JPH0433751A - Manufacture of mold for casting metal - Google Patents

Abstract

PURPOSE:To form a mold having a desired shape and providing high thermal conductivity together with heat resistance under good balance by using a precipitation hardening type copper alloy as base material and executing a prescribed plastic working treatment. CONSTITUTION:By applying pipe contracting and/or pipe expanding works, solution treatment and age hardening treatment in combination after extruding the precipitation hardening type copper alloy material, uniform and fine precipitation harden of components of Cr, Zr, Ni, etc., is displayed. The material performance providing high degrees of the thermal conductivity together with the heat resistance needed to the mold for casting the metal derived to the max. through these work-forming processes. In this way, the high quality mold having the desired size can be continuously work-formed with the same equipment, and further, as the solution treatment can be inserted at the optional step, so as to match with the aimed material quality level, not only cold working degree after that, but also the precipitation hardening degree of Cr, Zr, etc., can be selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a metal casting mold made of a precipitation hardening copper alloy.

[Conventional technology]

Molds for metal casting are required to have high thermal conductivity and heat resistance as material properties. The reason for this is that a material with high thermal conductivity improves cooling efficiency, making the casting cycle more efficient, and high heat resistance increases resistance to deformation and cracking, resulting in stable castings and mold life. This is because it is possible to improve the However, high thermal conductivity and heat resistance generally have contradictory characteristics, and no mold material has been found that satisfies both of these properties. For example, pure copper, which has been commonly used as a mold material, has excellent thermal conductivity, but it does not have sufficient heat resistance and has a short lifespan.

Furthermore, conventionally, large-sized metal casting molds have been made by the mold forging method, but this method requires only one mold for each size! There was a problem in that it was not possible to efficiently manufacture molds of various sizes in terms of process.

[1 ill to be solved by the invention] As a result of repeated research in order to solve the problems in the material and manufacturing process of the prior art, the inventors have developed a method using a precipitation hardening copper alloy as a base material among various metal materials. It was confirmed that by applying a specified plastic working treatment, it is possible to form a mold with a desired shape that has a well-balanced combination of high thermal conductivity and heat resistance that satisfies the required performance.

The present invention was developed based on the above technical knowledge, and its purpose is to provide an efficient manufacturing method for metal casting molds that can stably cast high-quality cast products over a long period of time. It is in.

[Means to solve the problem]

A method for manufacturing a metal casting mold according to the present invention to achieve the above object is to extrude a precipitation-hardened copper alloy material into a tapered tube shape, and then perform tube contraction processing and/or tube expansion processing, solution treatment, and age hardening treatment. The structural feature is that it is applied in combination to form an annular mold shape.

The precipitation hardening copper alloy material serving as the base material of the present invention includes Cr
Cu alloy (chromium copper alloy) containing 0.5-1.5%,
Cu alloy (zirconium-chromium copper alloy) containing Zr 0.1-1.0% and Cr 0.3-1.0%, for example Cr0.8%, Ni1.8%, Si0.3%, Fe0.
Examples of Cu alloys containing 2% include nickel-chromium copper alloys.

Precipitation hardening copper alloy materials are produced from billet ingots to tapered tubular shapes (
Usually, the tube is extruded into a shape with the small-diameter end sealed, and then subjected to an appropriate combination of tube shrinking and/or tube expansion, solution treatment, and age hardening treatment. The combination of processing processes mainly depends on the pipe diameter size of the mold to be manufactured.For example, when a large diameter mold with an outer diameter exceeding 3001 mm is to be manufactured, as shown in the flow sheet of Fig. 1. The tube is processed in the order of tube contraction, softening/expansion, solution treatment, tube contraction or tube expansion, and age hardening treatment, and is finally cut into an annular mold shape and manufactured into a product. In addition, when targeting small diameter sizes with an outer diameter below 3001,
As shown in the flow sheet of Figure 2, solution treatment, tube shrinkage,
The best process is to perform age hardening treatment followed by cutting.

In the above-mentioned processing, cold forging by ordinary material drawing is applied to tube contraction and tube expansion. There are no particular restrictions on the conditions for solution treatment and age hardening treatment, but when using a chromium copper alloy or a zirconium-chromium copper alloy as a precipitation hardening copper alloy material, the solution treatment should be performed at a temperature of 950 to 1
It is preferable to set the conditions such that the material is heated to 430 to 480°C and then cooled with water, and the age hardening treatment is performed to be heated to 430 to 480°C and then air cooled.

(Function) According to the present invention, a precipitation-hardened copper alloy material is extruded in advance and then subjected to a combination of tube shrinking and/or tube expansion, solution treatment, and age hardening treatment, thereby forming a uniform and fine material. Precipitation hardening of components such as Cr, Zr, and Ni occurs. Through this processing and forming process, the material's performance, which combines high thermal conductivity and heat resistance required for metal casting molds, is maximized.

For example, in the process shown in Figure 1, precipitation-hardened copper alloy material is extruded and then subjected to tube shrinking, which densifies the structure and grain boundaries and prevents cracking during tube expansion. Through the tube shrinking and tube expansion processes, the processing rate increases and precipitation hardening of finer alloy components progresses, and a homogeneous precipitation hardening form is formed by the subsequent age hardening treatment.

Similarly, in the process shown in Figure 2, a sufficiently uniform and fine precipitation hardening form is formed by performing age hardening treatment after passing through a stage with a large degree of cold working consisting of extrusion, solution treatment, and tube shrinking. At this time, material properties can be further improved by performing tube shrinking processing an appropriate number of passes before solution treatment, depending on the processed size and degree of work hardening.

As described above, according to the working mechanism of the present invention, it is possible to continuously process and mold high-quality molds of a desired size using the same equipment, and furthermore, since solution treatment can be inserted at any stage, it is possible to mold the desired material. It becomes possible to select the degree of subsequent cold working, and further the degree of precipitation hardening of Cr, Zr, etc., depending on the level.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

Example 1 A precipitation hardening copper alloy (zirconium-chromium copper alloy) billet having a composition of 0.25% Zr, 0.45% Cr, and the balance Cu was prepared with a large diameter end outer diameter of 340 m11 and a small diameter end face diameter of 3.
A tapered tube (with a closed end on the small diameter side) having a diameter of 30 mm and an inner diameter of 2351 mm was extruded. The extruded tapered tube is drawn with a die with a core metal inserted, and the outer diameter is 3.
After shrinking a cylindrical tube with a diameter of 301 m11 and an inner diameter of 232+g+i, the outer diameter is 4 by pushing out a plug in a softened state.
The tube contraction/expansion process was repeated for 5 passes to expand the tube to a diameter of 20 IIm and an inner diameter of 340 mm. Next, the tube material was heated to 980'C (D
Solution treatment was carried out under the conditions of maintaining the temperature for 1 hour and then cooling with water.

The pipe material after solution treatment has an outer diameter of 4001 mm and an inner diameter of 335 mm.
After shrinking the tube to a size of m, the tube was subsequently held at a temperature of 450'C for 3 hours, and then subjected to an age hardening treatment under conditions of air cooling.

The thus processed pipe material was cut and finished to produce a large-diameter annular metal casting mold.

Table 1 shows the properties of the obtained metal casting mold in comparison with the properties of a conventional pure copper mold (comparative example).

Table 1 From the results in Table 1, it can be seen that the implemented product has improved various property values compared to the comparative product, and has a well-balanced combination of high thermal conductivity and heat resistance required for metal casting molds, as well as other properties. It turns out that the strength properties of the mold are also satisfactory for mold performance.

In addition, when the metal casting mold according to the example was put into practical use,
Compared to conventional pure copper molds, Vf! has a durable life that is about 5 times longer! It has been certified.

Example 2 A precipitation-hardening copper alloy (chromium-copper alloy) billet having a composition of 1.5% Cr and the remainder Cu was made into a billet with an outer diameter of 340 mm at the large diameter end.
It was extruded into a tapered tube (small diameter end sealed) with an outer diameter of 330 mm at the small diameter end and a 200 mm inner diameter. The extruded tapered tube was solution-treated by holding it at a temperature of 980°C for 1 hour and cooling with water, and then the outer diameter was 30011 m.
The operation of shrinking the tube into a cylindrical tube with an inner diameter of 19 hm was repeated for three passes.

After shrinking, the cylindrical tube is held at 450℃ for 3 hours and air-cooled for age hardening, and then finished by cutting to an outer diameter of 29 mm.
A small-diameter annular metal casting mold having an internal diameter of 180+ m was manufactured.

The characteristics of the obtained metal casting mold showed almost the same high performance as the mold of Example 1.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to manufacture a highly durable metal casting mold that can consistently cast excellent quality casting products over a long period of time. Furthermore, the same equipment can be used to continuously mold molds of a predetermined size, making it possible to mold multiple molds depending on the size, and because the material is strong, the wall thickness of the mold can be made thinner, improving manufacturing efficiency. The effect on cost reduction is brought about.

[Brief explanation of drawings]

FIGS. 1 and 2 are flow sheets illustrating a method for manufacturing a metal casting mold according to the present invention. Applicant Sumitomo Light Metal Industries Co., Ltd. Agent Patent Attorney Masaya Takahata (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] 1. Metal casting characterized by extruding a precipitation-hardened copper alloy material into a tapered tube shape, and then applying a combination of tube shrinking and/or tube expansion, solution treatment, and age hardening treatment to finish it into an annular mold shape. Method for manufacturing molds for