ESU / ESR remelting – what it is and what you gain

What happens in the furnace

An electrode of the required steel is melted down through a bath of molten slag. The steel solidifies again under controlled conditions. The slag collects impurities along the way. The result is the same alloy – the same W.Nr. – but with fewer and finer inclusions than in the first melt. It is not a new grade. It is an extra process on top of it.

• ESU = German name · ESR = English name – same process
• W.Nr. and EN designation remain the same
• The certificate must carry ESU, ESR or equivalent – otherwise it is not remelted

What the benefit is

Cleaner material gives more uniform material. It typically shows where inclusions would otherwise turn into cracks, fractures or visible defects: mirror-polished mould tools, knives with a sharp edge, hot-work tooling under thermal shock, and shafts or gears that have to live long under alternating load. Homogeneity through the cross-section also becomes more predictable in hardening and machining.

• Fewer and finer non-metallic inclusions
• Better isotropy – less difference across and along the bar
• More stable polishing and surface in mould steel (e.g. 1.2083 / Stavax family)
• A better starting point for fatigue and impact in critical tools and machine parts

When it is worth requiring

Require ESU/ESR when the drawing, the tool standard or the end customer requires it – or when you have seen yourselves that conventional material does not hold up to polishing, edge or service life. It is most common on tool steel (mould, cold and hot work) and selected special steels. On merchant steel and ordinary S355 it rarely makes sense. Price and lead time are higher because the process costs time and energy.

What to write on the enquiry

Grade (name or W.Nr.), dimension, condition – and explicitly “ESU”, “ESR” or “remelted” if it is a requirement. “1.2344” alone is not the same as “1.2344 ESR”. We only lock in remelted material when the certificate carries it. VAR (vacuum arc remelting) is a different process – write that if it is what the drawing requires.

• Write ESU/ESR as a separate requirement – not only the W.Nr.
• Check the certificate: the process name must be there
• VAR ≠ ESR – do not mix them up on the PO