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Castings versus Forgings
- Thread starter cussons
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There must be many links. Are you looking for a comparison of the manufacturing processes; or aspects such as the reliability of the end products?
Cast valves have much greater porosity than forged valves and fittings. This could be an issue in hydrogen service where the small molecules could pass through the pours. Cast valves are made by pouring molten metal into sand molds. Forged valves are beaten into shape from solid blocks of metal.
Cast valves have much greater porosity than forged valves and fittings. This could be an issue in hydrogen service where the small molecules could pass through the pours. Cast valves are made by pouring molten metal into sand molds. Forged valves are beaten into shape from solid blocks of metal.
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Only an analyzis of failure rate, type and probabel cause could give you a startpoint for improvement. Start with this.
If you have a too high failure rate, my tip is to check your QA-system and procedures as next step.
First when you have established that you a have procedure and a control system that works, is the time to go for metallurgy and casting processes improvement.
Questions of improving castings should be launched in other forums, and castings compared to castings.
Concentrate a search on grain structure. Also check the ASTM specs for mechanical properties on the same materials casted by different methods and different heat-treats. The properties, in this case, have much to do with the quality of the material and not solely the chemistry.
For example you could look at 316 stainless in a wrought form, a forged form, a sand cast form, and any one of several investment cast forms. The options are many.
For example you could look at 316 stainless in a wrought form, a forged form, a sand cast form, and any one of several investment cast forms. The options are many.
You could also increase the amount of X-ray analysis. this itself won't necessarily increase your casting quality but it will help you weed out the bad castings and also tell you where your patterns are not feeding properly.
you could also invest in foundry software that models your patterns and optimizes gating.
you could also invest in foundry software that models your patterns and optimizes gating.
You need to order to a higher quality ASTM Standard, such as ASTM A743 or 744 and apply radiographic examination. You need to look at ASTM AE446, E186, or E280, as applicable for your casting to determine what quality level you require. A good start for a good qualit casting would be the following requirements:
TYPE DEFECT MAXIMUM ALLOWABLE LEVEL
GAS POROSITY 3
SAND & SLAG INCLUSION 3
SHRINKAGE
TYPE 1 (CA) 3
TYPE 2 (CB) 3
TYPE 3 (CC) 3
TYPE 4 (CD) 3
CRACKS NONE ALLOWED
HOT TEARS NONE ALLOWED
INSERTS NONE ALLOWED
If you want higher quality you can go to level 2 on any or all of porosity, slag, and shrink
Bare in mind, when you apply radiography to a standard casting from most of the major suppliers, you double the cost.
TYPE DEFECT MAXIMUM ALLOWABLE LEVEL
GAS POROSITY 3
SAND & SLAG INCLUSION 3
SHRINKAGE
TYPE 1 (CA) 3
TYPE 2 (CB) 3
TYPE 3 (CC) 3
TYPE 4 (CD) 3
CRACKS NONE ALLOWED
HOT TEARS NONE ALLOWED
INSERTS NONE ALLOWED
If you want higher quality you can go to level 2 on any or all of porosity, slag, and shrink
Bare in mind, when you apply radiography to a standard casting from most of the major suppliers, you double the cost.
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