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  1. kumkumvijay

    Cracking associated with less severe quench

    Hi The company crack must be checked under microscope to identify is it quench crack. Quench crack passes through grain boundaries. The crack zone is high stress area due to bending process. So there is a possibility for crack while bending it. It must be hot forged to avoid crack for this...
  2. kumkumvijay

    L-80 material

    My opinions are as below: Low carbon steel - C% <0.3 Medium Carbon steel C%- 0.3-0.6 High Carbon steel C% -0.6-0.99 L80 (API 5CT) type-1 will be comming under medium carbon steel and L80 type-1 is equivalent to SAE 4140. Because both need oil quenching in heat treatment process quenching and...
  3. kumkumvijay

    MAXIMUM HARDNESS HRA

    Generally the high hardness material will have very small amount of plastic deformation during impact load, so the impact test and results are not much widely available or useful for high hardness material.
  4. kumkumvijay

    Micro analysis

    To come to the conclusion, parts are not heat treated properly, you have to mention the specification given to the supplier. The hardness is more related to the severity of quenching. More sever quenching --> More Martensite--> High Hardness Less Sever Quenching--> Less Martensite--> Less...
  5. kumkumvijay

    Hardness results

    API 5CT page 9- chapter 4.1.6 says that The hardness numbers and/or mean hardness numbers obtained shall comply with the requirements in Table C.5 or Table E.5. So if the supplier mentioned several surface hardness value then it can be accepted if the average is confirms to max HRc-23. Another...
  6. kumkumvijay

    Micro analysis

    Hello Metboss sorry, HRC 60 is in carburized condition. Q&T: BHN 235-240 Annealed: BHN 150-170 Normalized: BHN 160-190 Thanks
  7. kumkumvijay

    BE2519 tool steel

    Hello European equivalent for BE2519 is 1.2519. Refer the link below for the HT cycle http://www.metalravne.com/selector/steels/ow3.html
  8. kumkumvijay

    CF8M hardness/toughness

    My opinion is to eliminate the root cause from casting ( Material) just compare the microstructure of your supplier difficult to machine casting and competitor casting in thin and thick sections. If you find same microstructure then its something related to your machining process. the following...
  9. kumkumvijay

    Micro analysis

    The chemistry is the basic building block for getting microstructure and hardness. Microstructure and hardness is linked to each other very much. The chemistry can give different microstructure (hardness) based on heat treatment process. Surface Hardness: Quenching and tempered SAE 4130 -...
  10. kumkumvijay

    Heat Treating 4130

    you need to do the tempering after quenching with in 1.5hrs ( best) to avoid cracks or distortion of the part due to stress gained in the quenching process. Also tempering break the martensite needle structure. Tempering & normalizing both relieve the stress, so there is no need to tempered it...
  11. kumkumvijay

    process to stress relived the distorted 7075-T6 parts

    Hello My opinion is, its not possible to change the distortion with press for 7075-T6. the distortion must be controlled in quenching and machining process. The machining might have done with compensation for distortion and appropriate machining technique. If you want to releive the stress then...
  12. kumkumvijay

    D2 and water

    I share my opinion from metallurgical point of view: D2 material is high carbon low alloy steel. High carbon gives high hardness and wear resistance when quenched from austunitie zone. When it get very high amount of stress from cooling & high martensite % then it will tend to break. soft...
  13. kumkumvijay

    Pressure Required for Green Compact

    Hello davyjacob I am not sure whether you are doing Selective Inhibition Sintering (SIS) which use salt. what is the prupose of the salt? Are you making ceramic coating over the metal powder or salt will be dissolved in solvent to create porous structure. In case if you planning to use the...
  14. kumkumvijay

    Pressure Required for Green Compact

    Hello I would like to share my opinion as below: The compacting pressure must be decided based on the density of metal required in the final part. Also based on the method of pressing, you can change the pressure eg: die pressing, hot isosatic, cold isostatic etc. If you have decided the...
  15. kumkumvijay

    Hardness value verifcation

    I share my opinion as below: 1. There is nothing like environmental aging for steel grade 4130. 2. High hardness can be possible due to following reason: 1. quenched with high severity instead of required: wrong HT cycle followed or part wrongly mixed with other part HT cycle for making full...
  16. kumkumvijay

    low ferrite in weld of Duplex steel

    Also high nitrogen content in parent metal increases the precipitation of austenite during casting & welding and prevent high ferrite content in the rapidly cooled welds. So please check the nitrogen gas content of PM also in a gas analyser.
  17. kumkumvijay

    low ferrite in weld of Duplex steel

    I share my opinion as below: 1. Due to high possibility of ferrite formation the filler metals for duplex ss has high amount of Ni which is austunite stabilizer. If you get low ferrite in weldmed & alos in PM means, i suspect the heat treatment furnace may not reach the proper temp or time...
  18. kumkumvijay

    17-7 PH S.S., Condition CH900 - Need Consistent Color After Heat Treatment

    If you need to bring the customer expected color then i would suggest to analyze the following parameter for the prefered color formed process: 1. Temperature with tolerance followed 2. Microstructure analysis for the thickness of the oxide layer 3. controlled atmosphere followed eg: steaming 4...
  19. kumkumvijay

    17-7 PH S.S., Condition CH900 - Need Consistent Color After Heat Treatment

    I would like to share my opinion as below: Science behind the color: Thin-film interference is the phenomenon for the coloring. The thin oxide film formed during heating and cooling cycle allows the light to pass through the film and give different color based on the thickness and other several...
  20. kumkumvijay

    Definitition of full hard, half hard and 40% cold reduced

    I share my opinion as below: Generally 95% reduction done to achieve the full hard. So I feel it’s not direct calculation to calculate the original thickness for H12, H14, H16 by applying the % cold reduction. Also if the metal is annealed after the orginal thickness then it can be again cold...

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