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Any problem with your carburising / carbonitriding process?

Author David Pye
29 Mar 2017

Are you facing any problem with your carburising / carbonitriding process? Mr. David Pye is here to help you.

David Pye

Author:

Mr. David Pye (View Profile)
Pye Metallurgical International Consulting.

  1.  Are you having high retained austenite in your carburised case?
  2. Are you getting non-martensitic transformation products in your carburised case?
  3. Is your carburising cycle time too long?
  4. Are you getting non-uniform hardness on carburised parts?
  5. Are you getting too high core hardness on carburised parts?
  6. Are you getting inconsistent results in carburised parts?
  7. Are you getting low surface hardness on carburised parts?
  8. Any other problems?

Please feel free to share your problem/s by leaving your reply in the comments box below and I will be happy to help you.

Yours Sincerely,

David Pye

Course on "Carburising and Carbonitriding of Steels" by Mr. David Pye is available online. 

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7 Responses

  1. Parag Bhusari

    Dear Mr.David Pye,
    Greetings for the day!
    I am Parag Bhusari working in the field of heat treatment since 22 years. My present organization is M/s Kirloskar Pneumatic Co.Ltd in Pune India. We are supplying traction gears to Indian railways. In one particular type of gear (Part No.6.851) we are facing the problem of excessive distortion. After case carburising and hardening we get the face run out of 0.3 MM and also getting uneven material stock on gear tooth for teeth grinding operation. The material grade is SAE8822H and required effective case depth after carburizing is 2.5 to 2.8 MM at 500HV. Besides taking various trial we are not able to resolve the warpage issue. Kindly guide in this.

    1. Good day to you Mr Bhusari,
      I have visited Pune on two previous occasions and thoroughly enjoyed my stay in Pune.(On consulting projects). Thank you most sincerely for your comment and question. Please let me have a sketch of the gear, and how it is manufactured up to the heat treat (carb and quench). Please also let me know how it is quenched and from what case austenitizing temperature it is quenched (I would assume that you are oil quenching? As much process info as you can send to me would be graciously received.
      Sincerely,
      David

  2. Anil Gupta

    I am working with a commercial heat treater in Noida, near Delhi. I would like to know why could we not use through hardened steel for the manufacture of say, a rotary shaft as opposed to a carburized shaft?

    1. Good day to you Mr.Gupta,
      A carburized shaft will impart greater strength within the core of the material than could be accomplished by say through hardening. It will further offer a hard wearing surface after the process of carburizing as opposed to a through hardened shaft.
      The rotating shaft will always impart a torque (twisting action) loading on the shaft when the shaft is rotating. The rotating shaft can also undergo bending stress due to the application of the operational load environment.
      The rotating carburized shaft will have a feature (property) that a through hardened shaft will not have and that is it will possess a compressive stress along with a toughened core. The carburizing will always improve the surface strength in terms of hardness and wear resistance due to the compressive stresses generated as a result of carburize and quench.
      Sincerely,
      David

    2. David Pye

      Hello once again, I would like to give further explanation to what I already said yesterday.I would like to add that it will be the engineering requirements that will determine (operating environment and conditions) that will determine what the material section would be and then what the final heat treatment would be. I am suggesting that if the application of the shaft will be for it to operate under high torque and wear conditions then a low carbon alloy steel(3.1/4 Nickel chrome (BS EN970A 36B) carburized with a surface hardness of say 61 to 63 (HRC) and a core hardness of say 34 to 37 HRC may be a better choice than a through hardened shaft with a through hardness of say 55HRC. The chance of a torque related failure/fracture would be considerably higher. I hope that helps to clarify what I was trying to say. Your comments are great appreciated and please keep them coming. I will be happy to help you. Sincerely David

  3. Akshay Bondge

    Hello Mr. David Pye,
    I am Akshay Bondge having our own commercial heat treatment plant in Kolhapur district. We supply variety type of gears to OEM customers. One perticular type of Spindle 740 weaighing 15kgs facing a problem of distortion in form of face runout more than 0.2MM which is not acceptable to customer. Material grade is SAE8620 and required ECD is 2.15-2.4MM. All metallurgical parameters are well controlled after case hardening but the only issue is face runout. Loading pattern has been done properly and taken care all the time.but still few location job shows run out more than 0.3MM . Even after many trials we are not able to control it within 0.2MM. please guide and help us to solve the issue.

    1. Hello Mr. Akshay,
      For effective case depth of 2.15 to 2.4, it must be a very long cycle time. Distortion is quite likely due to such long holding times at carburising temperatures. Please provide more information on the complete heat treatment cycle, including whether you do any pre-heting and stress relieving. The method of loading (Fixturing) is also extremely important. Please provide information about how you are loading these parts.

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