it contains between .55 percent and 2 percent carbon. It’s the hardest and strongest type of steel, but it can be a real pain to cut and form. Manufacturers use high carbon steel to make things like cutting tools, files, and hammers because those items need to be strong enough to keep their shapes and integrity through years of heavy abuse.
Steel is manufactured in many different forms, and each form has its own use for welding projects. Here are a few of the more common forms that you’re likely to run into as you weld:
❯❯ Flat steel is exactly what it sounds like – a flat piece of steel. It’s also called sheet steel. It comes in a range of thicknesses and sizes, but when it’s larger than 12 inches wide, it’s called plate steel.
❯❯ Steel bars are made in an array of shapes, but the most common are round, square, or flat. You can see some examples of steel bar shapes in Figure 2-1.
FIGURE 2-1: Square (a), flat (b), and round (c) steel bar shapes.
❯❯ Rolled steel comes in two forms.
● Hot rolled steel is made to its finished size while the steel is still red hot. Iron oxide forms on the hot steel after it’s rolled. It’s a grayish-black coating that helps protect the steel from rusting. Hot rolled steel is used for piping, tubing, tanks, and other products.
● Cold rolled steel is made by rolling the steel to its finished size after it’s cooled to room temperature. It doesn’t get the iron oxide that hot rolled steel gets, so cold rolled steel is smooth and bright looking. It’s used for making things like nails and screws.
Steel is such a ubiquitous metal that it’s hard to imagine life without it. It has become an important part of everyone’s life, and the ways you live, play, and travel certainly wouldn’t be the same if steel was no longer available.
You can use steel for a wide variety of welding projects; it’s cheap, readily available, and pretty easy to weld. If you’re looking to weld objects such as farm equipment, tools, cars, automotive equipment, specialty containers (drums, pipes, and boilers), or even bridges and parts of buildings, you should strongly consider steel as your metal of choice.
When is steel not appropriate for welding? Well, if you’re working on or repairing a piece of metal that’s definitely not made of steel, such as repairing an aluminum piece on a boat, using steel won’t work for that project.
If you’re starting a new welding project from scratch and really need to end up with a lightweight product, steer away from steel. Steel is durable and cheap, but it’s also pretty heavy compared to many other metals. Steel also doesn’t work if you’re welding something to be used for any sort of food service application; food almost always involves water of some sort, and water rusts steel, creating an unsanitary environment. For the same reasons, using steel for anything in a medical setting is also a bad idea.
It’s a little hard to believe how many different kinds of metals are out there. Metals run the gamut from tungsten, which is one of the hardest materials on Earth, to mercury, which is a liquid at room temperature. Here are a few of the physical properties of metals that combine in different ways to make metals unique.
● Strength: How much external force the metal can take without breaking.
● Ductility: The ability to change shape without breaking.
● Magnetism: Some metals (like steel) are magnetic; others (like aluminum) aren’t.
● Hardness: The resistance of a metal to being damaged when another metal is applied to it.
● Resistance to oxidization: When metals combine with oxygen, they become oxidized. That’s what causes steel to rust, for example. Some metals – tungsten, for instance – are very resistant to oxidization.
● Electrical conductivity: Some metals conduct electricity much more efficiently than others. For example, silver is an incredible conductor of electricity, but stainless steel doesn’t conduct well at all.
● Melting point: Every metal has a melting point – the temperature at which the metal turns from a solid to a liquid. This property is critical in welding because, of course, you’re trying to melt metal. Tungsten has the highest melting point; you need temperatures of 6,170 degrees Fahrenheit to melt tungsten. That’s remarkably high compared to, say, tin, with a melting point of only 450 degrees Fahrenheit.
All metals have to be cleaned and prepared before you weld them, and steel is definitely no exception. Quality welds aren’t going to happen if your steel is covered with surface contaminants. And some of those contaminants can be downright dangerous to your health if they’re heated up and converted to fumes while you’re welding. (Flip to Chapter 3 to read all about the safety gear you can get to protect yourself from fumes.)
You especially need to do your best to remove rust from the surface of your steel. Rust is especially common on mild steel (covered earlier in this chapter), and it can wreak havoc when you’re trying to produce a high quality weld. The most common defect you experience as a result of rust is porosity (the presence of lots of little holes) in your welds, and porosity can really ruin a good weld joint.
You can use one of two methods for cleaning your steel prior to welding: chemical or mechanical. The method you choose depends on the metal type, the condition of the metal, the welding process you’re planning to use, and the equipment available.
Cleaning steel with mechanical methods
When you clean your steel mechanically, you clean the surface by scraping, brushing, or grinding. I usually clean pieces of steel by hand (without power tools) only when the pieces are very small because power tools are just faster otherwise. If you opt to clean steel by hand, I recommend using a very sturdy wire brush. (Check out Chapter 4 for information on wire brushes and other basic tools you need for welding.)