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Tham khảo tài liệu 'navfac p-433 welding materials handbook_8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | REBUILDING AND HARD-FACING CRUSHER ROSimpo PDF Mergenand Split Unregistered Version - http www.simpopdf.com When to Reapply Hard-facing Additional hard-facing should be applied after 70-80 percent of the previous overlay has worn away but before the base metal is exposed. Hard-facing can be repeated several times depending on how much of the previous overlay is allowed to wear away. Generally wear is uneven and eventually excessively thick hard metal deposits on some areas of the roll may span. When this occurs the roll should be allowed to wear until all the hard metal is gone and the shell casting has been worn 1 8 - 3 16 in. The roll can then be restored to size with recommended buildup alloys. After rebuilding the shell should be overlaid with a wear-resistant alloy. If sufficient welding time is available all striping should be reapplied. FIGURE 2-65. Insufficient and Proper Stepover Techniques Examples If time is limited apply only every second or third gripper bead. Do not apply more welding beads to one side or section of the roll than another. This will put the roll out of round reduce sizing efficiency and accelerate wear on other crusher components. 2-71 R SimpoDDDF MergeHiancdSplit Unregistered Version - http www.simpopdf.com Rebuilding Shells with the Manual Process Always rebuild badly worn dished rolls before hard-facing. On manganese castings use electrodes on pages 1-22 or 1-20 with the manual process. NOTE NEVER USE MILD STEEL FOR Rebuilding ROLLS Rebuilding Procedure Using the skip weld process apply transverse beads in the center section of the roll in the area of deepest wear. Deposit three or four beads about 6 in. apart and turn the roll to a new position. Follow this pattern until weld beads are applied to the entire circumference of the roll. Continue the skip weld process until successive spaces between the original beads are gradually closed in and the entire center area of the roll is overlaid. See steps number 1 through 3 in Figure .
