304H Stainless Steel

  • 304H Stainless Steel

     

    Type 304H is the high carbon version of 304 and 304L. T304H (high carbon) in a wide range of gauges and finishes. Type 304H has a carbon content between .04% and .10%

    Grade 304H with its higher carbon content finds application at elevated temperatures. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures.

    It is common for certifications of Grade 304H to be dual certified as 304/304H when the material has a higher carbon content.

    These properties are specified for ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.

    Specifications

    AMS 5513, ASME SA240, ASTM A240, ASTM A959, UNS S30400, UNS S30409

    Composition

    Grade C Mn Si P S Cr Mo Ni N
    304 min.max. -0.08 -2.0 -0.75 -0.045 -0.030 18.020.0 - 8.010.5 -0.10
    304L min.max. -0.030 -2.0 -0.75 -0.045 -0.030 18.020.0 - 8.012.0 -0.10
    304H min.max. 0.040.10 -2.0 -0.75 -0.045 -0.030 18.020.0 - 8.010.5 -


    Mechanical Properties
    Grade Tensile Strength (MPa) min Yield Strength 0.2% Proof (MPa) min Elongation (% in 50mm) min Hardness
    Rockwell B (HR B) max Brinell (HB) max
    304 515 205 40 92 201
    304L 485 170 40 92 201
    304H 515 205 40 92 201
    304H also has a requirement for a grain size of ASTM No 7 or coarser.

     

    Physical Properties
    Grade Density (kg/m3) Elastic Modulus (GPa) Mean Coefficient of Thermal Expansion (mm/m/°C) Thermal Conductivity (W/m.K) Specific Heat 0-100°C (J/kg.K) Electrical Resistivity (nW.m)
    0-100°C 0-315°C 0-538°C at 100°C at 500°C
    304/L/H 8000 193 17.2 17.8 18.4 16.2 21.5 500 720

     

    Grade Specification Comparison
    Grade UNS No Old British Euronorm Swedish SS Japanese JIS
    BS En No Name
    304 S30400 304S31 58E 1.4301 X5CrNi18-10 2332 SUS 304
    304L S30403 304S11 - 1.4306 X2CrNi19-11 2352 SUS 304L
    304H S30409 304S51 - 1.4948 X6CrNi18-11 - -
    These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.

     

    Grade 304H has higher strength at elevated temperatures so is often used for structural and pressure-containing applications at temperatures above about 500°C and up to about 800°C. 304H will become sensitized in the temperature range of 425-860°C; this is not a problem for high temperature applications, but will result in reduced aqueous corrosion resistance.

    Applications:

    Pressure vessels, petrochemical equipment, welded components or chemical,