Metallurgical Approach for Improving Life and Brinell Resistance in Wheel Hub Units

Raceway Brinell damage is one major cause of wheel bearing (hub unit) noise during driving. Original Equipment Manufacturer (OEM) customers have asked continuously for its improvement to the wheel bearing supply base. Generally, raceway Brinelling in a wheel hub unit is a consequence of metallic yielding from high external loading in a severe environment usually involving a side impact to the wheel and tire. Thus, increasing the yielding strength of steel can lead to higher resistance to Brinell damage. Both the outer ring and hub based on Generation 3 (Gen. 3) wheel unit are typically manufactured using by AISI 1055 bearing quality steel (BQS); these components undergo controlled cooling to establish the core properties then case hardening via induction hardening (IH). This paper presents a modified grade of steel and its IH design that targets longer life and improves Brinell resistance developed by ILJIN AMRC (Advanced Materials Research Center). And also, this focuses on demonstrating the improved Brinell resistance using exclusive Brinelling test. The strengthening mechanism is the fine grains generated by restriction of grain growth via precipitated micro alloying which leads to the increased yield stress in the base steel. Regarding that, all experimental verifications are introduced in this study.