The simple answer is "no, it's not suitable". A longer answer is that the XT38 (and all other connections) have dimensional requirements that match or are based on the material grade ... and 75ksi is a long, long, long way from 120ksi.
Hope that helps.
James Drouin -
Posted from Houston - 2019-07-01 14:36:09replyResponse
I believe that the reason to suggest a material with a minimum yield strength of 125ksi is coming from the Grand Prideco procedure. As per GP procedure, the minimum yield strength of a sub which is intended to connect with drill pipe should be a minimum of 120ksi. AISI 4145H and AISI 4145Mod are fit for the purpose. It is simply because of the higher percentage of carbon content in 4145 material. Higher the carbon percentage higher the strength in terms of tension, compression and torsional stresses.