Forge Ratio

[WeldGk]

Hello all, does anyone have advice regarding 4130 minimum forge ratio? In many industry specifications, a forge ratio of 4:1 is seen, while many times 3:1 is accepted. Does anyone know the source of the 4:1 forge ratio as I have been unable to find descriptions in literature shwing this produces a wrought structure throughout (is 3:1 not enough?)

 

[arunmrao]

weldgk,please refer to your earlier participation on this topic and also a few other thread links provided in those discussions.

http://www.eng-tips.com/viewthread.cfm?qid=237898

 

[WeldGk]

Actually, my previous post does not really address this question. I also completed a search before posting this.

 

[CoryPad]

Forge ratio for what step? Producing what product? There is no generic answer.

 

[Wrenchbender]

I've never seen anything published in an ASTM or Mil-spec on forging reduction ratios. I've seen one application that successfully uses 3:1 for a Ni-Cr-W alloy steel. I think it may depend on what is design intent is. If all you want to do is heat & beat something into a certain geometry, forging temperatures and reduction ratios are not too important. If the intent is to optimize the subsequent microstructure and grain morphology, that's another matter. The variables are material chemistry, forging temperatures and reduction ratio. Higher reduction ratios are good for mechanically breaking up any dendritic structure from the original cast ingot and constantly creating new grains out of the old ones (the definition of hot working). Typically it’s the last pass on the press, when the temperature has dropped close to the A1, that (I think) leaves some strain energy in the material for further grain refinement during further heat treatment.

So in summary, more forge ratio = finer grains = better chem homogenation = better mech'l properties. Is 3:1 enough? Probably yes. Is >3:1 better? Yes, maybe. But there are diminishing returns, economic factors on press cycle time, reheating, etc.

 

[metengr]

To put it more simply, forging ratio or work reduction ratio (for products other than forgings) is typically defined by the end user or design organization, and is based on intended service conditions of the end product. It really is an engineering process detail step that has been developed by experience from the end user. As mentioned previously, there is no common recommendation or standard.

 

[arunmrao]

This is typically a 1 mark question in a 100 level,"metal forming" course.