"Stainless steel mills compete in the arena of abrasive environments."
Every application is unique and each dictates what type of steel should be applied. In corrosive environments, the shaft of choice remains stainless steel. In this article, we provide some background on the different categories of steel and then explore the different types of stainless steel shafts in more detail, including their properties and applications in industrial automation.
Preliminary Information About Steel
There are four broad categories of steel. In addition to stainless, they include carbon steels, alloy steels, and tool steels. Carbon steels are the most common and are characterized by their dull, matte appearance, and each grade contains different percentages of carbon. Alloy steels contain a mixture of alloys such as silicon, copper, and aluminum, which offer varying degrees of corrosion resistance and strength. Tool steels are hard and sought after for their resistance to heat and scratching.
The fourth type, stainless steel, uses a mixture of low carbon content combined with at least 10.5% chromium. This group is the bright group that excels in strength and resistance to high temperatures and corrosion, as well as offering options for special requirements. The group is divided into five types: ferritic, austenitic, martenistic, duplex, and precipitation hardened. In this article, we focus primarily on austenitic steel, which is the most common and makes up our 300 series stainless steel shafts. Below is an in-depth look at the most common types of stainless steel used in industrial automation.
303 Stainless Steel
Type 303 stainless steel is non-magnetic and cannot be hardened by heat treatment, making it unsuitable for use with rolling element bearings. The basic alloy composition is 18% chromium and 8% nickel stainless steel, and the addition of selenium or sulfur makes it highly machinable. Type 303 is designed with added sulfur content to allow for improved machinability over other similar materials, but also has good mechanical and corrosion resistant properties. While the sulfur content helps make 303 stainless highly machinable, it also reduces corrosion resistance and toughness relatively.
Magnetic: No
Hardenable: No (Limited bearing options and reduced life)
Machinability: High
Weldability: Poor
Corrosion resistance:
High, but less than other 300 series types
Washing environments: Not preferred
Cost: Expensive compared to other materials
Applications: Areas where parts require intensive machining
304 Stainless Steel
Type 304 is the most popular type of 300 series stainless steel, accounting for over 50% of worldwide use. Like Type 303, it is non-magnetic and is not suitable for use with rolling bearings due to its non-hardenable heat treatment properties. The advantage of 304 is that it provides high resistance to oxidation and exceptional corrosion resistance to chemical and atmospheric exposure. 304 is also the most weldable type of 300 series stainless, which can aid in ease of fabrication.
Magnetic: No
Hardenable: No (Limited bearing options and reduced life)
Machinability: Poor compared to 303 stainless steel
Weldability: Most weldable form of the 300 series
Corrosion resistance: Exceptional
Washable environments: Preferred material
Cost: Expensive compared to other materials
EApplications: Food industry
316 Stainless Steel
Type 316 stainless steel contains 3% molybdenum, which helps provide the best corrosion resistance among the grades in the 300 series. Like Types 303 and 304, it is non-magnetic and unsuitable for use with bearings due to its non-hardenable properties via heat treatment. Type 316 is often better suited for chloride environments prone to structural pitting and crevice corrosion. It performs well at high temperatures and offers excellent tensile strength and weldability. Many applications benefit from the superior properties of 316, and it is widely regarded as a premium grade in the industrial automation industry.
Magnetic: No
Hardenable: No (Limited bearing options and reduced lifespan)
Machinability: Lowest in the 300 series
Weldability: Excellent with high tensile strength
Corrosion Resistance: Highest in the series
Washable Environments: Preferred material
Cost: Expensive compared to other materials
Applications: Food preparation equipment and systems, evaporators and tanks, condensers, marine environments, textiles, and pharmaceuticals
Ceramic Coating
A ceramic-coated (aluminum-based) shaft has several unique characteristics that make it a valuable product. It is exceptionally lightweight compared to all other linear shaft products, with the weight difference becoming more pronounced as the shaft diameter increases. As typical with this type of material, the cost becomes more competitive with other materials as the diameter increases. Due to the coating, the ceramic-coated shaft is non-magnetic and extremely hard. However, the depth of hardness is nominal, which makes it a poor choice for applications involving bearings.
Magnetic: No
Hardenable: No (Limited bearing options and reduced lifespan)
Weight: Very lightweight
Corrosion Resistance: High
Washable Environments: Yes, depending on conditions
Cost: Low, particularly for larger sizes
Applications: Medical, medical devices, aerospace, and some washable environments
Carbon Steel
Common types of carbon steel include 1060, 52100, and 1566. While there are slight differences among these material types, they are generally interchangeable in similar applications. Carbon steel is the dominant material in industrial automation, accounting for approximately 85% of all shafts sold. It is the most affordable option and is easily hardenable, making it ideal for use with all types of bearings, especially ball bearings. Its high carbon content allows for excellent machinability but also makes it susceptible to corrosion. Various coatings, most commonly chrome, are used to slow the corrosion process. Carbon steel is widely used in factory automation applications where the environment can be controlled.
Magnetic: Yes
Hardenable: Yes (compatible with all bearing types)
Machinability: High
Weight: Heavy
Corrosion Resistance: Poor
Washable Environments: No
Cost: Low, widely available material
Applications: Ideal surface for ball bearings
400 Series Stainless Steel
The 400 series is a popular material type for industrial automation linear shafting because it combines moderate corrosion resistance with the ability to be hardened, making it suitable for use with bearing applications. While it represents a compromise—offering neither the hardenability of carbon steel nor the corrosion resistance of the 300 series—it is an acceptable option for many consumers whose needs fall between these extremes.
Magnetic: Yes
Hardenable: Yes (compatible with bearing applications)
Machinability: High
Weight: Heavy
Corrosion Resistance: Moderate (suitable for some applications)
Washable Environments: No
Cost: More expensive than carbon steel, less than coated carbon steel
Applications: General factory automation where some corrosion concerns exist
Comentarios