Question 1

What is a chrome steel ball?

Accepted Answer

A chrome steel ball is a bearing-grade steel ball made from high-carbon chromium-bearing steel, typically AISI 52100 (DIN 100Cr6 / JIS SUJ2 / GCr15). It is the most widely used material for ball bearings, precision races and rolling-element applications, offering high hardness (HRC 60-66 after heat treatment), excellent dimensional stability, and a long service life under heavy radial loads.

Question 2

What is the chemical composition of chrome steel balls (GCr15)?

Accepted Answer

Gcr15 / AISI 52100 chrome steel composition is 0.95-1.05% C, 1.40-1.65% Cr, 0.25-0.45% Mn, 0.15-0.35% Si, ≤0.025% P, ≤0.025% S, with balance iron. The chromium content provides through-hardening response, deep hardenability (full martensitic structure up to large sections) and improved wear resistance, which is why chrome steel is preferred over plain carbon steel for bearing balls.

Question 3

How hard is a chrome steel ball?

Accepted Answer

After quenching and tempering, AISI 52100 / GCr15 chrome steel balls reach HRC 60-66 (Rockwell C). Sizes up to ~25 mm reach uniform through-hardness; larger sizes (e.g., 3-inch 75 mm G200) are usually surface-hardened to HRC 60 min with a tough core of ~HRC 35-45 to balance impact resistance. We can adjust tempering temperature to hit hardness targets down to HRC 58 for shock-loaded applications.

Question 4

What is the density of chrome steel (52100)?

Accepted Answer

The density of AISI 52100 / GCr15 chrome steel is 7.81 g/cm³ (0.282 lb/in³). This makes it about 3 times denser than silicon nitride ceramic and 25% denser than 440C stainless, which matters when calculating valve-ball weight, dynamic balancing, and centrifugal force in high-RPM spindle bearings.

Question 5

Are chrome steel balls magnetic?

Accepted Answer

Yes. Chrome steel (GCr15 / 52100) is ferromagnetic in all conditions because its martensitic matrix contains no austenite. Magnetic permeability is similar to low-carbon steel. This makes it incompatible with non-magnetic requirements such as MRI equipment, magnetic flow meters, and electronic sensors that must avoid ferrous contamination.

Question 6

Will chrome steel balls rust?

Accepted Answer

Yes, chrome steel balls will corrode and rust if exposed to moisture, salts, acids, or mild humidity over time. The 1.5% chromium provides only mild corrosion resistance, far below the 11%+ Cr in 440C stainless. For humid or wash-down environments, we recommend a protective oil film, vacuum packaging, or switching to 440C / 316 stainless steel balls.

Question 7

Which standards apply to chrome steel balls?

Accepted Answer

Chrome steel bearing balls are typically produced to ASTM A295 for high-carbon anti-friction bearing steel, ISO 683-17 for wrought steels for rolling bearings, DIN 5401 for ball dimensions and tolerances, and AFBMA/ISO 3290 for precision grades G10-G1000. Mill certs reference EN 10204 3.1 for chemical and mechanical traceability.

Question 8

What precision grades do you offer for chrome steel balls?

Accepted Answer

We produce chrome steel balls in AFBMA / ISO 3290 grades G10, G16, G20, G25, G40, G60, G100, G200, G500, G1000. G10-G25 are used for high-precision spindle bearings and instrumentation; G100-G200 are typical for general-purpose bearings and ball screws; G500-G1000 serve bicycle wheels, casters, and low-cost industrial applications.

Question 9

What size range of chrome steel balls can you manufacture?

Accepted Answer

We produce chrome steel balls in AFBMA / ISO 3290 grades G10, G16, G20, G25, G40, G60, G100, G200, G500, G1000. G10-G25 are used for high-precision spindle bearings and instrumentation; G100-G200 are typical for general-purpose bearings and ball screws; G500-G1000 serve bicycle wheels, casters, and low-cost industrial applications.

Question 10

What size range of chrome steel balls can you manufacture?

Accepted Answer

Our standard chrome steel ball range covers 0.5 mm to 150 mm (3/32 inch to 6 inch). Production lots are held to AFBMA lot diameter variation (Vdw) for the chosen grade, with finished ball roughness (Ra) typically 0.02-0.05 µm after mirror polishing. Custom non-standard sizes up to 300 mm are available on request with extended lead time.

Question 11

What are chrome steel balls commonly used for?

Accepted Answer

Chrome steel balls are widely used in ball and roller bearings (skateboard to wind turbine main shafts), ball screws for CNC machines, linear guides, automotive transmissions, constant-velocity joints, steering racks, conveyor rollers, water pumps, and pivot bearings. Their high load rating and low cost make them the default choice wherever corrosion is not the primary concern.

Question 12

Chrome steel vs stainless steel ball - which is better?

Accepted Answer

Chrome steel (52100) is harder (HRC 60-66 vs 440C's HRC 58-60), cheaper, and supports 15-30% higher load ratings in bearings. Stainless (440C / 316) wins on corrosion resistance, magnetic neutrality (austenitic grades), and temperature tolerance. Choose chrome steel for dry, high-load, precision applications and stainless steel for medical, food, marine, or chemical exposure.

Question 13

What is the equivalent material to AISI 52100?

Accepted Answer

AISI 52100 (USA) is equivalent to DIN 100Cr6 / 1.3505 (Germany), JIS SUJ2 (Japan), GB GCr15 (China), BS 534A99 (UK), and UNI 100Cr6 (Italy). All refer to a 1% C, 1.5% Cr bearing steel with virtually identical performance after proper heat treatment. We cross-reference the grade you specify and supply material traceable to the requested standard.

Question 14

What is the maximum operating temperature for chrome steel balls?

Accepted Answer

We supply mirror-polished balls (Ra ≤0.01 µm) for silent bearings, standard lapped (Ra 0.02-0.05 µm) for general purpose, ground (Ra 0.1-0.2 µm) for G500-G1000 industrial use, and passivated / oil-coated finishes for corrosion protection during storage. Electroless nickel or zinc plating can be applied where cosmetic or anti-rust layers are required.

Question 15

How are chrome steel balls heat treated?

Accepted Answer

After cold heading or hot forging into near-net shape, chrome steel balls are quenched in oil from ~830 °C austenitizing temperature, then tempered at 150-180 °C for 1-3 hours. This yields a tempered martensitic structure with retained austenite <2%, hardness HRC 60-66, and minimal dimensional change. For large balls, marquenching or interrupted quenching avoids quench cracks.

Question 16

What is the minimum order quantity for chrome steel balls?

Accepted Answer

Our standard MOQ is 100 kg for stocked GCr15 sizes 1 mm to 50 mm, which corresponds to roughly 5,000 to 5 million pieces depending on diameter. Custom sizes, special grades, or non-standard heat-treat hardness carry a 500 kg MOQ. Sample orders of 50-100 pcs are accepted for existing catalog sizes with a slight sample surcharge.

Question 17

Our standard MOQ is 100 kg for stocked GCr15 sizes 1 mm to 50 mm, which corresponds to roughly 5,000 to 5 million pieces depending on diameter. Custom sizes, special grades, or non-standard heat-treat hardness carry a 500 kg MOQ. Sample orders of 50-100 pcs are accepted for existing catalog sizes with a slight sample surcharge.

Accepted Answer

Stocked GCr15 sizes ship in 5-7 business days from China. Custom sizes, special grades, or heat-treated large balls (≥100 mm) typically need 20-30 days for raw material procurement, forging, heat treatment, lapping and inspection. Tooling for a brand-new diameter requires 35-45 days plus sample approval before mass production.

Question 18

Do you provide material certificates for chrome steel balls?

Accepted Answer

Yes. Every shipment includes an EN 10204 3.1 mill test certificate covering chemical composition, hardness, microstructure, and inclusion rating. On request we provide a 3.2 certificate witnessed by a third-party inspector (SGS / BV / TUV), batch traceability for each ball lot, and dimensional inspection reports per the agreed AFBMA grade.

Question 19

How are chrome steel balls packaged for export?

Accepted Answer

Chrome steel balls are vacuum-packed in anti-rust PE film inside steel drums (20-25 kg net per drum) or export cartons, with desiccant bags inside. Drum/carton labels list size, grade, batch, weight, and HS code 8482.91. Palletized loads are stretch-wrapped for sea container transport; air shipments use reinforced cartons with foam inserts.

Question 20

What factors affect chrome steel ball pricing?

Accepted Answer

Chrome steel ball price depends on diameter (bigger = heavier = more steel per pc), grade (G10 / G25 cost 3-6× more than G500), tolerance, surface finish, order quantity, and whether heat treatment and grinding are in-house. Raw-material surcharges, currency exposure, and inspection level also shift the final figure. We send firm quotes within 24 hours against your inquiry.

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