AISI 1117 Free-Machining Carbon Steel: Properties & Machinability Guide

ASTM A108 / AISI 1117 · Published: 2026-06-01 · Updated: 2026-06-02

AISI 1117 is a resulfurized and rephosphorized free-machining carbon steel. With sulfur content of 0.08-0.13% — significantly higher than the 0.05% maximum in standard carbon steels — the manganese sulfide (MnS) inclusions produced during solidification act as chip breakers during machining, resulting in short, brittle chips and a machinability rating of approximately 90% (relative to AISI 1212 at 100%). The 0.14-0.20% carbon content provides moderate strength after heat treatment (through-hardening to approximately 58 HRC maximum in sections up to 25mm).

1117 is the preferred material for high-volume screw machine production of couplings, bushings, hydraulic fittings, and automotive components requiring moderate strength and excellent machinability. The trade-off: the high sulfur content reduces ductility (elongation ~15% vs ~25% for 1018), limits formability (not suitable for severe cold heading or bending operations), and degrades weldability (sulfur promotes hot cracking during solidification). For applications requiring both machinability and weldability, specify 1144 (stress-proof) or 12L14 (lead-containing) with the understanding that leaded steels are restricted in certain markets under RoHS and ELV directives.

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