The invention relates to a testing unit for a straight welded
pipe, in particular to an automatic magnetic particle testing unit for
toe cracks at inner wall of the straight welded
pipe, comprising a car body consisting of a sweep template, a driving wheel, a stop block, a supporting plate, universal wheels and a guide bar which are connected with each other coaxially, and a rotary bearing, a driving motor, a control part, a steering engine, a position switch arranged on the two ends of one end of the car body, and a
transformer bearing, a camera bearing, a
sprayer bearing, a crossed yoke, an
ultraviolet lamp bearing, and a water pump water tank bearing which are successively arranged on the top of the sweep template from left to right, wherein, the upper end of the stop block is fixedly connected with the two sides of the rear end of the sweep template bottom in parallel, the output end of the steering engine is fixedly connected with the universal wheels through the guide bar, the upper end of the rotary bearing is fixedly connected with the two sides of the rear end of the sweep template bottom in parallel, the lower end of the rotary bearing is fixedly connected with one end of the supporting plate, the other end of the supporting plate is fixed connected with the sweep template bottom, and output shaft of the driving motor is respectively connected with the two driving wheels fixedly. The invention can completely takes the place of manual work to carry out automatic magnetic particle testing, and has the advantages of compact structure and convenient operation.