EN36A – CASE HARDENING STEEL
EN36A is a 3.2% nickel – chromium high harden ability, case hardening (carburizing) steel, generally supplied in the annealed condition with a maximum brinell hardness of 255 (Rc26).
Characterised by the high core strength, excellent toughness and fatigue resistance in relatively large section with case hardness up to Rc26 when carburized, hardened and tempered.
EN36a can also be used (uncarburised) as a high tensile steel, which when suitable hardened and tempered can be utilize for various applications requiring good tensile strength and excellent toughness.
Pre hardened and tempered (uncarburized) EN36a can be further surface hardened by nitriding but will not respond satisfactorily to flame or induction hardening due to its low carbon content.
EN36A (carburised) is used extensively by all industry sectors for components and shafts requiring high surface wear resistance, high core strength and impact properties. Typical requirements: Heavy duty Bushings/Collets/Conveyor Pins/Heavy Duty Gears/King Pins/Ring Gears/Sprockets/Shafts etc.
COLOUR CODE: Orange bar end.
STOCKED SIZES: 14mm – 610mm Diameter
BAR FINISH: Peeled, Turned
AUSTRALIAN SPECIFICATIONS: AS 1444-1996-X3312/X3312H
Carbon – Min 0.10%, Max 0.16%
Silicon – Min 0.10%, Max 0.40%
Manganese – Min 0.35%, Max 0.60%
Nickel – Min 3.00%, Max 3.75%
Chromium – Min 0.70, Max 1.00%
Phosphorous – Min 0%, Max 0.04%
Sulphur – Min 0%, Max 0.04%
MECHANICAL PROPERTY REQUIREMENTS – AS SUPPLIED AS1444-1996 X3312:
Annealed condition – Brinell Hardness 255 Maximum
FORGING: Heat to 1150°C and hold until temperature is uniform throughout the section. Soaking time at forging temperatures should be as short as possible to avoid heavy scaling and excessive grain growth. This will vary depending on furnace conditions but 15 minutes per 25mm of section may be used as a guide.
Do not forge below 850°C.
Following completion of forging operation, work piece should be cooled as slowly as possible in sand or dry lime etc.
Note: Case hardening steels due to their low carbon content are less susceptible to cracking than medium or high carbon steels, and may therefore be heated and cooled more rapidly.
ANNEALING: Heat to 830°C- 850°C, hold until temperature is uniform throughout the section and cool in furnace.
CARBURIZING: Pack, salt or gas carburise at 900°C - 950°C, holding for sufficient time to develop the required depth and carbon content, followed by a suitable hardening and tempering cycle to optimise case and core properties.
HARDENING: Refer Refining and Hardening.
NITRIDING: EN36A suitably hardened and tempered (uncarburised) will respond to nitriding giving a surface hardness up to Rc 60.
Nitriding is carried out at 490°C - 530°C followed by slow cooling (no quench), reducing the problem of distortion.
N.B. The fairly high nickel content in EN36A will result in a lower case harness, or a longer nitriding cycle than with other alloy grades containing less nickel.
NORMALIZING – FOR IMPROVED MACHINABILITY: Heat to 880°C - 920°C, hold until temperature is uniform throughout the section. Soak for 10 – 15 minutes and cool in still air.
Temper immediately at 650°C - 660°C and air cool.
REFINING & HARDENING:
CORE REFINING: Slow cool from carburizing temperature and re-heat to 830°C - 880°C, hold until temperature is uniform throughout the section, quench as required in water, oil or air cool. Alternatively quench in salt bath held at 150°C - 250°C, followed by air cool.
CASE HARDENING: Following core refining, re-heat to 760°C - 800°C, hold until temperature is uniform throughout the section, and quench in oil.
Temper immediately while still hand warm.
DIRECT QUENCH: Cool from carburizing temperature to 810°C - 830°C, hold until temperature is uniform throughout the section. Quench as required in water, oil and air cool. Alternatively quench in salt bath held as 150°C - 250°C, followed by air cool and temper immediately.
OR: Cool from carburizing temperature to room temperature, re-heat to 810°C - 830°C and hold until temperature is uniform throughout the section and quench or air cool as previous. Temper immediately.
Note: When air cooling large sections a uniform fan cooling is recommended, especially when direct cooling from carburizing temperature.
*Suitable for fine grained steels only.
STRESS RELIEVING: Heat to 600°C - 650°C, hold until temperature is uniform through the section, soak for 1 hour per 25mm section, and cool in still air.
TEMPERING: Heat to 150°C - 200°C as required, hold until temperature is uniform throughout the section, soak for 1 – 2 hours per 25mm if section, and cool in still air.
N.B. Tempering will improve the toughness of both case and core, with only a slight reduction in core strength and case hardness. It will also reduce the susceptibility of the case to grinding cracks.
NOTES ON HEAT TREATMENT: Heating temperatures, rate of heating, cooling and soaking times will vary duet to factors such as work piece size/shape also furnace type employed, quenching medium and work piece transfer facilities etc. Please consult your heat treater for best results.
MACHINING: EN36A is the annealed as supplied condition has very good machinability and all operations such as turning, drilling, milling and tapping etc. Can be carried out satisfactorily as per machine manufacturers’ recommendations for suitable tool type – feeds and speeds.
WELDING: EN36A is readily weldable in the annealed as supplied condition. Following welding, the work piece immediately upon cooling to hand warm should be stress relieved at 600°C - 650°C is possible.
N.B. Welding in the carburized and heat treated conditions is not recommended.
WELDING PROCEDURE: Welding of EN36A should always be carried out using low hydrogen electrodes – please consult your welding consumables supplier.
SUGGESTED PRE-HEAT TEMPERATURES:
POST WELDING: Maximum cooling rate 100°C per hour down to 100, followed by cooling in still air. It is recommended that the work piece if possible is buried in sand or dry lime etc.
Category: MERCHANTS & BRIGHTS