Honeycomb Die Joining Interface Strength via Carbon Elution Control
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Solution Overview
Problem
The existing honeycomb structure forming dies experience a lowering of strength around the joining interface due to the transformation of stainless steel from a martensitic to an austenitic structure caused by carbon elution from tungsten carbide, leading to cell block tilting and defects in the honeycomb structure.
Innovation Solution
A joined article comprising a tungsten carbide base cemented carbide and a martensitic stainless steel with a carbon equivalent of 2.5 to 3.5 and sulfur content of 0.030 mass % or less is used, preventing the strength reduction at the joining interface by maintaining a stable martensitic structure and ensuring high hardness, thereby preventing cell block deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If precipitation hardening stainless steel (SUS630) is used for the die base member, then the die can be manufactured with good machinability and initial strength, but the strength around the joining interface lowers due to martensitic to austenitic structure transformation caused by carbon elution from tungsten carbide
Solution Approach 1:
The invention changes the material parameter by selecting a specific stainless steel grade (SUS420J2) with controlled carbon content (0.15-0.40%) and chromium content (12-14%), replacing the conventional SUS630. This parameter change ensures the steel maintains martensitic structure stability even when carbon elutes from the tungsten carbide, preventing the strength reduction that occurs with SUS630.
Solution Approach 2:
The invention creates a composite structure where the die base member is made of a specific martensitic stainless steel (SUS420J2) that is chemically compatible with tungsten carbide. The controlled composition of the stainless steel creates a material system that resists structural transformation when exposed to carbon elution, maintaining the integrity of the joined interface between the steel and carbide components.
2Ease of operation
If the stainless steel changes from martensitic to austenitic structure due to carbon elution, then the steel becomes more ductile, but the strength lowers causing cell blocks to fall down
Solution Approach 1:
The invention optimizes the chemical composition parameters of the stainless steel, specifically controlling carbon content at 0.15-0.40% and chromium at 12-14%, to achieve a balanced microstructure. This parameter optimization allows the steel to maintain adequate ductility for forming operations while preserving sufficient strength to prevent cell block collapse during honeycomb structure formation.
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 effectively prevents the lowering of strength at the joining interface, ensuring the honeycomb structure forming die maintains its integrity and prevents cell block tilting, resulting in high-quality honeycomb structures with improved forming properties.
Implementation Method 1
the stainless steel joined to the tungsten carbide base cemented carbide around an interface between the stainless steel and the tungsten carbide base cemented carbide changes from a martensitic structure to an austenitic structure owing to the elution/diffusion of carbon contained in the tungsten carbide base cemented carbide
Data Source
AI summary
A joined article in which a first metal member made of a tungsten carbide base cemented carbide and a second metal member made of a martensitic stainless steel having a carbon equivalent of 2.5 to 3.5 and containing 0.030 mass % or less of sulfur are joined. The martensitic stainless steel having the carbon equivalent of 2.5 to 3.5 is preferably at least one selected from the group consisting of SUS431, SUS420J1, SUS420J2, SUS410, SUS410J1, S-STAR, PROVA-400, HPM38, STAVAX ESR, and SUS403 in the joined article. There is disclosed a joined article in which the lowering of the strength of a second metal member around a joining interface thereof is prevented.