JPS5935607A - Production of bonded sintered hard alloy member - Google Patents

Abstract

PURPOSE:To join securely a sintered hard alloy plate and a ferrous sintered plate in the stage of joining the sintered hard alloy plate and the ferrous sintered plate by stacking an infiltration material for joining, the ferrous sintered plate and the sintered hard alloy plate successively from below and pressing and heating the laminate. CONSTITUTION:WC powder which is a superhard material is sintered with >=10% Co as a binder to manufacture a sintered hard alloy plate A. Iron powder contg. 0.8wt% C is separately sintered to manufacture a ferrous sintered plate B. The plate B and the plate A are superposed on the infiltration material C consisting of alloy powder having the compsn. composed of Cu-Mn5%-Fe4%. The thickness of the plate A is regulated to 1/10-1/3 of the entire part in this case and while the laminate is pressed with a weight D from the upper part, the laminate is heated for 1hr to 1,150 deg.C in ammonia cracking gas. The material C is melted and is sucked up by capillary force in the small holes in the plate B, whereby the plates A and B are securely joined without joining both in an excess amt.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) [Technical Field] The present invention relates to a method for manufacturing a mold material in which a thin cemented carbide plate and an iron-based sintered body are joined.

This mold material is applied to dies, punches, etc. used for punching precision parts, and is processed into any shape by electric discharge machining, wire cutting, etc.

(b) [Technical background] Cemented carbide exhibits excellent performance as a material for such molds, etc., but is expensive, so cemented carbide is used only in the necessary parts, and steel is used as a supporting material for the other parts. Conventionally, a composite material in which the two are joined by brazing has been used. However, when using such materials, tensile stress is applied to the cemented carbide during cooling due to the difference in thermal expansion coefficient between the cemented carbide and steel, which causes brazing misalignment due to brazing over a large area such as for molds. There were many problems such as cracks forming in the hard metal.

(c) Purpose of the invention The mold material of the present invention solves the above problems,
Because the cemented carbide and the ferrous sintered steel that serves as the supporting material are completely bonded, there is no possibility that the steel and cemented carbide may come off or the cemented carbide may come apart during post-bonding heat treatment or machining such as wire cutting. The present invention provides a mold material that does not cause alloy cracks.

B) Disclosure of the Invention The mold material of the present invention is a composite material consisting of a cemented carbide containing a bonding metal (mainly Co) of 10% by weight or more and an iron-based sintered body infiltrated with copper, and the iron-based sintered body contains carbon. This product is made by infiltrating and sintering an infiltration material mainly composed of copper into a stamped body (molded body) of iron powder containing 0.8% or more of iron powder. It is to be bonded to the alloy. The thickness of the cemented carbide is 1/10-t/a of the total thickness of the material.

If the bonding metal content in the cemented carbide is 10% or less, it will not be able to sufficiently withstand the tensile stress applied to the cemented carbide after joining, so it is preferably 10% or more. Of course, the main component of cemented carbide is WC.

The reason why the thickness of the cemented carbide is 1/10 to 1/3 of the total thickness is that if it is less than 1/10, the compressive strength as a mold material is insufficient, and if it is more than 1/3, the cemented carbide has a binder content of 10% or more. However, this is not desirable because it causes cracks. For ordinary materials, cemented carbide having a thickness of 1 to 10 UL is used.

Further, for the iron-based sintered body, the carbon content is 0.3% or more. If the carbon content is less than 0.3%, the hardness of the Fe-Cu-C sintered body will be low even after heat treatment, making it unsuitable as a mold material. If it is 0.3% or more, a desired high hardness can be ensured by heat treatment after bonding.

The reason why the iron-based sintered body is infiltrated with copper is to fill the pores in the sintered steel to ensure the necessary hardness after heat treatment, and to prevent cracking as described below.

The reason why copper-infiltrated sintered steel is used as the supporting material is that the metal powder sintered body is porous and can absorb the difference in thermal expansion when heated, and the stress during cooling is absorbed by the copper filling. This is because the stress is absorbed by the cemented carbide and no large stress acts on the cemented carbide, which has the advantage of preventing disconnection or cracking of the cemented carbide during heat treatment or processing by wire cutting.

Next, the joining method will be described.

As a joining method, it seems easy to join the cemented carbide and the iron-based sintered body using a brazing material such as Ag e Cu, but in this case, the brazing material is mixed into the iron-based sintered body. It is absorbed and cannot be joined.

The present inventors investigated a method of diffusion bonding molten copper and cemented carbide by drawing copper to the joint surface of the alloy by utilizing the phenomenon of copper infiltration into an iron-based sintered body.

The copper infiltration method for sintered steel is usually a method in which a copper-based infiltrant is layered on an iron-based powder stamped skeleton and heated at a temperature of 1120°C to 1150°C. Sintering proceeds by penetrating through the continuous pores of the stamped body and filling the voids in the skeleton.

If there is more infiltrant than fills this space-time pore and there is cemented carbide in close contact with the sintered steel, the excess infiltrant will be absorbed into the thin gap between the sintered steel and the cemented carbide. The leaching causes an alloying reaction on the surface of the cemented carbide, resulting in a bonded member of copper infiltrated steel and cemented carbide. However, if the cemented carbide, iron-based sintered body, and infiltrated material stamped body are stacked one on top of the other in order from the bottom and heated and sintered, a large amount of infiltrated copper will flow in, making it difficult to adjust the gap between the bonding layers. Problems arise in which the sintered body moves or copper flows out of the system along the cemented carbide.

As a result of the study of the joining phenomenon, the above problems are due to the fact that the molten copper is affected by gravity, and because a large amount of infiltrated copper enters the joint surface, the frictional force between the sintered steel and the cemented carbide becomes small.
It turned out that this was due to slipping. As a result of considering this point, the present inventor, Kasa, changed the method of layering each member from the bottom to the infiltration material stamped body, iron-based stamped body (skeleton), and cemented carbide, and then the top two layers. It was confirmed that a good bonding state could be obtained by heating and sintering with a load applied, such as by placing a weight. According to this method, the infiltrated copper is sucked up only by capillary force from the bottom upwards, preventing more copper than necessary from entering the joint surfaces, and since the load is visible, slipping between the joint surfaces is prevented. It seems that good results were obtained.

The inventors conducted further studies and found that a stronger bond could be achieved by using the above method in combination with a brazing material. Ag-based and C-based materials commonly used in brazing materials such as steel
As mentioned above, the U-based brazing metal penetrates into the sintered body when melted, making it useless for joining, but when used in conjunction with the copper infiltration method, penetration of the brazing metal into the sintered body is also prevented. It was found that stronger bonding strength could be obtained than with only copper infiltrated material. In this case, the amount of copper infiltrant can be smaller than when no brazing material is used.

As the wax 4J, a normal brazing material may be used, but powder of a brazing material (Anchor Blaze M2) exclusively for sintered steel manufactured by Hoganäs Co., Ltd. in the United States may also be used. In this case, a part of it melts and alloys with iron, raising the melting point and solidifying the solder metal, causing penetration of the solder metal.Even without copper infiltration, sintered steel and carbide Although it can be joined to alloys, it is necessary to infiltrate it in terms of strength as a support member and stress absorption.

Next, an example will be explained.

Example 1 80% by weight of 1μ WC powder and 20% lμ Co powder were mixed and sintered after stamping to produce 1100xlOOx2.
A cemented carbide plate (5) of No. 1111 was manufactured.

Next, add 100% of mixed powder containing 0.8% by weight of carbon to the iron powder.
Emboss it to x100x100x40 B). Also Cu
An alloy powder having a composition of -Mn 5%-Fe 4% was pressed to produce an infiltration material (C) of 100xlOOxlOFuL. These were stacked as shown in FIG. 1, a weight () was placed on the top layer, and heated at 1150° C. for 1 hour in ammonia decomposition gas.

After heating, the infiltrant diffuses into the iron sintered body and penetrates into the gap between the iron-based sintered body and the cemented carbide, resulting in complete bonding between the cemented carbide and the iron-based sintered body. It was conducted. At this time, the hardness of the iron sintered body is H
It was Rc 20. This bonding material was heated at 84° C. for 1 hour, quenched, and tempered at 180° C. for 1.5 hours. The hardness was HRc 40, and no cracks were generated during the heat treatment.

The bonded product was cut out by wire cutting, a punch for punching a silicon steel plate was made, and a punching test was conducted, which showed that the life was about 10 times longer than that of die steel. In addition, the punched products had fewer cracks and were highly accurate.

Example 2 Cemented carbide with the same composition as Example 1 (80X100X2 N)
It was manufactured using the mIrL\'' method. Next, add 0.4% by weight to iron powder.
B) The mixed powder containing carbon is embossed into 1oOXloOx40au. In addition, loOxloox is made by stamping a powder mixed with alloy powder of Cu-5%Mn-4%Fe composition.
An infiltration material (C) of 1Omx is prepared, and a brazing material powder exclusively for sintered steel is embossed into a block of 10100X20X1O (E).

As shown in FIG. 1, (C), (B), and (5) were stacked in this order, and then a brazing material (E) was placed on the stack, followed by a weight () and heated at 1160° C. for 2 hours in an ammonia decomposition gas.

The cemented carbide and iron-based sintered body containing copper are perfectly joined,
The bonding strength was also sufficient.

As described above, according to the present invention, it is possible to join a large area of cemented carbide and the sintered steel that is its supporting material, and the mold material used as a large bonded cemented carbide member has wear resistance as an ultra-precision cutting die material. As a result, it has become widely used as a material with excellent edge sharpness. In addition to the above applications, it can also be used as a civil engineering tool, such as crushing, excavating, and processing tools.

[Brief explanation of the drawing]

1 and 2 are front sectional views for explaining the present invention in detail. 'A: Cemented carbide, B: Iron skeleton, C: Infiltration material, D
; Weight, E; Wax wood.

Claims (1)

[Claims] (]) A laminated composite cemented carbide member consisting of a WC-based cemented carbide and an iron-based sintered body, in which the bonding metal of the cemented carbide is 10% by weight.
above, and its thickness is 1/10 to 1/3 of the total thickness, and the iron-based sintered body is an infiltration material mainly composed of copper in an iron-based skeleton containing carbon content of 0.3% by weight or more. In the production of bonded cemented carbide parts, the cemented carbide and the iron-based sintered body are firmly joined via an infiltrant. The iron-based powder stamping body and the cemented carbide are seeded in that order, and then a weight is placed on the top two stages and heated and sintered under a load to bond the copper-infiltrated sintered steel and the cemented carbide. A method for manufacturing a bonded cemented carbide member, characterized by joining using four components. (2) A composite part consisting of a WCC cemented carbide iron-based sintered body, in which the bonded metal in the cemented carbide is 10% by weight or more, or the thickness is 1/10% of the whole. ~1/3,
The iron-based sintered body has an iron-based skeleton containing 0.3% by weight or more of carbon and is filled with an infiltrant whose main component is copper. In the production of laminated cemented carbide parts that are firmly bonded together, a stamped body of copper infiltration material, a sintered iron-based powder, and a cemented carbide are stacked in this order from the bottom, and then a weight and brazing material are stacked on the top layer. 1. A method for manufacturing a bonded cemented carbide member, characterized in that the copper infiltrated steel and the cemented carbide are joined together using a copper infiltrated component and a brazing material.