Method for nitriding metal in salt bath and metal manufactured using the same

a technology of salt bath and nitrided metal, which is applied in the direction of manufacturing tools, heat treatment equipment, furnaces, etc., can solve the problems of high cost, waste water and gas processing cost, and the nitriding method using cyanide salt, so as to improve the tensile strength of steel and iron, the surface hardness of the iron nitrided by the present invention is also improved

Inactive Publication Date: 2007-08-23
ILJIN LIGHT METAL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0020]The ultra-low carbon steel nitrided by the present invention has the surface hardness ranging from more than 120 Hv to equal to or less than 450 Hv. The low carbon steel has the surface hardness being more than 200 Hv to equal to or less than 410 Hv. The medium carbon steel has the surface hardness being more than 130 Hv to equal to or less than 420 Hv. The high carbon steel has the surface hardness being more than 150 Hv to equal to or less than 400 Hv. The alloy steel has the surface hardness being more than 200 Hv to equal to or less than 410 Hv. IF steel has the surface hardness being more than 165 Hv to equal to or less than 400 Hv. The surface hardness of the steels nitrided by the present invention can be improved to a maximum of 420 Hv. The surface hardness of the iron

Problems solved by technology

Since the cyanide ion is classified as a toxic chemical, it must be carefully and tightly controlled, and this can be an expensive proposition.
Also, there is a problem of a cost involved for processing waste wat

Method used

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  • Method for nitriding metal in salt bath and metal manufactured using the same
  • Method for nitriding metal in salt bath and metal manufactured using the same
  • Method for nitriding metal in salt bath and metal manufactured using the same

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Experimental program
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Effect test

first embodiment

[0044]In accordance with the first embodiment of the present invention, steel is nitrided using the NaNO3 molten salt. The nitrided steel includes ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel and alloy steel.

[0045]Each of the ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel and alloy steel is submerged in the NaNO3 molten salt bath for 2 hours at a temperature of 500° C.

[0046]Table 2 shows changes in surface hardness and tensile strength of the samples nitrided in the molten salt bath, wherein the hardness was measured using a Vickers hardness tester under a load of 1 kgf.

[0047]In case of ultra-low carbon steel, the surface hardness increases by 119% and the tensile strength increases by 47%. In case of low carbon steel, the surface hardness increases by 47% and the tensile strength increases by 19%.

[0048]In case of medium carbon steel, the surface hardness increases by 32% and the tensile strength increases by 18%....

second embodiment

[0061]In accordance with the second embodiment of the present invention, steel is nitrided by using the NaNO2 molten salt.

[0062]Steels including ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel and alloy steel are submerged in the salt bath at 450° C. for 2 hours.

[0063]Table 4 shows changes in surface hardness and tensile strength of the samples nitrided in the molten salt bath, wherein the surface hardness is measured using a Vickers hardness tester under a load of 1 kgf.

[0064]For ultra-low carbon steel, the surface hardness increases by 54% and the tensile strength increases by 21%. For low carbon steel, the surface hardness increases by 32% and the tensile strength increases by 15%.

[0065]For medium carbon steel, the surface hardness increases by 19% and the tensile strength increases by 13%. For high carbon steel, the surface hardness increases by 18% and the tensile strength increases by 12%.

[0066]For alloy steel, the surface hardness increases by...

third embodiment

[0069]In accordance with the third embodiment of the present invention, steels are nitrided using the KNO2 molten salt.

[0070]The steels including ultra-low carbon steel, low carbon steel, high carbon steel and alloy steel are submerged in the molten salt bath at 480° C. for 2 hours.

[0071]Table 5 shows changes in hardness and tensile strength of the samples submerged in the molten salt bath, wherein the surface hardness is measured using a Vickers hardness tester under a load of 1 kgf.

[0072]For ultra-low carbon steel, the surface hardness increases by 45% and the tensile strength is increases by 15%. For low carbon steel, the surface hardness increases by 25% and the tensile strength increases by 11%.

[0073]For high carbon steel, the surface hardness increases by 17% and the tensile strength increases by 10%. For alloy steel, the surface hardness increases by 12% and the tensile strength increases by 11%.

[0074]That is, when the steels are nitrided using the molten salt bath nitriding ...

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Abstract

Provided is a method for nitriding a metal in a salt bath by using a non-cyanide salt and a nitrided metal manufactured using the same. The method includes the steps of: immerging at least one salt selected from the group consisting of KNO3, KNO2, Ca(NO3)2, NaNO3 and NaNO2 into the salt bath; melting the salt by heating and maintaining the molten salt at a predetermined temperature; and submerging the metal in the salt bath. Nitriding in non-cyanide salts, such as potassium nitrate (KNO3), potassium nitrite (KNO2), sodium nitrate (NaNO3), sodium nitrite (NaNO2), calcium nitrate (Ca(NO3)2) and their mixtures, is capable of solving an environmental pollution problem and reducing a cost. Also, the method is capable of increasing nitrided depth of the metal two to six times compared to conventional nitriding methods. As a result, the method can be carried out in various application fields.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method for nitriding metal in a salt bath and nitrided metal manufactured using the same; and, more particularly, to a method for nitriding iron or steels by using non-cyanide salt bath, and nitrided iron or steels manufactured using the same.[0003]2. Background of the Related Art[0004]Steels have been widely used for machine parts because of their inherent properties. To be used for machine parts, steels are usually first heat-treated to impart thereto strength, toughness and durability, all of which are the qualities machine parts require. In addition, for machine parts that are often exposed to corrosive environment, surfaces thereof are further heat-treated to impart thereto corrosion resistance.[0005]Nitriding is one of the methods for processing the metal surface to impart thereto a corrosion resistance thereof. The nitriding methods include gas nitriding using NH3 gas, salt bath...

Claims

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Application Information

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IPC IPC(8): C23C8/26
CPCC23C8/50C21D1/06C21D9/0068
Inventor JUNG, HEE WONLEE, DONG NYUNGPARK, YOUNG JUNEKIM, DONG SAMOH, KYU HWANSHEN, YINZHONG
Owner ILJIN LIGHT METAL CO LTD
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