Written by: Dr. Conor McCaughey, Metallurgist, Institute of Spring Technology
As some of you might be aware, in September a new standard was published, ISO 6931-1: “Stainless Steels for Springs. Wire” replacing the existing standard, EN 10270-3: “Stainless spring steel wire”. As this is a widely used standard within the industry, I thought I would use this post to look at the differences in these standards to help the transition.
The first thing I would like to mention is that the majority of what is in ISO 6931-1 is the same as EN 10270-3. All the alloys that were in EN 10270-3 are now in the ISO version with minimal changes to the strength, tolerances, surface quality etc. The first major difference is the addition of two new alloys (see Table 1). These two alloys are widely used around the world and will probably be more recognisable to our members as alloys 302 and 304. This should eliminate the need for using equivalent alloys, or different national specifications. Within the other wire grades there are some minor changes to the allowable compositional range of some alloys. Changes, if any, are limited to differences of 0.5% or less and are usually an increase to the allowable composition, meaning EN wire could be certified to the ISO standard if necessary.
The other significant change is the alloy numbers. As you can see in Table 1 the Euronorm numbers have been removed and replaced with an international number. This does include both the Euronorm numbers and the AISI numbers that are familiar to us all. For example, X10CrNi18-8 is now denoted by the number 4310-301-00-I, containing both the Euronorm numbering (1.4310) and the AISI number (301). Making it easier to identify grades requested by customers in whatever format they are requested. The names of the alloys remain as they were in EN 10270-3.
There are some other variations between the two standards, but these mainly consist changing reference standards from EN version to the equivalent ISO versions. For example, the compositions are now dictated by ISO 16142-2 not EN 10088-3, hence some of the slight variations in composition between the standards.
If you are a member of IST and you have any further questions about the changes from EN 10270-3 to ISO 6931-1 please feel free to drop me an email and I will try and clear up any issues you may have.
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