Why does the R disappear?
Customers sometimes ask why a steel mill certificate identifies SWRCH10A while the finished-wire inspection report identifies SWCH10A. Our light-hearted answer is that we “ate the R”. The technical answer is a change in product form under the JIS G 3507 series.
Wire rod and wire are different products
JIS G 3507-1 covers carbon steel wire rod for cold heading and uses SWRCH identifiers. JIS G 3507-2 covers finished carbon steel wire and uses corresponding SWCH identifiers. The examples checked here use G 3507-1:2021 and G 3507-2:2005; the edition agreed in the order must govern acceptance.
| Wire rod: JIS G 3507-1 | Wire: JIS G 3507-2 |
|---|---|
| SWRCH6A | SWCH6A |
| SWRCH8A | SWCH8A |
| SWRCH10A | SWCH10A |
| SWRCH22A | SWCH22A |
Table 1 note (1) of JIS G 3507-2:2005 states that the wire symbol is obtained by deleting the third letter R from the corresponding wire-rod symbol. R identifies the rod context; its absence distinguishes the wire product. This is a naming rule, not permission to alter the original steel mill certificate.
Processing is selected for the order
A manufacturing route may include pickling, drawing, annealing or spheroidizing annealing, phosphating, lubrication and finishing. This is an illustrative sequence, not a requirement that every low-carbon wire receive every treatment. The grade, target dimensions, deformation route and specified delivery condition determine the actual sequence.
Drawing and heat treatment can change dimensions, microstructure and mechanical properties. The corresponding grade family does not mean that processing leaves all properties unchanged.
A new identifier does not establish conformity
The original mill certificate should retain its original wire-rod identifier. A finished-wire report should identify the product and the standard actually ordered and verified. Deleting R by itself does not demonstrate compliance with Part 2, cold-heading suitability or customer approval.
Some suppliers continue to use the incoming rod designation in commercial documents. If a finished wire is identified as SWRCH10A, clarify whether that describes the input material or the delivered product, and state the product standard, edition and delivery condition.
What matters beyond the letter
- Effective scale removal and controlled surface preparation.
- Drawing reductions and the specified annealing route.
- Microstructural uniformity and spheroidization where required.
- Stable surface treatment and lubrication.
- Consistent mechanical properties, dimensions and traceability.
- Verification for the customer’s cold-heading, cold-extrusion and subsequent heat-treatment requirements.
The R has not been lost: the product has moved from the wire-rod stage to the wire stage. Creation Group’s role is to control and verify that processing route rather than rely on a letter change as evidence of quality.