JPS6049880A - Production of joining tool of sintered hard alloy and steel - Google Patents

Abstract

PURPOSE:To provide a titled tool which is inexpensive and is usable under high forging pressure by welding a sintered hard alloy and a steel by a high energy beam in the annealed state of the steel material then subjecting the welded material to hardening and tempering thereby distributing uniformly the hardness of the steel material. CONSTITUTION:A cold, warm and hot forged tool is constituted of a steel and a sintered hard alloy and an annealed material is used for the steel. The sintered hard alloy to be used in direct contact with the material to be worked is pressed thereto directly or via a metallic filler and a high energy beam is irradiated to the contact part to weld both materials. The entire part of the joined tool after welding is subjected to a heat treatment such as hardening, tempering, etc. to distribute uniformly the hardness of the steel. The sintered hard alloy consists of WC having 1-20mu average drain size and 15-40wt% bond metal of 1 or >=2 kinds among Co, Ni, Cr and Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a method for manufacturing molds and punches for cold and hot forging tools.

(B) Conventional technology and its problems Cold and hot forging tools are used to forge heated and cooled steel pieces to make parts, and are used at room temperature or at 600 to 12
It is used for cutting steel bars heated to 00°C and forging billets.

Because forging metal requires a large amount of force, the molds used are also large in shape. Conventionally, die steel, which exhibits little loss of hardness during high-temperature cutting, or high-speed steel, which has high compression distribution strength, have been mainly used. However, even if die steel or high-speed steel is used, the mold life is 3000 to 10,000.
If it exceeds 15 times, the product's skin will become rough and the mold life will be shortened. Although the effectiveness of using cemented carbide for forging is widely recognized, the reason for its limited application is that the mold has a short lifespan, which increases costs. In addition, there are various savings in the use of cemented carbide in the full forging field, but the first is the heavy weight, the second is the high cost, and the third is the risk of breakage due to thermal cracking. However, it has not been put into practical use yet.

(c) Disclosure of the Invention The present invention was obtained as a result of intensive studies to solve these problems. The gist of the present invention is that a cold or hot forging tool is made of steel and cemented carbide, and at least a portion in contact with a workpiece is made of cemented carbide, and the tool is made of steel and cemented carbide. The present invention relates to a method for manufacturing cold and hot forged tools in which welding is performed by high-energy beams. Furthermore, the average grain size of the WC of the cemented carbide is 1 to 20μ.

The present invention provides a cold-warm forging tool in which the bonding metal is one or more of Co+Ni, Cr, and Fe, and the content is from 15 to 40% by weight.

A feature of the present invention is that in welding cemented carbide and steel, the steel is welded with a high-energy beam in a burnt state, and then the welded product is quenched and tempered. Brazing is widely used for joining, and sometimes the hardness of the steel is too low - and later hardening is not possible with brazing.

Since a forging die reaches a temperature of about 500 to 600°C, conventionally known brazing cannot use brazing material due to insufficient heat resistance.

In addition, brazing sometimes raises the temperature of the steel and causes it to be annealed, making it impossible to increase the forging pressure to 300Kg7m4.

In the present invention, such problems can be solved by bonding the cemented carbide and steel using an all-electron beam or a laser beam.

That is, welding using an electron beam or a laser beam can locally obtain high temperatures. However, in high-temperature joining of cemented carbide and steel, Fe is present in the cemented carbide.

Due to the diffusion of C, the formation of double carbides such as Fe8W3C, rapid cooling of Fe, etc., the bonding layer does not necessarily become strong.

Co, Ni, Cu, Fe on the contact surface of cemented carbide and steel
By inserting pure metal fillers such as these and melting and bonding these pure metals using beam energy, strong bonding strength can be obtained.

A further problem to be solved is that the temperature at the joint surface rises to a point where the metal melts, which increases the hardness near the joint surface, and lowers the temperature a little farther away to the annealing temperature.

Figure 1 shows that when cemented carbide and hardened high speed steel are welded,
It shows the change in hardness of the steel part. There is a part where the hardness decreases a few inches away from the bonding layer.

If such areas with uneven hardness are formed, the steel will buckle in forged tools that require high compressive strength. In the present invention, after welding the raw material, by heat-treating the welded product,
Hardness distribution can be made uniform.

Figure 2 shows the change in hardness distribution before and after welding.

1 indicates the hardness of the steel part immediately after welding, and 2 indicates the hardness when heat treated after welding. They discovered that a tool for joining steel and cemented carbide with high toughness could be obtained by welding after annealing and heat treating after welding. Further, since the cemented carbide used in the present application is particularly required to have heat-resistant strength, the grain size of the WC is preferably in the range of 1 to 20 μm. Below 1μ,
Thermal crack resistance decreases, and if it is 20μ or more, it is virtually impossible to manufacture it industrially, and as a bonding metal, carbon
o, Ni, Cry Fef as main components, 15 to 40
weight%, and in order to improve properties such as oxidation resistance, corrosion resistance, and wear resistance, kl, Zr, B+ Sit Ti,
It is also possible to use one or more of Ta or the like in an amount of 0 to 0.5% by weight. If the amount of bonding metal exceeds 15% by weight, the impact resistance will be poor, and if the amount of the bonding metal exceeds 15% by weight, the hardness will decrease.

The forged tool obtained by the present invention has less surface roughness than the forged tool made of die steel or high-speed steel, and can be used under high forging pressure. At the same time, the entire tool is lighter and less expensive than a forged tool made of cemented carbide, and furthermore, the steel part can be machined with cooling grooves and screws. Therefore, as this type of forging tool, it is possible to obtain a cold and hot forging tool that combines the advantages of both die steel and cemented carbide forging tools. The tool of the present invention can be used, for example, in cold forging punches, hot forging dies, hot heading dies, and the like.

Example 1 The hot forged punch shown in Fig. 3 has a body diameter of D-30, a tip diameter of d=260, and a total length of L=+50 mm. I made it. The cemented carbide used here is made of WC with an average particle size of 6μ, mixed with 112% by weight of Co, 12% by weight of Ni, and 1% by weight of Crf.
Sintered cemented carbide was used. The body is annealed 1sKD-6
1, and the entire contact area between steel and carbide was electron beam welded.

After welding and preheating at 800-850°C 1000-10
Post-heat quenching fL-2 was performed at 50°C in a Nord bath for 15 minutes. Furthermore, tempering was performed at 600 to 680°C. The joint between the cemented carbide and the steel was a strong bond with no cracks or peeling. The shear strength of this punch was measured and was 35
1 (g/mff1).

Using this forged punch, 545cy material temperature 900°C
Hot forging was performed at a forging pressure of 200 tons. It is possible to punch 50,000 pieces, and the conventional 5KD6
The life a when using No. 1 was about 17 times that of ooo pieces. Example 2 In the hot Shadai shown in FIG. S K D 6 '1 of sintered cemented carbide containing 2% by weight of Tl and 1 between yanks.
Electron beam welding was performed with a 00μ steel filler added.

The hardness of the bonded product was made uniform under the heat treatment conditions shown in Example 1.

190 pieces of steel material were cut with this joining machine. Traditionally 4
When using light welding, the lifespan was 145,000 pieces, but when welding cemented carbide, it was possible to cut 10,000 pieces.

Example 3 Cold forged punch odor shown in Fig. 1, average particle size 3μ
18% by weight of Ni and 2% by weight of co in WC, /Vk
Electron beam welding was performed on steel (SKH9) using 1% by weight cemented carbide. Electron beam welding conditions are 150KV,
1 (h+zA, 500mm 7mm.

N beam is inserted into the cemented carbide and the contact surface of the carbide and steel.
The i-filler was dissolved and complete bonding was performed. 850° after welding
Preheated at 1180°C for 160 seconds and then quenched.
Tempering was performed at 0°C. Hot forging was performed at a forging pressure of 300 tons, and 100,000 pieces could be processed using this punch.

[Brief explanation of the drawing]

Figure 1 shows the hardness distribution of steel after electron beam welding of hardened material and cemented carbide, Figure 2 shows the hardness distribution of raw steel and cemented carbide immediately after welding and after heat treatment, and Figure 3 shows the hardness distribution of the steel in this application. FIG. 4 is a diagram of a hot forging punch obtained by the invention, and FIG. 4 is a hot forging punch obtained by the invention. The shaded area in the figure is a cemented carbide, where D is the diameter and L is the total length. I. Hardness distribution of raw steel after welding, 2. Hardness distribution after heat treatment after welding, 3. - Cemented carbide, 4. Steel. 17:, -'1, -'-

Claims (2)

[Claims] (1) In the manufacturing method of a joining tool for cemented carbide and steel, an annealed material is used for the steel, and the cemented carbide used in contact with the workpiece is directly brought into contact with this material through a metal filler. Welding is performed by irradiating high-energy beams on the relevant joints, and after welding, the entire joining tool is subjected to heat treatment such as quenching and tempering to make the hardness distribution of the steel uniform. Manufacturing method for joining tools. (2) The cemented carbide contains W with a grain size of 1 to 20μ and C of 60 to
85% by weight of Co, Ni, Cr, Fe
Selected from n'#L 1 or 2 or more bonding metals 15~
A method for producing a joining tool for cemented carbide and steel according to claim (+), characterized in that the production component is 40% by weight.