Localized Induction Heating for Weld Seam Stress Optimization
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Solution Overview
Problem
Welding processes in metals, particularly steel, often introduce unwanted residual tensile stresses in weld joints, increasing the risk of failure in critical load-bearing components.
Innovation Solution
A method and apparatus for inducing residual compressive stresses in weld joints by heating the steel beyond its austenitic temperature and then quenching it to form martensite, which increases the volume and creates compressive stress, using inductive heating and quenching with water, steam, or mass effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If welding is used to join metal pieces to form complex shapes, then manufacturing efficiency and joint strength are improved, but residual tensile stresses are introduced in the weld joints
Solution Approach 1:
The patent applies phase transition of steel from austenite to martensite through controlled heating and quenching. The weld joint is heated to austenitic temperature and then rapidly cooled to induce martensitic transformation, which creates beneficial compressive residual stresses while eliminating harmful tensile stresses from the welding process
Solution Approach 2:
The patent changes thermal parameters by heating the weld joint to austenitic temperature and then rapidly cooling it through quenching. This parameter change induces phase transformation and volume expansion, converting harmful tensile stresses into beneficial compressive stresses in the weld joint
2Stress or pressure
If traditional induction heating is used for stress relief, then residual tensile stresses are reduced, but beneficial compressive stresses are not induced
Solution Approach 1:
The patent goes beyond simple stress relief by inducing phase transition from austenite to martensite. This phase change causes volume expansion that actively creates beneficial compressive residual stresses in the weld joint, rather than merely reducing tensile stresses through conventional heating
Solution Approach 2:
The patent utilizes thermal expansion during phase transition from austenite to martensite. The volume expansion during quenching creates compressive forces that induce beneficial compressive residual stresses, transforming the thermal process from passive stress relief to active stress induction
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 enhances the load-bearing capacity and fatigue resistance of weld joints by converting residual tensile stresses into compressive stresses, reducing the risk of premature failure.
Implementation Method 1
electrical induction heating, which is monitored, e.g., using a radiation pyrometer, is briefly applied to the area to be stress relieved
Implementation Method 2
heating element to heat a portion of the weld seam past the austenitic temperature
Implementation Method 3
After heating, the compressive stress is created within the selected volume by quenching the steel to a temperature below its austenitic temperature
Implementation Method 4
heating the volume to a final temperature greater than the austenitic temperature of the steel. After heating, the compressive stress is created within the selected volume by quenching the steel to a temperature below its austenitic temperature. This imparts a short-range compressive stress in the selected volume, e.g., via the formation of martensite
Implementation Method 5
quenching the steel to a temperature below its austenitic temperature. This imparts a short-range compressive stress in the selected volume
Data Source
AI summary
An apparatus for the heat-treating of a heat-hardenable steel cruciform article having a weld seam includes a heating element to heat the weld seam to a point that an austenitic transformation occurs, and a quenching chamber to cool the weld seam, causing the formation of Martensite and an associated expansion. The quenching is rapid since slow quenching may allow a crystalline phase other than martensite to form. The apparatus may comprise rollers operable to convey the welded cruciform article through the apparatus at a speed such that the weld seam is subjected to heating for a predetermined heat time sufficient to cause a formation of martensite there within, and such that the heated portion reaches the quenching chamber and is quenched to create a substantial amount of martensite, e.g., an amount sufficient to cause expansion of the part.