one station heat treat furnace

[pardal]

I want to develop a heat treatment station to treat aisi 1070 1 mm thick about 160 to 280 mm diameter.
It will be under atmosphere controlled using mixture of a inert gas plus methane or propane to have the same Carbon potential.
This material comes from a laser cutting vendor , cold rolled , with 102 HRB [HRC 25.6 ]
It shall be harden to HR 45N : 67 min [ HRC 61] at 850 °C
The quenching will be with oil at 100°C or other if better.
Then temper under inert atmosphere in a fixture that will press it so it get flatten, with a harden of HRA 70 71 [ HRC 39 14 ] as resultant
The temper will be at 520°C for 4 hours
The chamber shall be about 300 x 300 x 300 mm
Because the rise of the u$s from 1 to 3,80 in the last 3 months, in my country , it is impossible to buy from any vendor, and furthermore, I take it as a challenge.
I thought in some thing like a top loading, with internal oil under the same atmosphere, but it shall be temporally closed while heating, this is the not know by me how to do this device .

The scope is to have the piece with the same surface when coming from the vendor, a brigth clean surface.

The piece will be cleaned after quenching and the tempered in the same chamber but with a pure inert gas , could be N2 or , Ar,

The production rate is from 1 to 20 pieces . We can say at lab rate.

Pardal

 

[gdodd]

I started life out as a heat treater and remember a number of novel techniques for heat treating different steels.

If you only have a few of these parts to heat treat why don't you try packing the part in a mild steel box or 316 stainless steel for larger numbers, loosely pack the parts in cast iron chips to protect against decarb.
Use tie wire to secure the part leaving a loop above the surface of the C/I chips.
Heat to above austenitizing temperature ie about 780 degrees C for 1070 until heated uniformly then quench in preheated oil as indicated above.

According to temper graphs, to achieve 39HRC you will need to temper at 520 as you suggest, but the old rule of thumb was to temper 1 hour per inch of section. So I think 1 hour maximum is all you will require.

Clamping during tempering will reduce distortion however it may be necessary to put packers in positions to reverse any serious bends.

We used to use an electric air recirculating furnace for tempering everthing from tool steel to spring steel and found the surface was generally only lightly oxidized.

Hope this helps

 

[pardal]

Hi GDodd , thanks for your reply to my query.

One thing shall be stated: The material is cold rolled on the last 0,2 mm and the surface is brigth ,clean, just about the finish that the old razor baldes had.

I need to mantain such feature, because it will be electro zinc plated , and black chromatized, and any inperfection on the surface is enlarged after this treatment.

As you have a lot experience in heat tretament , could you help me any more please?

Gracias. (thanks)




Pardal