JPH02255267A - Production of metallic mold for molding tire - Google Patents

Abstract

PURPOSE:To prevent the generation of detects in the molding surface of a metallic mold for molding tires by using a metallic material having a specific average coefft. of thermal expansion in a specific temp. range as metal pieces for internal chill. CONSTITUTION:The metallic mold for molding tires having the metal pieces 1 is produced by casting an aluminum alloy into a casting mold 2 implanted with the metal pieces 1 and internally chilling the metal pieces 1. The metallic material having the characteristics of <=10X10<-6>/ deg.C average coefft. of thermal expansion in the temp. range from a room temp. to 400 deg.C is used as the metal pieces 1 for internal chill Invar, 'Kovar(R)', etc., are used as the material of metal pieces 1. The generation of cracks and peel around the metal pieces 1 is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a tire mold.

(Prior art) When forming a narrow slit with a width of about 1 inch on the surface of a tire, a tire mold is used that has metal pieces called sipes protruding from the inner surface of the tire. There is.

When manufacturing such tire molding molds by casting, sipes are generally implanted into the surface of the plaster mold, and the surface shape of the plaster mold is reversed as the molding surface of the tire molding mold during casting. A method has been adopted in which the sipes are cast in at the same time.

However, the conventional sipe is SO340g, 5US304
The sipes are usually made of stainless steel alloys, so there is a large difference in thermal expansion between them and the plaster mold, and when pouring hot molten aluminum alloy, the sipes expand thermally and the plaster around the sipes expands. The mold sometimes peeled off due to cranking of the mold. Since such a peeled part of the mold causes a concave defect, which is a serious defect on the molding surface of a tire mold, there has been a strong demand for measures to prevent this.

(Problems to be Solved by the Invention) The present invention provides a tire molding tool that does not cause the risk of cracking around the sipes, even when manufacturing a tire molding mold by casting an aluminum alloy into a mold in which sipes are implanted. It was completed to provide a method for manufacturing molds.

(Means for Solving the Problems) The above III is a method for manufacturing a tire molding die having sipes by casting an aluminum alloy into a mold in which sipes are embedded and casting the sipes into the mold. This problem can be solved by a method for manufacturing a tire molding die, which is characterized in that the sipe is made of a metal material having an average coefficient of thermal expansion of 10XIO-6/°C or less in the temperature range from room temperature to 400°C.

In the present invention, the above-mentioned sipes for castings are used in order to reduce the difference in thermal expansion between the sipes and plaster and to prevent the occurrence of cranks due to thermal expansion. The reason for using a metal material as the material for the sipes is that the average coefficient of thermal expansion in the temperature range from room temperature to 400°C is 10 x 10-"/"C or less.
From the relationship between the solidification rate at the mold surface layer when the molten aluminum alloy cast at 700"C solidifies and the temperature rise of the sipe itself, the mold can be However, if it is outside this range, the mold is likely to be damaged due to the difference in thermal expansion between the sipes during casting of the aluminum alloy and the gypsum, which is the mold material.

The material of the sipe has a coefficient of thermal expansion within the above range, and
It must be easy to process such as rolling, bending, and punching, and it must not melt at the aluminum casting temperature.
From the above point of view, it is most preferable to use an iron-based invar type alloy.

(Example) Commercially available Invar (Fe-36%Ni) Kovar (Fe-29%Ni-17%Co), SO
5403 (Fe-12%Cr), SO5304 (F
e -8%Ni-18%Cr) from each metal plate with a thickness l
A large number of plate-shaped sipes (1) each having a length of 30 mm were manufactured, and 50 of them were each implanted on the surface of a plaster mold (2) as shown in the drawing. 25 pieces of this plaster mold (2)
After drying at 0℃, insert the aluminum alloy 630, which is equivalent to JIS ACdA, into the main mold (3).
``The sipe cast in C, separated from the mold, and then casted again.
2) The number of defects caused by mold breakage around the mold was investigated. The results are shown in the table below.

As mentioned above, the number of defects caused by mold breakage was seven in Example 1 in which Invar was used as the sipe material, but the degree of defects was at a level that could be easily corrected. Further, in Example 2 using Kovar, the number of defects was O.

On the other hand, in Comparative Examples 1 and 2, in which the average coefficient of thermal expansion exceeds 10 x 10-'/'C in the temperature range from room temperature to 400°C, defects occurred at 21 and 46 locations, respectively, and most of them were It was at a level that was impossible to correct.

In addition, in Comparative Examples 1 and 2, cranks were already observed around half of the sipes at room temperature after drying the plaster mold at 250°C, but in Examples 1 and 2, cranks were already observed at this stage. No cracks were observed at all.

(Effects of the Invention) As explained above, the present invention uses a metal material having an average coefficient of thermal expansion of 10×10-”/”C or less in the temperature range from room temperature to 400°C as a sipe for casting. This reduces the difference in thermal expansion between the sipes and the gypsum during drying of gypsum molds and casting of aluminum alloys, and prevents or significantly reduces the occurrence of cracks and peeling around the sipes. be. Therefore, according to the present invention, concavities, which are serious defects, do not occur on the molding surface of a tire molding die due to peeling of the mold, and the number of man-hours for repairing the molding surface of the mold can be significantly reduced. can. Further, the present invention has the advantage that it can be incorporated into the production process extremely easily, since the conventional process can be carried out as is by simply changing the material of the sipe.

Therefore, the present invention greatly contributes to the development of industry as a method for manufacturing a tire molding die that solves the conventional problems.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating the steps of an embodiment of the present invention. (1): Sipe, (2): Mold.

Claims (1)

[Claims] In a method of manufacturing a tire molding mold having sipes by casting an aluminum alloy into a mold with sipes implanted and casting the sipes, the sipes for casting have an average coefficient of thermal expansion in the temperature range from room temperature to 400°C. A method for manufacturing a tire mold, characterized in that a metal material having a characteristic of 10×10^-^6/°C or less is used.