JPH0635027B2 - Copper alloy permanent mold for discontinuous casting - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a copper alloy mold for casting, which has good thermal conductivity and thus can be easily temperature-controlled, and has problematic wear resistance and durability. To a copper alloy mold for discontinuous casting having improved

[Prior Art and Problems to be Solved by the Invention] From Japanese Patent Publication No. 61-5819, a Ni plating layer is formed on the inner surface of a mold, and Co: 45 to 65 wt%, Mo: 20 to 40 wt% are formed on the Ni plating layer.
A continuous casting mold is known in which a Co-Mo-Cr alloy layer consisting of 10% and the balance Cr is sprayed.

In this publication, a relatively large amount of cobalt molybdate (CoMoO ₄ ), which exerts an excellent effect on wear resistance and seizure resistance of the alloy layer in which the above Co-Mo-Cr composition occurs, is generated. It is also disclosed that it is possible. When this continuous casting mold is used as a mold for customary discontinuous casting, for example, low pressure casting, gravity casting, etc., it is not possible to sufficiently eliminate gas during casting, so "blind" ( There is a drawback that irregularities are generated and the surface condition of the molded product is poor.

A further drawback of this prior art mold is that it requires frequent coating with a soft coating agent such as water glass containing ceramic powder. Therefore, the time and economical cost for the work are enormous, and there is a problem in this respect as well.

DISCLOSURE OF THE INVENTION The present invention does not have the drawbacks of the prior art, has a very long life without applying a mold, and discontinuous casting with good thermal conductivity that always makes the surface condition of the obtained molded body good. It is an object to provide a casting mold.

[Structure of the Invention] The present inventor has made a nickel alloy layer having good thermal conductivity and a nickel plating layer on the inner surface of a mold, on which a Co-Mo-Cr- alloy coating of a specific composition ratio and an outer layer are provided as an intermediate layer. It has been found that such problems can be solved when an Al ₂ O ₃ -ZrO ₂ -porous coating having a specific composition ratio is provided as a layer.

Therefore, the object of the present invention is that a Ni plating layer having a thickness of 50 to 300 μm is formed on the inner surface of the mold, and then 50 to 300 as an intermediate layer.
A Co-Mo-Cr-alloy coating with a thickness of 600 μm and an Al ₂ O ₃ -ZrO ₂ -porous ceramic coating with a thickness of 50-500 μm as outer layer are provided, the composition of the alloy of the intermediate layer. Is 45-65 wt% Co, 20-40 wt% Mo and the balance Cr, and the composition of the ceramic layer is 40-60 wt% Al ₂ O ₃ and 60-
The present invention relates to a copper alloy permanent mold for discontinuous casting, which is characterized by containing 40% by weight of ZrO ₂ .

The copper alloy used in the present invention is a good heat conductive copper alloy having an appropriate strength and a thermal conductivity of 4 or more. For example, as described in "Metal Data Book", edited by The Japan Institute of Metals, published by Maruzen Co., Ltd., July 20, 1974, strength is increased and appropriate by mixing a small amount of various non-ferrous metals with copper. It retains excellent thermal conductivity. This is, for example, a copper alloy containing a slight amount of 0.05 to 1% of at least one member of the group Sn, Zr, Zn, Si, Be, Cr and Ti. In the present invention, 0.15 wt% Zr, 0.85 wt%
Cr, 0.2 wt% Ti or 0.15 wt% Zr and 0.85 wt
Copper alloys containing% Cr are particularly advantageous.

Since copper alloys generally have a low softening point, the Ni plating layer serves to help the copper alloy's low softening point. Further, this Ni plating layer serves to further strengthen the adhesion by thermal spraying of the Co-Mo-Cr alloy layer to be formed next. This Ni plating layer needs to have a thickness of at least 50 μm so as not to reach the steel alloy of the Co-Mo-Cr alloy during thermal spraying, and if it is more than 300 μm, the temperature gradient in the Ni plating layer is Becomes larger and the thermal stress becomes larger, which causes N
The problem of peeling of the i-plated layer occurs. Therefore, the thickness of this layer is advantageously between 50 and 300 μm.

As described in Japanese Patent Publication No. 61-5819, the Co-Mo-Cr alloy layer contains a relatively large amount of cobalt molybdate (CoMoO ₄ ) that exhibits excellent wear resistance and seizure resistance. It should have the above compositional range which can occur. This alloy layer serves to enhance the durability and wear resistance of the mold. This layer is generally preferably 50 to 600 μm thick. If it is less than 50 μm, the effect of the alloy layer cannot be obtained because it is too thin, and it may be thicker than 600 μm, but the thermal stress in the alloy layer increases, causing a problem of insufficient adhesion.

The ceramic layer has the function of eliminating gas during casting,
It also serves to significantly improve the heat resistance and durability of the mold. The structure of this layer is as described above, but this is because the eutectic point in the alloy of aluminum oxide and zirconium oxide is at the aluminum oxide content of 42.6%. It melts at 1710 ° C. The composition ratio of aluminum oxide and zirconium oxide was determined in consideration of the lowest possible melting temperature required for thermal spraying and the thermal spray adhesion associated therewith. The thickness of this ceramic layer is generally 50-500.
It is preferably μm. If the thickness is less than 50 μm, gas escape during casting becomes insufficient, and if it is thicker than 500 μm, the ceramic sprayed layer is physically weakened, which is inconvenient for the surface layer of the casting mold.

An advantageous manufacturing example of the copper alloy mold for discontinuous casting of the present invention will be described below. First, a Ni plating layer of 50 to 300 μm, especially 100 to 200 μm, is formed on the inner surface of a copper alloy mold made of the copper alloys listed in the table below (the remaining components of each alloy in the table are all copper).
m-thickness by a conventional method, and a Co-Mo-Cr alloy having the above-mentioned alloy composition is deposited on the Ni plating layer at about 10,000 to about 5,000 ° C while cooling with water by a water cooling device inside the mold, if necessary. 50 by plasma spraying or jet coating at about 2,700 ° C
Coating to a thickness of ~ 600 µm, especially 200-300 µm. Then, a ceramic coating layer having the above composition is sprayed by a spraying method under similar conditions to a thickness of 50 to 500 μm, especially 200 to 300 μm. A large number of continuous holes are formed in the ceramic layer, which makes the ceramic layer porous. This porous hole is not large enough to cause unevenness on the surface of the molded body,
It can be seen under a microscope.

The copper alloy mold of the present invention has a porous ceramic layer consisting of continuous pores, and since the continuous pores serve to contain the gas generated during casting and guide it to the outside, No gas damage to the surface. That is, there is no occurrence of swelling (unevenness).

The mold of the present invention having a ceramic layer has high durability and abrasion resistance, and has a very large number of shots as compared with a conventional mold, without the need to apply a soft coating agent to the inner surface of the mold. For example, it can withstand casting of 30,000 shots or more.

The mold of the present invention is an aluminum alloy that is generally difficult to cast.
-And a mold suitable for producing magnesium alloy casting products.

The present invention will be described in more detail below with reference to Examples and Comparative Examples.

Example 1 The inner surface of a mold made of a copper alloy having a thermal conductivity of 7 and containing 0.15% by weight of zirconium was coated with an electroplating method.
Provide a Ni plating layer with a thickness of μm. Then 50% Co, 30% Mo and 20% by plasma spraying
An alloy consisting of Cr is sprayed at 8000 ° C to form a coating film of 150 µm.

On the Co-Mo-Cr coating layer thus formed, 57 wt% Al ₂ O ₃ and 43 wt% ZrO ₂ were deposited by the same thermal spraying method.
The ceramic mixture consisting of is coated to a thickness of 250 μm. The thermal spraying temperature at that time is 8000 ° C. The ceramic layer has many small pores and is porous.

The permanent mold manufactured in this way is
When it was used for casting a magnesium alloy casing of an automobile engine while being cooled to 0 ° C., the surface was not changed even after 30,000 shots, and the surface condition of the molded product was good.

Example 2 A mold made of a copper alloy containing 0.2 wt% Ti and having a thermal conductivity of 6 was used, and the alloy layer to be sprayed was 60 wt% Co, 25
Consisting of wt% Mo and 15 wt% Cr and 54 wt%
A permanet mold was prepared as in Example 1 except that a ceramic mixture of Al ₂ O ₃ and 46% by weight of ZrO ₂ was used. A casting experiment for casting an aluminum alloy casing for an automobile engine with this mold was performed in the same manner as in Example 1, and even after 30,000 shots, the surface did not change and the surface condition of the molded body was good. .

Example 3 Thermal conductivity containing 0.15 wt% Zr and 0.85 wt% Cr
A permanet mold was prepared and the same casting experiment was performed as in Example 1, except that a mold made of copper alloy 5 was used.

Results similar to those in Example 1 were obtained.

Comparative Example A mold was manufactured in the same manner as in Example 1 except that the ceramic layer was not provided, and tested in the same manner as in Example 1.

In the case of this mold, 8,000 shots were made while coating with a commercially available mold maker (ceramic kneaded into water glass) every 200 shots, and no distortion or cracks were found on the mold surface. It occurred and became unusable. Also, 3,0
From around 00 shots, the surface condition of the molded product deteriorated.

[Effect of the Invention] Compared with the conventional copper alloy mold, the mold of the present invention has good heat conductivity of copper alloy and therefore easy temperature controllability, and complicated coating process. It has an excellent effect that it can be omitted and has an extremely long life, and its contribution to the industry is remarkable.

Claims (1)

[Claims] 1. A Ni plating layer having a thickness of 50 to 3 .mu.m is formed on the inner surface of a mold, a Co--Mo--Cr alloy coating having a thickness of 50 to 600 .mu.m is then used as an intermediate layer, and an outer layer having a thickness of 50 to 600 .mu.m. 600 μm
Al ₂ O ₃ -ZrO ₂ porous ceramic coating with a thickness of 0.5 to 65 wt% Co, 20 to 20% Co,
40% by weight Mo and the balance Cr and the composition of the ceramic layer is 40-60% by weight Al ₂ O ₃ and 60-40% by weight ZrO ₂
A copper alloy permanent mold for discontinuous casting characterized by the following.