GMS Ball Company
Welcome to GMS Ball Co Ltd
We are an independent suppler of all types of steel balls - and balls in many other materials, in quantities ranging from tens to millions.
We deal with ball manufacturers in all parts of the world and our purchasing volumes allow us to negotiate extremely competitive pricing.
How can GMS help you
If you already buy steel balls you will know that over the last few years a significant proportion of ball production has moved from Europe and the USA to India and the Far East. Some of these sources are very reliable others are not.
GMS deals with many of the more reliable of these manufactures, but we fully inspect all of the balls we buy. In this way we can offer you a reliable European source of steel balls, guaranteed to meet your specification every time.
Balls are made in a large range of different materials. Some of the more common ones are listed here. Particular materials are chosen for their properties and the requirement of the application. However, the material properties also influence the quality of ball that can be produced, a factor which can make the correct choice difficult.
Carbon Steel (AISI 1010/1020)
Carbon steel balls are generally case hardened with a soft core giving resistance to shock loads and surface wear but with a limited load carrying capacity. For this reason carbon steel balls of this type are generally used in applications where there are only moderate loads and slow rotating parts, for example Castors, Drawer Slides and low precision bearings. They offer a significant cost saving as compared to chrome steel balls.
Chrome Steel (AISI 52100, 100cr6 SUJ2, EN31B, 1.3505)
AISI 52100 Chrome Steel was developed for the manufacture of bearings. It is very widely used and has properties optimised for the manufacture of bearing components.
For this reason balls manufactured from Chrome steel represent the bulk of all precision ball production worldwide, and balls are available in the widest range of size and grade of any material.
Balls are manufactured in a number of "Stainless Steel" material each having different properties and applications
An austenitic stainless steel AISI 304 is non-magnetic and has very good resistance to corrosion. The material can not be hardened - other than by work hardening, and the balls are soft and susceptible to mechanical damage. The are used in applications where corrosion resistance outweighs the mechanical performance limitations.
An austenitic stainless steel like AISI 304 it is non-magnetic and non-hardenable, AISI 316L has improved corrosion resistance as compared with 304. It is widely used within the chemical industry, food processing, and for medical applications. Finished balls are soft and can be machined by conventional techniques applied to stainless steel.
A martensitic stainless steel AISI 420 is magnetic and hardenable. It is resistant to corrosion and can be used effectively in non-aggressive environments. Balls produced in AISI 420 are hardened to 50 to 56 HRC - slightly less than chrome steel, and can be used in place of chrome steel in all but the most severe applications.
AISI 440C is a martensitic stainless steel similar to AISI 42o, is magnetic and hardenable. It offers the best combination of hardness and corrosion resistance available from steel and is widely used within the bearing industry for the manufacture of corrosion resistant bearings. Balls produced in AISI 420 are hardened to 58 to 62 HRC - the same as chrome steel, which it can replace in most applications.
Tungsten Carbide, or more correctly cemented tungsten carbide is a composite material in which hard ceramic particles (Tungsten Carbide) are cemented together with a metal binder. The properties of the material are a combination of the properties of the 2 constituent parts. Hardness and wear resistance is provided by the carbide particles, while the binder provides some measure of elasticity and shock resistance. Different binder materials and percentages can used to produce material with particular properties.
Specification AISI 52100, 100Cr6, 1.3505, SUJ2, EN31B
Description A low alloy chrome steel specifically formulated for use in bearings.
Material Composition Carbon (C) 0.98% to 1.1%
Chrome (Cr) 1.45%
Silicon (Si) 0.23%
Manganese (Mn) 0.35%
Phosphorous (P) < 0.025%
Sulphur (S) < 0.025%
Mechanical Properties Density: 7.81 g cm-1
Hardness: 58 to 62 HRC
Modulus of Elasticity: 210GPa
Shear Modulus: 80GPa
Poisons Ratio: 0.3
Electrical Properties Electrical resistivity: 2.19 µ Ohm mm
Thermal Properties Coefficient of thermal expansion @20-300C: 12.00x10-6 K-1
Thermal conductivity: 46.6 W m-1 K-1
Corrosion Resistance Low resistance to corrosion, and particularly prone to pitting in damp atmosphereric conditions.
Care must be taken to avoid moisture in both use and storage.
Available Sizes 0.35mm (1/64") to 150mm (6") although availability of sizes above 75mm is limited
Available Grades AFBMA Std 10: 3, 5, 10, 15, 20, 25, 28, 50, 100, 200, 500, 1000, 2000
ISO 3790: 3, 5, 10, 15, 20, 25, 28, 50, 100, 200, 500, 1000, 2000
DIN 5401:Class I, Class II, Class III, Class IV, Class V, Class VI
Applications Ball Bearings, Valves, Measuring Equipment, Ball Screws,
General Information By far the most used ball material, Chrome steel balls provide the most cost effective solution for the vast majority of applications
What is stainless steel?
"Stainless" is a term coined early in the development of these steels for cutlery applications. It was adopted as a generic name for these steels and now covers a wide range of steel types and grades for corrosion or oxidation resistant applications.
Stainless steels are iron alloys with a minimum of 10.5% chromium. Other alloying elements are added to enhance their structure and properties such as formability, strength and cryogenic toughness.
These include metals such as:
Non-metal additions are also made, the main ones being:
The main requirement for stainless steels is that they should be corrosion resistant for a specified application or environment. The selection of a particular "type" and "grade" of stainless steel must initially meet the corrosion resistance requirements. Additional mechanical or physical properties may also need to be considered to achieve the overall service performance requirements.
Why is stainless steel "stainless"?
The corrosion resistance of stainless steel arises from a "passive", chromium-rich, oxide film that forms naturally on the surface of the steel. Although extremely thin at 1-5 nanometres (i.e. 1-5 x 10-9 metres) thick, this protective film is strongly adherent, and chemically stable (i.e. passive) under conditions which provide sufficient oxygen to the surface.
The key to the durability of the corrosion resistance of stainless steels is that if the film is damaged it will normally self repair (provided there is sufficient oxygen available). In contrast to other steel types which suffer from "general" corrosion where large areas of the surface are affected, stainless steels in the "passive state", are normally resistant to this form of attack.
Stainless steels cannot be considered "indestructible", however. The passive state can be broken down under certain conditions and corrosion can result. This is why it is important to select carefully the appropriate grade for a particular application.
Families of stainless steels
There are several families of stainless steel: FERRITIC, MARTENSITIC, AUSTENITIC and DUPLEX. These names are derived from the crystal structure of the steels, which governs their metallurgical behaviour.
FERRITIC stainless steels are magnetic, have a low carbon content and contain chromium as the main alloying element, typically between 13% and 17%.They are not hardenable by heat treatment.
MARTENSITIC stainless steels are magnetic, containing typically 12% chromium with a higher carbon content than the ferritic types. They are hardenable by quenching and tempering like plain carbon steels and find their main application in cutlery, aerospace and general engineering.
AUSTENITIC stainless steels are non-magnetic and, in addition to chromium typically around 18%, contain nickel. This enhances their corrosion resistance and modifies the structure from ferritic to austenitic. They are the most widely used group of stainless steels. They are not hardenable by heat treatment.
DUPLEX stainless steels are used where combinations of higher strength and corrosion resistance are needed. They have a mixed structure of austenite and ferrite, hence the term "duplex". They are not hardenable by heat treatment.
PRECIPITATION HARDENING stainless steels, like the martensitic types, can be strengthened (ie hardened) by heat treatment. The mechanism is metallurgically different to the process in the martensitic types. This means that either martensitic or austenitic precipitation hardening structures can be produced.
"Super" austenitic or "super" duplex grades have enhance pitting and crevice corrosion resistance compared with the ordinary austenitic or duplex types. This is due the further additions of chromium, molybdenum and nitrogen to these grades.
Corrosion and oxidation resistance of stainless steels
In general the corrosion and oxidation resistance of stainless steels improves as the chromium content increases. The addition of nickel to create the austenitic stainless steel grades strengthens the oxide film and raises their performance in more aggressive conditions. The addition of molybdenum to either the ferritic or austenitic stainless steels improves their pitting corrosion resistance.
The austenitic stainless steels are resistant to the wide range of rural and industrial atmospheres encountered in the United Kingdom, resulting in extensive use in architectural, structural, and street furniture applications. Their resistance to attack by acids, alkalis and other chemicals, has led to a wide use in the chemical and process plant industries.
The ferritic stainless steels are used in the more mildly corrosive environments, being often used in trim work and somewhat less demanding applications.
Martensitic stainless steels have similar corrosion resistance to the ferritic types, whilst that of the precipitation hardening stainless steels is claimed to be similar to the 304 (1.4301) austenitic type stainless steel.
Duplex stainless steels are alloys designed to have improved localised corrosion resistance, specifically to stress corrosion cracking, crevice and pitting corrosion.
Corrosion attacks at the surface of a material. It is important therefore to ensure that the surface finish is suitable and that the surface is clean and uncontaminated (particularly from non-stainless steel contact). This enables the "inherent" corrosion resistance conferred by the additions of chromium, nickel, molybdenum etc. to be fully exploited.
Benefits and properties of stainless steels
In economic terms stainless steels can compete with higher cost engineering metals and alloys based on nickel or titanium, whilst offering a range of corrosion resisting properties suitable for a wide range of applications. They have better strength than polymer products such as GRP. Stainless steels can be manipulated and fabricated using a wide range of commonly available engineering techniques and are fully "recyclable" at the end of their useful life.
In addition to their corrosion resistance, stainless steels also offer other useful properties, depending on their "family".
The austenitics, in the fully annealed heat-treated condition, are:
Fracture tough at cryogenic temperatures
Para-magnetic with relative magnetic permeabilities around 1.05
The martensitic and precipitation hardening families are hardenable by heat treatment.
The duplex stainless steels are stronger than the austenitics in the annealed condition and so can be used in thinner sections to save weight and cost.
The ferritics are lower cost stainless steels.
Stainless steel and the environment
The main source of raw material for making stainless steels is re-cycled scrap metal. This re-cycling route has been established for many years and the economics of the stainless steel making industry depend on recycling. Over 90% of new stainless steel is produced from recycled scrap.
The steel is melted electrically and in most cases refined by using inert air distilled gases, such as argon. Great care is taken to minimise fume and dust emissions. Some plants are equipped to re-cycle dust into the steel making process.
Most of the steel processing consumable materials, including cooling water, lubricating oils, pickling acids and "inter-leaving" paper are re-cycled in the plant or by specialist contractors. Stainless steel fabricators and processors re-cycle their scrap arisings and in-process consumables, including "caking" pickling acid residues for re-cycling.
As stainless steels are corrosion resistant alloys their life expectancy is usually long. A minimum of maintenance is needed and so, although more expensive initially, they offer attractive "life-cycle cost" benefits over alternatives such as carbon steels.
Stainless steels are easily cleanable and so an obvious choice for food and beverage manufacturing industries and catering equipment. There are no proven health risks from the normal use of stainless steels. The possible risks from alloying elements such as nickel and chromium are under constant review by experts.
What is Tungsten Carbide?
Tungsten Carbide or more correctly Cemented Tungsten Carbide is strictly a "cermet" - ceramic metal combination, where particles of ceramic, tungsten carbide, are bonded together in a metal matrix. Originally produced as a cutting tool material - a market which it now dominates, Tungsten Carbide is widely used where hardness and high wear resistance is required. Variation in the binder percentage, and the size of the carbide particles allows fine control over the properties of the material, hardness reducing and toughness increasing with increasing binder content. The binder material also contributes to the overall properties of the material.
Two types common:-
Cobalt Binder Tungsten Carbide
By far the most common form of Tungsten Carbide, Cobalt binder material is made in a range of compositions with up to 25% binder. Balls are generally made of material with a 6% binder content. It is susceptible to corrosion of the cobalt binder, particularly in contact with water, and although this rarely results in structural failure it can cause severe degradation of the ball surface.
Nickel Binder Tungsten Carbide
Nickel binder Tungsten Carbide is far less common than cobalt binder material, is not made in same range of composition, and tends to be slightly softer. However. it offers significantly better resistance to corrosion. It is particularly useful in valve and pump applications, and it performs well in more aggressive chemical environments.
What are Ceramics?
Modern Engineering Ceramics are being used in increasing volumes throughout manufacturing industry. They offer a range of interesting and often valuable properties are difficult or indeed impossible to achieve with other materials. The nature of these materials, particularly the combination of hardness and stiffness makes them ideally suited to the production of high precision balls.
Three materials have attracted particular attention for ball manufacture:-
Combining hardness and toughness with low mass, Silicon Nitride offers significant advantages in high speed bearing applications, and for these reasons it is finding increasing application in arduous bearing applications such as machine tool spindles and vacuum pumps. Increasing use and production volumes have dramatically considerably reduced the once astronomic cost of the material so that silicon nitride balls can offer extremely cost effective solutions to common industrial problems.
Alumina (Aluminium Oxide)
Alumina is used in 2 forms for ball production.
Alumina balls range in colour from almost white to a creamy yellow colour. The material is very harder, but less tough than either silicon nitride or alumina. Structurally the balls perform well, but are prone to localised surface damage, which ultimately promotes failure. Alumina balls are widely used medical applications particularly for replacement hip joints, and in valves and pumps for aggressive chemical environments.
Single Crystal - Synthetic Ruby and Sapphire
Single Crystal alumina is widely use for contact point for measuring equipment, and in this application provides good wear resistance at an effective price. Sapphire balls are clear, perhaps with a blue tint, and are far less common than ruby which range in colour from almost clear to dark red, Balls are often supplied with drilled holes for mounting purposes.
Zirconia (Zirconium Oxide)
Zirconia in its partially stabilised form offers a number of useful properties. It can withstand very high temperatures without deterioration, it has a similar rate of thermal expansion to steel, it has a high toughness, and it is relatively inexpressive. It does have a tendency to porosity, and which can prompt failure in some circumstances, and tends to make it unsuitable for high stress applications, but it is widely used in pumps and valves for aggressive environments, and for measurement standards.
Balls shapes are made in other ceramic materials, usually for very specific applications. Cubic Zirconia balls are used as lenses in some very specialised fibre optic systems, but they are not generally available. Silicon Carbide is interesting for some applications, particularly its "conductive" forms, but its inherently low toughness makes ball production difficult and consequently expensive.