30, the seal in the space becomes difficult to break. The reliability of the welded product 30 can be improved.
As described above, the welding method according to the embodiment can suppress occurrence of defects at the welded portion between the first member and the second member. The method for manufacturing a welded product according to the embodiment can manufacture a welded product with less defects at the welded portion. The welded product according to the embodiment can improve the strength in the vicinity of the welded portion.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. Moreover, above-mentioned embodiments can be combined mutually and can be carried out.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-139421 | Jul 2018 | JP | national |
