JPH11320067A - Molten metal contactor having inner cooling hole and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a molten metal contactor having an inner cooling hole, and improved in crack resistance while maintaining superior erosion resistance. SOLUTION: In this molten metal contactor having the inner cooling hole Z, the hardness of the inside is <=42 HRC and a surface treated layer is formed on the face in contact with a molten metal. The molten metal contactor can be manufactured by applying the surface treatment to the molten metal contact face after a steel having the refining hardness of <=42 HRC is worked into the shape in use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal welding apparatus having an internal cooling hole which has improved crack resistance while maintaining erosion resistance, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Die casting sleeves, cast pins, core pins, sluice gates and other molten metal fittings used for casting aluminum alloys, zinc alloys, etc. are usually made of hot die steel, etc. Surface treatment is applied.

[0003] During the casting, the hot die steel used for the molten metal contacting device reacts with the molten metal in a portion in contact with the molten metal, causing seizure and melting. When seizure occurs in a device such as a pin that performs direct molding, problems such as deterioration of the surface quality of the molded product and inability to release the molded product occur. Further, when the erosion proceeds, the iron content of the molded article increases, thereby causing a decrease in mechanical properties and the like of the molded article.

[0004] Although surface treatment has been attempted to prevent seizure and melting, there is a case where a sufficient effect cannot be obtained only by surface treatment, and a rise in temperature of a contact portion with the molten metal is suppressed. Therefore, a cooling hole may be provided inside.

[0005]

When the internal cooling holes are provided, the temperature rise of the contact portion of the molten metal appliance with the molten metal can be suppressed to some extent, but the temperature difference between the surface of the molten metal appliance and the internal cooling holes can be reduced. In addition, since a large tensile stress is generated in the internal cooling holes, cracks are generated from the internal cooling holes at an early stage, and the operation is greatly hindered due to water leakage or the like.

Accordingly, the present invention has been made in view of the above,
It is an object of the present invention to provide a molten metal welding device having an internal cooling hole with improved crack resistance while maintaining erosion resistance, and a method for manufacturing the same.

[0007]

Means for Solving the Problems The present inventor first sought to clarify the causes of cracks from the internal cooling holes of the molten metal welding equipment. As a result, the present inventor has focused on damage due to stress corrosion cracking as a major factor in this cracking,
Hardness conditions effective to prevent the occurrence were specified. Furthermore, it was confirmed that when the surface treatment was performed, the base metal hardness did not significantly affect the erosion resistance, and the present invention was achieved.

In other words, according to the present invention, there is provided a welding apparatus having an internal cooling hole, the internal hardness of which is 42 HRC.
It has a surface treatment layer on the molten metal contact surface. In addition, the contact melting device of the present invention has a tempering hardness of 42 HR.
This can be achieved by applying a manufacturing method in which a steel having a temperature of C or less is processed into a shape at the time of use and then a surface treatment is performed on the contact surface of the molten metal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most important feature of the present invention resides in that a hardness that can suppress cracks from internal cooling holes while maintaining erosion resistance is specified.

[0010] Cracks of the smelting device, which has been a concern in the past, originate from the surface of the internal cooling hole. A detailed investigation of the location of occurrence revealed that the cracks in the internal cooling holes were corroded by the cooling water.

As described above, in the molten metal contact device, tensile stress is generated on the surface of the internal cooling hole due to the temperature difference between the molten metal contact surface and the internal cooling hole generated during use. In other words, cracks from internal cooling holes that occur in
It is considered to be stress corrosion cracking, in which a tensile stress is applied to the internal cooling hole portion that has been corroded by the cooling water in use and a crack develops. For stress corrosion cracking and further research was performed.

As a result, in order to prevent stress corrosion cracking, which is a main cause of cracking, the hardness of the portion concerned should be around 40 HRC,
Alternatively, it has been found that it is effective to adjust the value below that. In the present invention, the specific hardness is 42 HR.
C or less.

On the other hand, erosion resistance is the most important required characteristic in a molten metal appliance, so it is necessary to have sufficient erosion resistance even at a hardness of 42 HRC or less.
Surface treatment is effective for improving erosion resistance, which has been conventionally proposed. Then, the present inventor studied on the effect of base metal hardness on erosion resistance when a surface treatment was applied. As a result, it was confirmed that the base metal hardness did not significantly affect the erosion resistance, and sufficient erosion resistance was obtained even with a base material hardness of 42 HRC or less.

In other words, the hardness of the inside having the internal cooling holes is 42 HRC or less, and the crack resistance can be improved while maintaining the erosion resistance by the molten metal fitting having the surface treatment layer on the molten metal contact surface. It is. In this case, this can be achieved by applying a manufacturing method in which a steel having a temper hardness of 42 HRC or less is processed into a shape at the time of use and then a surface treatment is performed on the contact surface of the molten metal. Since the hardness is adjusted to not more than 42 HRC at the time of processing, a predetermined shape can be easily obtained.

[0015] The above-mentioned molten metal contact device of the present invention has a nitriding treatment,
Sulphinitriding, oxidation, physical vapor deposition, chemical vapor deposition,
A hard film treatment by a plasma chemical vapor deposition method or the like can be applied, and a nitride layer, an oxide layer, a sulfide layer, a hard film (Ti
N, TiC, TiCN, TiAlN, CrN, W ₂ C, etc.).

[0016]

EXAMPLES (Example 1) In this example, in order to explain the effect of the present invention, a die-casting sleeve of the present invention and a comparative die-casting sleeve were manufactured and their characteristics were compared by actually using them. FIG. 1 shows a cross-sectional shape of a sleeve applied to the present embodiment. Since the sleeve 1 is poured from the upper pouring port 3, the lower portion has the highest temperature. Therefore, in order to suppress excessive temperature rise in the lower part, a = 1 from the molten metal contact surface.
An internal cooling hole 2 is provided at a position of 5 mm.

Both of the sleeve of the present invention and the comparative sleeve use hot tool steel SKD61, and the temper hardness and surface treatment of the base material are as shown in Table 1. The sleeve No. of the present invention. 1 and Comparative Sleeve No. 1
No. 2 is obtained by adjusting the hardness of a steel which has been roughly worked in an annealed state by quenching and tempering, finishing the work into a sleeve shape, and performing a surface treatment.

[0018]

[Table 1]

In Table 1, the conventional sleeve No. 2
(45HRC, nitrosulphurized product) was discarded due to cracks from the internal cooling holes at 12,000 shots during the die casting. On the other hand, in the sleeve No. of the present invention. When No. 1 was applied to die casting, no cracks were generated from the internal cooling holes, and the erosion was slight.
It can be used continuously even at the time of 000 shots.

(Example 2) In this example, the cast pin of the present invention and a comparative cast pin were manufactured, and their characteristics were compared by actually using them for die casting. FIG. 2 shows a cast pin applied to the present embodiment. Also in this cast pin 4, in order to suppress excessive temperature rise, the tip (outer diameter b
The internal cooling hole 5 is provided at a position c = 4 mm from the molten metal contact surface (= 15 mm).

Each of the cast pins of the present invention and the comparative cast pins uses hot tool steel SKD61. The temper hardness and surface treatment of the base metal are as shown in Table 2. The cast pin No. Nos. 1 and 2 and comparative cast pin Nos. No. 3 is obtained by adjusting the hardness of a steel which has been roughly worked in an annealed state by quenching and tempering, finishing the work into a cast pin shape, and performing a surface treatment.

[0022]

[Table 2]

In Table 2, the conventional cast pin No. 3
(47HRC, nitridation product) was discarded due to cracks from the internal cooling holes at 26,000 shots during the die casting. On the other hand, according to the cast pin No. When 1 and 2 were applied to die casting, no cracks were generated from the internal cooling holes, seizure and erosion were slight, and they were in a state where they could be used continuously even at 58,000 shots.

From the above results, the molten metal contact device of the present invention can be prevented from being disposed of early due to cracks from the internal cooling holes.
It can be seen that the life is improved.

[0025]

According to the present invention, in addition to maintaining the excellent erosion resistance, the internal cooling hole in use is excellent in crack resistance, so that its life can be extended. . Further, according to the manufacturing method of the present invention, in addition to shortening the manufacturing time and the manufacturing cost because the processing into the shape at the time of use is easy, the molten metal that is excellent in accuracy and long life is also provided. The equipment can be manufactured and its industrial benefit is very high.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a die casting sleeve of the present invention.

FIG. 2 is a view showing an example of a cast pin of the present invention.

[Explanation of symbols]

1. Sleeve, 2. 2. internal cooling holes; 3. pouring port; Cast pins, 5. Internal cooling holes

Claims (2)

[Claims] 1. The internal hardness having an internal cooling hole is 42H.
A molten metal contact device having an internal cooling hole, which is not more than RC and has a surface treatment layer on a molten metal contact surface. 2. A method for manufacturing a molten metal contact device having an internal cooling hole, wherein a steel having a temper hardness of 42 HRC or less is processed into a shape at the time of use, and then a surface treatment is performed on a molten metal contact surface.