Electrogalvanized Hot-Stamped Steel Plating Adhesion
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Solution Overview
Problem
Hot stamping of aluminum-coated steel sheets leads to counter diffusion and the formation of intermetallic compounds, compromising paint adhesiveness, while zinc-coated steel sheets face productivity issues due to soft plating sticking to molds during rapid heating methods like Joule or induction heating.
Innovation Solution
A hot stamp molded body produced from electrogalvanized steel sheets with controlled Zn-Fe intermetallic compound amounts and fine particulate oxides, ensuring minimal sticking and improved paint adhesiveness without post-treatments like shotblasting, using a method involving hot rolling, pickling, continuous annealing, and electrogalvanizing with specific temperature and bending processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If aluminum-coated steel sheets are used for hot stamping, then weight reduction is achieved, but intermetallic compounds form compromising paint adhesiveness
Solution Approach 1:
The patent controls the heating temperature range (700-950°C) and heating time (0.5-2 seconds) to prevent excessive formation of intermetallic compounds while achieving the desired strength through hot stamping. By precisely controlling these parameters, the process maintains paint adhesiveness while still providing weight reduction benefits.
2Productivity
If zinc-coated steel sheets are heated rapidly using Joule or induction heating, then productivity is improved, but soft plating sticks to molds
Solution Approach 1:
The patent specifies a heating temperature range of 700-950°C and limits heating time to 0.5-2 seconds. This precise parameter control prevents the plating from becoming too soft and sticking to the mold, while still achieving rapid heating for improved productivity. The controlled heating parameters ensure the plating maintains sufficient structural integrity.
Solution Approach 2:
The patent applies a zinc-based plating layer with specific properties (thickness 3-10 μm, containing 80-95 wt% Zn) before hot stamping. This preliminary plating layer acts as a protective barrier that prevents sticking to the mold during rapid heating, while still allowing the hot stamping process to achieve the desired strength and surface finish.
3Object-affected harmful factors
If Fe scale forms on steel sheet surface during heating, then oxidation protection is provided, but productivity is impaired and appearance is disfigured
Solution Approach 1:
The patent uses a composite structure consisting of a zinc-based plating layer (80-95 wt% Zn) on the steel sheet surface. This composite plating layer provides superior oxidation resistance compared to conventional coatings, preventing Fe scale formation while maintaining productivity and appearance quality during hot stamping.
4Strength
If high strength steel sheet is pressed directly, then strength is maintained, but scoring or fracture occurs during molding
Solution Approach 1:
The patent applies hot stamping by heating the steel sheet to 700-950°C before molding, which temporarily reduces the material strength and increases ductility, allowing complex shapes to be formed without scoring or fracture. After molding, rapid cooling restores the high strength (1300-1800 MPa), achieving both formability and strength requirements.
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 enables efficient production of hot stamp molded bodies with reduced plating sticking and enhanced paint adhesiveness, maintaining productivity and surface quality.
Implementation Method 1
a steel sheet to be molded is heated in advance for facilitating molding
Implementation Method 2
subjected to press molding keeping the high temperature, and a higher strength is achieved by quenching on the occasion of cooling after pressing
Implementation Method 3
when an electrogalvanized steel sheet with a light plating weight is hot-stamped using a rapidly heating method such as Joule heating and induction heating
Implementation Method 4
when an electrogalvanized steel sheet with a light plating weight is hot-stamped using a rapidly heating method such as Joule heating and induction heating
Data Source
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AI summary
The invention provides a hot stamp molded body that can be produced highly efficiently without causing sticking of plating to a mold, when an electrogalvanized steel sheet with a light plating weight is hot-stamped using a rapidly heating method such as Joule heating and induction heating, and can secure favorable paint adhesiveness without a posttreatment such as shotblasting after hot stamping, as well as a method for producing the same. A hot stamp molded body is produced by hot-stamping an electrogalvanized steel sheet which is composed of predetermined components, and is electrogalvanized on each face with a plating weight not less than 5 g/m2 and less than 40 g/m2; and therein a galvanized layer of the hot stamp molded body is configured with 0 g/m2 to 15 g/m2 of a Zn-Fe intermetallic compound and a Fe-Zn solid solution phase as a balance, and in the galvanized layer of the hot stamp molded body 1x10 pcs to 1x104 pcs of particulate matter with an average diameter of from 10 nm to 1 µm are present per 1 mm length of the galvanized layer.