IS 1570 : 2017Schedules for Wrought Steels

IS 1570:2017 is the schedules for wrought steels — the master reference that designates and tabulates the chemical composition (and grade families) of carbon steels, alloy steels and free-cutting steels. It is the *materials dictionary* engineers use to specify, substitute or interpret a steel grade across machine parts, fasteners, shafts, fixtures and fabricated components.

It is read with the steel-materials stack:

• IS 2062 — structural steel (the construction-steel spec) · IS 1786 — reinforcement
• IS 1608 Part 1 — tensile testing · IS 1501 / IS 1500 — hardness
• IS 1367 Part 3 — fastener steels · IS 1030 / IS 1865 / IS 210 — castings

IS 1570 is a multi-part schedule that classifies and designates wrought steels by chemical composition:

• Carbon steels — by carbon (and Mn) content bands; the workhorse machine/fabrication steels
• Alloy steels — Cr/Ni/Mo/etc. families for higher strength, hardenability, toughness or wear resistance
• Free-cutting (re-sulphurised/leaded) steels — for high-volume machined parts where machinability matters
• A designation system (the grade code) that encodes composition, so a drawing can call up a steel unambiguously and a different mill's equivalent can be identified

It fixes *chemistry*, not finished-product mechanical properties — those come from the relevant product spec (bar/forging/fastener) and the heat-treatment condition. The engineering use is specification and substitution: pick the grade whose composition gives the hardenability/strength/machinability the part needs, and use the schedule to find a valid equivalent when the called-up grade is unavailable.

Scenario: a moderately-loaded machined shaft needing strength + toughness, to be heat-treated.

Step 1 — function → property need: the part needs medium strength with good toughness and adequate hardenability for through/section heat treatment.

Step 2 — pick grade family: from IS 1570, a medium-carbon (or low-alloy Cr/Mo) grade with the carbon/alloy content giving the required hardenability — designated by its IS 1570 code.

Step 3 — product + condition: call up the grade *with* the product form (bar/forging) and the heat-treatment condition (normalised / quenched-and-tempered to a hardness/strength) — IS 1570 gives chemistry; the property comes from form + heat treatment.

Step 4 — verify: acceptance on chemical composition vs IS 1570 + mechanical tests (IS 1608 tensile, IS 1501 hardness) for the supplied condition.

Step 5 — substitution: if the exact grade is unavailable, use the IS 1570 schedule to identify a compositionally-equivalent grade (and re-confirm heat-treat response) rather than guessing — uncontrolled substitution is the classic field failure.

1. Treating an IS 1570 grade as a strength. It fixes *chemistry*; strength/hardness depend on product form + heat-treatment condition — specify the condition, not just the grade.

2. Uncontrolled substitution. Swapping to 'a similar steel' without checking the IS 1570 composition and heat-treat response can change hardenability/toughness drastically — substitute via the schedule, then verify.

3. Confusing it with construction-steel codes. Structural members are IS 2062, rebar IS 1786; IS 1570 is for machine/component wrought steels — using the wrong code family mis-specifies the part.

4. Ignoring machinability needs. High-volume machined parts may need a free-cutting grade; specifying a plain medium-carbon steel there wrecks machining economics.

5. No composition acceptance. Accepting on a grade stamp without a mill cert/independent chemical analysis — composition is the whole point of IS 1570.

• IS 2062 — hot-rolled structural steel · IS 1786 — reinforcement bars
• IS 1608 Part 1 — tensile testing · IS 1501 / IS 1500 — hardness
• IS 1367 Part 3 — fastener mechanical properties (fastener steels)
• IS 1030 / IS 1865 / IS 210 — steel / ductile-iron / grey-iron castings
• IS 4432 / IS 5517 — case-hardening / hardenability references

IS 1570:2017 is a current revision and is the steel-grade reference rather than a design code — its day-to-day value is *specification and defensible substitution* of machine/component steels, with the grade designations broadly mappable to international (EN/AISI/JIS) systems suppliers quote. On construction projects it surfaces for machined embeds, anchor/holding-down assemblies, equipment foundations, fixtures and fabrication hardware — anywhere a *component* steel (not structural section or rebar) is needed.

The practitioner discipline: select the grade by the property need (hardenability/strength/toughness/machinability), always specify the product form + heat-treatment condition alongside the grade (chemistry alone is not strength), accept on composition + mechanical tests for that condition, and when substituting use the IS 1570 schedule to find a true compositional equivalent and re-verify heat-treat response. The recurring failure is an uncontrolled 'equivalent steel' swap that quietly changes hardenability — exactly what the schedule exists to prevent.