Overview

ISO 20198:2026 specifies a standardized test method for determining the brittle crack arrest temperature (CAT) in metallic materials, specifically focusing on ferritic and bainitic steels. This international standard applies to rolled steel plates with a body-centred cubic (BCC) crystal lattice structure, which exhibit a ductile-to-brittle transition. The CAT test is relevant for steels with a maximum tensile strength of 950 MPa and thicknesses ranging from over 6 mm up to 200 mm, within a temperature range of −196 °C to +100 °C. The document also provides detailed requirements for isothermal crack arrest tests and the associated test procedures to ensure valid and reliable results.

Key Topics

Scope and Applicability:
- Focuses on ferritic and bainitic rolled steel plates.
- Applicable to steels with tensile strength ≤ 950 MPa and thickness between >6 mm and ≤200 mm.
- Arrest temperature range of −196 °C to +100 °C.
Test Equipment and Calibration:
- Use of hydraulic or mechanical testing machines capable of applying the requisite tensile load.
- Calibration requirements refer to ISO 7500-1 for static uniaxial testing machines.
- Precise temperature control and measurement, using calibrated thermocouples according to ASTM E220-19.
Test Methods:
- Isothermal crack arrest tests under controlled temperature conditions.
- Brittle crack initiation methods include both impact (drop-weight or air gun) and double tension tab plate techniques.
- Strict requirements on test piece configurations, side grooves, and embrittled zones (created via electron beam welding or local temperature gradient techniques).
Test Procedure:
- Accurate pre-loading and meticulous temperature control.
- Detailed procedures for crack initiation, propagation, and observation of fracture surfaces to judge arrest or propagation.
- Clear criteria for result validation, including multiple test pieces for statistical reliability.

Applications

The test method defined in ISO 20198:2026 is vital for industries where steel structures are exposed to low temperatures and high mechanical stresses, such as:

Shipbuilding: Ensuring structural plates in vessels can arrest brittle cracks and prevent catastrophic failure, particularly in cold environments.
Civil Engineering and Infrastructure: Assessing steel plates used in bridges, offshore platforms, and pressure vessels for their ability to resist brittle fracture propagation.
Automotive and Transport: Relevant for heavy vehicles, railway carriages, and containers using high-strength rolled steels.
Material Research and Quality Control: Enabling manufacturers to evaluate and certify new steel grades for critical applications, enhancing safety and longevity through robust material property assessment.

Related Standards

ISO 20198:2026 is complemented by several related documents for comprehensive testing of steel materials:

ISO 20064:2019: Metallic materials - Steel - Method of test for the determination of brittle crack arrest toughness, Kca. Provides a related method for evaluating the lowest temperature at which crack propagation stops under a temperature gradient.
ISO 7500-1: Metallic materials - Calibration and verification of static uniaxial testing machines - Ensures accurate force application during testing.
ASTM E220-19: Standard Test Method for Calibration of Thermocouples by Comparison Techniques - Supports precise temperature measurements during fracture testing.

By following ISO 20198:2026, organizations ensure consistent, repeatable, and internationally recognized test results, supporting material selection, compliance, and safety for a broad range of engineering applications.

Keywords: ISO 20198:2026, brittle crack arrest temperature, CAT, rolled steel plates, ferritic steel, bainitic steel, isothermal crack arrest test, metallic materials, fracture testing, standard methods, temperature control, steel toughness, structural safety.

Overview

Key Topics

Scope and Applicability:
- Focuses on ferritic and bainitic rolled steel plates.
- Applicable to steels with tensile strength ≤ 950 MPa and thickness between >6 mm and ≤200 mm.
- Arrest temperature range of −196 °C to +100 °C.
Test Equipment and Calibration:
- Use of hydraulic or mechanical testing machines capable of applying the requisite tensile load.
- Calibration requirements refer to ISO 7500-1 for static uniaxial testing machines.
- Precise temperature control and measurement, using calibrated thermocouples according to ASTM E220-19.
Test Methods:
- Isothermal crack arrest tests under controlled temperature conditions.
- Brittle crack initiation methods include both impact (drop-weight or air gun) and double tension tab plate techniques.
- Strict requirements on test piece configurations, side grooves, and embrittled zones (created via electron beam welding or local temperature gradient techniques).
Test Procedure:
- Accurate pre-loading and meticulous temperature control.
- Detailed procedures for crack initiation, propagation, and observation of fracture surfaces to judge arrest or propagation.
- Clear criteria for result validation, including multiple test pieces for statistical reliability.

Applications

The test method defined in ISO 20198:2026 is vital for industries where steel structures are exposed to low temperatures and high mechanical stresses, such as:

Shipbuilding: Ensuring structural plates in vessels can arrest brittle cracks and prevent catastrophic failure, particularly in cold environments.
Civil Engineering and Infrastructure: Assessing steel plates used in bridges, offshore platforms, and pressure vessels for their ability to resist brittle fracture propagation.
Automotive and Transport: Relevant for heavy vehicles, railway carriages, and containers using high-strength rolled steels.
Material Research and Quality Control: Enabling manufacturers to evaluate and certify new steel grades for critical applications, enhancing safety and longevity through robust material property assessment.

Related Standards

ISO 20198:2026 is complemented by several related documents for comprehensive testing of steel materials:

ISO 20064:2019: Metallic materials - Steel - Method of test for the determination of brittle crack arrest toughness, Kca. Provides a related method for evaluating the lowest temperature at which crack propagation stops under a temperature gradient.
ISO 7500-1: Metallic materials - Calibration and verification of static uniaxial testing machines - Ensures accurate force application during testing.
ASTM E220-19: Standard Test Method for Calibration of Thermocouples by Comparison Techniques - Supports precise temperature measurements during fracture testing.

ISO 20198:2026 PDF

Technical details

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

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