Hot Press Die Coating for Wear-Resistant Forming of Plated Steel
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Solution Overview
Problem
Existing methods for hot press forming of plated steel sheets, including those with zinc-based plating, face challenges in reducing die wear and maintaining surface quality due to high surface pressure and oxidation issues during the process.
Innovation Solution
A method involving a plated steel sheet with a hot-dip galvanizing or zinc nickel plating layer, combined with a die having a hard layer with specific skewness and hardness, and a nitride layer, to reduce die wear and enhance surface texture and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel sheet is heated to a high temperature of 800°C or higher for hot press forming, then the steel sheet can be easily stamped and mechanical strength is enhanced by quenching, but the surfaces of the steel sheet are oxidized to cause the generation of scales
Solution Approach 1:
A die coating layer is introduced as an intermediary between the steel sheet and the oxidizing atmosphere during hot press forming. This coating layer prevents direct contact between the steel sheet surface and oxygen, thereby preventing scale generation while allowing the steel sheet to achieve high mechanical strength through quenching
Solution Approach 2:
The die coating layer creates a protective environment around the steel sheet during heating, effectively isolating the steel sheet from the oxidizing atmosphere. This inert barrier prevents surface oxidation even though the steel sheet is heated to high temperatures
2Reliability
If a steel sheet having Zn-based plating is heated for hot press forming, then corrosion protection is provided, but the plating layer may evaporate at heating temperatures of 700 to 1,000°C and cause significant deterioration in surface texture
Solution Approach 1:
A protective coating layer is applied to the die surface before hot press forming. This preliminary coating prevents direct contact between the zinc-based plating and the die, reducing zinc evaporation and preventing surface texture deterioration during the heating process
Solution Approach 2:
The die coating layer serves as an intermediary barrier between the zinc-based plating and the hot die surface. This intermediate layer prevents direct interaction that would cause zinc evaporation and surface deterioration, while still allowing effective heat transfer for forming
3Ease of manufacture
If conventional dies are used for hot press forming of plated steel sheets, then forming is achieved, but wear occurs on sliding surfaces of the die due to high surface pressure
Solution Approach 1:
The die coating layer undergoes phase changes and softening at high temperatures during hot press forming, allowing the plated steel sheet to be formed. After cooling, the coating layer hardens again, providing wear resistance for the next forming cycle. This parameter change enables both forming capability and extended service life
Solution Approach 2:
The die coating layer acts as a sacrificial cushioning layer that absorbs wear and adhesion damage during hot press forming. This beforehand protection prevents direct wear on the die substrate, significantly extending die service life while maintaining forming capability
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 reduces die wear and improves the surface quality of press-formed products by minimizing adhesion and friction, while maintaining high mechanical strength and corrosion resistance.
Implementation Method 1
The method effectively reduces die wear and improves the surface quality of press-formed products by minimizing adhesion and friction
Implementation Method 2
a die having a hard layer with specific skewness and hardness
Implementation Method 3
a steel sheet, which is an object to be formed, is heated to a high temperature, and the steel sheet softened by the heating is subjected to stamping to perform forming
Implementation Method 4
the mechanical strength of the steel sheet can be enhanced by a quenching effect provided by the cooling after the forming
Implementation Method 5
Steel sheets having zinc (Zn)-based plating, which are steel sheets plated with zinc having a sacrificial corrosion-protective effect
Data Source
AI summary
A method of producing a hot press-formed product, in which a die includes a hard layer having a skewness (Rsk), as measured in a direction from the outside of a die hole toward the inside of the die hole, of from −5.0 to 1.2, and a hardness Hv_Die of from HV 1,000 to 1,550, over the entirety of a region of a steel sheet contact surface that is adjacent to a die shoulder portion. The steel sheet contact surface is a surface located outside of the die hole and configured to contact a plated steel sheet (a plated steel sheet including at least one kind of plating layer selected from the group consisting of a hot-dip galvanizing layer and a zinc nickel plating layer) that is to be subjected to hot press forming.