JPH04259344A - Alloy for metal mold for molding - Google Patents

Abstract

PURPOSE:To obtain a copper alloy for metal mold for plastic molding excellent in mechanical strength, castability, workability, and weldability by adding specific amounts of Al, Fe, Ni, Mn, etc., to Cu. CONSTITUTION:As a stock for metal mold for molding plastics, a copper alloy having a composition consisting of, by weight, 5-15% Al 2-5% Fe, 1-4% Ni or Co, 3-10% Mn, and the balance Cu is used. This copper alloy is cast into a metal mold of the desired shape and then finished into the metal mold for plastic molding excellent in dimensional accuracy, increased in mechanical strength and wear resistance, and having superior durability by means of machining.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention has excellent mechanical strength and
This invention relates to an alloy for forming dies that is easy to cast and process and has good weldability.

0002

BACKGROUND OF THE INVENTION Conventionally, S55C carbon steel for mechanical structures has been widely used as a material for plastic molding molds, particularly injection molding molds. This carbon steel for machine structures not only has good strength, weldability, graining workability, polishing workability, etc., but also excellent machinability, and is relatively inexpensive among mold materials. This is because it has the following characteristics. On the other hand, pre-hardened steel and the like have been used especially in molds that require a mirror finish.

[0003] In recent years, housings and constituent parts of various types of equipment such as office equipment, and automobile constituent parts have been made of plastic, and frequent model changes are being made to improve their performance and change their designs. . As a result, the life cycle of plastic molded products has become shorter, leading to high-mix, low-volume production. Therefore, there is an increasing demand for lower prices and shorter delivery times for molds for molding such plastic molded products.

By the way, when manufacturing a mold using a material such as the carbon steel for machine structures, many machining processes such as cutting are required, and the machining cost increases the mold manufacturing cost. occupies the majority of As a result, it was not possible to meet the requirements for lower mold prices and shorter delivery times, which are required for molds for high-mix, low-volume production. Therefore, by sand casting a zinc-based alloy with a low melting point and good workability, such as ZAS (trade name, manufactured by Mitsui Kinzoku Kogyo Co., Ltd.), for the prototype mold, it is formed into a shape that requires as little machining as possible, such as cutting. A method has been proposed in which a metal mold is manufactured by shaping the mold and subjecting it to finishing processes such as copying and polishing.

[0005] According to this method, compared to a mass-produced mold that is manufactured by cutting a large forged steel block, the machining speed is faster, which has the advantage of being cheaper and shortening the delivery time. have. However, the mechanical properties of the zinc-based alloys mentioned above, such as strength and hardness, are considerably inferior to those of forged steel materials, so a considerable margin must be taken into consideration in the design, and mirror finishing is not possible, making it difficult to use. The range of products was limited. Furthermore, it is difficult to prevent casting defects such as pinholes and shrinkage cavities, which requires repair by welding, etc. However, since the cooling conditions change significantly near the weld, unevenness occurs in the structure and There were problems such as transfer of the image onto the molded product.

[0006] Aluminum alloys and copper alloys have also been used for similar purposes, but the former have poor specularity due to their low hardness and are susceptible to casting defects such as pinholes and shrinkage cavities. Since weldability was also extremely poor, it was virtually impossible to repair casting defects once they had occurred or to repair molds caused by processing errors. The latter copper alloy has problems such as low hardness and lack of specularity.

[0007]

[Problems to be Solved by the Invention] In view of the above-mentioned current situation, the present invention has been made to provide a plastic mold that has excellent mechanical strength, is easy to cast and process, and has good weldability. The purpose is to provide alloys.

[0008]

[Means for Solving the Problems] The alloy for forming molds of the present invention has a weight percentage of 5 to 15% aluminum and 2 to 5% iron.
%, 1-4% nickel or/and cobalt, 3-10% manganese, and the balance copper. In the alloy of this invention, aluminum is a main component along with copper, and the mechanical strength is improved by alloying with copper, and the reason why the content is 5 to 15% by weight is that This is because if it is less than 5%, no great effect can be expected, and if it exceeds 15%, brittleness increases and impact strength is significantly reduced.

Mechanical strength, especially hardness, can be improved by including iron, but the content is 2% by weight.
The reason why it is set at ~5% is that if it is less than 2%, it will not have sufficient hardness for a mold, and if it exceeds 5%, it will become extremely brittle. Nickel or (and) cobalt improves the hardness and corrosion resistance of the alloy, and the total content of nickel or cobalt is 1 to 4% by weight.
This is because if it is less than 4%, a sufficient effect will not be obtained, and if it exceeds 4%, brittleness will increase.

[0010] Manganese is also necessary to improve mechanical strength, and its content should be adjusted to 3 to 10% by weight.
% because if it is less than 3%, a sufficient effect cannot be obtained, and if it exceeds 10%, brittleness increases. Furthermore, in the alloy of the present invention, all elements that may be mixed in other than the above-mentioned elements are allowed to exist as impurities (inevitable impurities). Its content varies depending on the extent to which intergranular corrosion becomes a problem, but it is usually preferably within 0.1% by weight.

[0011] The alloy of the present invention is normally used to produce a mold by casting it into a shape close to the final mold shape and finishing this cast product through post-processing.
It is also possible to manufacture a mold by casting into a material block and machining it.

0012

[Function] The alloy of the present invention is an aluminum-bronze alloy with the composition as described above, and has good weldability and significantly improved strength and hardness, so it has excellent wear resistance and durability. This makes it an extremely suitable material for casting molds.

[0013]

[Example] Next, an example of the present invention will be described. Alloys with compositions as shown in Table 1 (Examples 1 to 5, Comparative Examples 1 to 4)
) was melted and a test piece was cast using a closed sand mold. In addition, Comparative Example 4 is a zinc-based alloy ZAS
It is. The tensile strength and Brinell hardness of the obtained test piece were measured. The results are also shown in Table 1.

[0014] As raw materials, each component has a purity of 9
A high purity product of 9.99% or higher was used. As is clear from the results, all of the alloys of the examples exhibited tensile strength of 65 kg/mm2 or more and Brinell hardness of 160 or more, and were significantly superior in both mechanical strength and hardness compared to the comparative example alloys. It was found that the material was excellent and suitable as a casting mold material.

[0015]

[Table 1]

[0016]

[Effects of the Invention] As described above, the alloy of the present invention has extremely high mechanical strength and hardness and is excellent in wear resistance as a casting alloy. Therefore, by using this alloy, it is possible to easily manufacture molding dies with excellent durability using the casting method, and the number of machining steps can be significantly reduced compared to using forged steel. It is possible to achieve lower prices and shorter delivery times.

Claims (1)

[Claims] [Claim 1] 5-15% aluminum by weight percentage
, 2-5% iron, 1-1% nickel or/and cobalt
4% manganese, 3 to 10% manganese, and the balance copper.