JPH0617523B2 - Low melting point alloy for simple mold - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low melting point alloy used for a simple mold as a press mold or an injection molding mold.

(Prior Art) There are various methods for manufacturing a simple type,
For example, a general-purpose gravity casting method using a sand mold to which a model such as gypsum is transferred ("Toyota Technology" Vol. 27, No. 4, P102-11).
5), the dual-form method in which a sheet metal model is immersed in molten metal and solidified as it is (“Machine and Tool”, June 1975, P21).
No. 25, JP-A-51-55733), a direct casting method in which a plurality of casting spaces are formed in a casting frame and the molds are sequentially poured to successively cast a plurality of molds (Japanese Patent Application No. 62- No. 175641, Japanese Patent Application Sho 62
-251259) is already in practical use.

And, conventionally, Bi, Pb,
Low melting point alloys consisting of two or more of Cd, Sn, Sb, etc. were generally used (“Mold technology”, Vol. 2, No. 10, P26, 1987).

(Problems to be Solved by the Invention) By the way, among the low melting point alloys, the melting point is low (50-
At 200 ℃), and because it expands a little during solidification and is excellent in manufacturability, alloys containing Bi as the main component have attracted attention and are widely used in the above-mentioned dual foam method and the like. However, conventional Bi-based alloys not only have low mechanical strength but also poor wear resistance, and it is extremely impossible to apply them to the processing of high-tensile steel sheets as a press die, for example. There was a problem that the life was short. Further, due to its low melting point, it is impossible to apply it to, for example, an injection mold having a high molding temperature.

Therefore, in many cases, an alloy containing Zn as a main component (Mitsui Mining & Smelting ZAS) is used in place of the Bi-based alloy. This Zn-based alloy has high mechanical strength as high as mild steel and good wear resistance, and is used for processing high-strength steel sheets as a press mold, or as a resin mold with a high molding temperature as an injection mold. There are advantages that can be applied to. However, this Zn-based alloy has a relatively high melting point (approximately 380
Since it has the property of shrinking significantly at the time of solidification), it has problems in productivity and cost.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a low melting point alloy for simple molds which is excellent in mechanical properties and wear resistance, and is also excellent in manufacturability. To do.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides Bi50-60 wt%, Sb
The gist is that it is composed of 4 to 10 wt% and the balance is Sn.

In the present invention, the component ratio of Bi and Sn is the eutectic ratio [58: 4
2] is preferable. This is because the Bi—Sn alloy has the lowest melting point at this ratio (139 ° C.) and the molten metal flowability is good. Therefore, the Bi content is preferably 52.5 to 55.5 wt%. The type of simple mold to which the alloy of the present invention is applied is not particularly limited, and it can be applied to, for example, a press mold or an injection mold. Further, a simple type manufacturing method is also arbitrary, and the gravity casting method, the dual foam method, the direct casting method or the like described above can be selected.

(Operation) In the low-melting-point alloy having the above structure, by adding a predetermined amount of Sb to the Bi-Sn alloy, mechanical strength and wear resistance are improved as compared with the conventional Bi-based alloy. Also, due to the predetermined Bi-Sn-Sb component ratio, there is almost no volume change during solidification, or only a slight expansion or contraction,
In addition to this, the melting point can be suppressed to be relatively low as compared with the conventional Zn-based alloy, and the manufacturability is improved.

However, if the Bi content is less than 50 wt% or exceeds 60 wt%, the amount of shrinkage and expansion during solidification increases and the melting point increases, so this was made 50 to 60 wt%. Also
If the content of Sb is less than 4 wt%, the effect of improving the mechanical strength and wear resistance is small, and if it exceeds 10 t%, on the other hand, the mechanical strength and toughness decrease, and the melting point rises. It was set to ~ 10wt%.

(Example) Hereinafter, an example of the present invention is described based on an accompanying drawing.

Example 1 The composition ratio of Bi and Sn was kept constant at a eutectic ratio [58:42] by weight ratio, and Sb was added thereto at various ratios to cast a block of a predetermined size. Test pieces, mechanical test pieces, impact test pieces, melting point measuring test pieces, etc. were cut out and subjected to respective tests. FIG. 1 shows the results of these tests. From the results shown in FIG. 1, the tensile strength A
Was found to increase linearly until the Sb content up to about 7 wt% and conversely decrease as the Sb content further increases. Further, the compressive strength B increases linearly until the content of Sb reaches about 7 wt%, and does not increase so much even if the content of Sb further increases, and the hardness C and the melting point D show that the content of Sb is Sb. It was revealed that the amounts increased linearly as the amount increased. On the other hand, the impact value E sharply decreases when the Sb content exceeds 10 wt%. Comprehensively judging these results, it was confirmed that the addition amount of Sb was desired to be 4 to 10 wt%.

Example 2 A press die was cast by the above-mentioned direct casting method using an alloy composed of 55 wt% Bi-40 wt% Sn-5 wt% Sb, and a high-strength steel sheet (J
IS SCP45, thickness 1mm) was pressed, and the relationship between the number of press shots and die wear was investigated. For comparison,
Using a conventional eutectic alloy composed of 58 wt% Bi-42 wt% Sn, the same press die was manufactured by the same method as this example, and the same investigation was conducted. The mechanical properties of the product of this example and the comparative product are as shown in the table below, and the mechanical strength of the product of this example is significantly higher than that of the comparative product.

FIG. 2 shows the results of the above investigation. From this, the number of press shots that reach the specified wear amount of 0.3 mm is 90 as shown by the line Pa in the case of the product of this example, and the number of press shots of the comparative product is as follows.
As shown by the line Pb, with 50 sheets, it was confirmed that the press die made of the alloy of the present invention had a remarkably long life. this is,
As shown in the above table, it is estimated that the hardness and mechanical strength of the product of this example are large.

Example 3 Using the same press die as in Example 2, press working of steel sheets (pressed materials) having various tensile strengths was performed, and the forming strength (sheet thickness × tensile strength) and die wear amount of the pressed articles. I investigated the relationship with. The same investigation was conducted for the above comparative product.

FIG. 3 shows the results of the above-mentioned investigation. The molding strength of the material to be pressed which falls within the detailed wear amount is about 45 for the comparative product, while that for the product of this embodiment is about 45. It was 70, and it was confirmed that the alloy of the present invention can sufficiently cope with the processing of high-power steel plates.

In Examples 2 and 3 above, as a result of investigating the amount of volume change at the time of casting a press die using the alloy of the present invention, only a slight shrinkage (0.2%) was observed from 0 volume change. , An extremely accurate mold was obtained. Further, since the volume change was small, there were no internal defects such as shrinkage cavities and a mold having a good casting surface was obtained. Further, the press molds produced in Examples 2 and 3 were tested for heat shrinkage. As a result, the value was 1.0 / 1000, and the heat shrinkage of the wooden mold used in the direct casting method was 1/1000, dual. It was confirmed that the heat shrinkage was 1.2 / 1000 in the sheet metal model used in the foam method, which was almost equivalent.

(Effects of the Invention) As described in detail above, the low melting point alloy according to the present invention is a Bi-Sn alloy in which the volume change during solidification is small by adding a predetermined amount of Sb to the Bi-Sn alloy. Which can improve the mechanical strength and wear resistance as much as possible without deteriorating the properties of the cubic alloy, and can set the melting point to an appropriate temperature, and remarkably improve the applicability to the press mold or the injection mold. Became. In addition, since the volume change during solidification is small, good manufacturability can be ensured, and the raw material cost can be increased, which is advantageous in cost.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of Sb on the mechanical and physical properties of a Bi—Sn low melting point alloy, and FIGS. 2 and 3 are simple wear resistances using the alloy of the present invention. It is a graph which shows.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Kadota 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Hiroyuki Somoto 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Masato Ito 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) Reference JP-A-53-117627 (JP, A) JP-B-43-4105 (JP, B1)

Claims (1)

[Claims] 1. A low-melting-point alloy used as a simple mold such as a press mold or an injection molding mold, wherein Bi50-60 wt%, Sb4
A low melting point alloy for simple molds consisting of ~ 10wt% and the balance Sn.