Focus on Standards – ISO/TR 15608
03 April 2017
In this edition of Focus on Standards we discuss ISO/TR 15608 which has recently been revised and was released for publication by ISO in February 2017. Now in its fourth edition, this technical report provides guidelines for a uniform system for grouping materials not only for welding purposes, but can also be used for heat treatment, forming and non-destructive testing. The standard covers grouping systems for the following standardized materials and alloys: steel; aluminium; copper; nickel; titanium; zirconium and cast irons.
The materials are grouped according to their chemical and mechanical specifications. Metallurgically there are two routes to influence a material’s properties, the chemical composition of the material and the mechanical processing route to obtain the required micro-structure and properties. The two routes may be interdependent.
These groupings are important as materials in the same group have similar weldability and therefore react in a similar manner when welded. Therefore as per table 3 in ISO 15614-1, if a test piece is welded in a particular group, all materials in the range of qualification groups specified are qualified by that particular Welding Procedure Qualification Record (WPQR or PQR).
The American system similarly classifies materials into groups, however ASME IX in QW422 explicitly classifies grades of materials to groups and not on the chemical composition and mechanical properties such as is the case with ISO 15608. Should a material not be specified to a grouping in the American system, it may be regarded as unassigned and therefore requires independent procedure qualification despite the material technically fulfilling the requirements of a particular grouping. As ISO 15608 is based on the properties of the material, all materials can be grouped according to the properties and weldability of the material. QW422 has for a number of years now also included the ISO 15608 classification of materials. Whilst there are similarities between the groupings of ISO 15608 and QW422, the systems do not equate to one another and need to be considered independently.
In ISO 15608, group 1 contains steels with a specified yield strength upto a maximum of 460MPa, there are 4 sub groups within this group. The first three sub-groups are for different strength levels as per the detail in the table below with the fourth group reserved for steels with improved corrosion resistance such as the weathering steels produced under the CORTEN trademark.
The common structural steel now used in South Africa conforms to the specification EN 10025-2 S355JR which is classed as group 1 and sub-group 1.2 (QW422 – P1 Group 2).
Carbon steels that have been thermo-mechanically treated or quench and tempered are included in groups 2 and 3. A common example of this type of material is Weldox 700™ (EN 10025-6 S690) which is classified as group 3.1 (QW422 – P11B Group 3).
Creep resistant materials which are primarily alloyed with Chromium and Molybdenum are classified in group 5. The commonly used creep resistant alloys 1Cr ½Mo (13CrMo4-5) is classified as group 5.1 (QW422 P4 Group 1) while the 2¼Cr 1Mo (10CrMo9-10) creep resistant alloy is classified in group 5.2 (QW422 P5A Group 1). As the new generation high temperature creep resistant alloy P91(X10CrMoVNb9-1) alloy contains vanadium, the material is classified as group 6.4 (QW422 P15E Group 1).
The generally difficult to weld Ferritic / Martensitic and Precipitation hardened alloys are grouped together in group 7. Austenitic Stainless Steel alloys are in Group 8 while the Duplex Stainless Steels are together in group 10. Nickel alloys are grouped in group 9. High carbon steels are classified in group 11. Aluminium alloys are covered by groups 21 to 26. Common alloys found in the market are grouped as follow: Alloy 1050 – Group 21; Alloy 5083 – Group 22.4; Alloy 5182 – Group 22.4; Alloy 6061 – Group 23.1; Alloy 6082 – Group 23.1
If you are having problems assigning particular grades to a group as per ISO 15608, there is help at hand. There are three further technical reports which assign the material classification to the intended group. ISO/TR 20172 is for Welding – Grouping systems for European materials, ISO/TR 20173 for American materials and ISO/TR 20174 for Japanese materials.
Click on images below to view groups