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Casting green sand mold for forming cast steel article and its production method, and method for producing cast steel article using such green sand mold

Inactive Publication Date: 2017-03-23
HITACHI METALS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention is a process for making green sand molds for casting steel articles. By using a special type of sand that contains a small amount of carbon, and coating it with a special resin, the resulting mold has a recess that allows the as-cast surface of the steel article to have fewer carburized surfaces. This process results in a high-quality cast with good surface quality.

Problems solved by technology

With the carburized as-cast surface layers, cast steel articles are not easily machined.
This problem is particularly serious in cast stainless steel articles needing high heat resistance and corrosion resistance, which are used, for example, as exhaust members for internal combustion engines.

Method used

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  • Casting green sand mold for forming cast steel article and its production method, and method for producing cast steel article using such green sand mold
  • Casting green sand mold for forming cast steel article and its production method, and method for producing cast steel article using such green sand mold
  • Casting green sand mold for forming cast steel article and its production method, and method for producing cast steel article using such green sand mold

Examples

Experimental program
Comparison scheme
Effect test

first example

(A) FIRST EXAMPLE

[0059](1) Mold-Forming Step

[0060]As shown in FIG. 3(a), casting sand obtained by blending predetermined amounts of sand, a binder, a carbonaceous component and water is formed into an upper mold part 1a and a lower mold part 1b having recesses 1g-1, 1g-2 for an article-forming cavity 1c and a runner 1d. To provide a green sand mold with enough strength with easy forming, the amounts of a binder and water added to the casting sand are generally 5-12 parts by mass of a binder and 1-5 parts by mass of water per 100 parts by mass of sand, though properly adjustable depending on the characteristics of a green sand mold.

[0061]The upper mold part 1a and the lower mold part 1b are formed, for example, by charging the casting sand into each flask in which a casting model for an article-forming cavity, a runner, etc. is placed, compressing the casting sand by a jolt squeeze method, etc., and finally removing the casting model.

[0062](2) Coating Step

[0063]In the upper mold part...

second example

(B) SECOND EXAMPLE

[0069]The second example of the production methods of a green sand mold 1 is explained referring to FIG. 4. In FIG. 4, the same reference numerals are assigned to the same portions as in FIG. 3, with their detailed explanations omitted. The second example of the production methods of a green sand mold 1 is the same as the first example, except for having the first and second hardening steps shown in FIGS. 4(c) and 4(e).

[0070]In the second example, the recesses 1g-1, 1g-2 of the upper mold part 1a and the lower mold part 1b formed in the mold-forming step shown in FIG. 4(a) are coated with a coating solution 1k in the coating step shown in FIG. 4(b), and hot air is supplied from a blower 11 to heat the coating solution 1k, thereby forming a semi-hardened layer 1L, in the first hardening step shown in FIG. 4(c). After the upper mold part 1a and the lower mold part 1b each provided with a semi-hardened layer 1L are combined in the molds-combining step shown in FIG. 4(...

example 1

[0076](1) Sand-Preparing Step

[0077]100 parts by mass of silica sand was mixed with 8.1 parts by mass of bentonite, 3.0 parts by mass of water, and 3 parts by mass of carbon powder, to prepare casting sand.

[0078](2) Mold-Forming Step

[0079]Casting sand was charged into flasks in each of which a casting design model was set, and compressed by a jolt-squeeze method to form upper and lower mold parts. Measurement at five points by a self-hardening mold hardness tester (NK-009 available from Nakayama Co., Ltd.) revealed that the average hardness of each recess of the upper and lower mold parts was 20. FIG. 8(a) is a SEM photograph (100 times) showing a recess surface of the formed green sand mold. As is clear from FIG. 8(a), there were a lot of voids between binder-covered sand particles.

[0080](3) Coating Step

[0081]As shown in Table 2, a coating solution (viscosity: 20 mPa·s) comprising 40% by mass of a phenol resin and 60% by mass of ethanol was applied to the recesses and parting surfac...

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Abstract

A green sand mold for producing a cast steel article, which is formed by casting sand comprising sand, a binder, and 3 parts or less by mass of a carbonaceous component per 100 parts by mass of sand, and provided with a coating layer of a thermosetting resin formed at least on a recess including a cavity for forming the cast steel article, the coating layer having average hardness (measured by a self-hardening hardness meter) of 50-95 and a thickness of 0.5-2.5 mm.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a green sand mold suitable for producing a cast stainless steel article known as a particularly hard-to-cut material, and its production method, and a method for producing a cast steel article using such a green sand mold.BACKGROUND OF THE INVENTION[0002]Casting sand constituting green sand molds for producing cast steel articles generally comprises aggregates (sand), a binder such as bentonite, etc., carbonaceous components (coal, starch, etc.) as secondary additives, and water. The ratios of aggregates, a binder, etc. in the casting sand are properly determined to provide the green sand molds with desired properties [air permeability, strength, the stability of cavity surfaces, and compactability (CB), etc.]. Carbonaceous components such as coal powder, coke powder, graphite powder, pitch powder, etc. added to the casting sand prevent the sticking of aggregates (sand) to castings (sand seizure), thereby stabilizing the a...

Claims

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Application Information

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IPC IPC(8): B22C9/02B22D23/00B22C3/00B22C9/12B22C1/18B22C1/20
CPCB22C9/02B22C1/181B22D23/00B22C3/00B22C9/12B22C1/20
Inventor FUKUMOTO, KENTARO
Owner HITACHI METALS LTD
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