Production Machining

OCT 2016

Production Machining - Your access to the precision machining industrial buyer.

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productionmachining.com :: 21 Helping Precision Machine Shops Be More ProducƟ ve and Profi table Technical Regulatory Management Quality Technical Regulatory Management Quality Craftsman's Cribsheet Miles Free – Director of Technology and Industry Research NUMBER 48 Six Reasons Steel is Vacuum Treated Vacuum treated or vacuum degassed steel is used for critical applications that require steel with an exceptionally high degree of structural uniformity, internal soundness and other characteristics that may be impaired by the effects of uncontrolled amounts of dissolved gases. Vacuum degassing treatments, along impaired by the effects of uncontrolled amounts of dissolved gases. Vacuum degassing treatments, along with various de-oxidation practices, are specifi ed to control the amounts of dissolved gases in the steel. Vacuum treatment of molten steel: • Reduces hydrogen content. This reduc- es the tendency of steel to "fl ake" or become "embrittled." • Reduces oxygen content. This makes it easier for the steel to conform to restrictive micro- cleanliness requirements. • Improves the recovery and uniformity of • Improves the recovery and uniformity of distribution of alloying elements and other additives. • Helps control the composition of the steel closer than without vacuum treatment. • Results in higher and more uniform transverse ductility, improved fatigue resistance and im- proved high temperature performance. proved high temperature performance. • Can be used to achieve exceptionally low car- bon content that are otherwise unobtainable bon content that are otherwise unobtainable by conventional means. What are some situations where vacuum treat- ment is employed? • Large forgings and large cross-sections where hydrogen would otherwise remain and con- hydrogen would otherwise remain and con- tribute to fl aking and embrittlement. • Bearings where uniformity throughout the section is important for critical performance. section is important for critical performance. section is important for critical performance. • Inverted delta, human-critical safety applica- • Inverted delta, human-critical safety applica- tions where steel toughness and performance tions where steel toughness and performance place high demands on the steel's properties place high demands on the steel's properties in all directions. The removal of oxygen by degassing is a chal- lenge for the steelmaker, because this element is extremely reactive and can exist in the steel in many forms, such as free oxygen, dissolved in the melt as a soluble nonmetallic oxide, com- bined with carbon to form gaseous oxides and as complex oxides in the accompanying slags and refractories in the process. All Craftsman's Cribsheets are available for viewing and download at short.productionmachining.com/cribsheets. Photo credit: Siemens

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