JP2007160390A - Paste agent for metallic mold repair - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paste agent for metallic mold repair capable of repairing cracks by a simple operation. <P>SOLUTION: The paste agent for metal mold repair has solid components comprising, by mass, 15 to 20% Mn (manganese), 8 to 15% W (tungsten), 2 to 12% Fe (iron), ≤7% Co (cobalt), ≤7% Cr (chromium), ≤7% Si (silicon), ≤2% C (carbon), ≤2% B (boron), and the balance Ni (nickel). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mold repair paste agent for repairing a crack portion such as a die casting mold.

As shown in Fig. 4, the general repair method when a crack occurs in a die-casting die is to 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.

JP-A-2005-97743 JP 2004-68047 A

  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.

  On the other hand, the contents disclosed in Patent Document 2 can improve various properties of the surface of the base material, but the coating agent itself does not become an alloy by heat treatment, so it should be applied to repair cracks in the mold. I can't.

  An object of the present invention is to provide a paste for repairing a mold, which is applied directly to a crack of a mold and then heated to diffuse inside the mold and be alloyed to fill the crack.

That is, the solid component of the paste for repairing a mold according to the present invention 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

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 increases. 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. Make carbide 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.

The general characteristic of B (boron) is that the hardenability is remarkably increased by addition of a small amount, but when it is added excessively, Fe ₂ B is produced 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 paste according to the present invention, a crack can be repaired by a simple operation, and no trouble such as second cracking occurs after the repair.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The following (Table 1) shows an example of blending the mold repair paste according to the present invention.

Next, a mold repair method using the above-mentioned mold repair paste will be described with reference to FIG.
First, the above-mentioned mold repair paste is applied around a crack portion generated in the mold.
Next, a decarburization inhibitor is sprayed on the surface of the mold repair paste, and salt (Nacl) is placed on the mold repair paste for the purpose of oxidation inhibition treatment.

  Thereafter, the surface of the salt is baked and hardened, and further, the portion of the paste for repairing the mold is avoided and heated until the surface of the base material becomes incandescent (about 1100 ° C.).

  Thereafter, the salt is heated to be liquefied, the surface of the mold repair paste is coated with the liquefied salt, and the mold repair paste is further heated. The mold repair paste is melted by the heating so far and penetrates into the crack and is alloyed.

  When it is confirmed that the mold repair paste is melted, it is heated to finish the outline of the last melted mold repair paste.

  FIG. 2 is a cross-sectional micrograph of the mold after repair, and FIG. 3 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).

  The above is an example of implementation, and a heat treatment method using a burner has been described as a repair method, but as a heating means, local heating using a high frequency, whole heating using a temper furnace, or whole heating using a vacuum furnace Etc. are also applicable.

  Further, in the examples, a paste in which a plurality of metal powders are dispersed in a binder (solvent) was used, but a powder obtained by alloying two or more metal powders and dispersed in the binder. It may be a

The figure explaining an example of the mold repair method using the paste agent for mold repair concerning the present invention Cross-sectional micrograph of the mold after repair Enlarged photo of Figure 2 A diagram explaining the conventional mold repair procedure

Claims (1)

After filling in the cracks generated in the mold, the mold repair paste becomes an alloy by heat treatment, and the solid component of the mold repair paste is the following ratio (mass%) A mold repair paste.
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