Recently-Asked Questions: 
Stainless Steel Bearing Balls

What materials are recommended for stainless steel bearing balls
used in corrosive environments? 

Austenitic types are the most common; the reason is their chromium and nickel content
(16% or higher for chromium, at least 6% for nickel) provides good corrosion protection. 
Also, austenitic steels have low magnetic properties, and can be strengthened by cold working.
Austenitic grades also retain their high strength properties at high temperatures. Unlike ferritic,
martensitic and precipitation hardened steels, austenitic stainless can also be used in sub-zero
working environments.

What specific austenitic materials are recommended for stainless steel bearing balls?

Hartford recommends the basic grades, 302, 304; 304L, the low carbon alternative;
316 for highly corrosion environments; and 321, which contains titanium and provides
greater strength.

What stainless steel balls are best for applications involving rolling fatigue?

A martensitic type, 440C, is highly resistant to rolling contact fatigue.  This is a straight
chromium steel, and also provides maximum hardness and dimensional stability.  440C
stainless steel balls are always used in a hardened condition, perform similarly to tool steels,
and are ideal for rolling bearings. 420, which provides higher corrosion resistance, but less
hardness, is an economical alternative for many applications.

Can you recommend an economical alternative to 302/304 for
corrosive environments and conditions?

430 stainless steel bearing balls meet that need.  This ferritic steel offers good resistance to
mild atmospheric conditions. It also provides superior resistance to chloride stress corrosion
at elevated temperatures, compared to 302/304 or 316 materials.  

Is 430 a suitable grade for applications involving petroleum products?

Yes, 430 stainless bearing balls can be used in those environments, also where there's
exposure to steam, dairy products, nitric acid and many organic materials. 

Is there a stainless ball grade that resists attack by sulfuric and
phosphoric acids?

316 stainless steel balls provide excellent resistance to these compounds, thanks to a
high nickel and molybdenum content.  316 is used extensively in applications involving
photographic chemicals, inks, rayon, rubber, textile bleaches, dyestuffs and high
temperature equipment. Notably, 316 is also FDA approved.

We need stainless steel bearing balls for use in valves and pumps. 
What are our options?

304/302 18-8 stainless steel balls, which have 16-18% chromium, are ideal where
conditions demand levels of corrosion performance and toughness not possible with
hardenable stainless steels.  Couplings, valves and pumps are all common applications
for 304/302 stainless grades. 

We need hollow stainless steel balls for a valve application. 
What do you recommend? 

The primary material used for hollow steel balls is 440A, which has 16-18% chromium,
also small amounts of moly, manganese, and silicon.  440A stainless steel balls are
stronger than their plastic counterparts, and provide excellent corrosion resistance. 
They're widely used in liquid float systems, conveyor systems, palletizers, overflow
and vent valves, and ball transfer units.

What  quality standards do you apply to stainless steel bearing balls?

Hartford Technologies' manufacturing operations are ISO 9001:2008 certified.
We also conform to ABMA standards regarding surface, sphericity and size.
Our quality commitment also includes APQP, a process that ensures that product
design meets customer expectations, while promoting strategies that “design-out”
potential problems and boost productivity for Hartford customers.

Hartford Technologies is a leading manufacturer of stainless steel bearing balls, bearings and bearing assemblies,
and precision rollers, pins, and shafts, with manufacturing facilities in the U.S. and China.  We provide comprehensive
value-added services, including application engineering and inventory management, to a customer base that spans
automotive to medical, leisure products to agriculture.

Hartford customers include leading OEMs, and diverse, specialized manufacturers on four continents. Our commitment
is to combine technical innovation with agility, responsiveness and institutional strength – strength that comes from a
conservative management team, global manufacturing and logistics capability, and more than 80 years of leadership.

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