JPS62142744A - Cast iron for glass forming - Google Patents

Abstract

PURPOSE:To obtain a cast iron for glass forming combining superior machinability with thermal conductivity and giving improved service life of dies, by providing a composition containing prescribed amounts of C, Si, Al, Mo, Cr, Ni, and Cu and having vermicular graphite structure. CONSTITUTION:The cast iron for glass forming has a composition consisting of, by weight, 2.5-3.5% C, 3.00-6.00% Si, 0-2.0% Al, 0-2.0% Mo, 0-2.0% Cr, 0-2.0% Ni, 0-3.0% Cu, and the balance Fe with usual impurity components and having vermicular graphite structure. The cast iron for glass forming of this invention has excellent machinability similar to that of conventional gray cast iron, when used for glass forming, and is easy to be worked. Moreover, owing to its superior thermal conductivity, said cast iron can produce glass products at high production speed, in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to cast iron for glass forming. 4. The present invention relates to the above-mentioned cast iron for glass molding, which has excellent machinability and thermal conductivity required as a glass mold material, and also has improved mold usage.

(Conventional technology) Mold materials for glass molding are characterized by machinability, thermal conductivity, and l1fF.
# Materials with excellent oxidation and oxidation resistance, high-temperature strength, and heat fatigue resistance are required, and gray cast iron has conventionally been used as a material that almost satisfies these requirements.

Generally, air remains in the corner of the inner surface of a glass molding mold during glass molding, so it is necessary to release this air to the outside of the mold.
A long hole leading to the outside of the mold is drilled. Since a thin drill or the like is used for this drilling, when drilling a deep hole, the drill becomes engorged, making the work difficult. Furthermore, the fact that the rejected portion is a corner portion also increases the difficulty of this work.

For the reason of the addition F: 1 as described in 1-4 below, it is first necessary that the mold material for crow molding has good machinability.

Here, there is a flaky graphite structure in the iron of the mouse #1.
Since this breaks up the chips generated during cutting without making them continuous, the machinability is extremely good.

Next, gray cast iron has the highest thermal conductivity among ferrous materials. For comparison, Table 1 shows the thermal conductivity at room temperature of gray cast iron, copper alloy steel, and stainless steel.

Table 1. Thermal conductivity of iron-based materials Materials Thermal conductivity (cat/cm, sec, ”0
) fT through gray cast iron 0.14 ~ 0.18f
Itsu steel material 0.08 ~ 0.09 Stainless steel w4 0.038 ~ 0.04 In this way, the thermal conductivity of gray cast iron is about 2 (r
j, which corresponds to about 4 times that of stainless steel.

Due to such excellent thermal conductivity, glass forming operations 117,
Among ferrous materials, gray cast iron has the smallest temperature non-uniformity throughout the mold, and the breakage rate due to thermal strain that occurs in glass products is the lowest in the first stage of slow cooling immediately after glass molding.

Furthermore, due to the excellent thermal conductivity of this mold, during glass molding, the rate of heat transfer to the mold is greater than that of high-temperature glass, and the glass is quickly cooled and removed from the mold, increasing productivity.

(Problems to be solved by the invention) As described above, gray cast iron is not suitable for use as a mold material for glass molding.
Although it is generally used at present because it satisfies most of the major conditions, it is not necessarily fully satisfied in practice.

A disadvantage associated with gray cast iron molds is their relatively short service life, as discussed below.

(+) The tip of flaky graphite that exists in gray cast iron is the second
As shown in the microscopic cross-sectional photograph (140x magnification) in the figure, it has a sharp shape, and thermal stress during glass manufacturing is concentrated in this part, making it easy for cracks to occur.

Furthermore, the mold surface deteriorates or is destroyed due to the propagation of this crack.

(2) The SiI & min of Samurai-dong gray cast iron is approximately 2%, and the A1 inflection point at which volume changes occur is as low as approximately 750°C.On the other hand, the temperature at which molten glass is charged into the mold is Approximately 800
°C, and the temperature at which the glass product is taken out is approximately 500 °C. For this reason, the mold surface is subjected to repeated thermal cycles in the temperature range of approximately 500 to 800 DEG C. over an operating range. Therefore, the mold surface is heated to approximately 750°C during each glass molding process.
A volume change occurs due to the transformation, and as a result, an extremely large thermal stress is generated repeatedly, causing rapid deterioration of the gold Jlj1 surface, leading to destruction.

(3) In addition, fIt gray cast iron has a Si content of about 2%, so it is inferior in terms of oxidation resistance and corrosion resistance.

As described above, glass molds made of gray cast iron have a short service life, so conventional production sites continuously observe the surface roughness of glass products during continuous operation.

When the surface roughness of a glass product exceeded a specified limit, the mold was immediately replaced.

The purpose of the present invention is to maintain the excellent machinability and thermal conductivity found in the conventional gray cast iron, while avoiding the disadvantages of relatively high thermal cracking susceptibility, oxidation resistance, bubble resistance, and high temperature. Our objective is to provide cast iron for glass molding with improved strength, etc.

(Means for Solving the Problems) The first aspect of the present invention is as follows: C: 2.5 to 3.5%, Si: 3.00 to 6.00%, Aλ: 0
~2.0%, MO20~2.0%, Cr: 0~2.0%, Ni: 0~2.0%, Cu: 0~3.0%, balance from iron and normal impurity components Note the composition (all the above component values are amount %), and the graphite M1 has a caterpillar shape.
This is achieved by using glass-forming cast iron with a texture.

(Function) In the cast iron for glass forming of the present invention, the machinability and thermal conductivity of the resulting glass mold material are basically higher than that of conventional glass mold materials due to the C flake graphite structure formed by the C component. It is extremely superior, just like cast iron, and not only makes complex machining such as drilling holes in molds easy,
It is possible to reduce the breakage rate of glass products due to thermal strain and to enable quick removal of products, thereby improving productivity.

In particular, the cast iron for glass molding of the present invention has improved oxidation resistance by increasing the Si content compared to conventional gray cast iron, and has an At transformation point higher than g1, which makes it difficult for the mold material to undergo thermal cycles. By avoiding the effects, the service life of the mold is improved. Furthermore, since the C component and other components are fixed within the above-mentioned specific range, a considerable portion of the flaky graphite structure is, for example, shown in the microscopic cross-sectional photograph (
As shown in the figure (140x magnification), it has a caterpillar-like shape with a rounded tip, suppressing the occurrence of cracks due to concentration of thermal stress, and preventing the surface of the mold material from deteriorating or breaking.

In the Ikemi invention, the alloying elements such as A, Xi, Cr, MOlCu, etc., which are combined in predetermined ranges, improve the IIt oxidation resistance and corrosion resistance of the mold material. The base metal structure becomes finer and the strength increases.

The effects of the above-mentioned components used in the cast iron for glass forming of the present invention, the significance of their numerical limitations, and the limitations of the shape of the graphite structure will be further explained below.

C is the main element that forms a graphite structure in the cast iron for glass forming of the present invention, and this stitch directly affects the degree of graphitization and its shape. The optimum range of C for obtaining the graphite form was set at 2.5 to 3.5% (weight %, the same applies hereinafter). 2
This is because if the C content is less than 65%, the amount of graphite is insufficient, while if it is more than 3.5%, it becomes difficult to obtain caterpillar-like graphite.

Si is added to raise the At transformation point of cast iron and improve its oxidation resistance, and its content ranges from 3.00 to 6.00%.
It is. In order to make the At transformation point 800℃ or higher, 3
% or more of Si is required, but if Si exceeds 6%, it is not preferable because a large amount of brittle intermetallic compound force (brittle intermetallic compound force) occurs in the base ferrite.

A content increases the A1 transformation point of cast iron and improves its oxidation resistance, but since the addition of multiple components impairs the castability of the molten metal, its range is set at 0 to 2%.

MO improves the strength of the base metal part of cast iron, especially for thermoelectric g
This element is added to reduce J sensitivity, but if the amount exceeds 2%, carbides will form at the grain boundaries and make the material brittle, so the range is set to 0 to 2%.

Cr is effective in making the base metal more dense and improving heat resistance. However, when 2% or more is added, M.

Similarly, since carbides are generated at grain boundaries and make the material brittle, the range is set to 0 to 1.5%.

Ni makes the base metal finer and contributes to the stability of the oxide film!
It has a great effect on However, this effect is not so effective even if the Ni content is 2% or more, so the Ni content is set in the range of 0 to 2%.

Cu, like Ni, is effective in making the base metal finer, but if it is added in an amount of 3% or more, the high-temperature strength is reduced, so the range is set to 0 to 3%.

The graphite structure directly affects the machinability and thermal conductivity of cast iron as a mold material, and as mentioned above, it is desirable to include as much of it as possible in the shape of flakes, but in practice Since it is impossible to specify the exact shape and quantity from the point, it was determined based on the observation of the graphite structure of the mold, which yielded good results in field experiments. The caterpillar-shaped graphite shown in micrograph 1 (140x magnification) in Figure 1 was taken as 20% of the total graphite powder.
Those containing the following are preferred.

EXAMPLE Cast iron for glass molding of the present invention with various components within the above ranges was manufactured by a conventional method, and the quality necessary for glass molds was maintained using conventional mouse molds.
A comparison was made with iron.

Table 2 shows the composition of each component of the cast iron samples (A-F) of the present invention in terms of oxidation increment (IIK/Cr) as a measure of their oxidation resistance.
n') and ζ. In the table, oxidative growth is 85Q°C1
This is a value measured under 24 hour conditions.

As is clear from Table 2 below, the degree of oxidation of the cast iron of the present invention is S.
Compared to conventional gray cast iron, the oxidation resistance has been reduced to about 115 to 1/9, and its oxidation resistance has been significantly improved.

Next, the yield strength of the cast iron of the present invention (Samples B and E) and the conventional gray cast iron was tested at room temperature (20°C) and 600°C, and the results are shown in Table 3.

Table 3 Proof strength (0.2%) test results 20℃ 600℃ (kg/cm') (kg/cm'
) Invention cast iron B 15.1 12.5E
13.6 10.3 Gray cast iron
7.8 3.4 (In terms of yield strength, the cast iron of the present invention has a di that is approximately three times that of conventional gray cast iron.

As already mentioned, the main cause of rapid deterioration due to high cycles in conventional gray cast iron glass molding molds is due to heat exhaustion. That is! 111, the mold surface is repeatedly heated and cooled in the temperature range of approximately 500 to 800°C, so the mold surface repeatedly passes through the Al transformation point (approximately 750°C), and the volume due to the change in t. Changes occur that translate into extremely large thermal stresses. In conventional gray cast iron, this thermal stress is concentrated at the tip of the flaky graphite, which has a sharp notch shape, so that many cracks easily occur, leading to destruction. In the cast iron of the present invention, in order to compensate for these drawbacks of the conventional cast iron, the Si component was increased and Ai was added as an alloy component having a strong effect of raising the Al f state E. Table 4 shows the rise in the At transformation point in comparison with that of conventional cast iron.

Table 4 Material type Al deformation point (°C) undeveloped 11 iron A
912 Mouse p1 iron 743 From Table 4 I! II. Cast iron of the present invention (Samples A, C)
, F), the A1 transformation points were all sufficiently higher than 800°C, and the effects of thermal cycles of the mold could be avoided. The same was true for other samples B, D, and H.

In addition to the thermal stress generated when passing through the Alz point, the mold also generates thermal stress due to simple heating and cooling, and this concentrates at the tip of the flaky graphite.In order to avoid this stress concentration, the flaky graphite The shape of the tip is rounded, and the shape of flaky graphite is similar to that of potato.

The microscopic cross-sectional photograph in FIG. 1 shows the graphite structure of Sample E of the cast iron of the present invention.

As shown in the photo, the graphite shape has rounded tips and is properly dispersed, so the excellent machinability and thermal conductivity of gray cast iron are maintained.

Table 5 shows the present invention cast iron and conventional gray cast iron.
71 thermal cycles of heating and cooling repeated 36,000 times to C.
The results are shown below.

Table 5 Crack test results Number of pieces 1i Uniform depth Maximum depth m+s) (m) Mainly generated 1#P1 iron B 27 0.043
0.140 38 0.048 0.18E
23 0.025 0. (19 Gray cast iron 7Ei O, 1030, 43 Both the number of cracks and their depth in the cast iron of the present invention are significantly reduced compared to the conventional gray cast iron.

(Effects) The #fi for glass molding according to the present invention has excellent machinability and is easy to process as in the case of conventional gray cast iron, and has good thermal conductivity. Product glass can be produced at high production speed and with good yield. In particular, the cast iron for forming glass molds of the present invention has excellent resistance to corrosion and thermal and mechanical stress, and the service life of the mold is significantly increased.

[Brief explanation of drawings]

FIG. 1 is a me mirror photograph showing an enlarged cross-section of the structure of the cast iron for glass forming of the present invention, and FIG. Patent applicant: Toyo Chuko Co., Ltd.□! Representative Patent Attorney: Mr. Ohara, 2nd Department (1 other person), District 1, Figure 2

Claims (2)

[Claims] (1) C: 2.5-3.5%, Si: 3.00-6.00%, Al: 0-2.0%, Mo: 0-2.0%, Cr: 0-2.0 %, Ni: 0 to 2.0%, Cu: 0 to 3.0%, the balance is iron and normal impurity components (all of the above component amounts are weight %), and the graphite is in the form of a caterpillar. A cast iron for glass forming characterized by having a structure. (2) The cast iron for glass forming according to claim 1, wherein the caterpillar-like graphite structure accounts for 20% or more of the total graphite.