JPH08232058A - Member for die casting and its production - Google Patents

Abstract

PURPOSE: To produce a member for die casting, having erosion resistance, deposition resistance, and heat crack resistance, excellent in mechanical properties and wear resistance, and having superior heat retaining property. CONSTITUTION: First the whole or a part of the surface of a base material composed of austenitic alloy is thermally sprayed with a self-fluxing alloy. Then the resulting self-fluxing alloy film is remelted. At this time, it is preferable that the self-fluxing alloy has a matrix structure composed of austenite and contains >=30wt.% Ni, >=1wt.% B, and >=3wt.% carbide. Further, it is preferable that age hardening elements are contained in the base material and aging treatment is done after remelting treatment for the self-fluxing alloy film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die casting member used as a plunger sleeve, a plunger tip, a casting pin, a die body and the like in die casting, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A die casting component such as a plunger sleeve and a mold body come into contact with a high temperature molten metal, and a violent heat cycle and a high load act on the component and the mold body. Cracks etc. occur.

Therefore, conventionally, die casting members have been
JIS with excellent strength and toughness even in high temperature environment
Hot work tool steels such as SKD61 are widely used.

When hot work tool steel is used as a member for die casting, in order to ensure fatigue strength and heat crack resistance, quenching and tempering are performed in consideration of harmony of tensile strength, yield strength, toughness, ductility, etc. Conditioning is performed.

However, when the hot work tool steel is subjected to the heat treatment as described above, the mechanical properties are improved, but the die casting parts and the die body are melted, welded or worn due to the reaction with the molten metal. Occurs.

The inventors of the present application have found that Ni-based W is used for melting loss, welding, and wear at high temperatures due to molten aluminum.
It has been found that a self-fluxing thermal spray coating containing C particles and containing B, Si, etc. as an additional element is effective in suppressing it.

[0007]

However, the self-fluxing sprayed coating is usually used in order to close the pores of the coating and improve the adhesion between the coating and the substrate after spraying.
The heat treatment is performed at a temperature of 10 ° C to 1090 ° C. For this reason,
JIS SKD6 normally used for die casting
One material has a drawback that it is heated above the quenching temperature, coarsening of crystal grains occurs, and the mechanical strength of the base material falls below a practical level.

The present invention has been made in view of the above problems, and has melting loss resistance, welding resistance and heat crack resistance, excellent mechanical properties and wear resistance, and is excellent. An object of the present invention is to provide a die casting member having excellent heat retaining property and a manufacturing method thereof.

[0009]

The member for die casting according to the present invention is characterized by having a base material made of an austenitic alloy and a self-fluxing alloy film sprayed on the surface of the base material. The self-fluxing alloy film is preferably remelted, and the matrix structure of the self-fluxing alloy is austenite, and in its component composition, Ni is 30 wt% or more, B is 1 wt% or more, and carbide is 3 wt% or more. It is preferable to contain. Further, it is preferable that the base material contains an age hardening element.

A method for manufacturing a die casting member according to the present invention comprises a step of spraying a self-fluxing alloy on the entire surface or a part of the surface of a base material of an austenitic alloy, and remelting of the self-fluxing alloy film formed by the above step. And a processing step. Further, it is preferable that the composition of the self-fluxing alloy or the base material is such that the base material simultaneously undergoes solid solution in the remelting treatment. Further, it is preferable that the self-fluxing alloy film is subjected to age hardening treatment after the remelting treatment.

[0011]

The inventors of the present application have found that the die casting member has not only the melting loss resistance, the welding resistance and the heat crack resistance but also the excellent mechanical properties and the wear resistance, and the good heat retention property. Various experimental studies were conducted to develop the manufacturing method.

As a result, a self-fluxing alloy film is sprayed onto a base material made of an austenitic alloy to form a self-fluxing alloy film having a thickness of more than 500 μm, and then the self-fluxing alloy film is subjected to flame or heat treatment. By remelting treatment (hereinafter referred to as "fusing treatment"), a non-porous weld coating is formed between the base material and the self-fluxing alloy film, and excellent die-casting with good adhesion and high toughness. It has been found that a member for use can be obtained.

The reasons for limiting the base material used and the self-fluxing alloy will be described below.

Substrate: When the austenitic alloy substrate is SKD steel, the adhesion between the substrate and the self-fluxing alloy can be improved by spraying the self-fluxing alloy, but at about 1100 ° C. The base material is softened by the fusing treatment performed at the temperature. For this reason,
Although the strength of the base material can be improved by quenching and tempering the base material on which the self-fluxing alloy film is formed after the fusing treatment, the self-fluxing alloy film peels off during the quenching. This is a so-called quenching transformation in which a part or all of the base material transforms from the austenite structure to the martensite structure or bainite structure in the cooling process after the fusing treatment. During this transformation, the coefficient of thermal expansion of SKD steel changes greatly, so SK
The self-fluxing alloy film formed on the surface of the D steel base material is cracked or peeled. Further, the molten metal penetrates into the cracked portion and becomes a starting point of heat cracking, and further, melting loss or welding occurs at the peeled portion, so that the original effect of thermal spraying cannot be exhibited.

Therefore, when an austenitic alloy is sprayed as a base material, the self-fluxing alloy film melted by the fusing treatment even after cooling does not cause quenching transformation like SKD steel, and adheres to the base material. The property is further improved, and a non-porous good self-fluxing alloy film is formed between the self-fluxing alloy film and the base material.

The thermal conductivity of an austenitic alloy having a crystal structure of face-centered cubic is as small as 1/2 or less than that of SKD steel having a crystal structure of body-centered cubic.
Therefore, when an austenitic alloy is used as a member for die casting, the die casting parts and the like have good heat retention.

Next, a self-fluxing alloy capable of more reliably preventing cracking or peeling of the self-fluxing alloy film will be described. Such a self-fluxing alloy has a matrix structure of austenite, and contains 30 wt% or more of Ni, 1 wt% or more of B, and 3 wt% or more of carbide as its component composition. The reasons for limiting the composition of the self-fluxing alloy will be described below.

Matrix structure of self-fluxing alloy: Auste
By making the structure of the night structure self-fluxing alloy the same austenite structure as the base material, in the cooling process after the fusing treatment, both the base material and the self-fluxing alloy film exist as the same stable austenite structure, so that the self-fluxing alloy It is possible to more effectively prevent cracking or peeling of the film. Therefore, the matrix structure of the self-fluxing alloy is an austenite structure.

Ni (Nickel): 30 Weight or More Ni is an element that improves the toughness of the self-fluxing alloy film. In order to exert this effect, it is necessary to add 30% by weight or more of Ni. Therefore, the Ni content is 30% by weight.
That is all.

B (boron): 1 wt% or more B is an element that suppresses the reaction of the base material and the self-fluxing alloy in the molten state. If boride is present in the self-fluxing alloy,
The wettability of the alloy in the molten state is increased, and thermodynamic stability is provided in the alloy in the molten state. In order to exert this effect, it is necessary to add B in an amount of 1% by weight or more. Therefore, the content of B is set to 1% by weight or more.

The method of adding B to the self-fluxing alloy is not particularly limited, but boride or B containing Ni or the like as a main component is used.
It can be contained depending on the form such as N.

Carbide: 3 wt% or more Since carbide easily fuses with Ni, it is an effective compound for improving the toughness of the self-fluxing alloy film. Further, since the hardness of the matrix in the self-fluxing alloy is increased, it is also effective in improving the wear resistance. In order to exert such effects, it is necessary to add 3% by weight or more of carbide. Therefore, the content of carbide is set to 3% by weight or more. In addition, as the carbide in this case, WC, SiC, NbC, Cr ₃ C ₂ or the like is preferable.

Next, the case of adding an age hardening element to the austenitic alloy as the base material will be described. As the age hardening element, C, P, N, Ti, Al, Nb or V
Etc. By adding these age-hardening elements, these elements are deposited on the surface of the substrate as an intermetallic compound such as a carbide, a nitride or a phosphide or a metal such as Ti or Al, which causes age-hardening.

By this age hardening, the strength of the base material is improved, and a die casting member having excellent durability can be manufactured. Further, since the base material has high strength, it is possible to reduce the wall thickness of the member and reduce the weight of the member.

Incidentally, such age hardening is performed by the melting temperature of the aluminum alloy (melting point of aluminum: 660.2).
(° C.) Or a temperature slightly higher than 700 to 750 ° C., it progresses effectively and a precipitate is stably present.

Therefore, in the case of manufacturing an aluminum die casting member by the method for manufacturing a die casting member according to the present invention, the age-hardening maintains the proper strength of the member and extremely improves the durability. .

Next, a case will be described in which a base material made of an austenitic alloy that has been sprayed with a self-fluxing alloy is subjected to a fusing treatment, and at the same time, the base material is solidified and then subjected to an age hardening treatment.

Usually, the age hardening treatment is carried out by solidifying (solutionizing) the age hardening element in the alloy and then holding the alloy at a temperature lower than the solution temperature. Therefore, also in the present invention, after the thermal spraying by the self-fluxing alloy and the fusing treatment, after the solid solution treatment of the die casting member,
It can be age-hardened by holding it at a temperature lower than its solid solution temperature.

However, since both the fusing treatment and the solution treatment for the age hardening treatment are treatments for heating the die casting member, the fusing treatment and the solution treatment are not carried out separately, but by one heating treatment at the same time. It is possible to do. That is, the fusing treatment can also serve as the solution treatment for the age hardening treatment. As a result, the step of solid solution in the age hardening treatment can be omitted, so that the production cost can be reduced.

Specifically, the solution temperature for the age hardening treatment and the heating temperature for the fusing treatment each have an appropriate temperature range. Then, if the heating of the fusing treatment is performed at a temperature higher than the proper range of the solution treatment, the crystal grains of the base material become coarse, while if the heating is performed at a low temperature, undissolved precipitates remain. If the solution treatment is performed at a temperature that is not within the appropriate temperature range for solution treatment, the mechanical properties of the base material will be impaired.

If the fusing treatment is carried out at a temperature higher than the proper fusing temperature range, the fluidity of the self-fluxing alloy film becomes high and the film thickness becomes non-uniform. On the other hand, if it is performed at a low temperature, remelting of the self-fluxing alloy film does not occur, so that the performance of the self-fluxing alloy film cannot be improved.

Therefore, the fusing treatment, which also serves as the solid solution treatment of the base material, needs to be performed at the temperature of the portion where the appropriate temperature ranges of the solution treatment and the fusing treatment overlap each other. Generally, the solution treatment in the age hardening treatment is performed in the temperature range of about 950 to 1150 ° C, while the heating in the fusing treatment is performed in the temperature range of about 1050 to 1100 ° C. Therefore, the fusing process is 10
It is preferably carried out in the temperature range of 50 to 1100 ° C.

In order to make the temperature ranges of the age hardening treatment and the fusing treatment overlap with each other, the component compositions of the self-fluxing alloy and the base material are adjusted, and especially B or Si added to the self-fluxing alloy is added. It is effective to properly adjust the eutectic element.

After the fusing treatment which also serves as a solid solution of the base material as described above, the strength of the base material is improved by holding the die casting member within a certain temperature range, and the durability of the die casting member is improved. It can be further improved.

The age hardening treatment after the fusing treatment varies depending on the composition of the self-fluxing alloy and the base material, the kind of the hardening element and the desired strength, but is 700 to 7
It is preferable to carry out at a temperature of 50 ° C. for 5 to 24 hours, whereby an intermetallic compound such as a carbide, a nitride, a phosphide or the like by C, P, N, Ti, Al, Nb, V or the like, or T.
A metal such as i or Al can be deposited.

[0036]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples that depart from the claims of the present invention.

As test materials in this example, SKD61 steel was used in the comparative example, and SUS310 steel, which is an austenitic alloy, and A286 alloy steel, which is an austenitic alloy containing an age hardening element, were used in the examples. In addition, A2
The 86 alloy steel contains 0.05 wt% C, 0.50 wt% Si, 1.35 wt% Mn, 15 wt% Cr, 26 wt% Ni, 1.24 wt% Mo, and Ti. It contains 2.1% by weight, 0.26% by weight of Al and 0.32% by weight of V, and the balance is Fe.

The material history of heat treatment and surface treatment of these test materials is shown in Table 1 below.

[0039]

[Table 1]

Using each of the test materials of Examples No. 1 to 4 and Comparative Examples No. 1 to 3 shown in Table 1 above, tests were carried out for mechanical properties, wear resistance, melt damage resistance and heat crack resistance. It was

In the mechanical property test, a sample after the final heat treatment was cut out and subjected to hardness measurement and U-notch Charpy impact test.

In the abrasion resistance test, a pin-on-disc type sliding abrasion test was conducted. In this case, a wear test was performed under the conditions shown in Table 2 below, using a disc that had been subjected to the same treatment as the surface of each test material and using aluminum alloy (6021) as a pin.

[0043]

[Table 2]

In the corrosion resistance test, A at a temperature of 750 ° C. was used.
After C8C aluminum was melted and the test material was immersed in it for 3 hours, the cross section was observed.

In the heat crack resistance test, a 1000-cycle heat cycle test is performed by alternately moving the test material to the environment in water and in a furnace at a temperature of 650 ° C. under atmospheric pressure. After the test, the number of cracks generated per unit area on the cross section or the surface of the test material was observed.

Through the above tests, the test results were evaluated by comparing each test with a four-level relative evaluation. Excellent, good, good and bad were evaluated in the order of excellent evaluation, and each is shown in Table 3 below by "⊚", "○", "Δ" and "x".

[0047]

[Table 3]

As shown in Tables 1 and 3 above, SKD61 steel conventionally used as a member for die casting was subjected to tempering heat treatment for quenching and tempering, nitriding treatment, and self-fluxing spray. Are all inferior to Examples No. 1 to 4.

That is, in Comparative Example No. 1, since only quenching and tempering are performed, mechanical properties are excellent, but other properties such as abrasion resistance are extremely poor.

Further, since the comparative example No. 2 was subjected to the same treatment as the comparative example No. 1 and then subjected to the surface treatment by nitriding, the wear resistance was slightly improved as compared with the comparative example No. 1.
It was not yet sufficient, and conversely, mechanical properties were deteriorated by nitriding as compared with Comparative Example No. 1. In addition, the melting resistance and heat crack resistance were not improved at all. Furthermore, since Comparative Example No. 3 is subjected to the same treatment as Comparative Example No. 1 and then subjected to coating film formation by self-fluxing spraying, abrasion resistance is improved as compared with Comparative Example No. 1, and melt loss resistance is also increased. Also, the heat crack resistance was slightly improved. However, the self-dissolving thermal spraying treatment resulted in extremely deteriorated mechanical properties as compared with Comparative Example No. 1.

On the other hand, Example Nos. 1 to 4 have different conditions in surface treatment and the like, but all show excellent results in total.

That is, since Example No. 1 was subjected to the coating forming treatment by self-fluxing spraying using SUS310 which is an austenitic alloy, good results were obtained with respect to wear resistance, melt damage resistance and heat crack resistance. Was obtained. However, although it cannot be said that the mechanical properties are good, it has characteristics that it can be sufficiently used as a member for die casting.

The example No. 2 has the same S value as the example No. 1.
Although US310 is used, the structure of the self-fluxing alloy is austenite similar to that of the base material, and since Ni, B and carbides are contained in a predetermined amount, the cracking or peeling of the self-fluxing alloy film is further ensured. Example N by preventing
The melting resistance was further improved as compared with o1.

Example No. 3 uses A286, an austenitic alloy containing an age hardening element,
Further, since the coating forming treatment by spraying a self-fluxing spray alloy similar to that of Example No. 2 is performed, the strength of the base material is improved,
The mechanical properties and wear resistance were further improved as compared with Example No2.

Further, in Example No. 4, A286 was used in the same manner as in Example No. 3, the same heat treatment as in Example No. 3 was carried out, and then an aging treatment was carried out at a temperature of 720 ° C. for 15 hours. Thereby, the strength of the base material is further improved, so that the mechanical properties and the heat crack resistance are further improved as compared with Example No. 3, and the characteristics are the best among Examples No. 1 to 4. It was

[0056]

As described above, according to the present invention,
By spraying a self-fluxing alloy on the surface of the base material of the austenitic alloy, and then by remelting the sprayed coating, while having melt loss resistance, welding resistance and heat crack resistance,
It is possible to manufacture a member for die casting which has excellent mechanical properties and wear resistance and also has good heat retention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C23C 4/08 C23C 4/08

Claims (7)

[Claims] 1. A base material made of an austenitic alloy,
A die casting member having a self-fluxing alloy film sprayed on the surface of the base material. 2. The die casting member according to claim 1, wherein the self-fluxing alloy film is remelted. 3. The matrix structure of the self-fluxing alloy is austenite, and the composition of the composition is 30% Ni.
The member for die casting according to claim 1 or 2, characterized by containing 1% by weight or more of B, 1% by weight or more of B and 3% by weight or more of carbide. 4. The member for die casting according to claim 1, wherein the base material contains an age hardening element. 5. A method comprising: spraying a self-fluxing alloy on the entire surface or a part of the surface of a base material of an austenitic alloy; and remelting the self-fluxing alloy film formed by the step. A method for manufacturing a die casting member. 6. The production of a die casting member according to claim 5, wherein the composition of the self-fluxing alloy or the base material causes the solid solution of the base material at the same time in the remelting treatment. Method. 7. The method for manufacturing a die casting member according to claim 6, wherein the self-fluxing alloy film is subjected to age hardening treatment after the remelting treatment.