There are many considerations when buying wheels for your industrial applications; not the least of these is the material from which the wheels are made. As with any equipment, correct selection depends on the specific use. Choices include cast steel, cast iron, ductile iron and various alloys. Here we will be looking at the pros and cons of steel v. iron, but bear in mind you may want to consult an engineer regarding all of the factors discussed.
A wheel that is harder than the track it runs on will cause wear to the track. It follows that if your track is harder than the wheels, the wheels will wear out faster. Generally, if you must choose track or wheels of a softer material, you will want to choose wheels that are softer, because wheels are less expensive to replace. Cast iron is harder than steel, so this is one factor in favor of steel wheels.
Track twists and turns
- One of the biggest advantages of cast iron is that it is extremely long-wearing. Even when its exterior rusts after periods of exposure, its structural integrity can remain intact.
- But be aware that iron’s life may be cut short when you have applications that add a lot of stress such as tracks with twists, turns and level variances. Steel is more elastic than cast iron and is more forgiving of irregularities. Flanges on cast iron wheels are more easily broken by irregular tracks than steel, and broken wheels can create not only downtime, but safety hazards.
- If you have an irregular track, the elasticity of steel wheels means you will likely need to replace them less than you would iron wheels. For many applications, this is the deciding factor between steel and cast iron.
Exposure to corrosive chemicals, grease and oil
Cast iron stands up better than steel under the harshness of messy applications, all else being equal.
Extreme high or low temperatures
If your equipment will be operating under extreme temperatures, you may want to consult an engineer regarding materials. They may recommend a custom steel alloy and heat treating.
High Impact and Weight
- If you evenly disperse loads in your carts, cast iron offers greater resistance to fatigue. If your loads vary and shift, you may want to choose steel.
- Some wheels are constantly subjected to jarring high impacts, often during loading or unloading. Constant high impacts cause fatigue in the metal over time. Although cast iron has better fatigue resistance than steel, because steel is more elastic than iron, it can adapt better to stresses. Usually you will want to choose steel in high impact situations, because steel is much less likely to shatter, creating a safety hazard. If there is any doubt, consult an engineer.
- An intermediate option to consider is ductile iron, which has features somewhere between cast iron and steel; it has much more impact and fatigue resistance than cast iron. Ductile iron cracks less easily than iron under stresses, because the graphite of the composition is in the form of nodules rather than flakes. In cast iron, the sharpness of the flakes can create stress points that result in cracks.
- Whatever material you choose, make sure the wheels stands up to manufacturer’s limits. Reliance Foundry uses a Safe Working Load standard, but you must consider that your load may not be subjected to ideal conditions and may require a heavier duty wheel than the SWL indicates.
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A wheel’s elasticity helps to keep the load stable, and we have already seen that steel is more elastic than iron. If you have a load that must be kept extremely stable such as a dry kiln lumber cart where lumber is stacked optimally for drying, steel may be the best choice.
- Cast iron wheels are usually priced lower than steel wheels, but if you need the elasticity steel offers because your track is inconsistent or your loads vary, steel may last longer and thus be more economical in the long run. Downtime can quickly eat up any savings you realize by buying less expensive wheels.
- An intermediate option to consider is ductile iron, which may be less expensive than steel.
Usually aesthetics are unimportant in industrial applications, but if your use is the exception, cast iron may be your best choice. Cast iron is better than steel for intricate, detailed designs, and may also be used for ornate reproductions.
When choosing the best wheels for your application, Reliance Foundry can give you guidance. But if there is any doubt, you will want to consult with an engineer. Ultimately, the best choice is the metal wheel that will keep your production line running efficiently and safely.