Hollow Stabilizer Quenching for Bent Section Hardness

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Solution Overview

Problem

The bent portion of hollow stabilizers experiences reduced quenching hardness due to increased cooling rates and stress concentrations, particularly on the inner surface, which affects mechanical strength and fatigue durability, especially when the thickness-to-diameter ratio (t/D) is high.

Innovation Solution

A method involving a quenching process where the element pipe is immersed in coolant and coolant is sprayed onto the outer surface of the bent portion, or injected into the pipe, to enhance cooling rates and achieve uniform hardness distribution across both surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the bent portion is recessed, then the outer surface quenching is effective, but the cooling rate of the inner surface becomes slow

Engineering Contradiction:
Improvecooling rateVSAvoidinner surface hardness
Core Design Contradiction:
SpeedVSStrength

Solution Approach 1:

The internal coolant injection system acts as an intermediary mechanism to deliver cooling directly to the inner surface of the bent portion. By introducing coolant through injection holes in the quenching tool, the system overcomes the geometric disadvantage of the recessed bent portion and achieves rapid cooling and sufficient hardness on the inner surface

Inventive Principle:
Principle #24Intermediary (Mediator)

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 method increases the quenching hardness of both the outer and inner surfaces of the bent portion, improving the mechanical strength and fatigue durability of the hollow stabilizer, particularly at higher t/D ratios.

Implementation Method 1

a cooling process is performed by immersing the element pipe in coolant

Methodology Applied
Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

coolant is sprayed onto the outer surface of the bent portion, or injected into the pipe, to enhance cooling rates

Methodology Applied
Scientific EffectConvection: Convection

Data Source

PatentEP3281814B1Method for producing hollow stabilizer
Publication Date: 2020.04.22 NHK SPRING CO LTD
  • EP3281814B1 patent drawingFigure 1A~1B
  • EP3281814B1 patent drawingFigure 2
  • EP3281814B1 patent drawingFigure 3

AI summary

This method for producing a hollow stabilizer includes a forming step in which a pipe material (IS) is subjected to bending treatment in order to form a product shape provided with bent sections (1c, 1c) and a hardening step in which the pipe material (IS) that has been subjected to bending treatment is subjected to hardening. The method for producing a hollow stabilizer is characterized in that in the hardening step, the steel pipe material (IS) is immersed in a cooling agent and cooling treatment is carried out by spraying the cooling agent onto the outer surface (1e) of the bent sections (1c).