JPH08174215A - Method for repairing metallic mold - Google Patents

Abstract

PURPOSE: To execute the repair of a metallic mold which can improve the reliability to the repaired part, by repeating build-up weldings and peenings to a cut-off part in plural times after cutting off the crack in the damaged part in the metallic mold and removing foreign matter. CONSTITUTION: For example, to a design part A in the metallic mold 1 developing the damage of crack (h), etc., the crack (h) and the surrounding part are cut off and the foreign matter (d) stuck to the surrounding part is removed to apply the pretreatment. The build-up welding is applied to the cut-off part (a) formed with this work e.g. with a copper welding rod 4 having the same quality as the metallic mold 1 by using a plasma welder 3. The peening is executed to the build-up welding part (m), by continuously hitting with an air- hammer 5. By this method, the hardness of the build-up part (m) is uniformized and the hardness degree is improved and fatigue strength is improved. This build-up welding and the peening are repeated at least one or more times. By this method, the build-up welding part (m) is formed to the desired thickness and as necessary, the surface is finished with a finishing tool 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for repairing a casting mold for casting molten metal, for example.

[0002]

2. Description of the Related Art Conventionally, metal molds made of copper alloy for casting molten metal have been generally cast and molded to improve thermal conductivity. After casting, solution treatment, aging treatment, etc. After being heat treated, it is finished by machining. However, since such a mold receives heating and cooling repeatedly, if the number of shots is repeated, cracks such as cracks called heat checking (heat crack) may occur in the design part or product cavity part, When the molten metal is inserted into the cracks and burrs are generated, it is difficult to take out the cast product from the mold, or the mold life of the mold is shortened.

Therefore, conventionally, in the initial stage where the depth of the crack is shallow, the cracking portion is repaired by crushing the crack with an air hammer or the like at every predetermined number of shots as a coking repair so that the crack depth reaches a limit value. When it reaches, the cracked part is scraped off and weld overlay is repaired.

[0004]

However, since the die formed by casting as described above basically has coarser crystal grains than the forged material and the like, it has a difficulty in strength and is reliable even if caulking repair is performed. There is a problem that the durability is poor and the durability after repair is poor. Further, even if the overlay repair is performed, the fatigue strength of the repaired part is limited.

[0005]

In order to solve the above problems, the present invention provides, as a method for repairing a mold, a pretreatment for cutting out cracks and removing foreign matters adhering to the periphery thereof, and performing build-up welding on the cut portion. While applying, the padding portion was continuously hit by peening. Then, the work of overlay welding and peening was repeated at least once.

[0006]

[Function] By continuously striking the build-up welded portion by peening, plastic strain is given to improve fatigue strength. At this time, a thin buildup layer is formed, peening is performed, and this is repeated to form a thick buildup part, whereby plastic strain is applied to all parts of the buildup part and durability is increased.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a front view of a die-matching surface of a die, and FIG. 2 is a process diagram of the method of the present invention. The die repair method of the present invention is, for example, casting for casting a steering knuckle which is a component of an automobile. It is applied as a method for repairing a die, and this casting die is, for example, a copper alloy die having good thermal conductivity.

A cavity 2 as shown in FIG. 1 is formed on the die-matching surface of the die 1, and the cavity 2 has a vertical runner 2b extending downward from a top spout 2a in the center and a vertical runner 2b. From the horizontal runners 2c, 2c, etc., and a pair of left and right product cavities C, C. The high temperature molten iron-based metal poured from the spout 2a is vertical and horizontal runners. It is filled in the product cavity portion C through 2b and 2c and taken out when the surface layer is solidified into a shell shape, for example.

By the way, in such a mold 1, especially from the lower part of the vertical runner 2b to the peripheral part of the horizontal runner 2c, a heater for improving the hot running property is embedded and the molten metal is melted. A cooling water passage for quenching is provided. For example, the mold 1 is heated by a heater before pouring the molten metal, and after pouring the molten water, the cooling water is guided to the cooling water passage to remove the surface layer of the molten metal. I'm trying to quench it. Therefore, particularly in such a plan portion A, the thermal change is severe, and heat check (thermal crack) due to thermal fatigue is likely to occur.

Therefore, in the method of the present invention, a repair method as shown in FIG. 2 is adopted. That is, as shown in FIG. 2 (A), when a crack h is generated due to heat checking or the like, slag around the crack h generation part
The foreign matter d such as dust and oil is removed and cleaned, and the peripheral portion of the crack h is cut and removed as shown in FIG. Then, in this way, the foreign matter d
By removing the foreign matter d, there is no risk that the foreign matter d will be mixed in the cut portion a or the build-up portion during the welding work after the welding, and there is no problem that the fatigue strength of the build-up welded portion is deteriorated. When removing the crack h, make sure that the cut-out part a is made slightly larger so that the crack h is completely removed. Also, be careful not to leave soot, rust, etc. that have entered the tip of the crack h. Cut in.

When the pretreatment process as described above is completed, FIG.
As shown in (C), for example, a plasma welding machine 3 and a welding rod 4 as a filler material are used to perform build-up welding in the excised portion a. Here, for example, the welding rod 4 is made of a copper-based material of the same quality as that of the mold 1, and an appropriate material is selected according to the repair location such as the vertical and horizontal runners 2b and 2c or the product cavity B.
Further, the welding current is finely adjusted according to the penetration state of the base material and the like, and the shield gas is used so as to increase the welding heat quantity by, for example, using helium gas in combination with argon gas. Then, the buildup portion m of the first layer is raised.

Next, as shown in FIG. 2D, the padding portion m is peened by an air hammer 5 or the like. And this peening is performed while moving the hitting point finely so that all the parts of the built-up part m have uniform hardness,
Aim to increase overall hardness. By thus uniformly hitting and giving plastic strain, the grain size of the built-up portion m is made finer and the fatigue strength is improved.

Next, as shown in FIGS. 2 (E) and (F),
The above build-up welding and peening are repeated a plurality of times to build up the layered build-up portions m ... to a desired height.
Then, by subjecting the multilayered built-up portions m ... to peening without leakage to impart a plastic strain, the fragile portion is eliminated and the fatigue strength can be increased. Further, by performing peening for each layer in this manner, it is not necessary to take measures such as strain relief after the subsequent polishing. The surface may be finished by using a surface finishing tool 6 as shown in FIG.

It has been confirmed that, when the above-described repair method of the present invention is performed, the conventional caulking repair at about 400 shot intervals can be extended to about 2500 shot intervals.

[0015]

According to the present invention as described above,
After removing the peripheral part of the crack and performing build-up welding, continuous impact is applied by peening to generate plastic strain and this is repeated, so the reliability and durability of the repaired part are improved. I was able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a mating surface of a general mold.

2A to 2G are views for explaining the steps of the repair method according to the present invention.

[Explanation of symbols]

1 ... Mold, 2 ... Mold matching surface, 3 ... Welding machine, 4 ... Welding rod, 5 ... Air hammer, A ... Design part, C ... Product cavity part, h ... Crack, d ... Foreign matter, m ... Meat Heap section.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshio Isobe 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture Honda Giken Industrial Co., Ltd. Saitama Factory

Claims (1)

[Claims] 1. A pretreatment step of cutting out cracks in a damaged portion of a mold to remove foreign matters adhering to the periphery thereof, a buildup step of applying buildup welding to the cut portion, and continuously striking the buildup portion. And a peening step, and a repeating step of repeating the above-mentioned build-up step and peening step at least once or more.