High-Pressure Gas Container Threads with Residual Compressive Stress

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

High pressure gas containers face issues with stress concentration and fatigue fracture at the thread portion due to high internal pressure, particularly in screw-type lid structures, which can lead to increased container size and cost with flange-based solutions, and stress concentration in screw-type lids.

Innovation Solution

Applying residual compressive stress to the vicinity of the thread bottom by filling the container with internal pressure during production, ensuring the maximum value of residual compressive stress at 0.4 mm depth from the thread bottoms is 100 MPa or more, less than the tensile strength of the materials, to alleviate stress and prevent fatigue fracture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a flange structure is used to connect the lid to the container, then the connection strength is improved, but the container size and cost increase

Engineering Contradiction:

Improveconnection strengthVSAvoidcontainer size

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

The connection structure is divided into a threaded portion formed directly on the container body and a separate lid with an internal thread, eliminating the need for a flange while maintaining connection strength through the threaded engagement

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The connection function is merged into the container body itself by forming threads directly on the outer peripheral surface of the container, combining the container and connection elements into a single integrated structure, thereby eliminating the flange

Inventive Principle:

Principle #5Merging (Combining)

2Volume of moving object

If a screw-type lid structure is used to reduce container size, then the container compactness is improved, but stress concentration and fatigue fracture risk increase at the thread portion

Engineering Contradiction:

Improvecontainer compactnessVSAvoidfatigue resistance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The thread portion is given special attention through localized heat treatment (quenching) to create a harder, more wear-resistant surface layer with improved fatigue strength, while the rest of the container maintains its base material properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The thread portion undergoes preliminary heat treatment during manufacturing to pre-establish improved mechanical properties and surface hardness before the container is put into service, preventing fatigue fracture during operation

Inventive Principle:

Principle #10Preliminary action

3Strength

If heat treatment is applied to improve container strength, then the container strength is improved, but scale and decarburized layer form on the inner surface

Engineering Contradiction:

Improvecontainer strengthVSAvoidscale and decarburized layer

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The harmful scale and decarburized layer are selectively removed from the inner surface through machining operations, extracting only the damaged surface layer while preserving the strengthened subsurface structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Heat treatment is applied selectively to the thread portion rather than the entire container, and the inner surface is subsequently machined to remove any scale or decarburized layer formed, creating a quality gradient where the thread portion has enhanced surface properties while the inner surface maintains smooth, contamination-free characteristics

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

The solution effectively reduces stress on the thread portion, preventing fatigue fracture and allowing for higher pressure and larger cross-section usage without increasing container size or cost.

Implementation Method 1

a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a plurality of thread bottoms of the female thread portion and the male thread portion is 100 MPa or more, less than or equal to tensile strength of a material of the metallic cylinder, and less than or equal to tensile strength of a material of the lid

Methodology Applied

Scientific EffectResidual stress:

Data Source

PatentEP4246019B1High-pressure gas container and production method therefor

Publication Date: 2025.12.31 JFE STEEL CORP

Figure 1
Figure 2
Figure 3

AI summary

To alleviate stress exerted on a thread portion of a high pressure gas container including a metallic container to prevent fatigue fracture, there is provided a high pressure gas container comprising a metallic container, wherein the metallic container includes: a metallic cylinder; a female thread portion on an inner peripheral surface of the metallic cylinder at at least one end; and a lid having, on an outer peripheral surface, a male thread portion configured to screw into the female thread portion, and a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a plurality of thread bottoms of the female thread portion and the male thread portion is 100 MPa or more, less than or equal to tensile strength of a material of the metallic cylinder, and less than or equal to tensile strength of a material of the lid.