Induction Quench Water and Rust

[induction31]

We operate a captive induction hardening operation where we harden shafts for the automotive industry. We use Lakos separators to remove the scale from our systems, but have not found an effective means of removing tramp oils. Our parts come out stained and seem to rust quickly after tempering in an electric oven. We use Ucon quenchant A in our systems and also use their rust inhibitor, but it has not prevented the rust from forming. We are limited to water based products because parts of the shafts are painted later in the process. Can anyone recommend a method of cleaning up our quench water, and any tips on preventing rust would be appreciated.

 

[swall]

First off all, find out exactly where in the process your parts are rusting. My experience has been that wet parts would flash rust in the temper furnace. The way to solve that is to make sure the parts are dry going in.We ended using air knives, with air supplied by a separate blower (i.e. not shop air)to dry the parts prior to entering the temper furnace.Rust went away.If parts are rusty coming out of the quench, then you have a different problem.

 

[induction31]

Thanks for the help Swall. The rust is not visible until after the tempering operation. The tempering furnaces use shop air that is high in humidity, probably the source of moisture needed to produce the rust. Anyone have a system to prevent the staining?

 

[NickE]

Be sure that there is a separate filter system on the shop air. (you mean compressed air right?) Water/oil coalescing filters are readily available and cheap. If the actual atmosphere inside your tempering furnace is of high enough humidity to condense on the parts before they get hot enough, maybe try a preheat. You also might find some use in a de-humidifier for the area around the furnace. Also maybe a preheat right after the quench so that you aren't putting a cold part into a hot humid furnace.

nick