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Spring and Bearing Steel

Spring steels are medium- and high-carbon steels (0.55–1.0 % C) alloyed with silicon, chromium or vanadium so that, quench-and-tempered to 42–50 HRC, they store elastic energy without taking a set: 6150 and 9254 reach 1,500–1,700 MPa yield at that hardness. Bearing steels — 52100, 100Cr6, GCr15 and SUJ2 are one grade under four names — carry about 1 % C and 1.5 % Cr and harden through to 60–64 HRC for rolling elements, races, hardened pins and precision wear parts. Both groups are bought for fatigue life, not for machinability or weldability.

Popular spring and bearing steel grades

Compare in the explorer
GradeYield, MPaTensile, MPaDensity, g/cm³MachinabilityWeldabilityBest for
521004156907.81FairNot recommendedBearings, races, hardened pins; 60–64 HRC
100Cr64206607.81FairNot recommendedEN name for 52100 on European drawings
61506009507.85FairPoorTorsion bars, valve springs, high-fatigue coils
92546201,0307.85FairPoorSi-Mn coil and clutch springs; sag-resistant
51CrV45208007.85FairPoorEN Cr-V leaf and heavy coil springs
10953806557.85FairPoorFlat springs, clips, knife blades in strip
65Mn4407607.85FairPoorGB volume spring strip and wire

All 83 spring and bearing steel grades

Choose spring and bearing steel for

Coil, leaf, torsion and flat springs, clips, spring washers and lock rings, blades that must flex, rolling-element bearings and their races, hardened pins, dowels, rollers, cam followers, linear-guide rails, gauge blocks and any small hardened part that needs 60+ HRC with fine grain and high cleanliness.

Look elsewhere when

The spring must live wet or in salt (17-7 PH, 301 stainless or phosphor bronze), it runs above about 250 °C (H13 or Inconel X-750 springs), the part is a structural shaft rather than a rolling surface (4140, 4340), the bearing is a bushing rather than a rolling element (bronze, or carburized 8620), or the design needs a case-hardened part with a tough core (8620, 16MnCr5) instead of a through-hardened 62 HRC that fractures under shock.

Yield strength against elongation at break, Spring & bearing steel among every steel grade

No materials in view have both of these properties.

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Spring and bearing steel by application

Coil and leaf springs
9254 / 9260 or 6150 for coil springs at 44–50 HRC; 5160 and 51CrV4 for leaf springs and bar over about 20 mm; 60Si2Mn / SUP9 on GB and JIS drawings. Shot-peen after tempering — it roughly doubles fatigue life at the surface.
Flat springs and clips
1074, 1075 and 1095 strip hardened to 44–50 HRC, or bought spring-tempered and cut by laser or stamping; 65Mn is the GB equivalent. Bend across the grain and keep the inside radius at least 1 t on tempered strip.
Bearings, races and rollers
52100 / 100Cr6 / GCr15 / SUJ2 hardened 60–64 HRC, ground and lapped; M50 and Cronidur 30 for aircraft-engine bearings at temperature; M50NiL where a carburized race is required.
Hardened pins, dowels and wear parts
52100 for dowels, pivot pins, detent balls, gauge pins and small cams at 60–62 HRC — cleaner and more dimensionally stable than 1095 and harder than any carburized case, with no soft core. Sub-zero treat and double temper for gauges.

Working with spring and bearing steel

Machining
Machine in the annealed or spheroidized state (52100 about 190–210 HB, spring steels similar): 52100 runs at about 40 % of 1212 with abrasive chips; the silicon spring grades are gummy. Turn and drill everything before hardening, leave 0.1–0.3 mm, then grind — a 62 HRC 52100 pin cannot be re-machined. Hard turning with CBN is possible for bearing races in production.
Heat treatment
52100: austenitize 840–860 °C, oil quench, temper 150–200 °C for 60–64 HRC; sub-zero at −80 °C and a second temper for gauges and precision bearings to convert retained austenite. Spring steels: 850–880 °C, oil, temper 400–500 °C for 42–50 HRC; 1095 strip at about 800 °C into fast oil, temper 300–400 °C for flat springs. Specify hardness, not just "harden and temper".
Forming
Coil and bend in the annealed state or use pre-tempered strip and wire within its bend limits; tempered 1095 strip cracks below about 1 t inside radius and along the grain. Hot-coiled heavy springs (5160, 51CrV4 bar over 12 mm) are formed at about 900 °C then hardened; cold-coiled light springs (9254 wire, A228 music wire) are formed hard and only stress-relieved at 250–400 °C.
Welding and finishing
Not weldable in any practical sense — 0.6–1.0 % C plus hardening cracks at the weld; join by clamping, riveting or brazing before heat treatment. Finish with black oxide, phosphate and oil, zinc plating with a hydrogen-embrittlement bake (about 200 °C for at least 4 h, within an hour of plating), or paint on leaf springs; bearing surfaces stay bright and oiled.

Other steel series

Spring and Bearing Steel — frequently asked

What is spring and bearing steel?

Spring steels are medium- and high-carbon steels (0.55–1.0 % C) alloyed with silicon, chromium or vanadium so that, quench-and-tempered to 42–50 HRC, they store elastic energy without taking a set: 6150 and 9254 reach 1,500–1,700 MPa yield at that hardness. Bearing steels — 52100, 100Cr6, GCr15 and SUJ2 are one grade under four names — carry about 1 % C and 1.5 % Cr and harden through to 60–64 HRC for rolling elements, races, hardened pins and precision wear parts. Both groups are bought for fatigue life, not for machinability or weldability.

Which grade of spring and bearing steel should I use?

52100 (100Cr6, GCr15, SUJ2) for anything that is a bearing or acts like one — races, balls, rollers, hardened dowels, cam followers, small gauges — at 60–64 HRC. For springs: 5160 and 51CrV4 / 50CrV4 for leaf springs and large coil springs (the chromium adds hardenability for heavy wire and bar), 6150 for torsion bars, valve springs and high-fatigue coils, 9254 and 9260 for silicon-manganese coil and clutch springs where sag resistance matters; 60Si2Mn and 65Mn (SUP9 and SUP10 in JIS) are the GB / JIS volume spring grades. Plain 1070–1095 strip and wire for flat springs, clips, washers and music wire (A228), hardened and tempered or bought pre-tempered.

Which grade of spring and bearing steel is the strongest?

A228 has the highest yield strength in the series at 1,950 MPa; VDSiCrV follows at 1,890 MPa. Values are for each grade's default condition.

Which grade of spring and bearing steel is easiest to machine?

8MnSi7 (machinability good, 58/100), then 50CrV4 (55/100).

Is spring and bearing steel heat-treatable?

Yes. These grades gain their strength from heat treatment; the conditions and their properties are listed on each grade page.

52100 or 100Cr6 — are they the same?

Yes: 52100 is the SAE name, 100Cr6 the EN (1.3505), GCr15 the GB and SUJ2 the JIS name for the same 1 % C, 1.5 % Cr bearing steel. Chemistry limits differ by a few hundredths of a percent and the cleanliness requirements differ by standard, but they heat-treat identically to 60–64 HRC and are interchangeable for pins, rollers and races. Specify the one your drawing standard uses.

6150 or 9254 for a coil spring?

9254 (0.55 % C, 1.4 % Si, 0.7 % Cr) is the automotive suspension and clutch spring steel — silicon gives it high resistance to sag (relaxation) at 100–150 °C and it cold-coils well as wire. 6150 (0.5 % C, 1 % Cr, 0.15 % V) has finer grain, better toughness and hardenability for larger bar, so it is the choice for torsion bars, valve springs and heavy coils hot-coiled from bar over 12 mm. Both are tempered to 44–50 HRC and shot-peened.