The Industrial Metal Supply Stainless Steel Guide

Stainless Steel is considered as one of the best metals, and provides various benefits including its ease of fabrication, strength, and anti-bacterial properties. We encounter different types of stainless steel in multiple places in our everyday lives whether we realize it or not. From its discovery in 1913, stainless steel has been a popular and preferred metal by many partly due to its lustrous appearance, as well as its durability and versatility.

In our guide, you’ll discover some more benefits and interesting facts about Stainless Steel.

Industrial Metal Supply Co. Stainless Steel Guide


What is Galvanized Steel?

Galvanized steel is coated with zinc oxide to prevent rusting, since the chemical compound takes far longer to corrode than steel. It also changes the steel’s appearance, giving it a rugged look that some people prefer. All in all, galvanization makes the steel stronger and harder to scratch, so it’s ideal for outdoor use.

How does galvanization work?

Typically, manufacturers will dip the steel into molten zinc, which bonds itself to the steel like any other alloy would. This makes zinc more than just a protective coating, because it’s actually becoming part of the steel’s chemical composition. The interior may be steel, and the exterior may be zinc, but in between are gradient mixtures of steel and zinc that combine both metals’ properties. This dipping process is the most common form of galvanization, called hot-dipped galvanization. It’s also possible to spray zinc onto the steel, but this method creates a weaker layer of zinc.

Advantages

  • Rust Resistance: Iron in steel is incredibly prone to rusting, but zinc acts as a protective buffer between moisture, oxygen, and the steel.
  • Easy Inspection: It’s fairly simple to tell how strong a galvanized coating is, just by looking at it. There are also quick stress tests that can tell you how thick the zinc is.
  • Sacrificial Anode: This ensures that any damaged steel is protected by the surrounding zinc coating. It doesn’t matter if the steel section is completely exposed; the zinc will still corrode first.
  • Longer Life: With galvanization, a piece of industrial steel is expected to last more than 50 years in average environments, and can last over 20 years with severe water exposure. No maintenance required.

Disadvantages

  • Impractical to Dip Certain Items: Some steel pieces are too tiny or too huge to be hot-dipped, and it doesn’t make sense to galvanize them using other methods.
  • Zinc Can Be Temperamental: It’s important to take enough time to let galvanized steel cool down and settle in, so that the zinc doesn’t peel off. Galvanization isn’t nearly as effective if the zinc is not binding to the steel. The right coating thickness must be applied.

Types of Steel

There are thousands of different steel alloys, but some are used more than others. Each alloy has its unique strengths and practical applications, but they all iron- and carbon-based. Below, we’ve shared the four most common types of steel.

Carbon Steel

With a carbon range between 0.04% and 1.5%, this alloy makes up about 90% of overall steel production. When carbon content is on the low side (called low carbon steel), the metal is considered “mild” and easy to shape. On the opposite end of the spectrum, high carbon steel is more difficult to weld or form, but it’s well-suited for tools. Carbon steel can be used for a huge variety of applications, including knife blades, automobile parts, structural beams, flat sheets, and other construction-related products. For rust protection, carbon steels are typically treated with hot-dipped galvanization.

Alloy Steel

To qualify as alloy steel, other elements must be included in the standard mixture of iron and carbon. The most common alloying elements are manganese, chromium, molybdenum, silicon, and nickel, and they all impart distinct properties on the final alloy. These include greater hardness, corrosion resistance, heat resistance, and overall strength. Depending on the composition, some specialty alloy steels can even be found on spaceships and airplane turbines.

Tool Steel

These unique alloy steels contain a larger proportion of tungsten, molybdenum, chromium, and vanadium. This makes an ideal alloy for crafting tools. Boasting serious hardness and wear resistance, the alloy can keep a sharp edge even in the hottest environments. That also makes it perfect for cutting, extruding, and molding other metals.

Stainless Steel

Finally, stainless steel is an extremely popular alloy with at least 10.5% chromium, which helps prevent corrosion and staining. Carbon steel is generally prone to rusting, so it’s not the best metal for handling moisture; on the other hand, stainless steel has a chromium film to block oxidization. Used for medical implements, structural parts, cookware, jewelry, and hundreds of other applications, stainless steel is better than carbon steel in many respects.


Grades of Steel

Around the world, a variety of organizations have developed standards for steel grading, including British Standards, Japanese Industrial Standards, and Germany’s GB Standard. However, SAE International’s steel grading system is the most common. Started in the 1930s as a joint effort between SAE and the American Iron and Steel Institute (AISI), the two designed a number system that is still used today. Here are SAE’s basic designations for carbon and alloy steel:

  • 1xxx: Carbon Steel
  • 2xxx: Nickel Steel
  • 3xxx: Nickel-Chromium Steel
  • 4xxx: Molybdenum Steel
  • 5xxx: Chromium Steel
  • 6xxx: Chromium-Vanadium Steel
  • 7xxx: Tungsten Steel
  • 8xxx: Nickel-Chromium-Molybdenum Steel
  • 9xxx: Silicon-Manganese Steel

How does the number grading work?

These steel alloys are distinguished with a four-digit number. As seen in the list above, the first digit represents the primary alloying element. In some cases, there are multiple elements, such as nickel-chromium-molybdenum steel (8xxx). If there are secondary elements, they are represented by the second digit in the sequence. Here are a few examples:

  • 10xx: Plain Carbon Steel
  • 13xx: Manganese Steel (Mn 1.75%)
  • 32xx: Nickel-Chromium Steel (Ni 1.25%, Cr 1.07%)
  • 34xx: Nickel-Chromium Steel (Ni 3%, Cr 0.77%)
  • 72xx: Tungsten-Chromium Steel (W 1.75%, Cr 0.75%)

Finally, the last two digits in the grading system are devoted to the alloy’s carbon percentage (in hundredths, by weight). If the last two digits are 45, that means the carbon content is 0.45 wt%.

How is stainless steel graded?

Unlike carbon and alloy steels, stainless steel has its own grading system. With three digits instead of four, there are less stainless steel alloys to categorize. Similar to the previous grading method, the first digit represents the primary alloy composition. Here are the main categories:

  • 1xx: Austenitic General Purpose Alloys
  • 2xx: Austenitic Chromium-Nickel-Manganese Alloys
  • 3xx: Austenitic Chromium-Nickel Alloys
  • 4xx: Ferritic and Martensitic Chromium Alloys
  • 5xx: Heat-Resisting Chromium Alloys

What is Alloy Steel?

Technically, every steel is an alloy, but not all of them have the “alloy steel” designation. To be called alloy steel, other elements must be intentionally added to the iron and carbon composition. A small percentage of alloying elements — typically, no more than 5% — is added to the mix, and these metals can improve corrosion resistance, machinability, and many other properties.

What’s the difference between high and low alloy?

Most people say that high alloy is any steel with alloying elements (not including carbon or iron) that make up more than 8% of its composition. These alloys are less common, because most steel only dedicates a few percent to the additional elements. Stainless steel is the most popular high alloy, with at least 10.5% chromium by mass. This ratio gives stainless steel more corrosion resistance, with a coating of chromium oxide to slow down rusting.

Meanwhile, low alloy steel is only modified slightly with other elements, which provide subtle advantages in hardenability, strength, and free-machining. By lowering the carbon content to around 0.2%, the low alloy steel will retain its strength and boast improved formability.

What are some common alloying elements?

  • Manganese: Used in tandem with small amounts of sulfur and phosphorus, the steel alloy becomes less brittle and easier to hammer.
  • Chromium: A small percentage (0.5% – 2%) can help to harden the alloy; larger percentages (4% – 18%) have the added effect of preventing corrosion.
  • Vanadium: With only .15%, this element can boost strength, heat resistance, and overall grain structure. Mixed together with chromium, the steel alloy becomes much harder, but still retains its formability.
  • Nickel: Up to 5%, this alloying element will improve the steel’s strength. In excess of 12%, it provides impressive corrosion resistance.
  • Tungsten: Boosts heat resistance, so the melting point is higher. Also improves the structural makeup of the steel.