... )6.Standard: ASME B16.20 HG20612 HG206337.Material: carbon steel, soft iron, inconel600, M-400, C-276, 10#,ss316,ss304.8 ... , wellhead assembly9.Hardness and Temperaturematerialmax hardness(HB)max temperature(degrees)soft iron90450carbon steel120450F51150540304160600316160600 API 6A R RX BX all series gaskets