Letter 40063

Scaling of heat treated screws made from boron steel material [India] 

March 28, 2006

We use screws made from boron steel. These screws are hardened and tempered in electric furnace to achieve hardness of 250 - 320 VPN. Recently we are having problem of scaling on the surface of the screws. Also threading diameter decreases after heat treatment process.

Is this due to basic raw material or this is due to oxidation in the furnace. We are not using controlled atmosphere in the furnace.

Kindly guide us for the same.

Zankar Desai
Manufacturer - Vadodara, Gujarat, India

This is not a raw material problem. The problem is oxygen in the furnace because you are not controlling the atmosphere. It is essential to control the furnace atmosphere in order to produce acceptable parts.

Toby Padfield
Automotive module supplier - MI, USA

You can remove heat treatment scale by the using of hydrofluoric acid 50% by volume & 5 gm/ ltr potassium per manganate. heat the bath up to 65 degree centigrade, bath should be pvc or rubber lined. dipping time of component 1 to 10 min depending upon the amount 0f scale

Vikas Shrama
metal finishing - Gurgaon, Haryana, India

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