Carbon steel is commonly used across many industries. It is affordable while still providing excellent mechanical properties. Carbon steel is typically composed of 0.05% to about 2.0% carbon measured by weight, along with iron and trace amounts of other elements. Since it is a very common selection for a variety of purposes, it is important to know how to choose the right carbon steel grade for your project.
7 Things to consider when choosing a Carbon Steel grade include:
- Does the carbon steel need to be machined?
- Does the carbon steel need to be welded?
- What are the strength requirements of the carbon steel?
- Does the carbon steel require good formability?
- Does the carbon steel need to be heat-treatable?
- Does the carbon steel need to have good corrosion resistance?
- What applications do you need the carbon steel for?
Does the carbon steel need to be machined?
There are many types of carbon steel that can be easily machined, but there are also many that may prove to be difficult. Grades of lower carbon steel such as C1010 and C1018 have good machinability. Alternatively, carbon steel with higher amounts of carbon such as C1141 and C1144 can also be machined without difficulty due to the sulfur that is added to their chemical composition. C1045 has a higher carbon content but no additional elements to aid in machining, making it a poor choice if machining is required.
Does the carbon steel need to be welded?
Certain types of carbon steel have very good weldability, however, there are several considerations to take into account when selecting a carbon steel to be welded. First, grades such as C1141 and C1144 that are great for machining are typically not weldable. The sulfur found in these grades can cause weld solidification cracking to occur. Grades with low carbon such as C1018 and A36 (or 44W in Canada) would be a better choice as they are readily welded. Higher carbon grades such as C1045 can also work, but may require preheat or post weld heat treatment.
What are the strength requirements of the carbon steel?
Low carbon steels tend to be lacking in terms of tensile strengths, comparative to other carbon steels. These should be avoided if high strengths are required. Choosing a carbon steel grade with a higher carbon content such as C1045 can provide more strength and hardness than a low carbon grade like C1008. However, a low carbon alternative is high-strength low-alloy steel (HSLA) which is a low carbon based steel specifically designed to possess higher strengths, while retaining formability.
Does the carbon steel require good formability?
Since carbon steel is such a broad category, many different combinations of mechanical properties can be achieved. If ductility is desired, lower carbon grades such as C1008 and C1010 should be considered. If you require sheet, consider using a DQ or DQAK grade. As a rule of thumb, lower carbon steels are much easier to form than higher carbon steels.
Does the carbon steel need to be heat-treatable?
Carbon steels with amounts of carbon greater than 0.30% by weight, such as C1045 and C1141 can be heat-treated with ease. Another option could be steels that have a carbon content that is just over 0.20% by weight. These carbon steels, such as A36, may have trace amounts of other elements added to them to increase their hardenability. Low carbon steels, those having carbon contents under 0.20%, are not capable of being easily heat treated. The lack of carbon does not allow the steel crystalline structure martensite to form, which gives carbon steel higher hardness and strength.
Does the carbon steel need to have good corrosion resistance?
It is not common for carbon steels to be chosen for their ability to resist corrosion. They are mostly composed of iron which can oxidize, forming rust. Without enough corrosion resistant elements added to their chemical composition, such as chromium, nothing prevents the iron from oxidizing. Choosing a galvanized or plated carbon steel is a viable option to prevent corrosion. Alternatively, adding oil or paint to the surface of a carbon steel is a good way to help prevent iron oxidation from occurring.
Knowing common applications of different grades of carbon steel can help you choose the right grade for your project. Here are some typical uses:
- Grade A36 / 44W: automotive components, cams, fixtures, tanks, forgings and structural applications such as buildings or bridges.
- Grades C1008, C1010, and C1018: machinery parts, tie rods, relatively low strength structural applications, mounting plates and brackets.
- Grade C1045: bolts, gears, crank shafts, cylinder shafts, die forges, and applications where more strength or higher hardness is required than that of C1008 or C1010.
- Grades C1141 and C1144: Pins, studs, bolts, shafts, tie rods and applications similar to those of C1045 when machinability is very important.
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