|
Pitting resistance equivalent number (PREN) is a measurement of the corrosion resistance of various types of stainless steel. Exact testing procedures are specified in the ASTM G48 standard.〔(【引用サイトリンク】url=http://www.astm.org/Standards/G48.htm )''Full text of standard not available free of charge online but available in libraries''〕 In general: the higher PREN-value, the more corrosion resistant the steel. The PREN-value is calculated using the following formula: PREN = 1 x %Cr + 3.3 x %Mo + 16 x %N (w/w) Steels with PREN-values above 32 are considered seawater (corrosion) resistant. Furthermore a PREN-value ≥ 40 for duplex steels is called for in the DIN EN ISO 15156 as well as the American NACE – a standard for use in hydrogen sulfide environments known in the oil and gas extraction industries. Exception: stainless steels with molybdenum content ≥ 1.5% may have a PREN-value ≥ 30. In these norms the PREN-value takes into account tungsten () in the alloy and is defined with the formula: PREN = 1 · %Cr + 3.3 ( %Mo + 0.5 · %W ) + 16 · %N ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pitting resistance equivalent number」の詳細全文を読む スポンサード リンク
|