1.2312 / P20+S: Fast Machining, Polishability and Mould-Steel Limits

The addition that speeds machining can also set the ceiling for the final surface

A practical guide to 1.2312 / P20+S for mould bases: sulfur-assisted machinability, polishability, texturing, repair welding, prehardened condition, UT and purchasing evidence.

1.2312 is commonly selected as a sulfur-modified prehardened mould steel where machining productivity matters. Sulfur helps chip breaking, but inclusion morphology and cleanliness can limit mirror polishing, demanding texture and repair welding.

This guide is intended for designers, buyers, heat-treatment teams and workshops supplying parts across Iran. It translates a familiar market enquiry into requirements that can be checked before payment, cutting, machining or furnace work.

Quick decision map

Identity, standard and the real engineering question

Order 40CrMnMoS8-6 / 1.2312 to the intended tool-steel specification and verify the certificate. P20+S is a useful market description, not a complete substitute for material number, delivered hardness, dimensions and inspection scope.

For mould bases, bolsters and moderately finished cavities, saved machining time can make 1.2312 economical. For optical or mirror surfaces, compare a low-sulfur mould grade and demand finish trials rather than assuming every P20 family member behaves alike.

Machining productivity

Sulfur can improve chip control and cutting consistency. Record Delivered hardness, sulfur range, tooling and removal strategy before commercial comparison begins. If this field remains verbal, purchasing, production and inspection can each interpret the same requirement differently.

Surface requirement

Inclusions may become visible during high polish or texturing. The order should therefore require Approved finish class, trial area and supplier cleanliness evidence. Catalogue data becomes useful only after product form, section and test condition are made comparable.

Section, process and delivered condition

Section size changes cooling rate, property distribution, sampling position and sometimes the applicable property range. Product form also matters: bar, plate and forging may share a grade name but follow different dimensional, testing and delivery requirements.

Large blocks need more than one surface hardness reading. Ask how hardness uniformity and internal soundness were assessed, where test values apply and whether UT acceptance is appropriate for the cavity location.

Inspection evidence that closes the decision

Evidence should answer a defined question. An MTC records heat identity and declared results; a process record proves the route used; a supplementary test report proves a result at a stated location. None of them should be treated as a substitute for the other two.

Prehardened section

Hardness uniformity can vary across large blocks. Define Block dimensions, hardness map and relevant test locations and identify the point where production must stop if the evidence is missing or outside the agreed range.

Repair and joining

Sulfur and prehardened structure raise welding sensitivity. Release should be based on Qualified repair procedure, preheat, consumable, tempering and NDT, attached to the same heat and piece identity. A valid test report has limited conformity value after traceability has been lost.

A defensible purchase specification

Specify 40CrMnMoS8-6 / 1.2312, standard, block dimensions, prehardened hardness range and locations, machining and final-finish class, texturing requirement, UT level, repair-welding restrictions, MTC type and traceable piece marking.

Grade/material number: [complete]; standard and edition: [complete]; form and dimensions: [complete]; delivery condition: [complete]; quantity and cutting tolerance: [complete]; MTC type: [complete]; supplementary test and acceptance rule: [complete]. Topic-specific requirement: Specify 40CrMnMoS8-6 / 1.2312, standard, block dimensions, prehardened hardness range and locations, machining and final-finish class, texturing requirement, UT level, repair-welding restrictions, MTC type and traceable piece marking.

Ordering checklist for Tehran, Tabriz, Isfahan and Yazd

• Write the recognised market term, but place 1.2312 / P20+S and the documented designation on the same enquiry.
• Close Machining productivity with Delivered hardness, sulfur range, tooling and removal strategy.
• Close Surface requirement with Approved finish class, trial area and supplier cleanliness evidence.
• Define Prehardened section before irreversible processing.
• Keep Repair and joining traceable through cutting, storage and loading.
• State destination, required dispatch date, packaging, piece count and who authorises release.

Related encyclopaedia pages and guides

• bohler m200
• Previous Week-01 technical guide
• Next Week-01 technical guide
• Alloy-steel encyclopaedia
• Evidence and calculation methodology
• Contact Shaygan Steel

Frequently asked questions

Why is 1.2312 easy to machine?

Its sulfur modification can improve chip breaking, while delivered hardness and microstructure still influence actual cutting performance.

Can P20+S reach a mirror finish?

Some finishes are possible, but demanding mirror quality may be limited by inclusions; verify with a representative polishing trial.

Can a 1.2312 mould be repair welded?

Only with a qualified procedure controlling preparation, preheat, consumable, heat input, cooling, tempering where needed and inspection.

Sources and method

This article uses the official references below as technical orientation and translates them into a procurement workflow for the Iranian market. A producer data sheet applies to the product and conditions it states; it does not replace the current purchase standard, drawing or MTC for the delivered heat.

• Swiss Steel Group — official technical reference
• Swiss Steel Group — official technical reference
• Steel-Iron-List — official technical reference

Conclusion and next step

Use 1.2312 where machining value and the required surface class agree. Write polish, texture, hardness uniformity, UT and repair expectations into the order before the block is cut.

For an enquiry, send material number, form, raw and final dimensions, quantity, delivery condition, inspection needs and destination in one message. Shaygan Steel can then review the evidence for current stock before proposing a supply route.