Ultrasonic nondestructive testing system for large blacksmith welding pieces

The invention relates to an ultrasonic nondestructive testing system for large blacksmith welding pieces, which comprises a computer with a human-computer interface, an FPGA (Field Programmable Gate Array), a network communication controller, an electric scanning device and a manual control panel, wherein the FPGA comprises a logic control unit (LCU), a pulse generator of a moving shaft, a control register, a status register, a parameter register and a decoding circuit, the electric scanning device comprises two ultrasonic angle probes transmitting and receiving ultrasonic signals on the same plane, an alternating servo motor driver and a driving motor, and the manual control panel comprises a manual selective switch, an inching button, a scram button and a limit switch. The position and the size of a defect in a weld joint is determined after SAFT (Synthetic Aperture Focusing Technique) treatment is carried out on ultrasonic signals of the two ultrasonic angle probes of the system, the testing precision and