Vacuum-Hardened Rolling Slide Member Without Cr-Deficient Surface
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Solution Overview
Problem
Rolling bearings made from martensite-type stainless steel face issues with rust formation due to Cr-deficient surface layers when heat-treated in vacuum atmospheres, leading to reduced corrosion resistance and necessitating cumbersome scale removal processes.
Innovation Solution
A rolling-sliding member with a specific composition, including 11.0 to 18.0 mass % Cr, is heat-treated in a vacuum atmosphere to prevent Cr-deficient layer formation, allowing for reliable passivation without scale removal processing, ensuring high hardness and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heat treatment is performed in air atmosphere, then scale is formed on the surface, but scale removal processing is necessary which is cumbersome and causes material loss
Solution Approach 1:
The patent applies vacuum heat treatment instead of air atmosphere heat treatment to prevent oxidation and scale formation on the stainless steel surface. By performing heat treatment in a vacuum environment, the harmful oxidation reaction is eliminated, thereby avoiding the need for subsequent scale removal processing and reducing manufacturing complexity
2Object-affected harmful factors
If heat treatment is performed in vacuum atmosphere, then scale formation is prevented, but Cr-deficient layer forms on the surface reducing corrosion resistance
Solution Approach 1:
The patent optimizes specific parameters including holding the chromium content at 13-17 mass%, controlling the carbon content at 0.10-0.35 mass%, and precisely controlling the heat treatment temperature range and holding time. These parameter changes ensure that vacuum heat treatment prevents scale formation while maintaining sufficient chromium content in the surface layer to prevent Cr-deficient layer formation and preserve corrosion resistance
3Manufacturing precision
If processing for removal of scale etc. is performed to depth of 1 mm, then scale and content variation regions are removed, but large material loss occurs
Solution Approach 1:
By performing heat treatment in vacuum atmosphere, the patent prevents scale formation and content variation in the first place, eliminating the need for extensive material removal processing and thereby preventing significant material loss
Solution Approach 2:
The patent performs vacuum heat treatment as a preliminary action before any surface processing, preventing scale and content variation formation upfront, which eliminates the need for subsequent scale removal processing that would cause material loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution prevents rust formation and maintains high corrosion resistance, reducing material loss and processing time, making the rolling-sliding member suitable for exposed environments without the need for extensive scale removal.
Implementation Method 1
heat treatment in a vacuum atmosphere (oxygen-absent atmosphere)
Implementation Method 2
oxygen in the air reacts with iron in the surface of the stainless steel, whereby an iron-oxide-based coating (what is called scale) is formed
Implementation Method 3
adding a proper amount of N in the matrix in the form of a solid solution... adding a corrosion resistance increasing element such as Mo
Data Source
AI summary
A rolling-sliding member that is high in hardness and continues to have a passivation film reliably even after being subjected to a process that does not require any processing for removal of scale etc., as well as a rolling bearing using the same and a method for manufacturing the rolling-sliding member.