AISI 440C Stainless Steel Balls – Hardened Martensitic Stainless Steel Balls
AISI 440C Stainless Steel Balls are hardened martensitic stainless steel balls designed for applications requiring high hardness, excellent wear resistance, good dimensional stability, and better corrosion resistance than standard chrome steel balls in mild environments. They are commonly selected for precision bearings, anti-friction bearings, pumps, valves, quick couplings, conveyor rollers, ballpoint pens, food-related equipment, medical instruments, and oil-related mechanical components.
SDBALLS supplies AISI 440C stainless steel balls in metric and inch sizes from 0.5 mm to 150.00 mm, with common precision grades including G20, G40, G80, G100, G200, G500, and G1000. Typical hardness is HRC 57-65 after heat treatment. For humid, mildly corrosive, or wear-critical applications, 440C offers a strong balance of stainless performance and bearing-grade hardness, while 316/316L should be considered for stronger chloride, marine, or chemical corrosion environments.
| غرض | Recommended Page Content |
| Product Type | Hardened martensitic stainless steel balls / bearing-grade stainless steel balls |
| مادة | AISI 440C / UNS S44004 hardened martensitic stainless steel |
| Diameter Range | 0.5 mm – 150.00 mm; |
| درجات الدقة | G20، G40، G80، G100، G200، G500، G1000 |
| صلابة | Typical HRC 57-65 after heat treatment; |
| التطبيقات النموذجية | Precision bearings, anti-friction bearings, pumps, valves, quick couplings, conveyor rollers, ballpoint pens, food-related equipment, medical instruments, oil refining devices |
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AISI 440C Stainless Steel Balls are high-carbon, high-chromium martensitic stainless steel balls produced for applications where hardness, wear resistance, and precision are more important than maximum corrosion resistance. After heat treatment, 440C can achieve one of the highest hardness levels among common stainless steel grades, making it suitable for stainless bearing applications, valve seating elements, pump parts, and repeated-contact mechanical assemblies.
Compared with AISI 52100 chrome steel balls, 440C stainless steel balls provide better corrosion behavior in many mild environments while maintaining high hardness. Compared with AISI 304 or AISI 316 stainless steel balls, 440C provides much higher hardness and wear resistance but lower corrosion resistance, especially in chloride-rich, seawater, or acidic conditions.
Material Selection & Technical Positioning
AISI 440C is a hardened martensitic stainless steel. It is selected when the buyer needs a stainless steel ball with high hardness, strong wear resistance, magnetic properties, and dimensional stability for precision rolling or seating functions. It should not be positioned as the best stainless grade for marine or chemical corrosion resistance. For those environments, AISI 316/316L, ceramic balls, or other corrosion-focused materials may be more suitable.
The correct industry terminology includes: AISI 440C stainless steel balls, 440C stainless balls, hardened martensitic stainless steel balls, bearing-grade stainless steel balls, high hardness stainless steel balls, and stainless bearing balls.
المواصفات الفنية
| ملكية | Recommended Content |
| Material Grade | AISI 440C / UNS S44004 |
| Equivalent Names | SUS440C, X105CrMo17 / 1.4125, 9Cr18Mo, 440C martensitic stainless steel |
| Diameter Range | 0.5 mm – 150.00 mm；other sizes subject to production confirmation |
| درجات الدقة | G20 – G1000 final range confirmed by size and order specification |
| صلابة | Typical HRC 57-65 |
| كثافة | Approx. 7.70 g/cm3 |
| Young’s Modulus | Approx. 210 GPa |
| قوة الشد | Approx. 1900-2000 MPa, depending on heat treatment and material condition |
| Supply Condition | Hardened, polished, passivated or oiled according to order requirements |
| المغناطيسية | Magnetic |
| مقاومة التآكل | Good in mild environments; not recommended as the first choice for seawater, chloride-rich, or acidic environments |
| تشطيب السعر | Polished, passivated, oiled, or other finish upon request |
Chemical Composition Reference
| درجة | Fe | C % | Cr % | Mo % | Mn max % | Si max % | P max % | S max % |
| AISI 440C | Balance | 0.95-1.20 | 16.00-18.00 | 0.75 كحد أقصى | 1.00 | 1.00 | 0.040 | 0.030 |
Note: Composition ranges are reference values. Final specification should follow the agreed material standard, purchase order requirements, and customer-approved drawing or datasheet.
International Grade Equivalents
| Standard / Region | Common Equivalent |
| AISI / ASTM | 440 درجة مئوية |
| UNS | S44004 |
| JIS | SUS440C |
| EN / DIN | X105CrMo17 / 1.4125 |
| Chinese reference | 9Cr18Mo / related high-carbon chromium martensitic stainless grade |
Heat Treatment, Hardness & Performance
AISI 440C stainless steel balls are normally heat treated to develop a hardened martensitic structure. This allows the balls to reach high hardness and strong wear resistance for repeated rolling contact, seating, and anti-friction applications.
- Typical hardness: HRC 57-65, depending on diameter, heat treatment and order requirement.
- High hardness supports wear life and dimensional stability in precision bearings, valves, pumps, rollers, and coupling mechanisms.
- Martensitic structure makes the balls magnetic, which can support automatic handling and feeding in assembly lines.
- 440C offers better corrosion behavior than chrome steel in many mild environments, but it is not equal to 304/316 stainless steel for corrosion resistance.
- For seawater, chloride-rich liquids, strong acids, or aggressive chemical exposure, buyers should confirm the media and consider 316/316L, ceramic, or other corrosion-focused alternatives.
Surface Finishes & Corrosion Resistance
Standard 440C stainless steel balls can be supplied with a polished metallic surface. Passivation may be used to remove free iron contamination and support formation of the stainless passive surface film. Anti-rust oil or customized cleaning and packing can also be discussed according to the application and shipping route.
| Environment / Media | General Suitability | Buyer Note |
| Fresh water / mild humidity | جيد | Confirm exposure time, temperature and cleaning condition. |
| Steam, oil, gasoline, alcohol | Generally suitable within normal operating limits | Confirm media concentration and operating temperature before final selection. |
| Food-related equipment | Application-dependent | Suitable where hardness and wear resistance are required and media exposure is mild; confirm food-contact and cleaning requirements. |
| Medical instruments / devices | Application-dependent | Confirm regulatory, passivation, cleaning, traceability and documentation requirements. |
| Seawater / chloride-rich environment | Limited | 440C may pit; consider 316/316L, ceramic or special corrosion-resistant grades. |
| Acidic chemical environment | Not recommended as first choice | Select material according to actual chemical concentration, temperature and exposure time. |
Applications & Application Fit
AISI 440C stainless steel balls are best used where the application requires high hardness, excellent wear resistance, dimensional precision, and moderate stainless corrosion behavior. They are not the first choice for low-cost general hardware or for aggressive corrosion environments.
| طلب | Fit Level | Why It Fits | Buyer Note |
| Precision bearings / anti-friction bearings | Very good | High hardness, dimensional stability and wear resistance support repeated rolling contact. | Confirm grade, noise, vibration, lubrication and fatigue requirements. |
| Pumps and valves | Very good | Hard surface supports seating, checking and repeated contact in fluid-control components. | Confirm media, pressure, temperature and corrosion conditions. |
| Quick couplings and fittings | جيد | Stable geometry and hardness support repeated engagement and release. | Confirm surface finish and contact stress. |
| Conveyor rollers and industrial movement systems | جيد | Wear resistance supports repetitive contact in mechanical systems. | Confirm load, lubrication and environmental exposure. |
| Ballpoint pens and precision consumer mechanisms | جيد | Fine finish and controlled diameter support smooth movement. | Confirm surface roughness, grade and cleanliness requirement. |
| Food-related equipment | Application-dependent | Useful where wear resistance is needed and exposure is mild. | Confirm cleaning chemicals, food-contact expectations and corrosion risk. |
| Medical instruments | Application-dependent | Precision and stainless behavior can be useful in selected device components. | Confirm documentation, traceability and regulatory needs. |
| Marine / acidic environments | Limited | 440C can suffer pitting or corrosion in aggressive media. | Consider 316/316L, ceramic or special stainless alternatives. |
Material Selection Guide
| Material Option | Typical Strength | Limitation | When to Recommend |
| AISI 440C stainless steel balls | Highest hardness among common stainless ball grades, excellent wear resistance, bearing-grade precision. | Moderate corrosion resistance; not ideal for seawater or acidic media. | Precision bearings, pumps, valves, anti-friction components, high-wear stainless applications. |
| AISI 420C stainless steel balls | Good hardness and wear resistance with practical stainless performance. | Lower hardness and bearing performance than 440C. | Cost-sensitive martensitic stainless applications with moderate wear demand. |
| AISI 304 / 304L stainless steel balls | Good general corrosion resistance, non-hardened austenitic stainless, non-magnetic or slightly magnetic after processing. | Much lower hardness and wear resistance than 440C. | Food, cosmetic, general corrosion-resistant and non-hardened stainless applications. |
| AISI 316 / 316L stainless steel balls | Better corrosion resistance, especially in chloride and marine-like environments. | Lower hardness; not ideal for high-wear bearing loads. | Marine, chemical, medical, food-contact or corrosion-critical environments. |
| AISI 52100 chrome steel balls | Very high bearing performance, hardness and fatigue resistance at lower cost. | Not stainless; poor corrosion resistance without protection. | High-speed bearings, motors, precision rolling assemblies in protected environments. |
Manufacturing & Process Control
SDBALLS controls 440C stainless steel ball production through raw material selection, wire drawing, cold heading, flashing, heat treatment, grinding, lapping or polishing, cleaning, passivation or oiling when required, inspection and packing. The production route is selected according to the required diameter, precision grade, surface finish and application requirement.
For precision applications, control of heat treatment, diameter variation, roundness, surface quality and final cleanliness is especially important. For valve, pump, coupling, food-related or medical equipment projects, SDBALLS can discuss additional inspection, cleaning, documentation and packing requirements before production.
Quality Control & Inspection
Typical inspection items for AISI 440C stainless steel balls include material verification, diameter, grade, roundness, surface appearance, hardness, surface roughness, corrosion-related requirements when specified, cleaning condition and packing condition.
- Dimensional inspection according to agreed precision grade and drawing requirement.
- Hardness inspection to confirm HRC range after heat treatment.
- Surface appearance control for scratches, dents, rust marks, stains and visible defects.
- Roundness and lot consistency control for precision rolling or seating applications.
- Optional passivation, cleaning, RoHS request, third-party testing or customer-specific report when required.
- Batch labeling and export packing control for traceability and international shipment.
Packing Options
SDBALLS can supply AISI 440C stainless steel balls in bulk industrial packing or customized OEM packing according to order quantity, ball size, cleanliness requirement and shipping method.
- Small-size balls: inner plastic bags, cartons, bottles, pails or drums depending on quantity.
- Bulk industrial orders: bag, carton, steel drum, plastic pail, wooden case or palletized export packing.
- Precision or clean applications: additional inner protection, labeling, batch separation or anti-contamination packing can be discussed.
- Customized label: material, diameter, grade, quantity, batch number, customer item number, barcode or OEM label upon request.
How to Specify for Quotation
To quote accurately, please confirm: material grade, diameter in mm or inch, precision grade, hardness requirement, surface finish, passivation or oiling requirement, corrosion environment, application, quantity, packing method, inspection documents, destination port and trade term.
For replacement or engineering projects, buyers are encouraged to provide drawings, current supplier specification sheets, photos, samples, media exposure, temperature, load, speed, lubrication condition and failure history if available.
Technical FAQ
Q: What is AISI 440C stainless steel ball?
A: AISI 440C stainless steel ball is a hardened martensitic stainless steel ball with high carbon and high chromium content. It is selected for high hardness, excellent wear resistance and bearing-grade stainless performance.
Q: Is AISI 440C stainless steel ball magnetic?
A: Yes. 440C is martensitic stainless steel and is magnetic. This is normal and can be useful for automatic sorting, feeding and assembly.
Q: What hardness can SDBALLS supply for 440C balls?
A: Typical hardness is HRC 57-65 after heat treatment. The final hardness range should be confirmed according to ball diameter, precision grade and purchase order specification.
Q: Is 440C better than 304 or 316 stainless steel balls?
A: It depends on the application. 440C is much harder and more wear resistant, making it better for bearings, valves and high-wear mechanisms. 304 and 316 are softer but offer better corrosion resistance, especially 316 in chloride or marine environments.
Q: Can 440C stainless steel balls replace chrome steel balls?
A: In some applications, yes. 440C can provide high hardness and better mild-environment corrosion resistance than chrome steel. However, chrome steel may still be preferred for cost-sensitive protected bearing applications.
Q: Are 440C stainless steel balls suitable for seawater?
A: Usually not as the first choice. 440C can suffer pitting in seawater or chloride-rich environments. For marine or chemical corrosion, 316/316L, ceramic, or special corrosion-resistant grades should be evaluated.
Q: Can SDBALLS supply passivated or polished 440C balls?
A: Yes. SDBALLS can supply polished, passivated, oiled, cleaned or specially packed 440C balls according to application and order requirements.
Q: What information is needed for quotation?
A: Please provide material, diameter, precision grade, hardness, surface finish, application, corrosion environment, quantity, packing, inspection documents, destination and trade term. Drawings or samples are helpful for replacement projects.
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