PH12013000066A1

PH12013000066A1 - Metal mold repair method

Info

Publication number: PH12013000066A1
Application number: PH12013000066A
Authority: PH
Inventors: Michiharu Hasegawa; Noriyuki Miyazaki; Masafumi Nakamura; Naoji Yamamoto; Kazuo Ueda
Original assignee: K And I Inc
Priority date: 2013-02-21
Filing date: 2013-02-21
Publication date: 2015-02-23

Abstract

A repair paste agent containing components that become an alloy is directly applied to a surface of a metal mold having a crack so as to cover the crack part, then the surface of the repair paste agent is coated with a solution which is made by adding silicone oxide (SiO2), alumina (AI2O3) and graphite (C) tp alcohol, and dry the solution to form a fireproof film which does not transmit gas on the surface of the repair paste agent, then a powder of Magnesium chloride (Mgcl2) or Sodium chloride (Nacl) is deposited on the surface of the film, and the surface of Magnesium chloride (Mgcl2) or Sodium chloride (Nacl) is baked, and the base metal surface where os outside penumbra of the crack avoiding the part which the paste impregnated by a burner, after the temperature of the penumbra become high, then heat the powder of the Magensium chloride or Sodium chloride until the powder liquefies, and remove the Magnesium chloride or Sodium chloride liquefied by a flame spouting out from the burner.

Description

[Document Name] Specification [Title of the Invention] Metal Mold Repair Method [Field of the Invention]

[0001]

The present invention relates to a metal mold repair method for repairing cracks in die-casting molds, etc. [ Background Art]

[0002]

In a common method for repairing a die-casting metal mold upon a crack occurring therein, as shown in Figure 10, a large part of the metal mold surrounding the crack is removed by means of a cutting tool, the part where the removal has been performed is subjected to build-up welding, and then subjected to surface finishing.

[0003]

As an improvement of the aforementioned common repair method, Patent

Document 1 discloses performing build-up welding while melting powder for metal mold repair by means of a plasma arc. As the powder for metal mold repair, ]

Patent Document 1 proposes an alloy powder consisting of a total 10 wt% or less of a carbide consisting of at least one of NbC, VC and WC, and the balance of a

Ni-Cr-Mo-based heat resistant alloy.

[0004]

Also, Patent Document 2 discloses applying a coating material, which has been prepared by dispersing metal powder in a solvent, to a base metal and heating the base metal to diffuse the metal in the base metal, and more specifically, it proposes: selecting at least one of Cu and Mn as an element to be diffused in the case where the base metal is a Zn alloy; selecting Cr in the case where the base ] metal is an Fe alloy, selecting at least one of Al, Cr, Ni and N in the case where the base metal is a Ti alloy; and selecting Ni in the case where the base metal is a

Cu alloy.

[0005]

As shown in Figure 2, Patent Document 3 discloses a metal mold repair method, in which a repair paste agent containing components that become an alloy is directly applied to a surface of a metal mold having a crack so as to cover the cracked part. A decarburization preventive layer is formed on the surface of the metal mold repair paste agent to prevent carbon from being lost by heating, and the surface of the repair paste agent is coated with an oxidation inhibitor (Nacl).

Furthermore, the repair paste agent is made to penetrate the inside of the crack by heating and become an alloy, thereby filling up the crack.

[0006]

Figure 3 shows a metal mold before repair, and Figure 4 shows a close-up of the part enclosed with the quadrangle shown in Figure 3. It can be seen from these photographs that a crack occurs in such a manner that it intersects with the down stroke of the reversed letter P on the metal mold surface.

[0007]

Figure 5 is a photograph illustrating a state in which the part enclosed with the quadrangle shown in Figure 3 has been cut out and the crack has been repaired by means of a method according to Patent Document 3, and it can be seen from this photograph that the crack disappears from the surface at the repaired part.

[0008]

Figure 6 is a photograph of a metal mold cut in such a manner that the cut ] intersects with the repaired part, Figure 7 is a microgram illustrating the cut surface, and Figure 8 is a close-up photograph of Figure 7. It can be seen from these photographs that: the metal mold repair paste agent melts and penetrates the inside of the crack and, after cooling, it becomes an alloy. Also, it partly diffuses at the boundary with the metal mold.

[0009]

Incidentally, the alloy is formed so that it reaches the part of the crack having a 1 width of 0.1 mm, the thickness of the alloy layer formed on the metal mold surface ]

was 0.15 mm, the hardness of the alloy part of the surface was HV356 (36HRC), the hardness of the alloy part in the crack was HV324 (33HRC), and the hardness of the base metal was HV637 (57HRC). [Prior Art]

[0010] [ Patent document] [ Patent document 1] Japanese Patent Laid-Open No. 2005-97743 [ Patent document 2] Japanese Patent Laid-Open No. 2004-68047 [ Patent document 3] W02007/069409 [ Disclosure of Invention] J [ Problems Solved by the Invention]

[0011]

In the method disclosed in Patent Document 1, when a crack is repaired, as in the conventional method, a part of the metal mold including the crack is cut out, and ] build-up welding is performed on the part where the cutting has been performed.

Where build-up welding is performed what is called secondary cracking, i.e., a crack occurring in a part that is somewhat outside the part where the build-up welding has been performed, is prone to occur due to a thermal effect caused by the welding.

[0012]

Also, in the conventional method, in some cases, a cutting tool cannot be used depending on the part where a crack occurs. In this case it takes a lot of trouble and time for repair.

[0013]

Meanwhile, the content disclosed in Patent Document 2 makes it possible to ] improve the properties of the base metal surface, but cannot be applied to ] repairing a crack in a metal mold because the coating material itself does not become an alloy by means of thermal treatment.

The method disclosed in Patent Document 3 is superior to other prior arts.

However, the effect of the decarburization preventive layer is insufficient when the salt coating comes off; the paste is oxidized and, as shown in Figure 9, an alloy may fail to be formed. [ Means For Solving Problems]

[0015] in the metal mold repair method according to the present invention, a repair paste agent containing components that become an alloy is directly applied to the surface of a metal mold having a crack so as to cover the cracked part, then the surface of the repair paste agent is coated with a solution which is made by adding silicon oxide (SiO2), alumina (Al203) and graphite (C) to alcohol, and on drying forms a fireproof film which does not transmit gas on the surface of the repair paste agent, then a powder of Magnesium chloride (Mgcl2) or Sodium chloride (Nacl) is spread on the surface of the film, and the surface of Magnesium chloride (Mgcl2) or Sodium chloride (Nacl) is baked. The base metal surface of the mold which is not adjacent to the cracked part, and avoiding the part coated with the repair paste, is heated with the burner until it reaches a high temperature.

Then the Magnesium chloride or Sodium chloride powder is heated until it liquefies, and the liquid Magnesium chloride or Sodium chloride is removed with the circular motion of a compressed burner flame.

[0016]

As materials forming a fireproof film, Silicon oxide and Alumina are superior in fireproof characteristics and function as a reducing agent. Also lubrication characteristics improve by adding graphite. Zeolite, Bidenite, Saponite are exemplified as materials which include silicon oxide and alumina. The preferred ratio of these is Silicon oxide: Alumina: Graphite=70: 15~20: balance. i

[0017] i

Alloy components contained in the metal mold repair paste agent include Ni ] (nickel) as a main component, with the addition of at least Mn (manganese), W

(tungsten) and Fe (iron). Also, other than an agent prepared by dispersing a plurality of metal powders in a binder (solvent) to be a paste, an agent prepared by reducing an alloy formed of two or more kinds of metal to a powder and dispersing it in a binder may used.

[0018]

The alloy components are specifically indicated below. The percentages mean mass%.

Mn (manganese): no less than 15% and no more than 20%

W (tungsten): no less than 8% and no more than 15%

Fe (iron): no less than 2% and no more than 12%

Co (cobalt): no more than 7%

Cr (chrome): no more than 7%

Si (silicon): no more than 7%

C (carbon): no more than 2%

B (boron): no more than 2%

Ni (nickel): balance.

[0019]

The above percentages of the components are determined for the following reasons.

Mn (manganese) is added because it has the general properties of enhancing hardenability, wear resistance and strength. Also, Mn exerts an effect as a deoxidizing agent, and prevents brittleness caused by S (sulfur). However, when it is added in a large amount, a hardening crack occurs or retained austenite is generated, thereby causing brittleness. In the present invention, the above-indicated percentage of Mn is added with the main aim of enhancing the wear resistance of an alloy to be formed.

[0020] !

W (tungsten) is added because it has the general properties of. producing a (structural) carbide, enhancing hardness, and increasing tempering resistance. ;

In particular, by the existence of Cr, tempering resistance is further increased, causing secondary hardening, thereby increasing wear resistance. However, addition of a large amount of W results in brittleness. In the present invention, the above-indicated percentage of W is added with the main aim of enhancing the tempering resistance of an alloy to be formed.

[0021]

Fe (iron) is a semi-essential component for alloy formation, and its properties cannot be exerted when the amount of Fe is overly large or small, and accordingly, the above-indicated percentage is employed.

[0022]

Co (cobalt) is added because it has the general properties of strengthening a martensitic matrix, increasing wear resistance, and hardness at high temperatures, and enhancing hot strength retention. In the present invention, the above-indicated percentage of Co is added with the main aim of retaining the hot strength of an alloy to be formed.

[0023]

Cr (chrome) has the general properties of: producing a stable carbide, thereby increasing corrosion resistance and wear resistance, and carbide suppresses the growth of crystal grains, promotes carburizing, enhances hardenability, increases oxidation resistance and improves toughness. Also, Cr produces a complex carbide together with V, Mo or W, etc., thereby increasing tempering resistance. In the present invention, the above-indicated percentage of Cr is added with the main aim of enhancing the wear resistance of an alloy to be formed.

[0024]

Si (silicon) has the general properties of having a high deoxidation effect and i increasing tempering resistance at low temperatures. The addition of a large amount of Si results in cementite graphitization, which causes brittleness or ] hinders castability. Also, the addition of a small amount of Si increases hardness and strength, increases oxidation resistance, and suppresses the growth of crystal grains due to heating. In the present invention, the above-indicated percentage of Si is added with the main aim of enhancing the oxidation resistance of an alloy to be formed.

[0025]

C (carbon) has the general properties of raising the distortion factor of martensite, thereby increasing hardening hardness. It produces a carbide together with Fe,

Cr, Mo or V, etc., thereby increasing strength. It increases tensile strength. As the amount of carbide is increased, wear resistance increases. In the present invention, the above-indicated percentage of C is added with the main aim of enhancing the tensile strength of an alloy to be formed.

[0026]

B (boron) has the general properties of drastically increasing hardenability when it is added in only a minute amount, while generating Fe,B thereby causing red i shortness when it is added in an excessive amount. The addition of a small amount of B increases durability for cuts. Also, it refines the eutectic carbide.

In the present invention, the above-indicated percentage of B is added with the J main aim of making finer the eutectic carbide in the alloy.

[0027]

Ni (nickel), as with Fe, is an essential component for alloy formation, and addition of a small amount of Ni increases hardenability and toughness, but the addition of an excessive amount of Ni generates austenite, causing brittleness, and accordingly, the above-indicated percentage is employed. [ Effects of the Invention]

[0028] ;

According to the metal mold repair method of the present invention, it is possible to repair cracks with simple work, and in addition, avoid problems such as secondary cracking from occurring after repair. ] [ Brief Description of the Drawings] ;

[0029] [ Fig 1] Afigure which explains an example of the metal mold repair method of the present invention. [ Fig 2] A diagram describing an example of a metal mold repair method according to Patent Document 3. [ Fig 3] A photograph illustrating the metal texture of a metal mold before repair. [ Fig 4] A close-up photograph of Figure 3. [ Fig 5] A photograph illustrating a state in which the part enclosed by a quadrangle in Figure 3 is cut out and a cracked part is repaired by a method according to Patent Document 3. [ Fig 6] A photograph in which a metal mold is cut in such a manner that the cut intersects with a repaired part. [ Fig 7] A microgram illustrating the metal texture of a cut surface. [ Fig 8] A close-up photograph of Figure 7. : [ Fig 9] A photograph which explains the nature of the problem to be improved over Patent Document 3. [ Fig 10] A diagram describing a conventional metal mold repair procedure. [ Best Mode For Carrying Out Invention]

[0030]

An embodiment of the present invention will be described based on the referenced drawings.

First, as shown in Figure 1 (a), using brush 3, the aforementioned metal mold repair paste agent 4 is applied to a metal mold 1 with the part of the metal mold i having a crack 2 determined as the center. A blending example of the metal mold repair paste agent 4 is indicated in (Table 1). J

[0031] 1 [table 1] !

Ce em eae 300g ]

Mass :

Jorn || wes

[0032]

Then as shown in Figure 1 (b), the surface of the repair paste agent 4 is coated with a solution which is made by adding silicon oxide (SiO2), alumina (Al203) and graphite (C) to alcohol, and the solution dries to form a fireproof film 5 which does 1 not transmit gas on the surface of the repair paste agent 4.

In addition, it is possible to add a ceramic fiber for improving the fireproof characteristics. 1

[0033] }

And as shown in Figure 1 (c), deposit a powder 6 of Magnesium chloride (Mgc!2) / or Sodium chloride (Nacl) on the surface of the film 5, the powder 6 of Magnesium 1 chloride (Mgcl2) or Sodium chloride (Nacl) functions as an oxidation inhibitor The 1 melting point of the magnesium chloride is 714 degrees Celsius, the melting point of sodium chloride is 800 degrees Celsius, thus magnesium chioride is more preferable.

[0034]

When magnesium chloride powder 6 or sodium chloride powder 6 is deposited on the surface of the film 5, it is preferable to provide barriers 7 to prevent the liquefied powder from flowing out to the surrounding area.

[0035]

Subsequently, as shown in Figure 1 (d), the surface of magnesium chloride powder 6 or sodium chloride powder 6 is baked by burner 8, to prevent the powder 6 from being scattered.

[0036]

And as shown in Figure 1 (e), the base metal surface is heated to a white heat (approximately 1100°C) except for the part coated with the metal mold repair paste agent.

The reason is because it allows the paste 4 to become an alloy even if heat is taken away from the surrounding area.

[0037]

Subsequently, as shown in Figure 1 (f), the powder 6 is heated until it liquefies, ] and the surface of the metal mold repair paste agent 4 is coated with the liquefied powder 6, and furthermore, the metal mold repair paste agent 4 is heated. 1

[0038]

Then the whole matrix is heated so that heat does not escape from the metal mold, and as shown in Figure 1 (g), the surface of the metal mold is heated while removing impurities by compressing the flame of burner 8 and moving burner 8 in a circular motion. Finally, as shown in Figure 1 (h), the work is finished by ] performing finish-heating. ;

The metal mold repair paste agent 4 is melted by means of the heating ] performed so far, penetrates the inside of the crack 2 and becomes an alloy. ;

Claims

[ Document name ] Claims

[Claim 1] A metal mold repair method comprising: a repair paste agent containing components that become an alloy is directly applied to a surface of a metal mold having a crack so as to cover the cracked part, then the surface of the repair paste agent is coated with a solution which is made by adding silicon oxide (SiO2), alumina (AI203) and graphite (C) to alcohol, and the solution dries to form a fireproof film which does not transmit gas on the surface of the repair paste agent, then a powder of Magnesium chloride (Mgci2) or Sodium chloride (Nacl) is j deposited on the surface of the film, and the surface of Magnesium chloride (Mgcl2) or Sodium chloride (Nacl) powder is baked. The base metal surface of the mold which is not adjacent to the cracked part, and avoiding the part coated with the repair paste, is heated with the burner until it reaches a high temperature. Then the Magnesium chloride or Sodium chioride powder is heated until it liquefies, and the liquid Magnesium chloride or Sodium chloride is removed with the circular motion of a compressed burner flame.
[Claim 2] A metal mold repair method according to claim 1, wherein solid components of the metal mold repair paste agent are contained according to the following percentages (mass %): Mn (manganese): no less than 15% and no more than 20% W (tungsten): no less than 8% and no more than 15% Fe (iron): no less than 2% and no more than 12% Co (cobalt): no more than 7% Cr (chrome): no more than 7% Si (silicon): no more than 7% C (carbon): no more than 2% B (boron): no more than 2% _

Ni (nickel): balance. * 1