The 7 Processes of Forged Steel Gear Production

 The 7 Processes of Forged Steel Gear Production

With the advancement of modern technology,the quality requirements for gears have become increasingly stringent. As acritical foundational transmission component in the automotive industry, thequality of gears directly impacts vehicle noise, smoothness, and service life.To achieve the dual goals of high quality, low noise, and efficient production,what are the 7 key processes involved in gear manufacturing?

1. Forging the Blank

Hot die forging remains the widely adoptedprocess for producing gear blanks in the automotive industry. In recentyears, cross wedge rolling has gained popularity for machiningshaft-type blanks. This technique is particularly suitable for complexstepped-shaft blanks, offering high precision, minimal post-forging machiningallowances, and high production efficiency.

2. Normalizing

After forging, some manufacturers optfor normalizing, while others use annealing. Bothprocesses refine grain structure, homogenize carbide distribution, and relieveinternal stresses. However, normalizing cools faster than annealing, resultingin finer microstructures and improved mechanical properties. Normalizing alsooffers higher productivity due to shorter furnace cooling times, making itpreferable over annealing in most cases. Isothermal normalizing furtherensures stable and reliable product quality.

3. Rough Turning

The outer diameter and end faces of thegear are roughly machined using conventional or CNC lathes. Since the workpieceundergoes subsequent heat treatment, a 3-5 mm machining allowance istypically left to accommodate final adjustments in later processes.

4. Tempering Heat Treatment

Gears require varying surface hardnessdepending on their operating conditions, but post-quenching hardness generallyexceeds HRC 45. For automotive gears subjected to heavy loads andfrequent impacts, 20CrMnTi steel is commonly used. Thismaterial achieves a surface hardness of HRC 58-62 and a corehardness of HRC 30-45 after quenching, enhancing wear resistanceand fatigue strength.

5. Finish Turning

The outer diameter and end faces areprecision-machined to meet dimensional specifications in the design drawings.If grinding is required later, a 0.2-0.3 mm allowance isretained to achieve higher precision post-grinding.

6. Gear Cutting

Gear teeth are typically machined usinggear hobbing or shaping machines. While these methods are easy to adjust andmaintain, efficiency becomes a bottleneck in mass production. Advances in coatingtechnology have addressed this issue: recoating hobs after sharpeningsignificantly extends tool life by over 90%, reducing tool changefrequency and sharpening time while boosting productivity.

7. Gear Grinding

As quality standards for forged gears riseand noise requirements tighten, higher-precision machining becomes essential.For mass-produced gears, grinding remains a highly effectivefinishing method. It is primarily used for hardened gear surfaces, correctingprocess errors from prior steps and achieving exceptional precision.Post-grinding surface roughness can reach Ra 0.63–0.16 μm, ensuringboth quality and noise reduction targets are met.

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