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Hot work tool steel and mold member excellent resistance to melting loss

a technology of hot work tools and mold parts, which is applied in the direction of manufacturing tools, foundry molds, foundry patterns, etc., can solve the problems of melting loss of base metals, product may not be easily separated from molds, etc., and achieve the effects of improving wear resistance, seizure resistance, and heat-check resistance of the produ

Inactive Publication Date: 2007-05-17
DAIDO STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010] It is therefore an object of the present invention to provide a hot work tool steel and a mold member each of which enjoys an excellent resistance to Al-melting loss while retaining excellent toughness and resistance to heat check.

Problems solved by technology

If the melting loss grows, then a product having a defect may result, or a product may not be easily separated from the mold.
Thus, thereafter, the melting loss may occur to the base metal, and the above-indicated problems may arise.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

embodiment 1

[0112] 50 kg of each steel having a corresponding composition shown in TABLE 1 is molten in a compressing and melting furnace that can compress, for the purpose of increasing a concentration of nitrogen in a steel ingot, a gas in a melting and casting device as a whole, up to 10 atmospheres, and the molten steel is cast. However, regarding conventional steels shown in TABLE 1, 50 kg of each conventional steel is molten in a vacuum melting furnace, and the molten steel is cast.

TABLE 1CHEMICAL COMPOSITIONCSiMnCrMoW½W + MoVONC + NINVENTION10.250.120.635.212.03—2.030.050.00120.1520.402EXAMPLES20.220.140.815.641.52—1.520.030.00250.2020.42230.310.170.625.432.98—2.98—0.00180.2830.59340.140.240.784.972.03—2.030.090.00220.2210.36150.220.050.635.523.04—3.04—0.00170.1570.37760.340.160.583.042.47—2.470.120.00140.1830.52370.110.080.755.891.97—1.970.090.00060.0980.20880.170.260.596.031.24—1.240.110.0010.1730.34390.230.280.846.540.38—0.380.250.00210.1850.415100.200.140.715.312.82—2.820.310.00130...

embodiment 2

[0138] A 50 kg ingot of each steel (an invention example and a conventional steel) having a corresponding composition shown in TABLE 4 is produced in a corresponding one of the same compressing and melting furnace (the invention example) and the same vacuum induction furnace (the conventional steel) each as used in Embodiment 1, and is forged into φ20-mm rods, which in turn are annealed at 870° C.

TABLE 4CHEMICAL COMPOSITIONSORTCSiMnPSCrMoVAlONC + NC / NREMARKSCONVENTIONAL0.380.940.560.0070.0035.431.230.810.0090.00160.0160.39623.75SKD61STEELINVENTION0.260.150.620.0090.0025.512.030.050.0080.00130.1570.4171.66—EXAMPLE

[0139] Subsequently, regarding each of the invention example and the conventional steel, the each steel is cut into three pieces each having a 200-mm length, and each of the three pieces is roughed, by lathe turning, so as to have dimensions of φ15 mm×200 mm. Then, after the three pieces are quenched under a condition of 1,030° C.×1 hr, those pieces are tempered, twice, un...

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Abstract

A hot work tool steel having a chemical composition in wt %: C: 0.10 to 0.35%, Si: less than 0.80%, Mn: 3.0% or less, Cr: 2.0% or more and less than 7.0%, N: more than 0.05% and 0.50% or less, O: 0.0100% or less, P: 0.050% or less, Al: 0.050% or less, with the proviso that ½W+Mo: 0.3 to 5.0%, C+N: 0.20 to 0.60% and C / N: 6 or less, and the balance: substantially Fe, and optionally V: 0.01 to 0.5%. The hot work tool steel exhibits excellent resistance to melting, while retaining good toughness and good resistance to heat checking.

Description

TECHNICAL FIELD [0001] The present invention relates to a hot work tool steel that is excellent in resistance to melting loss and is suitable for use as a mold member for Al die-casting, and also relates to the mold member. BACKGROUND ART [0002] As a material of a base, a core, a core pin, and a molten-metal supply tube of an Al-die-casting mold (hereinafter, generally referred to as the “mold member(s)”), a hot work tool steel such as JIS SKD61, SKD6, or SKD62 has been used. [0003] Meanwhile, Fe has affinity for Al. That is, a mold member considerably easily reacts with a molten Al, and an Fe—Al intermetallic compound is produced. Thus, a surface layer of the mold member may come off. This phenomenon is called “melting loss”. The melting loss encompasses coming-off caused by adhesion or seizing. [0004] The melting loss tends to occur to, e.g., a stepped part, or the core pin, of the mold that is located around a projection gate and contacts a high-temperature molten Al flow at a hi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C38/22B22C9/06B22D17/22B22D21/00C22C9/06C22C38/00C22C38/38C22C38/60
CPCB22C9/061B22D17/2209B22D21/007C22C38/04C22C38/22C22C38/24C22C38/60C21D8/021C21D8/0426C22C38/001C22C38/002C22C38/02C22C38/16C22C38/30C22C38/38C22C38/44C22C38/46C23C8/26C23C8/32C23C8/38C23C8/50C23C8/56C23C30/00
Inventor KURATA, SEIJIFUJII, TOSHIMITSU
Owner DAIDO STEEL CO LTD
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