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Method for hardening stainless steel and molten salt bath for realizing said method

A stainless steel, salt melting technology, applied in the field of hardened stainless steel, can solve the problems of high capital and energy cost, high equipment complexity, etc., to avoid equipment and energy consumption, easy to implement, and reduce adhesion loss.

Active Publication Date: 2008-08-06
DURFERRIT GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0014] But both methods require high equipment complexity and high capital and energy costs, and in order to operate the device, specially trained, often even scientifically trained personnel are required

Method used

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  • Method for hardening stainless steel and molten salt bath for realizing said method
  • Method for hardening stainless steel and molten salt bath for realizing said method
  • Method for hardening stainless steel and molten salt bath for realizing said method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0066] 42 kg dry potassium chloride, 34 kg dry lithium chloride and 20 kg dry barium chloride are weighed into a crucible made of refractory steel, eg raw material 1.4828, and mixed loosely. All salts must have a residual moisture of less than 0.3% by weight. The mixture was heated to 400°C to obtain a water clear melt. To this was slowly added 4 kg of potassium hexacyanoferrate(II) which had been dried in a muffle furnace at 140° C. for 12 hours before. When potassium hexacyanoferrate(II) was added, very small amounts of carbon were precipitated on the crucible walls and on the surface of the melt. Skim off the carbon with a sieve. There is then a water-clear melt which reaches an operating temperature of 400°C. 10 kg of workpieces made of stainless steel 1.4571 (raw material X6CrNiMoTi17-12.2) fixed on steel wires were immersed in the melt and exposed to the influence of the melt for 48 hours.

[0067] The result of this treatment is a 20 to 22 μm thick diffusion lay...

Embodiment 2

[0070] 43 kg dry potassium chloride, 30 kg dry lithium chloride, 17 kg dry strontium chloride and 3 kg dry barium chloride were weighed into a crucible made of high temperature resistant steel and mixed loosely. All salts must have a residual moisture of less than 0.3% by weight. The mixture was heated to 400°C to obtain a water clear melt. To this was slowly added 7 kg of potassium hexacyanoferrate(II) which had been dried in a muffle furnace at 140° C. for 12 hours before. There is then a water-clear melt down to the operating temperature of 370°C. 10 kg of workpieces made of stainless steel 1.4301 fixed on steel wires are immersed in the melt and exposed to the influence of the melt for 24 to 48 hours.

[0071] Depending on the treatment time, this treatment results in a 10 to 25 μm thick diffusion layer on the surface of the treated components and samples, which is visible metallographically by cross-grinding and etching with the etchant V2A-Beize.

Embodiment 3

[0073] In a crucible made of refractory steel, 37 kg dry potassium chloride, 26 kg dry lithium chloride and 17 kg dry strontium chloride were weighed and mixed loosely. All salts must have a residual moisture of less than 0.3% by weight. The mixture was heated to 400°C to obtain a water clear melt. 10kg KCN and 10kg NaCN were slowly added thereto. The formed melt reaches an operating temperature of 400 to 410°C. 10 kg of workpieces made of stainless steel 1.4301 fixed on steel wires are immersed in the melt and exposed to the influence of the melt for 24 hours.

[0074] The result of this treatment is an approximately 10 μm thick diffusion layer on the surface of the treated components and samples, which is visible metallographically by cross-grinding and etching with the etchant V2A-Beize. The hardness of this layer was measured to be 620 HV (0.5).

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Abstract

In the hardening of a stainless steel workpiece, the workpiece surface is exposed to an incoming diffused atmosphere of carbon and / or nitrogen. The workpiece is submerged in a hot molten salt solution of KCl (30-60 wt.%), LiCl (20-40 wt.%), BaCl 2 and or SrCl 2 and or MgCl 2 and or CaCl 2 (15-30 wt.%), and free or complex cyanide (0.2-25 wt.%). The bath solution is maintained at 450[deg]C and the workpiece is maintained in a submerged condition for 15 minutes to 240 hours.

Description

technical field [0001] The invention relates to a method for hardening stainless steel and a salt melt for carrying out the method. Background technique [0002] Due to their outstanding corrosion resistance, stainless steel is used in chemical plant construction, the food industry, petrochemical industry, the offshore sector, shipbuilding and aircraft construction, construction, building and plant construction, and many other industrial fields. [0003] When ferrous materials are alloyed with at least 13% by weight of chromium, they are called corrosion-resistant stainless steels. In most cases iron alloys additionally contain nickel, titanium and molybdenum, e.g. in Stahl Merkblatt 821 Edelstahl Rostfrei-Eigenschaften Informationsstelle Edelstahl, PF 102205, 40013 Düsseldorf www.edelstahl-rostfrei.de and in Rostfreie Sthle by P.Gümpel et al. , as illustrated in Expert Verlag, Band 349, Renningen Malmsheim 1998. Typical austenitic stainless steels are alloys of steel 1.4...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C8/40C23C8/46C23C8/50C23C8/56
CPCC23C8/46C23C8/50C23C8/56C21D1/46
Inventor U·鲍迪斯M·尼德迈尔
Owner DURFERRIT GMBH
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