Highly-efficient control the hardness on pipes with smooth coating

In the article considered the metal-roll quality control issue. It were conducted the comparison of eddy current method ofnondestructive testing and classic methods that using in metal-roll production by X-ray and supersonic methods. Description of developed automated line for testing was presented.
Materials and methods
Large diameter pipes were tested by eddy current and magnetic methods.
Results
Conducted theoretical and experimentalstudies revealed that eddy current testing is the only nondestructive method allows indicating local problems of hardness through protecting and isolating coats. It has high sensitivity and control speed and should apply in final testing the quality of pipe production. Other methods do not allow detecting this type defects.The validity of nondestructive control is significantly deteriorated without eddy current control in production large diameter pipes.
Сonclusions
1. Eddy current detector VD-90NP using ordinary probe knows area of increased hardness from area of original materialthrough 7 mm gap.
2. Improving detector's software allows to undercut influence the gap change on output signal.
3. Increasing of control speed is possible by applying multichannel system eddy current control and local or complete mechanization and automation this system.