National Standard Rail Welding Quality Control and Common Defect Handling
What are the core process parameters for flash welding of standard Chinese rails?
Four core parameters, including flash current, flash time, upsetting pressure and upsetting amount, need to be accurately controlled in flash welding of standard Chinese rails. The current determines the welding heating efficiency, and the upsetting parameters affect the bonding strength of weld metal. Parameter deviation will directly cause defects such as incomplete bonding and overburning at welded joints.
What are the fatal defects most likely to occur at the welded joints of standard Chinese rails?
Cracks, incomplete penetration and overburning are fatal defects of welded joints of standard Chinese rails. Cracks will spread rapidly under the alternating load of trains, incomplete penetration will reduce the bearing capacity of joints, and overburning will embrittle the metal structure. All these three types of defects must be cut off and rewelded and are not allowed to be put into use online.
What is the key inspection area of ultrasonic testing for welded rail joints?
The inspection focuses on the weld fusion zone, rail head, rail web and the triangular area of rail base. These areas are the high-incidence parts of welding defects. As the core stress-bearing area of wheel-rail contact, the rail head implements the most stringent testing standards to ensure no internal defects remain.
What welding problems will be caused by improper treatment of welded end faces?
If there are rust, oil stains, burrs or irregularities on the rail end face, it will lead to uneven welding heating, resulting in defects such as dark spots and air holes, and reduce the electrical connection performance of the joint. It may also cause abnormal signal transmission in the track circuit section and affect line safety.
How to improve the first-pass qualification rate of welded joints of standard Chinese rails?
Thoroughly clean the rail end faces before welding and calibrate the welding equipment parameters; monitor the core data such as current and pressure in real time during welding; carry out full-section ultrasonic testing immediately after welding, and rework unqualified joints in time. Control the whole process from technology, equipment and testing to improve welding quality.