JPS63235412A - Method for forming hardened layer - Google Patents

Abstract

PURPOSE:To make a step difference as less as possible even in the case of partially arranging hardened layer and to prevent the development of crack in the hardened layer by heating after sticking the specific Fe-W alloy powder sheet on surface of a C contained ferrous material and forming the hardened layer of Fe-W-C ternary system eutectic. CONSTITUTION:On the surface of the ferrous material containing >=3wt.% C, powder alloy composing of 10-25% W and 2% inevitable components and the balanced iron, is mixed with resin binder and stuck as the alloy powder sheet having 0.2-1.5mm thickness. Next, this is heated at 1,090-1,200 deg.C to diffuse C in the above ferrous material into the above sheet side and the Fe-Mo- C ternary system eutectic is crystallized, to form the hardened layer having <=5% shrinkage percentage, >=40% surface area ratio of carbide and >=10% porosity. By this method, at the time of crystallizing the liquid phase by restraining the shrinkage percentage to low, the crack is not developed on the hardened layer and even in the case of partially forming the hardened layer, the step difference can be made as less as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming a hard layer, particularly an iron-based hard layer containing 3% by weight or more of C! ; relates to a method of forming a hard layer on S material.

(Prior art) When the base material is cast iron, methods for hardening iron-based parts, such as the nose of a camshaft, include chilling by setting a chiller in a mold and rapidly cooling it, or by heating it with beam heat. A method of remelting and chilling by locally heating is known.

However, although the museum's method is inexpensive,
The hardness of the resulting hard layer is HRC50-57, and the chill structure is relatively rough, so pitching occurs when the contact surface pressure increases, so the critical surface pressure is 80 kOf/w.
I could only get about J.

In addition, the latter method has the disadvantage of increasing costs because each cam piece must be heated and melted.

Generally, if the base material is made of steel, induction hardening is applied.

There is also a method of forming a hard layer by flame quenching, etc., but the critical surface pressure of the hard layer formed by this method was 60 ka'/11 or less.

On the other hand, the present inventors have proposed a sheet method disclosed in JP-A-60-181202 and the like as a method for forming a hard layer on the surface of such an iron-based base material.

In the method shown in this publication, Fe-Metat
-C (tl: Metal is at least one of P, B, and W) based ternary crystal alloy powder and acrylic adhesive binder are mixed and formed into a sheet, which is adhered to an iron base material. By sintering in this state, a wear-resistant hard layer that can withstand high blood pressure can be obtained, but this method has the following problems.

(Problems to be Solved by the Invention) That is, in the method for forming a hard layer disclosed in the above publication, when forming an alloy powder into a sheet, the density is set to 3.5 to 6.0 l/c.
1i', and the required wear resistance cannot be secured unless the density during heating and sintering is increased to 90% or more of the theoretical density, so the shrinkage rate when the liquid phase is crystallized is as high as 7 to 20%. It had become.

When the shrinkage rate increases in this way, for example, if an attempt is made to provide a hard layer around the entire periphery of the cam piece, cracks in the hard layer are likely to occur in some part.

In order to avoid cracks in the hard layer, it may be possible to form it only in the necessary areas without providing it all around the circumference, but this method creates a large step between the hard layer and the base material, making post-processing difficult. It becomes troublesome.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to suppress the shrinkage rate during liquid phase crystallization to a low level so that cracks do not occur in the hard layer. It is an object of the present invention to provide a method for forming a hard layer that can minimize the step difference even when the hard layer is partially provided.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides that the chemical composition is 1.
W with a maximum weight of 0 to 25%, and unavoidable components of 2% or less by weight,
A resin binder is mixed with a powder alloy consisting of residual Fe to form an alloy powder sheet with a thickness of 0.2 to 1.5111111, and this is attached to the surface of an iron-based base material having a C content of 3% or more. Then, this is heated at a temperature of 1090 to 1200°C to diffuse the C of the iron-based base material to the alloy powder sheet side, thereby crystallizing a ternary eutectic consisting of Fe-W-C. The shrinkage rate is 5% or less, and the surface area ratio of carbide is 40.
% or more and a porosity of 10% or less is formed.

The above configuration requirements will be explained in detail.

W with a chemical structure of 10 to 25% by weight> W combines with C diffusing from the base material side to form Fe-W-C
This becomes a ternary eutectic and crystallizes a liquid phase, which is 10.0
If it is less than % by weight, the space between liquid phases decreases and the porosity decreases to 10%.
, the hardness decreases significantly and the bonding force becomes insufficient.

Moreover, when W exceeds 25% by weight, the fluidity of the liquid phase becomes excessive, and the number of liquid phases becomes too large, causing the liquid to flow down from the base material.

<Alloy powder sheet with a thickness of 0.2 to 1.5 mm> If the thickness of the alloy powder sheet is less than 0.211111, the hard layer formed will be too wide and there will be no machining allowance for finishing. , it becomes difficult to obtain a smooth decoy surface.

Also, the thickness of the alloy powder sheet is 1.5! If IIN is exceeded, a long time will be required for diffusion of C from the base material, and the shrinkage rate will exceed 5%.

<Iron-based base material having 3% by weight or more of C> C diffuses toward the attached alloy powder sheet side, forms a eutectic composition with W, and crystallizes the melt, resulting in liquid phase sintering. , bonding to the substrate, carbide is generated.

If the amount of C is less than 3% by weight, the amount of C that diffuses will be too small, making it difficult for the above phenomenon to occur.

Heating temperature: 1090-1200°C> When a ternary eutectic composition of Fe-W-C is formed due to the diffusion of C from the base material, the heating temperature must be set to the eutectic composition of this composition in order to crystallize the liquid phase. Must be above temperature.

The minimum temperature for this is 1090°C.

On the other hand, when the heating temperature exceeds 1200° C., the crystal grains of the iron-based base material become coarse and the strength is significantly reduced.

Shrinkage rate is 5% or less> If the shrinkage rate exceeds 5%, cracks may occur in the hard layer during shrinkage, and processing costs in post-processing will increase.

<Surface area ratio of carbide is 40% or more> The physical properties of the hard layer formed include a contact surface pressure of 80%/-
As described above, in order to ensure wear resistance and pitting resistance, it is advantageous to have a large surface area of carbide, which is a non-metallic part, and the lower limit thereof is 40%.

<Porosity 10% or less> If the porosity of the hard layer to be formed exceeds 10%, the wear resistance will be significantly reduced.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail.

Note that all chemical composition ratios shown in the following examples are (r
It is ω%.

*Example 1 FCD65 (chemical composition = 3.5%C, 2.8%s+
, 0.3%Mn, 0.11%P10.02%S, 0.8
%Cu, 0.04%Mg, balance Fe) 12X 12
It was cut into a size of x30mm+ and prepared as an iron-based base material.

A powder alloy with a chemical composition of 10.0% W, 0.4% $1, and residual Fe was prepared, and those with a particle size of 74% or less were selected, and 31% acrylic resin was added as a resin binder. and toluene were added and kneaded to produce an alloy powder sheet with a thickness of 5 mm.

Then, the obtained alloy powder sheet was used as a 12×3 sheet of the above base material.
The same area was cut and adhered to the 0 mm surface using an acrylic resin adhesive.

Thereafter, the base material to which the alloy powder sheet was adhered was preheated at 300°C for 60 minutes in an H2 gas atmosphere to volatilize the toluene and degrease it, and then heated in the same atmosphere for 11 hours.
A heat treatment was performed at a temperature of 30° C. for 20 minutes to diffuse C in the base material toward the alloy powder sheet side, thereby forming a hard pattern on the surface of the base material.

The hard layer obtained had a hardness of HV820. The porosity was 8% and the shrinkage rate was 4.8%.

*Example 2 The iron base material used was the same material and one dimension as in Example 1 above.

The chemical composition of the powder alloy is 18% W, 0.6% 3i, and the balance is Fe.
Prepare the particles, select those with a particle size of 74μ or less, and add 1 to 3% acrylic resin as a resin binder to this.
Luene was added and kneaded to prepare an alloy powder sheet with a thickness of 0°81 Il.

Then, (q) the alloy powder sheet is 12X of the above base material.
3011111, were cut into the same area and adhered using an acrylic resin adhesive.

After that, the base material to which the alloy powder sheet was adhered was preheated at 300°C for 60 minutes in an H2 gas atmosphere to volatilize toluene and degrease, and then heated to a vacuum degree of 2 x 10.
A heat treatment was performed at a temperature of 1100° C. for 20 minutes in a '-rorr to diffuse C in the base material to the alloy powder sheet side and form a hard layer on the surface of the base material.

Obtained fj! ! The quality layer had a hardness Hv of 905, a porosity of 6.2%, and a shrinkage rate of 4.3%.

*Example 3 The iron base material used was the same material and one dimension as in Example 1 above.

A powder alloy with a chemical composition of 25.0% W, 0.8% Si1 and residual Fa is prepared, and those with a particle size of 74IIJI or less are selected, and a 3% acrylic resin and toluene are added as a resin binder. Add and knead 1. An alloy powder sheet having a thickness of Q1 ml was produced.

Then, the obtained alloy powder sheet was used as a 12×3 sheet of the above base material.
The same area was cut and adhered to the 0em surface using an acrylic resin adhesive.

Thereafter, the base material to which the alloy powder sheet was adhered was preheated at 300°C for 60 minutes in an H2 gas atmosphere to volatilize toluene and degrease, and then heated at a vacuum degree of 5X 10'.
Heat treatment was performed in Torr at a temperature of 1120° C. for 30 minutes to diffuse C in the base material to the alloy powder sheet side and form a hard layer on the surface of the base material.

The hard layer obtained has a hardness of -IV 960. Porosity 6
The shrinkage rate was 4.9%.

Table 1 shown below shows the results of the abrasion test for each hard layer obtained in Examples 1 to 3 above.

In the abrasion test, the base material on which the hard layer was formed was divided into 9 x 5 III and 1. ? ll definitely, 5 on the hard layer side
A test piece t with a curved surface of 5R is prepared, and the test piece [is held in a holder h and a disc-shaped mating base material A
This was done by bringing a curved surface into contact with the (see Figure 2).

The test conditions were to apply a pressing force P of 1.8 k (l) to the holder h, and to apply a pressure of 19.811 I/S to the mating material without lubrication.
The test piece t was rotated for 10 minutes using eG, and the wear height of the hard layer of the test piece t was measured.

Note that a JIS Fe12 chilled disk was used as the mating material Δ.

[Table 1] As is clear from the results in Table 1 above, all of the hard layers obtained by the present invention have extremely little wear deposits.

In addition, FIG. 3 shows the hard layer obtained in Example 2 above.
This is a magnification microscopic photograph, and the white part in the photograph is a carbide of C and W, and the black part is sordoit.

From this photograph, it can be confirmed that, according to the method of the present invention, C diffuses from the iron-based base material to the alloy powder sheet side to generate W and carbide.

(Effects of the Invention) As described above in detail in the Examples, according to the method for forming a hard layer according to the present invention, C, which combines with W to crystallize a liquid phase, is not present on the alloy powder sheet side. Therefore, the thickness of the sheet can be reduced by that amount, and since C diffuses from the base material side during sintering, the volume on the sheet side increases by that amount, and the shrinkage rate is reduced.

Therefore, even when the hard layer is partially formed, the difference in level can be made as small as possible, and cracks in the hard layer do not occur.

[Brief explanation of drawings]

FIG. 1 is a plan view of a test piece for an abrasion test, FIG. 2 is an explanatory diagram of the test, and FIG. 3 is a microscopic photograph showing the structure of a hard layer obtained by implementing the present invention. Patent applicant Mazda Co., Ltd. Agent Patent attorney - Kensuke Shiro
Patent attorney Masatoshi Matsumoto Figure 1 Figure 3 Procedures available 1 Official document (method) June 9, 1985 Commissioner of the Patent Office Kuro 1) Akio Yu 1, Indication of the case 1988 Patent Application No. 65848 2, Invention Name of Formation Method of Hard Layer 3, Relationship with the Amendment Case Patent Applicant Address 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Name (3)
13) Ken Yamamoto, Representative Director of Mazda Corporation
- 4. Agent address: New TL, Minato-ku, Tokyo! i2 T number 12 number 7 number 5,
Date 6 of the amendment order, ``Simplified drawing mfj - Explanation J of the amendment subject book #I, 7, page 13, first line of the statement of contents of the amendment, ``Hard layer structure'' was changed to ``Hard layer structure.''"Metal structure of the hard layer" is corrected.

Claims (1)

[Claims] A powder alloy with a chemical composition of 10 to 25% by weight of W, 2% or less of unavoidable components, and residual Fe is mixed with a resin binder to form an alloy powder sheet with a thickness of 0.2 to 1.5 mm. This is pasted on the surface of an iron-based base material having 3% by weight or more of C, and then heated at a temperature of 1090 to 1200°C, so that the C of the iron-based base material is attached to the alloy powder sheet side. A ternary eutectic consisting of Fe-W-C is crystallized by diffusing the Fe-W-C, and the shrinkage rate is 5% or less and the surface area ratio of carbide is 4.
A method for forming a hard layer, comprising forming a hard layer with a porosity of 0% or more and 10% or less.