JP2014151354A - Die repairing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die repairing method capable of repairing a crack by an easy work.SOLUTION: A repairing paste agent containing a component to make an alloy in a crack of a mold is so directly applied to a mold surface as to cover the portion of the crack, and the surface of said repairing paste agent is then coated with an oxidation suppression material and is further heated so that the repairing paste agent is penetrated into the crack inside and buries the crack as an alloy.

Description

The present invention relates to a mold repair method for repairing a crack portion such as a die-cast mold.

As shown in FIG. 10, a general repair method when a crack occurs in the die-casting die is to largely remove the periphery of the crack occurrence portion of the die with a cutting tool and perform overlay welding on the removed portion. Then, the surface finish is performed.

Patent Document 1 describes, as an improvement of the above general repair method, overlay welding while melting a powder for mold repair by a plasma arc. In Patent Document 1, the powder for mold repair is made of at least one of NbC, VC, and WC, and a total of 10 wt% or less of carbide and the balance is a Ni—Cr—Mo heat resistant alloy. An alloy powder made of, for example, has been proposed.

Patent Document 2 discloses that a base material is coated with a coating agent in which a metal powder to be diffused is dispersed in a solvent, and heated to diffuse the metal into the base material. In the case of a Zn alloy, at least one of Cu or Mn is selected as an element to be diffused, Cr is selected when the base material is an Fe alloy, and Al when the base material is a Ti alloy. It has been proposed to select at least one of Cr, Ni or N, and select Ni when the base material is a Cu alloy.

Further, in Patent Document 3, as shown in FIG. 2, a repair paste containing a component that becomes an alloy is applied directly to the mold surface so as to cover the crack, and the surface of the mold is removed. A method is disclosed in which the paste agent is melt-alloyed by spraying a charcoal inhibitor, depositing salt (Nacl) thereon, baking the surface of the salt, and heat-liquefying the salt.

FIG. 3 shows a mold before repair, and FIG. 4 is an enlarged view of a portion surrounded by a square in FIG. From these photographs, it can be seen that cracks occur on the surface of the mold (characters with P reversed).

FIG. 5 is a photograph showing a state where a portion surrounded by a square in FIG. 3 is cut out and repaired a part of the crack by the method according to Patent Document 3. In the repaired portion from this photograph, the crack has a surface shape. It turns out that it has disappeared.

6 is a photograph of the die cut so as to cover the repaired portion, FIG. 7 is a photograph showing the cut surface, and FIG. 8 is an enlarged photograph of FIG. From these photographs, it can be seen that the mold repair paste melts and penetrates into the crack, becomes an alloy after cooling, and partly diffuses at the boundary with the mold.

Incidentally, the alloy is formed up to a crack width of 0.1 mm, the thickness of the alloy layer formed on the mold surface is 0.15 mm, the hardness of the surface alloy part is HV356 (36 HRC), The alloy portion had a hardness of HV324 (33HRC) and the base material had a hardness of HV637 (57HRC).

JP-A-2005-97743 JP 2004-68047 A WO2007 / 069409

In the method disclosed in Patent Document 1, when repairing a crack in the same manner as in the prior art, the mold including the crack portion is scraped off and overlay welding is performed at that location. When overlay welding is performed, a so-called second crack in which a crack is generated again easily occurs at a location slightly outside the location where overlay welding is performed due to the thermal influence during welding.

In addition, in the conventional method, the cutting jig may not be used depending on the location where the crack is generated, and repair takes time and effort.

The contents disclosed in Patent Document 2 can improve various characteristics of the surface of the base material, but the coating agent itself is not alloyed by heat treatment, so it cannot be applied to repairing a mold crack. .

  On the other hand, the method disclosed in Patent Document 3 is a mold repair method superior to other prior arts, but since the decarburization inhibitor is not sufficient, the paste is oxidized when the salt coating is peeled, and FIG. As shown, alloying may fail.

In the mold repair method according to the present invention, a mold repair paste containing an alloying component is placed on the mold surface so as to cover cracks generated in the mold, and then the surface of the mold repair paste As a solution for forming a refractory film that does not allow gas to pass through, a solution in which silicon oxide, alumina, and graphite are added to alcohol is applied and dried to form a refractory film, and then chlorinated so as to cover the refractory film. Magnesium or sodium chloride powder is placed, the surface of this magnesium chloride or sodium chloride powder is baked and hardened with a burner, and then the crack peripheral part impregnated with the paste is heated with a burner, avoiding the paste part Then, after this peripheral edge becomes high temperature, heat from the upper surface until the magnesium chloride or sodium chloride powder liquefies, from the burner Removing liquefied magnesium chloride or sodium chloride by flames out.

Silicon oxide and alumina are excellent in fire resistance and also function as a reducing agent as a material for forming a fire resistant coating. Graphite improves lubricity. Examples of the material containing silicon oxide and alumina include zeolite, bidenite, saponite, smectite and the like, and the ratio of these is preferably silicon oxide: alumina: graphite = 70: 15-20: balance.

In addition, as an alloy component contained in the mold repair paste, Ni (nickel) is a main component, and at least Mn (manganese), W (tungsten), and Fe (iron) are added thereto. Further, in addition to a paste in which a plurality of metal powders are dispersed in a binder (solvent), a powder obtained by alloying two or more kinds of metal powders may be dispersed in the binder. .

An example is as follows. In addition, a ratio is the mass%.
Mn (manganese): 15% to 20% W (tungsten): 8% to 15% Fe (iron): 2% to 12% Co (cobalt): 7% or less Cr (chromium): 7% or less Si (Silicon): 7% or less C (Carbon): 2% or less B (Boron): 2% or less Ni (Nickel): Remainder

The reason why each component is set to the above ratio is as follows.
The general characteristics of Mn (manganese) are added to improve hardenability, wear resistance and strength. Moreover, the effect as a deoxidizer is exhibited and the embrittlement by S (sulfur) is prevented. However, if it is added in a large amount, it causes burning cracks or residual austenite, resulting in embrittlement. In the present invention, the above ratio is added mainly for the purpose of improving the wear resistance of the produced alloy.

  The general properties of W (tungsten) are added to create (structural) carbides, increase hardness and increase tempering resistance. In particular, the presence of Cr further increases tempering resistance, causes secondary hardening, and increases wear resistance. However, it becomes brittle when added in a large amount. In the present invention, the above ratio is added mainly for the purpose of improving the tempering resistance of the produced alloy.

  Fe (iron) is a quasi-base component in forming an alloy, and if it is too little or too much, the characteristics as an alloy cannot be exhibited.

  The general characteristics of Co (cobalt) are added to strengthen martensite, increase wear resistance and hardness at high temperatures, and improve hot strength retention. In the present invention, the above ratio is added mainly for maintaining the hot strength of the produced alloy.

  The general characteristics of Cr (chromium) are to create stable carbides and increase corrosion resistance and wear resistance. Carbides suppress the growth of crystal grains, promote carburization, improve hardenability, and improve oxidation resistance. Increase and improve toughness. In addition, composite carbides such as V, Mo, and W are produced, and the tempering resistance is increased. In the present invention, the above ratio is added mainly for the purpose of improving the wear resistance of the produced alloy.

  The general properties of Si (silicon) have a high deoxidation effect and increase the low temperature tempering resistance. If added in a large amount, the cementite becomes graphitized and becomes brittle, and the malleability is impaired. Further, addition of a small amount increases hardness and strength, increases oxidation resistance, and suppresses crystal grain growth due to heating. In the present invention, the above ratio is added mainly for the purpose of improving the oxidation resistance of the resulting alloy.

  A general characteristic of C (carbon) is to increase the quenching hardness by increasing the strain rate of martensite. Form carbides with Fe, Cr, Mo, V, etc. to increase strength. Increase tensile strength. As the amount of carbide increases, wear resistance increases. In the present invention, the above ratio is added mainly for the purpose of improving the tensile strength of the resulting alloy.

A general characteristic of B (boron) is that the hardenability is remarkably increased by addition of a small amount, but when it is excessively added, Fe ₂ B is generated and red brittleness is caused. Addition of a small amount increases cutting durability. Also, the eutectic carbide is reduced. In the present invention, the above ratio is added mainly for the purpose of refining the eutectic carbide of the produced alloy.

  Like Fe, Ni (nickel) is a key component in forming an alloy. Adding a small amount increases hardenability and toughness, but adding excessively produces austenite and becomes brittle. To do.

According to the mold repair method according to the present invention, it is possible to repair a crack with a simple operation, and there is no occurrence of problems such as second cracking after the repair.

The figure explaining an example of the metal mold repair method concerning the present invention The figure explaining the metallic mold repair method of patent documents 3 Photo showing the metal structure of the mold before repair Enlarged photo of Fig. 3 A photograph showing a state where a portion surrounded by a square in FIG. 3 is cut out and a part of the crack is repaired by the method according to the present invention. Photo of cutting the mold so that it covers the repaired part Photo showing the metal structure of the cut surface Enlarged view of FIG. A photograph explaining the content of Patent Document 3 that should be improved A diagram explaining the conventional mold repair procedure

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, as shown in FIG. 1 (a), the above-mentioned mold repair paste 4 is applied with a brush 3 around the crack 2 generated in the mold 1. The compounding example of the mold repair paste is shown in (Table 1).

Next, as shown in FIG. 1 (b), a solution for forming a refractory film 5 that does not allow gas to permeate the surface of the mold repair paste 4 is sprayed. As the solution, a solution obtained by adding silicon oxide, alumina, and graphite to alcohol is used. In addition, ceramic fibers can be added to these to increase fire resistance.

And as shown in FIG.1 (c), the powder 6 of magnesium chloride or sodium chloride is put on the refractory film 5 obtained by drying the said solution. The magnesium chloride or sodium chloride powder 6 functions as an oxidation inhibitor, and magnesium chloride having a low melting point (714 ° C.) is preferable to sodium chloride (800 ° C.).

When the magnesium chloride or sodium chloride powder 6 is placed, a weir 7 made of clay is formed on the outer portion, and flows outside when the magnesium chloride or sodium chloride powder 6 is melted in a later step. It is preferable not to do so.

Thereafter, as shown in FIG. 1 (d), the surface of magnesium chloride or sodium chloride 6 is baked and hardened with a burner 8 so that the powder is not scattered.

Thereafter, as shown in FIG. 1 (e), the mold repair paste 4 is avoided until the crack 2 enters, and the mold surface is heated until incandescent (about 1100 ° C.). This is to replenish the heat taken away from the surroundings when alloying the paste agent 4 later so that it can be alloyed.

Thereafter, as shown in FIG. 1 (f), magnesium chloride or sodium chloride 6 is heated to be liquefied, the surface of the mold repair paste 4 is coated, and further, the mold repair paste 4 is applied. Heat.

Thereafter, the whole is heated so as not to deheat from the base metal, and as shown in FIG. 1 (g), the flame of the burner 8 is squeezed and the burner 8 is moved so as to draw a circle. The work is completed by heating while skipping and finally heating as shown in FIG. 1 (g). The mold repair paste is melted by the heating so far, and penetrates into the crack and is alloyed.

Claims (2)

A mold repair paste containing an alloying component is placed on the surface of the mold so as to cover cracks generated in the mold, and then a refractory film that does not allow gas to permeate is formed on the surface of the mold repair paste. As a solution, a solution in which silicon oxide, alumina and graphite are added to alcohol is applied and dried to form a refractory film, and then a powder of magnesium chloride or sodium chloride is placed over the refractory film, After the surface of the magnesium or sodium chloride powder is baked and hardened with a burner, the crack peripheral part impregnated with the paste agent is heated with a burner while avoiding the paste part, and the peripheral part is heated to a high temperature. Heated from the top until the magnesium chloride or sodium chloride powder liquefied, and liquefied by a flame ejected from a burner Mold repairing method characterized by removing the magnesium or sodium chloride. The mold repair method according to claim 1, wherein the solid component of the mold repair paste is the following ratio (mass%).
Mn (manganese): 15% to 20% W (tungsten): 8% to 15% Fe (iron): 2% to 12% Co (cobalt): 7% or less Cr (chromium): 7% or less Si (Silicon): 7% or less C (Carbon): 2% or less B (Boron): 2% or less Ni (Nickel): Remainder