Hollow Stabilizer Weld Bead Geometry for Fatigue Resistance

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Solution Overview

Problem

Conventional hollow stabilizers produced using electric resistance welded steel pipes suffer from reduced fatigue characteristics due to stress concentration at the internal weld bead cut portions, especially in high-strength stabilizers, and the process of cold drawing to smooth the inner surface increases production costs.

Innovation Solution

The internal weld bead cut portion is shaped into a three-peak configuration with a trough depth of 0.3 mm or less and an angle of 160° to 180°, achieved through specific hot stretch reducing and heat treatment processes, to enhance fatigue resistance and maintain high strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If hot stretch reducing is applied to reduce the weld bead, then the production cost is reduced, but irregularities on the pipe inner surface are generated causing stress concentration

Engineering Contradiction:

Improveproduction costVSAvoidfatigue characteristics

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the hot stretch reducing conditions (temperature range of 650-1000°C, cumulative reduction ratio of 30-90%) to achieve the optimal balance between weld bead reduction and surface irregularity minimization. This resolves the contradiction by finding the right processing parameters that satisfy both cost efficiency and fatigue resistance requirements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by forming a three-peak shape at the internal weld bead cut portion with specific geometric parameters (trough depth ≤0.3mm, angle ≥160°). This localized geometric optimization reduces stress concentration at the critical weld zone while maintaining acceptable production costs, resolving the contradiction between manufacturing efficiency and component reliability.

Inventive Principle:

Principle #3Local quality

2Reliability

If cold drawing is applied to smooth the inner surface, then the fatigue characteristics are improved, but the production cost increases

Engineering Contradiction:

Improvefatigue characteristicsVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by performing hot stretch reducing during the manufacturing process to pre-form the internal weld bead cut portion into a three-peak shape that reduces stress concentration. This preliminary shaping eliminates or reduces the need for subsequent cold drawing operations, thereby improving fatigue characteristics while avoiding the additional production costs associated with cold drawing.

Inventive Principle:

Principle #10Preliminary action

3Strength

If the stabilizer strength is increased to 400 HV or more, then the durability is improved, but the likelihood of cracks at the weld zone increases

Engineering Contradiction:

ImprovehardnessVSAvoidcrack likelihood

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by optimizing the heat treatment parameters (quenching and tempering) to achieve a hardness of 400-580 HV while controlling the microstructure to prevent crack formation. The specific tempering temperature and holding time are adjusted to balance strength enhancement with crack resistance at the weld zone.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating a specific three-peak geometric configuration at the internal weld bead cut portion with controlled trough depth (≤0.3mm) and angle (≥160°). This localized geometric optimization reduces stress concentration at the weld zone, allowing the stabilizer to achieve high overall strength (400-580 HV) without increasing crack likelihood at the critical weld area.

Inventive Principle:

Principle #3Local quality

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 configuration improves the fatigue characteristics of high-strength hollow stabilizers, maintaining hardness above 400 HV while reducing the likelihood of cracks, thus enhancing the industrial applicability and durability of the stabilizers.

Implementation Method 1

electric resistance welded steel pipe produced by electric resistance welding

Methodology Applied

Scientific EffectElectrical resistance heating: Joule Heating

Implementation Method 2

heating the welded steel pipe to a temperature in the range of 850° C. or more and 1000° C. or less, and then applying hot stretch reducing thereto

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS11440125B2Electric resistance welded steel pipe for producing hollow stabilizer, hollow stabilizer, and production methods for same

Publication Date: 2022.09.13 JFE STEEL CORP

AI summary

There are provided an electric resistance welded steel pipe for producing a high strength hollow stabilizer excellent in fatigue resistance and a high strength hollow stabilizer. In an electric resistance welded steel pipe (5) for producing a hollow stabilizer, an internal weld bead cut portion (30) has a three-peak shape and a depth (H) of a trough portion (30a) of the three-peak shape is 0.3 mm or less and an angle (θ) formed by a central portion in the circumferential direction of the trough portion (30a) and the top of right and left peak portions (30b, 30c) located on both the right and left sides of the trough portion (30a) is 160° or more and less than 180°.