The Russian invasion of Ukraine and the short positions that traders were forced to cover impacted many global commodities markets, with one commodity, in particular, impacting our industry: nickel. During March, all concerned heard a great deal about the volatility in nickel prices on the London Metals Exchange (LME) and its impact on stainless steel. Why is Nickel so important for our industry?
Nickel traded on the LME is so-called Class 1 nickel, which must be at least 99.8% pure. But about half of the world’s nickel is less refined Class 2 metal, most of it in products such as ferronickel and nickel pig iron which can be cheaply converted into stainless steel at Chinese smelters.
Russia accounts for only about 9% of the nickel supply, but it has closer to a third of the world’s nickel sulfide ore. That gives the status of its exports an outsize impact on the price of the Class 1 metal traded on the LME. This grade is also currently most suitable for producing nickel sulfate. This chemical will have a growing importance in the coming years because of its use in electric vehicle batteries.
Most stainless steel contains about 18% chromium. Chromium is what hardens and toughens steel. Toughness is the ability of a material to absorb energy without breaking and increases its resistance to corrosion (especially at elevated temperatures). However, Chromium also induces ferromagnetism in steel in some applications. Ferromagnetism is the primary mechanism by which certain materials (such as iron) form permanent magnets or are attracted to magnets.
Nickel is used as a component in alloys such as monel, permalloy, cupro-nickel, and stainless steel, among others. Nickel offsets the decrease in such toughness caused by Chromium. Nickel also enhances corrosion resistance at elevated temperatures.
However, the critical purpose of adding nickel is to ensure the steel is intact at and below room temperatures. Many industries require materials that can withstand extreme cold. Certain materials, ductile at room temperature, abruptly lose their ductility when a given threshold is exceeded. Standard construction steels become brittle even at low temperatures.
Content steel becomes less susceptible to breaking with high nickel added, even after welding. Lastly, Nickel should also do away with the issues associated with steel ferromagnetism. Eight percent nickel and 18% chromium is the most typical stainless steel composition.
Stainless steel has many benefits when used in fasteners. First, it has high corrosion resistance. Stainless steel does not rust or tarnish, giving you a better look and longer lifespan. Secondly, stainless steel increases material strength and will hold up in harsh corrosive environments. It will also hold up in place with extremely high or low temperatures.
Each grade of stainless steel has a slightly different chemical composition and a distinct physical appearance. Some of the most common follow.
The two most popular stainless-steel fasteners are 18-8 (300 series) and 400 series. Of these two, the 18-8 series provides the best corrosion resistance and ductility (the ability to undergo deformations before failure). Each grade offers almost identical corrosion protection but varies in performance concerning installation and resistance to chemical attack. These grades cannot be heat treated and rely on cold working for additional strength.
One of the more popular grades is Type 302, which is typically used in sheet metal and machine screws. Although this grade provides exceptional corrosion resistance, it does not harden enough to produce the thread hardness required to minimize thread rollover caused by tapping high-tensile or thick steel.
The same problem occurs when using Type 305. To reduce the amount of thread failure, a special modified 304 stainless steel material is primarily for use in the building industry. This special grade of Type 304 stainless steel is more durable and hardens during the fastener’s fabrication, producing tougher threads. Type 304 has a higher level of carbon for better hardness.
Type 302 has higher carbon content than Type 304, making it tougher than Type 304. While Type 302 is tougher and stronger, the Type 304 material is more ductile.
Type 304 stainless steel fasteners are readily available in self-tapping screws. Using the proper hole size is critical to optimize fastener performance and minimize thread rollover, as with any self-tapping fastener. They are typically plated to provide additional lubricity for tapping and reduce thread failure.
Self-drilling fasteners are also available in Type 304 and can have a hardened carbon steel drill tip welded to the screw shank to drill steel. These fasteners are used in aluminum framing and a variety of panel applications. They are available in a wide range of sizes and head styles.
Another Type 300 series stainless steel grade is Type 316 and was initially developed for sulfurous acid applications. This grade has a higher molybdenum content, which provides additional corrosion protection in highly corrosive applications and works well in chloride-type environments. This grade is primarily available in self-tapping screws.
For less severe applications, Type 410 stainless fasteners are frequently specified. They are available in self-tapping and self-drilling styles and come in various diameters and lengths. Type 410 stainless fasteners provide good corrosion resistance in mild atmospheres like light industrial environments. In specific applications, Type 410 may show signs of red rust due to its lower chromium content (12% chromium) compared to 18-8 grades, and will continue to rust, although at a much slower rate than carbon steel.
If you are looking to improve your application effectiveness with the benefits of stainless-steel products, reach out to us on our contact page. Our team of supply chain management experts is ready and willing to assist you.