What is the main difference between corrosion fatigue fracture and stress corrosion fracture of drill pipe?

I. Crack initiation and expansion: Stress corrosion cracks and corrosion fatigue cracks are all sent to the surface of the material. Under strong corrosive media and large stress conditions, stress corrosion cracking can even occur from smooth surfaces (and of course in stress concentrations), and erosive fatigue cracks originate from stress concentrations without exception.

2. The relationship between the subcritical expansion rate of the crack and the stress advisory factor and frequency: The rate of corrosion fatigue crack growth is affected by the frequency. However, in most cases, the stress intensity factor is controlled. Stress corrosion cracking is different, mainly time controlled.

3. Fracture morphology: The strange velocity expansion zone of stress corrosion cracking cracks is generally rougher than the corrosion fatigue fracture, and there is no shelling pattern that is erosive fatigue. _

The drill pipe is an essential part of the drill string. Its main function is to transmit torque and transport drilling fluid, and the wellbore is deepened by the gradual lengthening of the drill pipe. Therefore, the drill pipe plays an important role in oil drilling.