Here’s some information on an interesting assignment we had. We will describe the situation and discuss the heat-treatment operation in this blog. Next time, we will finish with a discussion of our observations and the remedy. Can you figure it out before the reveal?

We were contacted for help on a new induction heat-treatment system used to harden, quench and temper on a relatively new heat-treatment line. The line was an integral unit in the production of a newly designed housing system, which was to be used in the manufacture of automotive engine components.

We were asked to investigate and evaluate the root cause of crack initiation, crack propagation and depth-of-hardening variances combined with as-quenched hardness variations on the “housing-support” unit. Before investigation, the resulting values (checked by Vickers microhardness with a 1,000-gram load) was seen to be 580HV and 645HV. The selected material was AISI 1548 with a nominal carbon content of 0.45-0.48%, and it was precision-machined.

The induction heat-treatment unit was less than 12 months old. It was purchased new from a reputable induction heat-treatment manufacturer. The unit was fitted with a rotary table that contained six individual rotating product tables.

The sequence of complete heat treatment was:

  • Place onto auto-load system.
  • Traverse into the induction unit area.
  • Auto load onto the individual component rotating tables.
  • Index round to the induction coil with the component rotating on its individual rotating table.
  • Preheat in 10 seconds (low induction power setting).
  • After preheat, ramp to austenitizing temperature.
  • At the selected higher power, in six seconds
  • Water quench down to ambient room temperature.
  • Index the main drive table to move the component ready for ejection.
  • Rack and wait for an air-circulating furnace for tempering.

We will discuss our observations and the results in part 2. What would you be looking for?