JPH01284494A - Method of welding metal mold - Google Patents

Abstract

PURPOSE:To prevent the generation of blow holes in a weld zone by heating base metals and welding rods in a reduced pressure atmosphere to degas the metal and rods, then welding the base metals by the welding rods. CONSTITUTION:The respective blocks which constitute a metallic mold for molding plastic are molded of an Al alloy and an Al alloy is used as the welding rods for assembling and joining. The blocks and the welding rods are then loaded into a vacuum heating furnace and are subjected to the degassing treatment in the high-temp. high-vacuum atmosphere. The gases remaining in the blocks and welding rod are thereby removed. The blocks and welding rods are taken out of the furnace and thereafter, the oxide in the groove part of the weld zone is physically removed by a brush, etc. The degassed blocks are then subjected to ordinary MIG welding in the atmospheric atmosphere by using the degassed welding rods. Finally, the surface of a core mold is machined and is subjected to removal of work seams by sandpaper, by which the desired final finishing is applied to the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold welding method for assembling or repairing a base material of a mold by welding.

[Conventional technology] Conventionally, molds have generally been machined from cast steel, cast iron, or forged steel, and there have been few molds manufactured with welded structures, and welding has only been used to repair molds. There are many things. In particular, large resin molding dies are often machined from forged materials.

However, as the size of the mold becomes larger, a huge forging material is required if the forging material is cut out. For this reason, the forging equipment for producing the forged material becomes large, which increases the cost of producing the die base material.

Therefore, by making the mold base material a welded structure, it is possible to reduce mold manufacturing costs, and it is often possible to easily meet the required specifications.Furthermore, as a mold material, it is lightweight. The number of molds made of alloys is gradually increasing, and from this material perspective, demand for molds with welded structures has recently increased.

[Problems to be Solved by the Invention] However, when molds are manufactured by welding in this manner, welding defects become an important problem. In other words, conventionally, welding work depends on the skill level of the welding engineer, so blowhole scars occur in the welded parts of manufactured molds, and the difference in the frequency of occurrence of these blowhole defects is large or small. Although it exists, it cannot be completely eliminated.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a mold welding method that can reliably avoid the occurrence of blowholes in welded parts.

[Means for Solving the Problems] A mold welding method according to the present invention includes a step of degassing gold by heating a base metal and a welding rod in a reduced pressure atmosphere, and then using the welding rod. and assembling or repairing the mold by welding the mold base material.

[In order to avoid blowhole defects in welded parts, it is appropriate for welding to be carried out by a welding engineer, and the welding method, including current value and welding position, must be in accordance with generally recommended methods. is necessary.

It is also necessary to remove oxides from the groove surface and sufficiently degrease it before welding, and appropriate preheating may be necessary depending on the material of the base material.

Furthermore, it is preferable that the environmental facilities are clean and air-conditioned.

However, conventionally, even if sufficient measures are taken regarding the external conditions as described above, it has not been possible to reliably prevent the occurrence of blowholes in welds.

In order to reliably prevent the occurrence of such blowholes, the inventors of the present application have repeatedly conducted various experimental studies and found that the gas contained within the base metal and welding rod has an important influence on the occurrence of blowholes in welded parts. It was found that

Therefore, in the present invention, prior to the welding process, the gold base metal and the welding rod are heated in a reduced pressure atmosphere.

This removes gas such as hydrogen gas stored inside the base metal and the welding rod. Next, by using this welding rod to weld the degassed gold to the base metal under appropriate welding conditions, it is possible to prevent blowhole defects from occurring in the welded portion during the welding process.

[Example] Examples of the present invention will be specifically described below.

In this embodiment, for example, the present invention is applied to a large-sized resin molding die of an assembly type having a welded structure.

As the mold becomes larger, as mentioned above, the traditional forging method requires a huge amount of material and the forging equipment becomes larger, which increases the cost of manufacturing the base material. It is a good idea to form the blocks and then integrate them with a welded structure.

Furthermore, among the molds, in particular, the surface of the core mold, which forms a portion corresponding to the surface skin of the resin molded product, needs to be smooth and free of concave defects such as pinholes or scratches.

In other words, such defects are transferred as protrusions on the important surfaces of resin molded products, and not only do they impair the aesthetic appearance, but in applications where cast products come into contact with the bare skin of the human body, these surface protrusions can cause damage to the human body. This is because there is a risk that the product may be damaged, leading to fatal defects. Therefore, it is required that there be no concave defects.

Therefore, when manufacturing this mold, it is preferable to first select an aluminum alloy as the mold base material, which has high thermal conductivity and increases the production efficiency of resin molded products. For example, JIS5052
There is an alloy. Then, each block constituting the resin molding die is molded from this aluminum alloy, and used as a welding rod for assembly and joining, for example, using aluminum JIS518.
3 alloys are used.

Next, these blocks and welding rods are placed in a vacuum degree of I
The sample is placed in a vacuum heating furnace with a heating temperature of 350° C. at 0-3 Torr and held in a high-temperature vacuum atmosphere for 2 hours for degassing treatment. This removes residual gas in the block and welding rod.

The higher the degree of vacuum, the better, but I
If it exceeds rr, the equipment will be large-scale and the equipment cost will also increase significantly. Furthermore, the degassing efficiency is not determined only by the degree of vacuum, but also by the balance between temperature and processing time. Therefore, considering the processing cost, it is preferable that the degree of vacuum in the depressurization process is around 1X10-'Torr.

The higher the heating temperature, the better the degassing effect, but it is necessary to choose a range that does not affect the material. For example,
Select 350°C.

The vacuum heating time is determined by the degree of vacuum, and I
At a vacuum level of X 10-' Torr, 2 hours is sufficient. Even if the vacuum heating time is made longer than this, there is no advantage in terms of degassing effect.

Next, the block and welding rod are taken out of the furnace, and then the oxide in the groove of the weld is physically removed with a brush or the like. This degassed block is then welded using a degassed welding rod in a normal atmosphere.
IG welding conditions: current 36OA, secondary voltage DC
MI by 24V and argon gas supply flow rate 22ρ/min.
G-weld. Finally, the surface of the core mold is machined according to the normal mold processing procedure, and the mechanical processing hole is removed using sandpaper, and the sandpaper sanding is repeated to obtain the desired trowel surface finish. give

By manufacturing a large resin mold in this manner, a sound welded portion without blowholes can be obtained.

In other words, in the normal welding method that does not employ vacuum degassing, pinholes with a diameter of 0.1 to 0.3++ ui occur, whereas in the present example, a sound welded part with no defects caused by pinholes is produced. I was able to get the surface. For this reason, conventionally large resin molding molds were difficult to weld into a welded structure, and were molded by cutting out forged steel in one piece.However, according to the present invention, this large resin molding mold can be manufactured by dividing and assembling the mold. It became so. As a result, the manufacturing cost of a large resin molding die could be reduced by 30 to 50% compared to the case of a conventional forging die. In addition, since it is molded as a divided welding block, it is possible to perform pre-processing such as drilling holes on each welding block, making it possible to add functions and performance not previously available, such as improving the cooling function. It's easy.

[Effects of the Invention] According to the present invention, since the base metal and the welding rod are heated and degassed in a reduced pressure atmosphere, and then the base metal is welded with the welding rod, blowhole defects are prevented from occurring in the welded portion. can be reliably prevented.

As a result, the mold can be manufactured as a welded assembly structure of a plurality of welded blocks, so the manufacturing cost can be significantly reduced compared to the conventional case of machining from a large forged steel product.

Claims (1)

[Claims] (1) A step of degassing the mold base material and the welding rod by heating it in a reduced pressure atmosphere, and then assembling the mold by welding the mold base material using the welding rod, or A method for welding a mold, comprising the steps of: repairing the mold.