Improving on an Ancient Process, Modern Methods of Heat Treating Sintered Steel

Innovative Solution #10942

The use of Sinter Hardened Powder Metal to achieve a microstructure optimized for yield strength and cost effectiveness.

Overview

An update to an existing appliance changed the lid from stamped metal to glass, increasing the weight of the lid.  As a result, the stress on the existing powder metal cam used in the hinge assembly also increased.

Challenge

The existing powder metal cam has geometric features that made it expensive to manufacture on a repeatable basis in high volumes using other processes, such as machining, welding or broaching. The key requirements of the component, a countersink into a bore and unequal hub lengths while maintaining balanced density, and keeping an eye on cost, lent itself to the powder metal process. This cam was made utilizing a common iron copper alloy which was not appropriate for the additional weight of the glass lid.

Results

Atlas Pressed Metals Engineers recommended the use of a sinter hardened material for this increased weight requirement. Typical iron copper alloy supports a yield strength of 50ksi/ (340MPa), while the sinter hardened iron chromium prealloyed powder supports a yield strength of 120ksi/ (830 MPa) in this application. Additionally, using sintered hardened material eliminates the requirement for a secondary heat treatment process, which adds cost, introduces warpage and dimensional concerns, and increased process time.