GB 20CrMnTi Alloy Carburizing Gear Steel Bar 20MnCr5

A: You will almost always need grinding. Carburizing and quenching distort the part, typically 0.05–0.15mm depending on size and geometry. For a gear that needs quiet running and proper backlash, leave 0.1–0.2mm grinding allowance on the flanks. If the gear is for a low-precision application like a hand winch, you might skip grinding, but you will see noise and uneven wear. Tell us your tolerance and we can advise the allowance before you cut the blank.

A: In the annealed condition it is soft, around HB 170–210, and cuts similar to 8620. Use carbide inserts with a positive rake and run 120–180 m/min for turning. Drilling is easy, but the titanium addition can cause slight gumminess if you push too hard. Keep coolant flowing. If you are hobbing the teeth before carburizing, use a good quality HSS or carbide hob and expect normal tool life. It is not abrasive like D2 or high-chromium steel.

A: Because of the titanium. 8620 is a solid carburizing steel, but 20CrMnTi has better hardenability and finer grain after carburizing. That means the case stays tough and the core resists fatigue cracking under repeated shock. For truck transmission gears or heavy-duty drive shafts, 20CrMnTi often lasts longer. 8620 is cheaper and easier to source in North America. If you are exporting to Europe or Asia, 20CrMnTi is more common.

A: We can cut short pieces from stock for trials. For round bars up to 200mm, we can supply 1–2 meter lengths or even shorter cut samples. There is a minimum for cutting and packing, but it is far below a full heat. If you need a forged blank for a specific gear, the minimum is higher because we have to set up the forging die. Tell us the diameter, length, and quantity you need to test, and we will quote the smallest practical lot.

A: You should avoid welding if possible. This steel is designed for carburizing, not for weldability. If you must weld, preheat to 200–300°C, use a low-hydrogen filler, and then re-normalize or re-anneal before carburizing. Otherwise the weld zone will have a different microstructure and may crack during quenching. For a repaired shaft, it is often cheaper to make a new part than to weld and re-treat.

A: You specify the effective case depth (ECD) at the finished surface, usually 0.6–1.0mm for medium gears, or 1.0–1.5mm for heavy-duty gears. We can supply a carburizing case depth inspection report per ISO 2639 with the shipment if you order the heat treatment from us. But we do not carburize every bar - we sell the raw material. If you need certified case depth, you must send us the finished part dimensions and we can quote the full heat treatment cycle, including case depth verification.