JP2002060895A - Member for molten nonferrous metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for molten metal which is used for melting or casting equipment for manufacturing products of nonferrous metal, such as aluminum alloy, zinc alloy and magnesium alloy, and has excellent erosion resistance to these molten alloys and can be used safely. SOLUTION: The member for molten nonferrous metal can be manufactured by previously forming, by nitriding, a nitrogen-enriched layer in the surface layer part of a steel material having a chemical composition consisting of, by weight, 0.95-1.5% C, 0.1-0.4% Si, 0.2-0.5% Mn, 3.0-5.0% Cr, 4.5-9.5% Mo, 1.5-4.5% V 1.5-7.0% W and the balance Fe with inevitable impurity elements and then immersing the material in Cr-containing molten salt to convert the nitrogen-enriched layer into a layer containing Cr nitride or carbonitride and form a coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member which is used for melting or casting equipment for manufacturing non-ferrous metal products such as aluminum alloys, zinc alloys, magnesium alloys and the like, and has excellent erosion resistance to molten alloys thereof.

[0002]

2. Description of the Related Art As a non-ferrous metal melt member, there are various members such as a gas injection pipe, a stalk, a sprue bush, a wrought sleeve, a die-cast sleeve, a die-casting mold and its insert, and a pin. For these members, depending on the application, cast iron materials, tool steel materials, etc.
Alternatively, they are used after nitriding or forming a coating layer. Furthermore, in recent years, the application of sialon ceramics to some applications has been expanding.

[0003] As an example of a molten metal member having a coating layer formed on the surface and having the same application as the present invention, JP-A-49-54229 discloses a composite oxide film on the surface of an iron-based material containing Cr and Al. A formed casting tool is disclosed.

Further, a technical paper (Surface Technology, Vol. 4)
6, No. 12, 1995, p. 1119 to 1124)
After nitriding the surface layer of various steel materials,
A technique of forming a coating layer of a nitride or carbonitride of Cr by immersing in a molten salt containing r powder is disclosed. Specifically, carbon steel (S45C), alloy tool steel (SKD61, SKD11), high-speed steel (SKH5
1), stainless steel (0.65% C-13.5% Cr-
After nitriding the surface portion of 0.3% Mo), the nitride layer is changed to a nitride layer of Cr or a coating layer containing carbonitride (Cr- (C, N)) to thereby provide wear resistance and seizure resistance. And improvement of oxidation resistance. It is reported that the durability of the mold can be greatly improved by using the aluminum die-casting insert, the aluminum high-pressure casting pin and the bush.

[0005]

When a conventional cast iron material, tool steel material, or the like is used in a non-ferrous metal melt member without any treatment, it reacts with the non-ferrous metal melt, gradually erodes and melts, and has dimensional accuracy. In addition to the inconvenience, there is a drawback in that Fe as the main component dissolves in the molten metal and deteriorates the properties of the cast product. In addition, even when the coating layer is formed, although the reaction with the non-ferrous metal melt is suppressed, a micro crack is generated in the coating layer by repeated use, and a minute portion of the coating layer is peeled off,
The exposed portion of the base material reacts with the molten non-ferrous metal, resulting in erosion. Furthermore, Sialon ceramics are not suitable for molten metal members because they do not react with the molten metal, and satisfactory results have been obtained depending on the application. However, there is a drawback that the material does not essentially exceed the range of the ceramic material and is more fragile than the metal material, so that it is easily broken and difficult to handle.

In order to solve the above problem, Japanese Patent Application Laid-Open No.
In addition to JP-A-9-54229, various heat-, corrosion-, and erosion-resistant members having a coating layer formed on the surface of an iron-based material have been provided. Also, in the above technical paper, the nitride or carbonitride (Cr- (C, N)) of Cr is formed on the surface of the steel material.
By forming a coating layer of abrasion resistance, seizure resistance,
It has been shown that oxidation resistance is improved. Also in the present invention, in order to solve the above-mentioned problems, an object of the present invention is to provide a member for a non-ferrous metal melt that can be used safely by using a steel material as a base material, further improving durability.

[0007]

According to the present invention, as shown in the enlarged explanatory view of the section of the surface layer portion of the molten metal member of the present invention shown in FIG. 1, the chemical components are C 0.95 to 1.5% by weight and Si 0 .1 to
0.4%, Mn 0.2-0.5%, Cr 3.0-
5.0%, Mo 4.5-9.5%, V 1.5-4.0.
After forming a nitrogen-enriched layer by nitriding in advance on the surface layer of the steel material 2 containing 5%, W 1.5 to 7.0%, balance Fe and inevitable impurity elements, immersion in a molten salt containing Cr This is a non-ferrous metal melt member in which the coating layer 1 is formed by changing the nitrogen-enriched layer to a layer containing Cr nitride or carbonitride.

In the course of the research of the present invention, in order to secure the adhesion and the erosion resistance of the coating layer, the surface layer portion of the steel material base material having the chemical components defined by the present invention is preliminarily nitrided, and then Cr It has been found that it is effective to immerse in a molten salt containing Cr to form a coating layer containing Cr nitride or carbonitride. That is, it is disclosed in the above-mentioned technical paper that this coating layer is excellent in wear resistance, seizure resistance, and oxidation resistance. It has been found that when the steel material as the base material is used as the base material, it is particularly excellent.

Generally, when the molten metal member is melted, the coating layer is subjected to a thermal stress load generated by rapid heating or cooling when immersed in or taken out of the molten metal.
It is considered that fine cracks and peeling occur, and the molten metal enters the cracks and peeling parts, starts to erode the base material, and eventually leads to large melting damage. The non-ferrous metal melt member of the present invention has good adhesion since the coating layer is metallically bonded to the underlying steel material base material due to the forming process. Furthermore, by limiting the chemical composition of the steel material base material, the coating layer itself is dense and strong. As a result, cracks and peeling are unlikely to occur, and melting damage due to invasion of the molten metal is unlikely to occur, so that the molten metal member can be used safely even when it comes into contact with the non-ferrous metal molten metal.

[0010] The surface layer of a steel material as a base material is made of Cr.
To form a coating layer containing nitride or carbonitride of
A nitrogen-enriched layer is previously formed on the surface layer by nitriding. Thereafter, the base material having the nitrogen-enriched layer is immersed in a molten salt containing Cr to change into a coating layer containing a nitride or carbonitride of Cr. A high-speed steel-based material is used for the steel material used as the base material, and the reasons for limiting the chemical components are as follows.

C strengthens the matrix of the steel material base material and combines with alloying elements such as Cr, Mo, V, and W to crystallize or precipitate various carbides of high hardness, so that it can be used even at high temperatures. Necessary to maintain a tough and hard matrix.
Further, the generated carbides also combine with nitrogen to form carbonitrides, which serve as a nitrogen storage source necessary for the surface layer. Further, as the most important feature of the present invention, C is effective for forming a dense and tough covering layer.

Thus, the content of C is 0.1% by weight.
95% to 1.5%. When the content is less than 0.95%, carbide is insufficient and the base material is softened. Furthermore, since microscopic voids are generated in the coating layer and the coating layer is not dense, the molten metal invades the voids and the coating layer is easily broken,
The erosion resistance decreases. If the content exceeds 1.5%, the effect is saturated, and the amount of carbides becomes excessive, so that the toughness of the base material is lowered.

Si and Mn each have a deoxidizing effect. Further, Mn has an effect of fixing S contained in the steel material to MnS and fixing the same. As a result, the weight ratio of Si normally contained in the high-speed steel-based material is set to 0.1 to 0.1% Si, respectively.
4% and Mn 0.2 to 0.5%.

[0014] Cr strengthens the matrix of the steel material base material and combines with C to form a Cr carbide, thereby improving wear resistance, corrosion resistance and heat resistance. In addition, it is easily combined with nitrogen by the nitriding treatment, and serves as a nitrogen storage source for forming a coating layer containing nitride or carbonitride of Cr. The content of Cr is preferably 3.0 to 5.0% by weight. If it is less than 3.0%, the reinforcement of the matrix is not sufficient, and if it exceeds 5.0%, it becomes excessive and saturated, and the abrasion resistance tends to decrease.

Mo strengthens the matrix of the steel material base material and combines with C like Cr and W to form carbides.
Improves wear resistance. Further, it is easily bonded to nitrogen by the nitriding treatment, and becomes a storage source of nitrogen like Cr. Further, the coating layer is finely densified, so that the above-mentioned coating layer is hardly cracked or peeled, and the base material of the steel material is hardly melted. The content of Mo is 4.5 to 9.5% by weight.
When it is less than 4.5%, the above-mentioned effects cannot be obtained, and 9.5 is obtained.
%, The effect saturates.

V forms strong bonds with C and N to form carbides and nitrides. These compounds strengthen the matrix of the steel material base material and significantly improve the wear resistance. In addition, it becomes a storage source of nitrogen like Cr and Mo. Further, the coating layer is finely densified, so that cracking and peeling of the coating layer are less likely to occur, and that the base material of the steel material is hardly melted. V
Is 1.5 to 4.5% by weight. 1.5%
When the content is not enough, the above-mentioned effects cannot be obtained. When the content exceeds 4.5%, the effect is saturated, and the amount of C dissolved in the matrix of the base material is reduced to soften the base material.

W, like Mo, has the effect of strengthening the base material matrix, forming carbides, improving wear resistance, and serving as a nitrogen storage source. The W content is 1.5 to 7.0% by weight. When it is less than 1.5%, sufficient effect cannot be obtained,
If it exceeds 7.0%, the effect is saturated.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to form a nitrogen-enriched layer on the surface layer of the steel material of the present invention by nitriding, a commercially available molten salt bath method, for example, a trade name Tuftlite (trade name: Nihon Parkerizing Co., Ltd.) )), By a general gas nitriding method or the like. The depth of the nitrogen-enriched layer is preferably set to 100 to 200 μm. Further, in order to immerse the nitrogen-enriched layer in a molten salt containing Cr and change it into a coating layer containing a nitride or carbonitride of Cr, a commercially available molten salt bath method, for example, a trade name D
By immersing in a bath composed of metallic Cr powder and a low-temperature molten salt by the CN process (executor: Dowa Mining Co., Ltd.), Cr is penetrated and diffused into the nitrogen-enriched layer of the steel material. The thickness of the obtained coating layer depends on the application, but is 5 to 5.
It is about 15 μm.

[0019]

EXAMPLES Example 1 The test pieces of the steel materials shown in Table 1 were examined for the erosion resistance to the molten aluminum alloy. The test piece was a round bar having a diameter of 10 mm and a length of 100 mm. The formation of the coating layer is performed by setting the depth of the nitrogen-enriched layer to approximately 150 μm by a gas nitriding method, and then performing the DCN process (implemented by Dowa Mining Co., Ltd.)
As a result, the nitrogen-enriched layer was changed to a coating layer containing nitride or carbonitride of Cr. The thickness of the coating layer of each test piece is 7 to
It was 10 μm.

[0020]

[Table 1]

Example Test Piece No. No. FIG. 2 shows the result of line analysis of the cross section of the surface layer No. 1 by EPMA.
In the portion of the coating layer, C, Cr, and N are increased from the portion of the steel material base material, and it is speculated that a coating layer containing nitride or carbonitride of Cr is formed. Other elements F
e, Mo, V, and W have a gradually decreasing tendency as the base material shifts to the coating layer. SE of surface section
The result of observation of the M image (not shown) is shown in Example No. 1 and No. 1 The coating layer of Comparative Example No. 2 was dense and hardly had microscopic voids. 3 and No. 3 In the coating layer No. 4, microscopic voids having a size of about 0.2 to 0.8 μm were scattered.

The test apparatus of FIG. 3 was used for the test pieces of Examples and Comparative Examples shown in Table 1 in the case of a steel material base material without a coating layer and the case of forming a coating layer, respectively.
The erosion resistance test for the molten aluminum alloy was performed. Each test piece was attached to the periphery of a disk-shaped test piece holding plate 5 by immersing a portion up to 50 mm from the tip into an aluminum alloy melt 4 like one test piece 3 showing an example of attachment. Was. Aluminum alloy held at 720 ° C (A
DC12) The test piece was immersed in the molten metal 4 and the time required for each test piece to start melting was examined. The start of erosion was defined as the point at which the diameter of the test piece decreased by 1 mm or more due to erosion. Table 1 also shows the time from the immersion of each test piece to the start of erosion.

From these results, it can be seen that the test piece of the example is a material that is less likely to be damaged by erosion than the comparative example even in the base material state where no coating layer is formed, but contains Cr nitride or carbonitride. It became clear that the formation of the coating layer dramatically improved the erosion resistance to the molten aluminum alloy.

Example 2 Example No. 1 in Table 1 Using the same material as the two test pieces as a base material, the same coating treatment was performed, and an aluminum die-casting mold casting pin was prototyped. The outline of the cast-in pin has the shape shown in FIG. 4, and is 25 mm in outer diameter of the mounting base 6, 15 mm in outer diameter of the cast-in tip 7, and 260 mm in length a.
The inside is hollow (not shown) for supplying a coolant. The comparative example is a tool steel which has been conventionally used. 4 The same material as the test piece (SKD61) was used, and only the nitriding treatment was applied to the surface layer.

As a result of test use, the cast-in pin of the present invention was subjected to 25,000 shots of die casting, but no fine damage to the surface due to erosion was observed.
It seemed that further use was possible. This is considered to be because the coating layer is dense and sound as described above. On the other hand, the cast-in pin of the comparative example used 5,000 shots, and fine damage due to erosion was observed on the surface.

Although the above embodiments are results for molten aluminum alloys, the invention is not limited to these embodiments and is applicable to other uses related to non-ferrous metal melts such as zinc alloy melts, magnesium alloy melts, sprue bushes, and molds. Is also expected to exhibit the same effect.

The non-ferrous metal melt member of the present invention can be obtained by limiting the contents of C and alloying elements in a steel material base material.
Since the coating layer containing the nitride or carbonitride of Cr has almost no microscopic voids and is formed densely, it is sound for non-ferrous metal melt members and has excellent erosion resistance. I have. Further, since the erosion resistance is good, the base metal component does not melt into the molten metal, and the quality of the non-ferrous metal casting product is improved. These greatly contribute to improving the efficiency of maintenance work of the melting or casting equipment for manufacturing non-ferrous metal products, reducing costs, and improving the quality of non-ferrous metal products.

[Brief description of the drawings]

FIG. 1 is an enlarged explanatory view of a cross section of a surface portion of a member for molten metal of the present invention.

FIG. 2 shows a test piece of Example of the present invention. E of surface section of 1
It is a figure which shows the line analysis result by PMA.

FIG. 3 is a schematic view of a erosion test apparatus used for the test of the present invention.

FIG. 4 is a schematic view of a cast-in pin of an embodiment member of the present invention.

[Explanation of symbols]

1: coating layer 2: steel material surface layer
3: Test piece 4: Non-ferrous metal melt 5: Test piece holding plate
6; mounting base 7; cast-in tip arrow a; range of length

Claims (1)

[Claims] 1. The method according to claim 1, wherein the chemical components are C 0.95-1.
5%, Si 0.1-0.4%, Mn 0.2-0.5
%, Cr 3.0 to 5.0%, Mo 4.5 to 9.5
%, V 1.5-4.5%, W 1.5-7.0%, after forming a nitrogen-enriched layer by nitriding in advance on the surface layer portion of a steel material containing Fe and unavoidable impurity elements. A member for molten non-ferrous metal characterized by forming a coating layer by immersing in a molten salt containing Cr to change the nitrogen-enriched layer to a layer containing Cr nitride or carbonitride.