JP2008169107A - Method for production of glass-forming die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die with high precision in its shape by preventing the occurrence of cracks on a surface coating layer at forming temperatures, while preventing plastic deformation of the die. <P>SOLUTION: A base material is produced by quenching a steel material which contains carbon of ≥0.3 and ≤2.7 wt.%, chromium of ≤13 wt.% and includes an additive satisfying at least one of 0.5-3 wt.% molybdenum, 0.1-5 wt.% vanadium and 1-7 wt.% tungsten, and then quenching the resultant steel material at a temperature of 400-650°C. A surface coating layer comprising an amorphous Ni-P alloy is formed on the surface of the above base material, is subjected to heat treatment and thus is converted into an eutectic structure of Ni and Ni<SB>3</SB>P. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a glass molding die that requires precise processing, and more particularly to a method capable of maintaining the shape of the die with high accuracy.

  In the field of plastic molding, precision processing technology for molding dies has been established, and mass production of optical elements having fine shapes such as diffraction gratings has been realized. In this case, the mold is manufactured by performing electroless Ni-P plating on the surface of a base material made of stainless steel, and then precisely processing the plated layer with a diamond bite.

  However, when a mold similar to this is applied to glass molding, there arises a problem that cracks occur in the electroless Ni—P plating layer. This phenomenon is due to the molding temperature. In other words, the Ni-P plating layer has an amorphous structure in the plating state, but when heated to about 270 ° C. or higher, crystallization starts, and at that time, the plating layer undergoes volume shrinkage and tensile stress Acts to cause cracks in the plating layer.

As a countermeasure against this problem, a base material having a thermal expansion coefficient of 10 × 10 ^{−6 to} 16 × 10 ⁻⁶ (K ⁻¹ ) is selected, and heat treatment is performed at 400 to 500 ° C. after plating. However, even if the thermal expansion coefficient of the base material is matched to that of the Ni-P plating layer, volume contraction due to crystallization occurs only in the plating layer during heat treatment, so that a large tensile stress acts on the plating layer, causing cracks. There was a case where it occurred (see, for example, Patent Document 1).

Further, when the temperature becomes high during use of the mold, there is a problem that plastic deformation occurs in the mold and the shape of the mold cannot be maintained with high accuracy.
JP-A-11-157852

  The present invention prevents the occurrence of cracks in the surface coating layer at the molding temperature, and prevents the plastic deformation of the mold, thereby maintaining the shape of the mold with high accuracy and increasing its life. It aims at providing the manufacturing method of the metal mold | die for glass molding which can be performed.

  In order to solve the above-described problems and achieve the object, the method for producing a glass molding die of the present invention is configured as follows.

Carbon is 0.3 wt% to 2.7 wt%, chromium is 13 wt% or less, molybdenum is 0.5 wt% to 3 wt%, vanadium is 0.1 wt% to 5 wt%, tungsten is 1 wt% to 7 wt% %. The steel material to which an additive satisfying at least one of the following is added is quenched, and a base material is formed by tempering at 400 ° C. or higher and 650 ° C. or lower, and the surface of the base material is amorphous. A surface coating layer made of a high quality Ni—P alloy is formed, and the surface coating layer is changed to a eutectic structure of Ni and Ni ₃ P by subjecting it to a heat treatment.

Carbon is 0.3 wt% to 2.7 wt%, chromium is 13 wt% or less, molybdenum is 0.5 wt% to 3 wt%, vanadium is 0.1 wt% to 5 wt%, tungsten is 1 wt% to 7 wt% %. A steel material to which an additive satisfying at least one of the following is added is quenched, and a substrate is formed by subzero treatment, and an amorphous Ni-P alloy is formed on the surface of the substrate. The surface coating layer is formed, and the surface coating layer is changed to a eutectic structure of Ni and Ni ₃ P by heat-treating the surface coating layer.

  According to the present invention, it is possible to maintain the shape of the mold with high accuracy and increase its life by preventing the surface coating layer from cracking at the molding temperature and preventing the plastic deformation of the mold. It becomes possible to make it.

  FIG. 1 is a block diagram showing an outline of a manufacturing process of a glass molding die according to an embodiment of the present invention. Manufacture of a glass mold is performed by the following process.

  In addition, as a base material, carbon is 0.3 wt% or more and 2.7 wt% or less, chromium is 13 wt% or less, molybdenum is 0.5 wt% or more and 3 wt% or less, vanadium is 0.1 wt% or more and 5 wt% or less, A steel material to which an additive satisfying at least one of tungsten in an amount of 1 wt% to 7 wt% is used.

  After roughing such a substrate (ST1), quenching and high-temperature tempering are performed (ST2). Next, after pre-plating processing (ST3), a surface coating layer (plating layer) made of a Ni-P alloy is formed by electroless plating (ST4). Next, heat treatment is performed on the base material and the surface coating layer (ST5) to crystallize the surface coating layer and change the base material into a tempered structure. Next, after finishing the substrate (ST6) and finishing the surface coating layer (ST7), the surface coating layer is coated with a release film (ST8).

  In the manufacturing method according to the present embodiment, the surface coating layer is prevented from cracking even when high-temperature tempering is performed by using a steel material in which Mo, V, and W are added to improve the high-temperature hardness. . This is because a large amount of retained austenite exists immediately after quenching, but when high temperature tempering is performed, the structure changes to a low carbon martensite and martensite structure.

  In addition, the temperature in high temperature tempering needs to be 400-650 degreeC or less. This is because at a temperature lower than 400 ° C., there is not much effect in reducing the retained austenite, and when it exceeds 650 ° C., the substrate is remarkably softened. Note that sub-zero treatment may be performed instead of high-temperature tempering. This is because the sub-zero treatment also has an effect of transforming retained austenite to martensite.

The surface coating layer is formed using a Ni-P alloy, for example, Ni-P, Ni-P-B, or Ni-P-W. These structures are amorphous or partially amorphous in a plated state, and are transformed into a completely crystallized mixed structure of Ni and Ni ₃ P by heating at about 270 ° C. or higher.

  The temperature of the heat treatment needs to be higher than the use temperature of the mold (that is, the glass forming temperature). This is because if the temperature is lower than the use temperature of the mold, a dimensional change occurs during use, and the dimensional accuracy of the molded product decreases. If the heat treatment temperature is raised too much, the plated surface is affected, so the upper limit of the heat treatment temperature is about 700 ° C.

  Next, the reason for using the steel material having the components described above as the base material will be described. That is, the C content was set to 0.3 wt% or more and 2.7 wt% or less. If the C content is lower than 0.3 wt%, the volume shrinkage of the base material during tempering becomes too small. On the other hand, when the C content exceeds 2.7 wt%, the volume shrinkage of the base material is sufficient, but adverse effects such as a decrease in toughness occur.

  Moreover, Cr content was 13 wt% or less. This is because if the Cr content exceeds 13 wt%, the retained austenite is difficult to decompose. In addition, there is no restriction | limiting in particular about the lower limit of Cr content.

  Regarding the additives Mo, V, and W, Mo was 0.5 wt% to 3 wt%, V was 0.1 wt% to 5 wt%, and W was 1 wt% to 7 wt%. This is because if the amount of these additives is too small, the high-temperature hardness of the substrate is not sufficient and plastic deformation may occur due to the pressing pressure. Note that the upper limit is set because the cost increases if the number is increased more than necessary.

  Fabrication of 100 μm electroless Ni-P plating on the base material of various components, the number of cracks generated during heat treatment and molding, and the plastic deformation of the base material when glass was molded The presence or absence was examined. Table 1 shows the relationship among the components of the base material, the tempering temperature, the crack generation rate, and the presence or absence of plastic deformation. The specimen 7 uses a plastic molding die subjected to conventional heat treatment as a comparative example. Moreover, all the molding temperatures were 550 degreeC.

  As can be seen from Table 1, cracks and plastic deformation were not observed in the molds (samples 5 and 6) manufactured based on the manufacturing method of the present invention.

  As described above, in the glass molding die manufacturing method and glass molding die according to the present embodiment, the surface coating layer is prevented from cracking at the molding temperature, and the plastic deformation of the die is prevented. In addition, it is possible to maintain the shape of the mold with high accuracy and to increase its life.

  The present invention is not limited to the above embodiment. For example, you may make it perform the heat processing of a base material and a surface coating layer after the finishing process of a base material, and the finishing process of a surface coating layer. Of course, various modifications can be made without departing from the scope of the present invention.

The block diagram which shows the outline | summary of the manufacturing method of the metal mold | die for glass forming which concerns on one embodiment of this invention.

Claims (4)

Carbon is 0.3 wt% to 2.7 wt%, chromium is 13 wt% or less, molybdenum is 0.5 wt% to 3 wt%, vanadium is 0.1 wt% to 5 wt%, tungsten is 1 wt% to 7 wt% %. The steel material to which an additive satisfying at least one of the following is added is quenched, and the base material is formed by tempering at 400 ° C. or more and 650 ° C. or less,
Forming a surface coating layer made of an amorphous Ni-P alloy on the surface of the base material,
A method for producing a glass molding die, wherein the surface coating layer is changed to a eutectic structure of Ni and Ni ₃ P by subjecting to heat treatment. The surface coating layer is formed by electroless plating including Ni and P, Ni and P and B or Ni, P and W,
The method for producing a glass molding die according to claim 1, wherein the heat treatment is at or above a glass molding temperature. Carbon is 0.3 wt% to 2.7 wt%, chromium is 13 wt% or less, molybdenum is 0.5 wt% to 3 wt%, vanadium is 0.1 wt% to 5 wt%, tungsten is 1 wt% to 7 wt% %. A steel material to which an additive satisfying at least one of the following is added is quenched, and a substrate is formed by sub-zero treatment.
Forming a surface coating layer made of an amorphous Ni-P alloy on the surface of the base material,
A method for producing a glass molding die, wherein the surface coating layer is changed to a eutectic structure of Ni and Ni ₃ P by subjecting to heat treatment. The surface coating layer is formed by electroless plating including Ni and P, Ni and P and B or Ni, P and W,
The said heat processing is more than the glass forming temperature, The manufacturing method of the metal mold for glass forming of Claim 3 characterized by the above-mentioned.

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