JPH0587346B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to casting molds that exhibit improved directional solidification, particularly those used in gravity casting or low pressure casting.

[Prior Art and Problems to be Solved by the Invention] When casting a relatively large and complex cast product or a cast product having a boss portion or an extremely thick wall portion, it is difficult to use conventional molds, such as steel molds. , uneven solidification, uneven solidification, solidification from the top, etc. occur, and cavities and cracks often occur in the thick wall parts and lower parts of cast products due to shrinkage caused by the conversion from molten metal to solid. It is. This tendency is particularly strong in the case of low-pressure casting.

The present inventor focused on configuring the mold by dividing it into three or more regions, that is, a region with heat retention, a region that can be cooled relatively quickly, and other regions,
Intensive research has been carried out to develop a casting mold that does not have the drawbacks of the prior art and exhibits improved directional solidification during casting.

[Structure of the Invention] As a result, the present inventor discovered that the casting mold part a, which includes a region corresponding to the thick part of the cast product near the runner channel and on the way to the riser part, is formed of a copper alloy. The other mold parts are made of steel, the inside of the riser part of the mold is covered with a heat-resistant insulation coating material, and the inside of the copper alloy mold part is made of Ni.
A plating layer, a Co/Mo/Cr alloy coating as an intermediate layer, and an Al ₂ O ₃ /ZrO ₂ -porous ceramic coating as an outer layer are provided, and the alloy composition of the intermediate layer is 45 to 65% by weight. Co, 20-40% by weight of Mo and the balance of Cr, and the composition of the ceramic layer is
It has been found that a casting mold characterized by 40-60% _by weight _Al2O3 and 60-40% by weight _ZrO2 can solve the above problems.

The copper alloy constituting the casting mold part a of the present invention, which includes a region corresponding to the thick wall part of the cast product near the runner channel and on the way to the riser part, is
The copper alloys described in No. 155532 are treated as described therein to improve wear resistance and/or durability. That is, in the patent application, a Ni plating layer is formed on the inner surface of the mold, followed by an alloy coating consisting of Co, Mo and Cr as an intermediate layer, and an outer layer.
A porous ceramic coating consisting of Al ₂ O ₃ and ZrO ₂ is provided, the composition of the alloy of the intermediate layer being 45-65% by weight Co, 20-40% by weight Mo and the balance Cr, and the ceramic layer Composition of 40-60% by weight
An alloy permanent mold for casting is described which is Al ₂ O ₃ and 60-40% by weight ZrO ₂ . The same alloy portion used in the present invention is also subjected to the same treatment as in this patent application. Therefore, the copper alloy used in the present invention contains Ni
Any material with a softening point of 400° C. or higher can withstand thermal spraying during intermediate coating and ceramic layer coating after plating. Examples of such alloys include the above-mentioned alloys described in Japanese Patent Application Laid-Open No. 159243/1983. This alloy is a copper alloy containing zirconium and titanium and in which there is a precipitated phase consisting of a compound of at least one of them and copper,
It has an electrical conductivity of 20% or more (IACS).
The copper alloy parts manufactured in this way have the thermal conductivity and temperature control properties of copper alloys, but also have wear resistance and durability, and are also made of ceramic layers with a large number of pores. Eliminate gas generated during casting to improve the surface condition of the product.

The heat-resistant, heat-retaining coating material of the casting mold of the present invention has the function of slowing down the solidification of molten metal in the area where the coating material is provided, compared to other areas. This material must have heat resistance that can withstand the temperature of the molten metal during casting, approximately 750 to 800°C (in the case of aluminum alloys and magnesium alloys).
Examples of such materials include a potassium titanate fiber-containing sheet, a potassium titanate fiber-containing coating layer, a tyranno fiber coating layer, an alumina fiber coating layer, a silicon carbide fiber coating layer, a carbon fiber coating layer, and the like.
Some of these coating materials are also the subject of unpublished inventions for which the present inventor has already applied for a patent.

The coating used in the patent application of the present inventor, JP-A-2-258140 entitled "Casting mold with coating containing potassium titanate fibers", is effective. The invention described in JP-A-Heisei discloses that an inorganic aqueous solvent has a length of 5 to 200 μm and a length of 0.05 to 0.05 μm.
A dispersion of potassium titanate (K ₂ Ti ₆ O ₁₃ ) fibers with a diameter of 5 μm is dispersed into at least one carbon fiber material of the group of cloth-like long carbon fibers, carbon fiber fabrics, and knitted fabrics with a diameter of 50 to 400 μm. The coating product is applied to the inner surface of the mold with a dry film thickness of A casting mold having a coating containing potassium titanate fibers as described above, wherein the inorganic solvent has a composition in which silica is a major component and zirconium oxide and sodium aluminate are minor components.

By providing a heat-resistant and abrasion-resistant coating containing potassium titanate fibers, as described in this patent, a heat-retaining mold area is obtained.

Another example of a heat-resistant heat-retaining coating material is the one used in the above-mentioned casting mold having a polytitanocarboxysilane fiber material-containing coating disclosed in Japanese Patent Application Laid-open No. 2-169150, which is a patent application filed by the present inventor. There are also coatings available. In this patent, a polytitanocarboxysilane fiber material is attached to the inner surface of a mold using an inorganic water-based adhesive, and the inorganic adhesive binds zirconium oxide and silica. It has a composition containing sodium aluminate as a major component and a minor component, the fiber thickness of the fiber material is 8 μm to 5 mm, and the total thickness of the fiber material and adhesive coating is 0.5 to 15 mm. , the above casting mold having a coating containing a polytitanocarboxysilane fiber material is disclosed. By providing this polytitanocarboxysilane fiber material-containing coating, a mold region with heat retention can also be obtained.

Further, as the heat-resistant heat-retaining covering material used in the present invention, a heat-resistant potassium titanate fiber-containing sheet disclosed in Japanese Patent Application No. 2-275743, which is also a patent application filed by the present inventor, is also effective. The sheet described in this patent application contains an inorganic mixture of zirconium oxide, silica, and sodium aluminate.
A heat-resistant potassium titanate fiber-containing sheet formed of dispersed potassium titanate (K ₂ Ti ₆ O ₁₃ ) fibers with a length of 200 μm and a diameter of 0.05 to 5 μm. This sheet provides heat retention and heat resistance, as well as thermal shock resistance, mold releasability, durability, and abrasion resistance to the covered area.

The part of the mold provided with this coating is in particular the part of the riser.

Methods for applying this coating are described in each of the above-mentioned patent applications.

The present invention will be explained in more detail with reference to the drawings: Fig. 1 is a drawing of an example of a gravity casting mold of the present invention.

FIG. 2 is a drawing of an example of a low-pressure casting mold of the present invention.

FIG. 1 is a schematic view of a mold for manufacturing a cast product that is cylindrical and has three thick annular portions in the middle and two bosses at the bottom annular portion.
In the figure, a shows a copper alloy mold part, b shows a steel mold part, and c shows a part in which a heat-retaining coating layer 6 is provided on a heat-resistant steel mold. In the figure, 1, 2
and 3 means the annular thick part of the cast product. 4 indicates a thin portion. 5 indicates a boss portion protruding from the thick annular portion.

FIG. 2 is a schematic diagram of a casting mold for manufacturing a product similar to that shown in FIG. 1 by a low-pressure casting method. a, b and c and 1 to 6 in the figure have the same meanings as above. 7 means a stalk placed under the casting mold.

The case where casting is performed using the casting mold of the present invention configured in this way will be explained below.

In the case of the gravity casting mold of Figure 1, the molten metal introduced through the sprue first enters the lowest region of the mold formed by the copper alloy, gradually rises to fill the steel region, and finally It ends with a steel top covered with a heat-retaining, heat-resistant cladding. After the mold is filled with molten metal, the areas of copper alloy are cooled with a cooling fluid. At that time, the area corresponding to the thick wall part uses a copper alloy with high thermal conductivity (approximately 7 times that of steel), so the cooling rate is fast, and the molten metal in the feeder area is absorbed by the coating material. Because it has increased heat retention,
The molten metal will solidify more slowly and will solidify after other areas of the mold have solidified. As a result, the molten metal solidifies from the bottom upwards, achieving optimal directional solidification.

In the case of the low-pressure casting mold shown in FIG. 2, the molten metal pushed up from the stalk rises upward from the bottom of the mold to fill the mold. The filled molten metal is
As with gravity casting, the lowest part formed of copper alloy solidifies first due to its high thermal conductivity and gradually solidifies in the upper part due to cooling. As the process progresses, a cast product of good quality can be obtained without forming cavities or cracks in the lowermost boss and pressure area. In the case of low-pressure casting molds, copper alloys are always used for reasons of cooling efficiency, since the part of the mold near the stalk is the hottest.

The present invention will be explained in more detail below using examples: Example 1 The gravity casting mold shown in Fig. 1 is manufactured: The product manufactured from this mold is cylindrical and has a wall pressure applied to the middle part. It has three annular parts, and the first annular part has two boss parts.

The a region of the mold is made of copper alloy. This copper alloy part is manufactured as follows: Electroplating is applied to the inner surface of a mold made of a copper alloy containing 0.18% by weight zirconium and 0.26% by weight titanium and having an electrical conductivity of 30% (IACS). by law
A Ni plating layer with a thickness of 200 μm is provided. Then 50 wt% Co, 30 wt% by plasma spraying method
An alloy consisting of Mo and 20 wt% Cr was heated to 8000℃
to form a 150μm coating film.

On the thus formed Co/Mo/Cr coating layer, 57% by weight of Al ₂ O ₃ was applied by a similar thermal spraying method.
and 43% by weight of _ZrO2 .
Coat with a thickness of 250 μm. The spraying temperature at that time is
It is 8000℃. Ceramic layers have many very small pores, making them porous.

b) The region is a steel section. This part is provided with a Co/Mo/cr coating and a ceramic layer, as in the case of the copper alloy described above. The thickness of the coating and ceramic layer is the same as for the copper alloy described above.

c) The area is provided with a potassium titanate fiber-containing coating. This coating is provided as follows.

50 g of a solvent consisting of 29.6% by weight zirconium oxide, 58.0% by weight silica and 2.4% by weight sodium aluminate are dispersed in 50 ml of water. 10 g of potassium titanate fibers having an average length of 20 μm and an average diameter of 0.9 μm are dispersed in this dispersion. This dispersion is applied to a 500 μm thick carbon fiber fabric to a wet coating thickness of 400 μm (dry coating thickness: approx.
215μm). This was dried at 90°C for 1 hour, then at 150°C.
Cure for 1 hour at a curing temperature of °C.

The cured carbon fiber fabric was then cured using a dispersion of 50 g of an adhesive consisting of 64.0 wt% zirconium oxide, 31.2 wt% silica, and 4.8 wt% sodium aluminate in 50 ml of water. , Paste it on the sprue and riser part.
This was similarly dried at 90°C for 1 hour, and then at 150°C.
Cure for 1 hour at a curing temperature of °C.

The copper alloy region of the above-mentioned mold thus produced is used to produce an aluminum alloy product having the above-mentioned shape while being cooled with water to 350-400°C.

We produced 1000 pieces and found no cavities or cracks.

Example 2 Repeat Example 1. However, the covering material in area c) is replaced with the following covering material containing a polytitanocarboxysilane fiber material. The coating is applied as follows: 50 g of an adhesive consisting of 64.0% by weight zirconium oxide, 31.2% by weight silica and 4.8% by weight sodium aluminate are dispersed in 15 ml of water. This dispersion was applied to the inner surface of the steel portion c to a wet film thickness of 300 μm and dried at room temperature for 1 hour.

On this adhesive coating, a polytitanocarbosilane (Tyrano fiber, manufacturer:
Ube Industries Co., Ltd.) Apply pressure to adhere fine fibers with uniform distribution, and spray the same adhesive solution as above on top of them. This is followed by drying at a temperature of 85°C for 1 hour, followed by curing at a curing temperature of 150°C for 1 hour. The total coating thickness is 1000μm.

The copper alloy part of the casting mold manufactured in this way,
It is used to produce aluminum alloy products of the above shape while cooling to 350~400℃.

We produced 1000 pieces and found no cavities or cracks.

Example 3 a Production of sheet 29.6% by weight of zirconium oxide in 50ml of water,
A dispersion was prepared in which 50 g of a mixture consisting of 58.0% by weight silica and 2.4% by weight sodium aluminate was dispersed, and this dispersion had an average length of 20 μm and an average diameter.
Further disperse 10 g of 0.9 μm potassium titanate fibers. A filter paper is placed on a filter paper having an inner diameter of 100 mm, and the dispersion is poured onto the filter paper to remove most of the water by suction filtration. A sheet approximately 1 mm thick when wet is obtained. Remove this along with the filter paper and place on a fresh filter paper to air dry for 1 hour at room temperature. It is then cured for 1 hour at a curing temperature of 150°C in a drying room. The resulting sheet is approx.
It has a thickness of 0.6m.

b Use in molds 64.0% by weight of zirconium oxide in 50ml of water,
The sheet produced according to a) with a dispersion of 50 g of adhesive consisting of 31.2% by weight silica and 4.8% by weight sodium aluminate was placed in the gravity casting mold shown in FIG. Attach to the inner surface of the sprue and riser. After being left to dry at room temperature for 1 hour, it is cured in a drying room at a temperature of 150°C. The other parts of the mold are the same as in Example 1.

The copper alloy part of the casting mold manufactured in this way
It is used to produce aluminum alloy products of the above shape while cooling to 350~400℃.

We produced 1000 pieces and found no cavities or cracks.

Comparative Example The aluminum alloy cast product described in Example 1 is cast by a low-pressure casting method after being soft coated in a steel mold.

Out of the 10 cast products manufactured, 5 had cavities in the thick wall parts and boss parts.

[Effects of the Invention] The casting mold of the present invention exhibiting improved directional solidification can prevent the occurrence of defective products due to cavities and cracks, and can omit the complexity of mold coating. Therefore, the contribution of this mold to industry is remarkable.

[Brief explanation of drawings]

FIG. 1 is a drawing of an example of a gravity casting mold of the present invention, and FIG. 2 is a drawing of an example of a low pressure casting mold of the invention. The symbols in the figure have the following meanings: 1 to 3... Annular thick part of the cast product, 4... Thin wall part of the cast product, 5... Boss part, 6... Heat retaining coating layer, a... Copper alloy mold part, b... Steel mold part, c... Steel mold part provided with a heat-retaining coating layer.

Claims (1)

[Claims] 1. The casting mold part a, which is close to the runner and on the way to the riser part and includes a region corresponding to the thick part of the cast product, is made of copper alloy, and the other mold parts are made of steel. The inside of the riser part of the mold is coated with a heat-resistant heat-retaining coating, and the inside of the copper alloy mold part is coated with a Ni plating layer, and an alloy coating consisting of Co, Mo, and Cr as an intermediate layer. A porous ceramic coating consisting of Al ₂ O ₃ and ZrO ₂ is provided as an outer layer, and the composition of the alloy of the intermediate layer is 45-65% by weight of Co, 20-40% by weight of Mo and the balance Cr. and the composition of the ceramic layer is 40
Casting mold characterized by ~60% _by weight _Al2O3 and 60-40% by weight _ZrO2 .