Impact values - Charpy V Notch
Impact values - Charpy V Notch
(OP)
I recently Charpy V notch tested some 50Mn2 steel (CMn steel %C 0.47 - 0.55, % Mn 1.4 - 1.8 & % Si 0.17 - 0.37), in both the quenched and tempered and forged conditions. I have a Rp0.2 of 650 - 700N/mm² & Rm value of 900N/mm² & a % elongation value of between 16 - 20%. Values were taken at 20°C, -25°C & -40°C. Expecting to see charpy values in the region of 50J figures have been returned with values in the region of 10 - 20J.
Any ideas as to why the charpy values are so low?
Any ideas as to why the charpy values are so low?





RE: Impact values - Charpy V Notch
Joe Tank
RE: Impact values - Charpy V Notch
I am not surprised at all because of the carbon content you reported at 0.47 to 0.55%. Carbon content is a major driver that affects CVN impact energy values. The higher the carbon the lower the CVN impact energy. This is one reason why pressure vessel steels are limited in carbon content to at or below 0.35%.
RE: Impact values - Charpy V Notch
What section size are you quenching and what is your quench media? With only a C and Mn as alloying elements, you don't have much hardenability and with that high of a carbon, you probably can't water quench without running into a cracking problem, but with an oil quench up to about 1 inch (25mm) should get decent transformation so, after tempering, you should get in the 40-50 J range on your CVN. I wouldn't expect much at the lower temperatures; you'd need a different steel to get those to improve.
rp
RE: Impact values - Charpy V Notch
Even with the best steel making and heat treating processes, I do not believe that the 50J impact value can be had at -40C.
RE: Impact values - Charpy V Notch
RE: Impact values - Charpy V Notch
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RE: Impact values - Charpy V Notch
When you evaluate the microstructure and hardness of a sample of the Q&T steel this will validate the type of heat treatment. I would be very cautious of any steel products supplied by China. The products (mostly boiler pressure parts) I have seen coming out of certain mills and fabrication shops has been marginal in quality, and I would not trust any material test reports. I believe in about 3-5 years the mills and fabrication shops will raise their level of quality, but for now buyer beware.
RE: Impact values - Charpy V Notch
RE: Impact values - Charpy V Notch
2- Chek the amount of Sulphur and Phosphorus in your steel
3- The Charpy valkue depend on carbon content see figure include (source : ASM HANDBOOK Heat Tretament )
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4- You can temper your steel to increase the value of charpy test