Difficulties and solutions for drilling rotary table production
Workpiece characteristics and welding requirements: the main steel plate is Q345 steel plate with thickness > 40mm, which has the characteristics of large bevels, large number of parts, compact structure, and not easy to weld. And the weld requirements are high, 100% UT flaw detection of important welds, butt welds according to GB/T 11345-1989 standards, acceptance level B, assessment level Ⅱ acceptance; fillet weld quality reference GB/T 3323-1987 standards, the defect indication length does not exceed Ⅱ, the rest of the weld for non-destructive Flaw detection.
① ultrasonic flaw inspection of all steel plates of 40 mm and above thickness to ensure that there are no unqualified internal defects, ultrasonic flaw detection according to GB/T 8651 "metal plate ultrasonic flaw detection methods".
②The lower material is reserved with proper allowance to compensate for shrinkage deformation.
③Control warpage and distortion deformation through reasonable assembly sequence and necessary process support.
④For the important welding seam use machine J507 welding rod hand welding.
⑤ For multi-layer weld channel, every weld should be cleaned and inspected. Defects found after removal, and then the next weld, clear the root must be cleaned up in a timely manner, with magnetic particle flaw detection inspection.
(6) After welding for 580 ~ 600 ℃ annealing, eliminate welding stress. Through the implementation of the above measures, the weld seam meets the requirements of the drawings, the external dimensions are controlled within the tolerance range, and the structure is stable.
2.drilling rotary table processing
There are problems. The workpiece shape size of the rotary table, lifting arm, ladle seat frame, portal frame, etc. is large and the precision requirement is high. If the machining accuracy cannot be guaranteed, it will directly affect the assembly and increase the difficulty of assembly. The process measures taken. The focus is on how to ensure the position accuracy, taking the turntable as an example for process description. The size of the turntable is 3.9 m x 4.44 m x 4.23 m. There are four parallel hole systems, and the two holes at a distance of 3.5 m require a coaxiality of 0.03 mm. To ensure the accuracy, the holes must be bored in one clamping, otherwise the coaxiality of the holes and the parallelism of the hole systems are difficult to guarantee.
The basic sequence of machining is as follows: In TK6920 CNC floor milling and boring machine, with the bending plate mounted, the milling hole is machined with the reference. In XKA2140×120 CNC gantry boring and milling machine, the contour pad is installed at one time to process each hole and ensure the position degree of each hole. In XKA2140×120 CNC gantry boring and milling machine, boring, milling end face and drilling. Milling vertical release with fixed center datum belt, remove the milling head and mill the upper end face. In TK6920 CNC floor milling and boring machine, according to the processing surface to find the right, milling surface, drilling. The machining of the whole rotary table was completed and the accuracy was tested to meet the requirements.
3. drilling rotary table assembly
Problems: The structure of the rotary table is as shown in the figure, the shape of the part is large, there are many hinge points, mutual constraints, assembly difficulties.
①The common assembly methods are press fitting, hot fitting and cold fitting. Due to the large size of the ladle seat frame, lifting arm, etc., it is not suitable for hot assembly, only cold or pressure assembly can be used. Considering that the assembly in the workshop is only pre-assembly, it also needs to be disassembled and transported, as well as the limitations of the on-site assembly conditions, it is not suitable for cold assembly. To reduce the difficulty of on-site assembly, try to use a larger assembly gap. Based on the feature that grinding is easier to control the dimensional accuracy than boring, in order to ensure a larger assembly clearance, the shaft was ground twice according to the actual size of the hole, in order to obtain a larger assembly clearance, reduce the difficulty of assembly and ensure the assembly accuracy at the same time.
All the rotating parts use spherical bearings, which have large rotation angles, and it is not easy to control the alignment when the long shaft is inserted into the compact part.