Tailored Welded Blank Coating Layout for Zoned Press Hardening

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Solution Overview

Problem

Current methods for producing press-hardened sheet metal parts from tailored welded blanks do not effectively achieve varying strengths and corrosion protection properties across different areas, limiting design and production flexibility.

Innovation Solution

A method involving a tailored welded blank with two pieces of sheet metal, each from a different press-hardenable steel alloy and with distinct metallic protective coatings of different thicknesses, is used. The blank is heated to austenitization temperature and formed in a press hardening tool, allowing for distinct strength and corrosion protection properties in the resulting sheet metal part areas, with the thicker coating providing enhanced corrosion protection and the thinner coating reducing embrittlement risk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a uniform metallic protective coating is applied to the entire tailored welded blank, then the manufacturing process is simple, but the corrosion protection properties are the same across all areas, which is insufficient for parts requiring different corrosion resistance in different regions

Engineering Contradiction:
Improvecorrosion protection propertiesVSAvoidcoating application process
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies different thicknesses of metallic protective coating to different areas of the tailored welded blank. Specifically, the first sheet piece receives a first metallic protective coating with a first layer thickness, while the second sheet piece receives a second metallic protective coating with a second layer thickness that is different from the first. This creates regionally differentiated corrosion protection properties tailored to the specific requirements of different parts of the final component.

Inventive Principle:
Principle #3Local quality

2Strength

If high-strength steel alloys are used to achieve high strength properties, then the strength requirement is met, but the ductility decreases and the risk of embrittlement increases

Engineering Contradiction:
Improvetensile strengthVSAvoidductility and embrittlement risk
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent employs different press-hardenable steel alloys for different sheet pieces in the tailored welded blank. The first sheet piece is formed from a first press-hardenable steel alloy, while the second sheet piece is formed from a second press-hardenable steel alloy. This allows each region to be optimized for its specific functional requirements, balancing strength and ductility locally rather than using a uniform high-strength material throughout.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent utilizes phase transformation during press hardening to achieve high strength properties. The steel alloys are heated to austenitizing temperature and then rapidly cooled, causing a martensitic phase transformation that significantly increases strength. By controlling the heating and cooling parameters, the process achieves high tensile strength (≥1350 MPa) while managing the inherent embrittlement risk through proper alloy selection and process control.

Inventive Principle:
Principle #35Parameter changes

3Object-affected harmful factors

If thicker metallic protective coating is applied to achieve high corrosion protection, then corrosion resistance is improved, but the risk of embrittlement during heating and press hardening increases

Engineering Contradiction:
Improvecorrosion protectionVSAvoidembrittlement risk
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies metallic protective coatings with different layer thicknesses to different sheet pieces. The first sheet piece receives a first metallic protective coating with a first layer thickness, while the second sheet piece receives a second metallic protective coating with a second layer thickness that differs from the first. This local differentiation allows thick coating where corrosion protection is prioritized and thinner coating where embrittlement risk must be minimized.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent controls the thickness parameters of the metallic protective coatings to optimize the balance between corrosion protection and embrittlement risk. By precisely controlling the coating thickness within specific ranges, the process achieves adequate corrosion protection while preventing excessive coating thickness that would cause embrittlement during the heating and press hardening process.

Inventive Principle:
Principle #35Parameter changes

4Weight of moving object

If different sheet thicknesses are used in the tailored welded blank, then weight optimization is achieved, but the manufacturing and forming process becomes more complex

Engineering Contradiction:
Improvepart weightVSAvoidforming process
Core Design Contradiction:
Weight of moving objectVSEase of manufacture

Solution Approach 1:

The patent uses sheet pieces with different thicknesses in the tailored welded blank, where the first sheet piece has a first sheet thickness and the second sheet piece has a second sheet thickness that is different from the first. This allows weight optimization by using thinner material where less strength is required and thicker material where higher strength and load-bearing capacity are needed.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent divides the blank into multiple welded sheet pieces with different thicknesses and materials. This segmentation allows each region to be independently optimized for its specific requirements, and the welded construction enables the integration of these different-thickness pieces into a unified blank that can be formed as a single piece during press hardening.

Inventive Principle:
Principle #1Segmentation

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

This approach enables the production of press-hardened sheet metal parts with specific strength and corrosion protection properties in different areas, optimizing weight and meeting diverse design requirements, such as high strength in non-wet zones and high corrosion protection in wet areas, while minimizing the risk of embrittlement.

Implementation Method 1

heating (typically to a uniform temperature > 850°C, so that austenitization takes place)

Methodology Applied
Scientific EffectAustenitization: Phase Change

Implementation Method 2

quench-cooled, which is known to achieve high strengths

Methodology Applied
Scientific EffectQuench cooling: Cooling

Data Source

PatentEP4043115B1Process for forming a press-hardened sheet-metal part having different properties in different areas
Publication Date: 2024.08.21 VOLKSWAGEN AG
  • EP4043115B1 patent drawingFigure 1~2

AI summary

The invention relates to a method for producing a press-hardened sheet metal blank with differently shaped properties, comprising the steps of: - providing a tailored welded blank (100) with a first sheet metal blank (110) made of a first steel alloy (L1) and having a first metallic protective coating (B1), and with a second sheet metal blank (120) made of a second steel alloy (L2) and having a second metallic protective coating (B2), wherein the first metallic protective coating (B1) and the second metallic protective coating (B2) have different layer thicknesses;- Heating, forming and press hardening or forming, heating and press hardening of the tailored welded blank (100), whereby a press-hardened sheet metal part is produced, which has a first sheet metal part area formed from the first sheet metal piece (110) and a second sheet metal part area formed from the second sheet metal piece (120), wherein these two sheet metal part areas differ from each other in their strength and corrosion protection properties. The invention further relates to a sheet metal part produced according to the method, which has different strength and corrosion protection properties in certain areas.