Monday, May 16, 2011

Steel Designations and Bellows Back Flash

How to prevent bellows Flash back and basis of steel designation.

Hello David

Thank you very much for the valuable information you have provided me so far, I am always looking forward to your next subject

I do have a few questions, although I heard that when using bellows, the bellows may be destroyed due to gases forming on the inside If the bellows were hung higher than the forge, would this prevent this from happening?

2. what would be the best metal to use, cold rolled steel or hot rolled steel and what is the meaning of 1030 or other number associated to the steel?

Thank you for helping the newbie’s like me, it is much appreciated

Good questions.
The bellows should be set up with a check valve inside so it can not draw gasses back in from the forge. The check valve originally was just a flap of leather on the exhaust that closes when the bellows is opened. This means all the air is sucked in through the inlet ports and none of the fuel gases from the fire which could be exciting indeed. Hanging the bellows higher than the forge will have little effect in preventing the problem.

Metal to use
The number designation refers to the type of steel and its alloy content.
The 1000 series means that it is just iron and carbon in the mix.
1018 or 1020 are both used for cold rolled and hot rolled. It is the same type of steel but as the name implies one is worked cold and the other hot. Cold rolled has tighter tollerances in size and requires more energy to make and costs a lot more. Hot rolled has more variation in sizing and has less stress put into the steel so it will bend easier. Once either are put into the forge they will work the same as there is no difference in the carbon content.

So back to the number designation. 1020 means a simple iron carbon mix with 20 points of carbon or .2% carbon. 1060 would have 60 points of carbon or .6% carbon.

5160 which is car or truck leaf or coil spring material is a different series. The 5000 series contains chrome. So 5160 has about 1% chrome and .6% carbon. Other series will have different major alloying components. Google knife making, and alloy steels, and metallurgy for information on each different steel series and their uses and properties.

Mostly for blacksmithing I will use hot rolled for general art work or 5160 if I am making cutting tools or hand punches. Other specific tools and punches I will use better suited materials such as S7 or H13 (yes there are letter designations as well).

Hope this helps
David Robertson
Ontario Artist Blacksmith