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A Quick Guide to the Chemical Elements Found in Steel
This guide gives the common chemical elements found in steel, how they affect steel properties and the machining process.
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This handy quick guide will give you the common chemical elements found in steel, how they affect steel properties and the machining process and a few tips on how to deal with them.
| Chemical Elements | Symbol | What does it do for the steel performance? | What does it do for machining? | What steps to take when you encounter this |
| Carbon | C | Strengthens, hardens, makes heat treatable. | Improves up to approximately 0.23. Gives steel its hardness. | Anneal if over 0.40% and alloy steel; if carbon steel and over 0.50%. |
| Manganese | Mn | Strengthens, hardens, enhances heat treatment. | Improves surface and machinability. |
No special techniques needed. Promotes machining. |
| Phosphorus | P | Ferrite strengthener. Lowers ductility. | Crisps up chip. Improves surface finish. | Be careful with subsequent cold work on rephosphorized steels. |
| Sulfur | S | Lowers ductility, toughness, weldability, surface quality. | Controls build up edge (BUE), improves machinability about 25%. | Increase speeds and feeds. Is machinist’s friend.* |
| Silicon | Si | Deoxidizer, makes steels sound. May degrade surface quality. | Abrasive on tools. | Want 0.01-0.02 maximum Si in 12XX steels; 0.10 maximum for 11XX for best machinability. |
| Copper | Cu | Negligible in our applications. | Usually it is a clue about how steel is made. |
Higher coppers tend to indicate electric furnace steel. |
| Nickel | Ni | Ferrite strengthener. Aids heat treatment. | Usually makes chips tough to separate. | Avoid dwell. Sharpen tools. Secure workholding. |
| Chromium | Cr | Corrosion resistance, high temperature strength and heat treatability. | Higher strength makes machining more difficult. | Can be abrasive. Pay attention to tool edges and wear. |
| Molybdenum | Mo | Increases hardenability, raises tempering temperatures. | Not noticeable. | No special precautions. |
| Aluminum | Al | Develops fine austenitic grain size. Can combine with nitrogen. | Decreases tool life. | Pay attention to tool edges and wear. |
| Lead | Pb | No effect on mechanical properties. | Promotes machinability about 25%. | Run at higher productivity. Take advantage of this. |
| Columbium (Nibium) | Cb/Nb | Grain refiner up to 0.05% in bars. Microalloy strengthener. Similar to Al as grain refiner. | As microalloy makes material harder and tougher to machine. | Pay attention to tools, understand condition if microalloy. |
| Vanadium | Va | Grain refiner and strengthener Microalloy in forging steels. | Decreases tool life. Harder steels more difficult to cut. | Pay attention to tools, understand condition if microalloy. |
| Bismuth | Bi | No strengthening effects. Possible embrittlement. | Improves machining. Substitute for lead. | Run at higher productivity. Take advantage of this. |
| Nitrogen | N | Strengthener and lowers ductiliy (notch toughness). Improves surface finish and promotes chipbreaking. | Crisper chip and improved surface finish. | Does not like to be cold worked. Avoid dwell, avoid in crimping applications. |
| *Sulfur: Plain carbon and alloy steels with sulfur below 0.010 wt % are problematic for machining and surface finish. 0.02 wt % minimum sulfer is optimum in these steels for machining. | ||||
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