Steel Casting Mould Surface Treatment for Crack-Resistant Hardening
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Solution Overview
Problem
Mould parts for light metal casting are prone to premature failure due to quick-developing cracks in the surface sections that come into contact with the light metal melt, despite edge layer hardening, which reduces their useful life.
Innovation Solution
A method involving nitrate treatment to generate a nitride-hardened edge layer on mould parts, followed by machine surface hammering to remove the compound layer, using a hammer tool aligned at an acute angle to the surface, which increases hardness and resistance to wear and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If gas nitriding is performed to harden the edge layer of mould parts, then hardness and wear resistance are improved, but the compound layer formed on the surface becomes prone to quick-developing cracks
Solution Approach 1:
The harmful compound layer is selectively removed through mechanical processing (shot blasting or grinding) after nitriding, extracting only the problematic surface layer while preserving the hardened diffusion layer beneath, thereby eliminating the source of cracks while maintaining hardness
Solution Approach 2:
The nitriding process is performed first to establish the hardened edge layer with improved wear resistance, and then the compound layer is removed in a subsequent step, preparing the surface in advance for optimal performance and reduced crack susceptibility
2Reliability
If the compound layer is removed to prevent cracks, then reliability is improved, but the protective hardening effect is reduced
Solution Approach 1:
The treatment creates different surface qualities at different depths: the diffusion layer retains high hardness and nitrogen enrichment for wear resistance, while the compound layer is selectively removed to eliminate crack sources, achieving local optimization of both hardness and reliability
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 method effectively removes at least 90% of the compound layer, reducing the risk of crack formation and enhancing the fatigue strength of mould parts by introducing internal compressive stresses, thereby extending their useful life.
Implementation Method 1
at least the following work steps are carried out: a) Nitrate treating the mould part to generate a nitride-hardened edge layer
Implementation Method 2
The nitrogen atoms diffusing from the surfaces of the respective mould part in the steel material form, with the alloying elements present there
Implementation Method 3
the compound layer is removed by the impact stress in the impact region of the hammer tool
Implementation Method 4
enhancing the fatigue strength of mould parts by introducing internal compressive stresses
Data Source
AI summary
With the method according to the invention, mould parts for casting moulds for light metal casting can be treated such that the danger of crack formation in the region of the surface sections of the mould part coming into contact with the light metal melt during casting is reduced to a minimum. This is achieved in that by means of nitriding treatment on the mould part a nitride-hardened edge layer adjoining its free surface is generated which is harder than the inner core region of the mould part and comprises a diffusion layer adjoining the core region and a compound layer located on the diffusion layer and adjoining the free surface of the mould part and in that at least one section of the surface of the mould part is mechanically processed by machine hammer peening, in the case of which a hammer tool, which, at a certain impact frequency, carries out an impact movement along a movement axis which is aligned in relation to the free surface at a certain acute angle, is guided continuously over the free surface of the mould part following a track determined in a preceding design step such that the compound layer is removed by the impacting stress in the impact region of the hammer tool.