JP2010174326A - Surface reforming material for iron-based alloy, surface reforming method for iron-based alloy, and casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface reforming material with which the surface of an iron-based alloy can be reformed at a relatively low temperature, and to provide a surface reforming method. <P>SOLUTION: The surface reforming material having the fowllowing component ratios is dissolved in an epoxy resin and a thinner to obtain a paste. Then, the paste is applied on the surface of a mold subjected to a soft-nitriding treatment, and the resulting mold is subjected to a heat treatment. The component ratios are as follows, by mass: 6-10% iron (Fe); 24-40% nickel (Ni); 5-10% cobalt (Co); 5-10% chromium (Cr); 1.3-10% aluminum (Al); 3-10% silicon (Si); 15-25% manganese (Mn); ≤15% tungsten (W); 0.1-2% boron (B); ≤2% carbon (C); ≤3.2% molybdenum (Mo); and ≤1% titanium (Ti). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an iron-based alloy surface modifying material, an iron-based alloy surface modifying method, and a casting mold to which these are applied.

  Since the surface temperature of the die casting mold is repeatedly changed rapidly from 100 ° C. to 700 ° C. for each shot, a large number of heat checks are generated on the mold forming surface by thermal shock, and this progresses to cracks. When cracks occur, they are transferred to the surface of the product and cannot be used, and the life of the mold is shortened.

  For this reason, Patent Documents 1 and 2 have been proposed as techniques for improving the mold surface to make it difficult for cracks to occur, and Patent Documents 3 and 4 have been proposed as techniques for repairing the generated cracks. Yes.

  Patent Document 1 discloses a technique for forming a hard coating film of a TiAlN layer on a mold surface to impart resistance to melting damage and heat check.

In Patent Document 2, as a surface modification method for a cast iron sliding part that is not a mold, a high hardness layer in which AlN and FeAl ₃ are mixed is formed on the surface of the cast iron sliding part by aluminizing treatment. Has been proposed.

In Patent Documents 3 and 4, Mn (manganese): 15% to 20%, W (tungsten): 8% to 15%, Fe (iron): 2% to 12%, Co (cobalt): 7 %, Cr (chromium): 7% or less, Si (silicon): 7% or less, C (carbon): 2% or less, B (boron): 2% or less, Ni (nickel): paste containing the remainder, It is disclosed that the cracks are covered so that the surface is coated with an oxidation inhibitor, and then the paste is heated and melted to penetrate into the cracks to be alloyed.

JP-A-7-112266 Japanese Patent Application Laid-Open No. 8-176695 JP 2007-160390 A JP 2007-160392 A

Since the TiAlN layer disclosed in Patent Document 1 does not decompose up to 800 ° C., it has excellent heat resistance and is suitable for a casting mold. However, in order to form a TiAlN layer, advanced technology and expensive equipment are required, and the processing days are also long. Even if it is applied to a casting mold to extend the life of the mold, there are many problems such as schedule and cost. Further, the aluminizing treatment temperature disclosed in Patent Document 2 is desirably a high temperature at which iron-based nitride decomposes, but the upper limit of the treating temperature is around 600 ° C. without modification and deformation of the material. Therefore, it is not suitable for articles exposed to higher temperatures.
Further, it is considered that a small part is immersed in aluminum or a molten aluminum alloy by the method of Patent Document 2 and surface effect treatment is possible. However, large products and long objects are difficult to handle by the above method, and a more general method is desired.

On the other hand, in Patent Documents 3 and 4, it is necessary to process at a temperature exceeding 1000 ° C. in order to dissolve the paste and form an alloy. Processing at a high temperature exceeding 1000 ° C. not only makes the work difficult, but also deteriorates the environment, causes distortion in the mold, and increases the hardness in the vicinity of the crack to increase the hardness and become brittle. There is.

In order to solve the above problems, the surface modification material of the iron-based alloy according to the present invention includes Fe (iron), nickel (Ni), cobalt (Co), chromium (Cr), aluminum (Al), silicon (Si), It consists of manganese (Mn), tungsten (W), boron (B), carbon (C), molybdenum (Mo) and titanium (Ti).

Preferred component ratios are described below, and this is used in the form of a mixture (paste) by adding a resin (such as an epoxy resin) and an organic solvent (such as thinner).
Fe (iron): 6 mass% to 10 mass% Nickel (Ni): 24 mass% to 40 mass% Cobalt (Co): 5 mass% to 10 mass% Chromium (Cr): 5 mass% to 10 mass Aluminum (Al): 1.3 mass% or more and 10 mass% or less Silicon (Si): 3 mass% or more and 10 mass% or less Manganese (Mn): 15 mass% or more and 25 mass% or less Tungsten (W): 15 mass % Or less Boron (B): 0.1% by mass or more and 2% by mass or less Carbon (C): 2% by mass or less Molybdenum (Mo): 3.2% by mass or less Titanium (Ti): 1% by mass or less

The reason why each component is set to the above ratio is as follows.
Iron (Fe) is a quasi-base component in forming the alloy, and if it is too little or too much, it will not be possible to exhibit the properties as an alloy, so the above ratio is used.

Nickel (Ni) is a super heat-resistant alloy-forming material, and is a key component for alloy formation like Fe. Addition of a small amount increases hardenability and toughness, but when added in excess, austenite is formed and embrittles. Therefore, the above ratio is set.

  The general properties of cobalt (Co) 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 chromium (Cr) are the formation of stable carbides to increase corrosion resistance and wear resistance, and 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.

  Aluminum (Al) is added in the above proportion for the purpose of deoxidizing effect. Aluminum has a melting point of 660 ° C., the lowest temperature in this mixture, and the next lowest melting point is manganese at 1245 ° C. Therefore, it is considered that an eutectic alloy film based on aluminum is formed by the treatment of the present application. It is considered that the eutectic alloy film was formed on the surface of the iron-based alloy by adding aluminum having a low melting point instead of a mere metal compound, and the surface modification was made possible.

  The general properties of silicon (Si) have a high deoxidation effect and increase 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.

The general properties of manganese (Mn) 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 tungsten (W) 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.

As for the general characteristics of boron (B), hardenability is remarkably increased by addition of a small amount, but when added excessively, Fe ₂ B is generated and red hot 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.

  A general characteristic of carbon (C) 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.

Molybdenum (Mo) is added in the above proportion for the purpose of preventing brittleness by tempering.

Titanium (Ti) is added in the above proportion for the purpose of refining crystal grains.

The resin functions as a binder (bonding material) and may be either natural or synthetic resin. However, it is preferable to use a synthetic resin that has stable properties, is easily available, and is inexpensive. In particular, a thermosetting epoxy resin is preferable because it is hard after curing and strong against solvents.
The organic solvent is added to make the entire system liquid in order to apply the present material to the surface of the iron-based alloy.
Examples of the organic solvent include hydrocarbon type: for example toluene, alcohols: for example ethanol, ketone type: for example acetone, ester type: for example ethyl acetate, ether type: for example methyl cellosolve, halogen type: for example methylene chloride (dichloromethane) and the like. Although it is good, thinner which is an organic solvent developed for thinning the paint and lowering the viscosity is suitable for applying the material of the present application to the surface of the iron-based alloy, not drying too early or too late.
Thinner is an organic solvent that is an organic composite mixture. Components differ slightly depending on the manufacturer, but mainly toluene, and includes xylene, methanol, air ethanol, methyl acetate, ethylbenzene, and the like.

Moreover, the surface modification method of the iron-based alloy according to the present invention is a step 1 in which the surface of the iron-based alloy is hardened by a gas soft nitriding method, and in step 2, the surface of the iron-based alloy cured in step 1 is used. Then, the surface-modified material is applied, and in step 3, the iron-based alloy to which the surface-modified material is applied in step 2 is heat-treated in a non-oxygen atmosphere at an annealing temperature.
Annealing is a treatment in which the steel is sufficiently retained in the austenite structure state and gradually cooled in the furnace, and the austenite structure is an iron phase in a temperature range of 911 ° C. to 1392 ° C. with pure iron. Stainless steel (for example, SUS304) has a low temperature range and can form austenite at 700 ° C. or higher.

The surface modification method for an iron-based alloy according to claim 3 or 4, wherein the non-oxygen atmosphere uses a decarburization inhibitor or an oxidation inhibitor, or is a reducing atmosphere. To improve the surface of iron-based alloys.

The decarburization inhibitor is an antioxidant capable of preventing deoxidation of the slab surface being heated in a heating furnace, or an antioxidant containing a reducing agent. Antioxidants generally comprise oxides such as Cr ₂ O ₃ , anhydrous water glass, and acrylic resin components. The antioxidant containing a reducing agent, for example, an oxide such as _Cr 2 _{O 3,} anhydrous water glass, acrylic resin, boron (B), aluminum (Al), consisting of reducing components, such as SiC. As a decarburization inhibitor, an antioxidant containing a reducing agent is preferable because it has a greater deoxidation preventing effect on the slab surface than an antioxidant containing no reducing agent. However, water glass may be used instead of anhydrous water glass.
As the oxide, one or more selected from Al ₂ O ₃ , Cr ₂ O _{3, and} ZrO ₂ is the ferritic stainless steel slab side that accompanies oxidation with oxygen in the furnace atmosphere. It is preferable because decarburization at the end can be suppressed.
In addition, the reducing agent is one or more selected from Si, SiC, Al, B, and C. It is easy to obtain and inexpensive, and it is a slab caused by oxide scale when heated in a heating furnace. Before the decarburization at the side end proceeds, the reducing agent is preferable because it reduces the oxide scale and suppresses decarburization.
Further, it is more preferable to use B and SiC or B and Al as the reducing agent because decarburization accompanying the participation of the oxide scale at the end portion on the slab side can be almost completely suppressed and the amount of edge seam penetration can be minimized.

The oxidation inhibitor may be sodium chloride, and the reducing atmosphere may be that the atmosphere is replaced with nitrogen gas, helium gas, neon gas, argon gas, or a vacuum.

Further, the object of the present invention includes a casting mold whose cavity surface is modified by the above-described surface modification method of an iron-based alloy.

According to the surface modification material and the modification method for an iron-based alloy according to the present invention, a surface of a modified iron-based alloy member having excellent heat resistance and less heat cracking is obtained by a relatively low heat treatment temperature. be able to.

Sectional drawing of the apparatus which tests the amount of molten loss with respect to molten aluminum. Table and graph showing the relationship between the immersion time in molten aluminum and the amount of erosion. It is the photograph which shows the heat crack property evaluation test result after 500 cycles, (a) shows the case where only the soft nitriding treatment is performed, and (b) shows the case where the surface modification according to the present invention is performed after the soft nitriding treatment. It is the photograph which shows the heat crack property evaluation test result after 1000 cycles, (a) shows the case where only the soft nitriding treatment is performed, and (b) shows the case where the surface modification according to the present invention is performed after the soft nitriding treatment. (A) is a graph comparing the maximum crack depth when only soft nitriding is performed and when surface modification according to the present invention is performed after soft nitriding, (b) is when only soft nitriding is performed And a graph comparing the number of heat checks generated when surface modification according to the present invention was performed after soft nitriding.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of an apparatus for testing the amount of erosion with respect to molten aluminum. In this test apparatus, a crucible 3 is arranged in an outer container 2 containing a heater 1, and the molten aluminum 4 is held in the crucible 3. ing.

A rotating body 5 is disposed above the crucible 3, and 3 to 6 rod-shaped test pieces 6 can be suspended from the rotating body 5. In this example, a test piece not subjected to surface treatment, a test piece subjected to soft nitriding treatment, and a test piece subjected to soft nitriding treatment and further subjected to the surface modification method according to the present invention are attached, and a maximum of 240 rpm It is designed to rotate by dipping in the molten aluminum at a speed of.

General gas soft nitriding conditions were adopted for the soft nitriding treatment. Specifically, NH ₃ gas is added in an amount of 30 to 50% in a carburizing gas or nitrogen gas atmosphere such as a rapidly denatured gas (Endo Gas) or a pyrolysis gas of an organic solvent, and a temperature range of 550 to 600 ° C. And heated for 1 to 5 hours to allow nitrogen to penetrate and diffuse to form carbonitrides on the surface.

Here, in the surface modification method according to the present invention, the surface modification material shown in the following (Table 1) is applied to the surface of the test piece after the soft nitriding treatment, and further annealed in a non-oxygen atmosphere. Heat treatment at temperature.

FIG. 2 is a table and graph showing the relationship between the immersion time in the molten aluminum and the amount of erosion. From FIG. 2, the amount of erosion of the test piece that has not been subjected to any surface treatment is extremely large, and the amount of erosion is reduced by applying soft nitriding, and the amount of erosion is reduced by applying the surface treatment of the present invention. It can be seen that is significantly reduced.

FIG. 3 is a photograph showing the results of a heat crack property evaluation test after 500 cycles, where (a) shows only the soft nitriding treatment, and (b) shows the case where the surface modification according to the present invention is applied after the soft nitriding treatment. Indicates. FIG. 4 is a photograph showing the results of a heat crack property evaluation test after 1000 cycles, where (a) shows only the soft nitriding treatment, and (b) shows the surface modification according to the present invention after the soft nitriding treatment. Shows the case.

FIG. 5 (a) is a graph comparing the maximum crack depth when only soft nitriding is performed and when surface modification according to the present invention is performed after soft nitriding, and FIG. 5 (b) is only soft nitriding. 6 is a graph comparing the number of heat checks generated when the surface modification according to the present invention is performed after the soft nitriding treatment.

From FIG. 3 to FIG. 5, the number of heat checks generated is reduced to ¼ when the surface modification according to the present invention is performed after the soft nitriding treatment than when only the soft nitriding treatment is performed. It can also be seen that the maximum crack depth is also reduced to 1/4.

The iron alloy surface modification material according to the present invention can be used for surface modification of a member made of an iron alloy such as a casting mold.

DESCRIPTION OF SYMBOLS 1 ... Heater, 2 ... Outer container, 3 ... Crucible, 4 ... Molten aluminum, 5 ... Rotating body, 6 ... Test piece.

Claims (8)

Fe (iron), nickel (Ni), cobalt (Co), chromium (Cr), aluminum (Al), silicon (Si), manganese (Mn), tungsten (W), boron (B), carbon (C), An iron-based alloy surface modification material comprising molybdenum (Mo) and titanium (Ti). The iron-based alloy surface modifying material according to claim 1, wherein the ratio is as follows, and a resin and an organic solvent are added to form a mixture.
Fe (iron): 6 mass% to 10 mass%, nickel (Ni): 24 mass% to 40 mass%, cobalt (Co): 5 mass% to 10 mass%, chromium (Cr): 5 mass% 10 mass% or less, aluminum (Al): 1.3 mass% or more and 10 mass% or less, silicon (Si): 3 mass% or more and 10 mass% or less, manganese (Mn): 15 mass% or more and 25 mass% or less, Tungsten (W): 15 mass% or less, boron (B): 0.1 mass% or more and 2 mass% or less, carbon (C): 2 mass% or less, molybdenum (Mo): 3.2 mass% or less, titanium ( Ti): 1 mass% or less. A method for modifying the surface of an iron-based alloy comprising the following steps 1 to 3.
Process 1
The surface of the iron-based alloy is hardened by a gas soft nitriding method.
Process 2
Fe (iron), nickel (Ni), cobalt (Co), chromium (Cr), aluminum (Al), silicon (Si), manganese (Mn), tungsten on the surface of the iron-based alloy cured in step 1 A surface modification material made of (W), boron (B), carbon (C), molybdenum (Mo), and titanium (Ti) is applied.
Process 3
The iron-based alloy coated with the surface modifying material in step 2 is heat-treated at an annealing temperature in a non-oxygen atmosphere. The iron-based alloy surface modification method according to claim 3, wherein the surface-modified material has the following component ratios, and a resin and an organic solvent are added to form a mixture. Surface modification material.
Fe (iron): 6 mass% to 10 mass%, nickel (Ni): 24 mass% to 40 mass%, cobalt (Co): 5 mass% to 10 mass%, chromium (Cr): 5 mass% 10 mass% or less, aluminum (Al): 1.3 mass% or more and 10 mass% or less, silicon (Si): 3 mass% or more and 10 mass% or less, manganese (Mn): 15 mass% or more and 25 mass% or less, Tungsten (W): 15 mass% or less, boron (B): 0.1 mass% or more and 2 mass% or less, carbon (C): 2 mass% or less, molybdenum (Mo): 3.2 mass% or less, titanium ( Ti): 1 mass% or less. The surface modification method for an iron-based alloy according to claim 3 or 4, wherein the non-oxygen atmosphere uses a decarburization inhibitor or an oxidation inhibitor, or is a reducing atmosphere. To improve the surface of iron-based alloys. 6. The surface modification method for an iron-based alloy according to claim 5, wherein the oxidation inhibitor is sodium chloride. 6. The method of modifying a surface of an iron-based alloy according to claim 5, wherein the reducing atmosphere replaces the atmosphere with nitrogen gas, helium gas, neon gas, or argon gas, or makes a vacuum. For surface modification of aluminum alloys. A casting mold, wherein a cavity surface is modified by the surface modification method for an iron-based alloy according to any one of claims 3 to 7.