Two single-roller crushers were installed in the front area. The single-roller crusher is located at the discharge port of the sintering machine and crushes large sinter at around 1000°C into small indium particles. The main form of damage is abrasive wear. It costs 3.2 million yuan to purchase a new set and 800,000 yuan to repair. Restoration and use can greatly reduce production costs. The single-roller crusher was originally an old equipment dismantled from abroad. The length of the star wheel shaft is 11 meters and the maximum diameter is 694mm. It is difficult to ensure that the strength and accuracy of the surfacing welding of the star wheel shaft are not reduced during repair. 1 Wear process analysis 1M wheel shaft wear process analysis The structure of the star wheel shaft and star wheel is shown in Figure 1 and Figure 2. The middle part of the star wheel shaft is severely worn due to the heavy working load in the middle part. The serious wear on one side of the hexagonal side and the lighter wear on the three sides are due to the structural design characteristics. In the design, the one-sided gap between the star wheel and the star wheel shaft is 1mm. It is assumed that the six sides of the star wheel are rigid bodies that cannot be worn. Due to the existence of the gap, during the initial transmission, the star wheel is only moved by two or three corners. After a period of running-in, it becomes hexagonal contact and enters a stable operating state. As the use time increases, the friction surface between the star wheel and the star wheel shaft gradually shifts from the corner of the star wheel shaft to the center of the hexagonal plane. The star wheel and star wheel shaft There will be relative rotation between the transmission positions. When the wear of the star wheel shaft reaches the ideal state as shown in Figure 5, it loses its transmission function. Since the six surfaces of the star wheel are not uniformly worn during use, some friction surfaces will continue to move toward adjacent corners after moving to the center until the surfaces are rounded and lose their transmission function. In the later stage, the friction surfaces gradually changed from 6 surfaces to 5 surfaces, 4 surfaces…1 surface. In practical applications, the six sides of the star wheel will inevitably wear. The result of simultaneous wear of both sides will shorten the time of simultaneous transmission of the hexagons, and the wear of the star wheel shaft will occur. The process won’t change much.
S2M wheel shows an analysis of the wear process of wheel A. The wear of the star wheel is mainly the abrasive wear between the working surface of the star wheel teeth and the sinter under high temperature.
1.3 Determination of the surfacing area According to the wear process analysis, the plane near the center of the hexagonal surface transitions faster during the movement of the friction surface and wears less. Its main function is to make the six sides of the star wheel shaft wear evenly and ensure smooth transmission. The spare parts near the two corners are the main load-bearing area of the transmission and are severely worn. When repairing and inspecting the old star wheel shaft, treat it differently according to the wear and tear of each surface. The rounded plane needs to be repaired on the entire surface, and the worn semicircular plane mainly needs to be repaired on the semicircular surface. Although the flat surface of the hexagonal surface near the center plays a small role in transmission, it will not return to a flat surface during repair. The main purpose of the star wheel is to restore the worn and broken teeth and increase the number of online repairs of the star wheel.
2 Preparation work 1 Inspection of old parts: The outer six sides of the star wheel shaft are unevenly worn, and the middle part is seriously worn. The minimum opposite side size is SW680. The drawing requires the opposite side SW700-0.5, which is 20mm smaller than the drawing size; the journal of the star wheel shaft, drawing The requirements are f36n6, f350u6, and 7. After disassembly, it was found that the geometric accuracy and roughness can meet the drawing requirements.
The geometric dimension inspection found that the six sides of the star wheel were worn and were SW716. The drawing requires SW701 +1, which is 16mm larger than the drawing. The remaining thickness of the star wheel teeth is about half of the original height, and the alloy layer on the remaining working surface is seriously peeled off.》2 Star wheel shaft 10 holes were drilled within the repair preparation area and 10 holes were drilled within the depth. The depth sampling test star wheel material is ZG30Mn. The star wheel shaft flaw detection was carried out through surface flaw detection and ultrasonic detection, and was judged according to the grade of defects not exceeding level 2. If there are cracks on the surface and inside the structure and other defects that affect the strength, they must be thoroughly dealt with before proceeding to the next step. Supplementary flaw detection results 3 Star wheel shaft surfacing processing implementation plan 1 Formulation of process plan Table 1 Before welding, north shaft head, middle and south shaft heads, pre-weld inspection The pre-weld inspection conditions of the shaft are shown in Table 1. During the original adjustment, the north shaft head It is 2mm higher than the south axis head. During the rotation of the north axis head, the outer circle moves 4mm, and the C and D surfaces are deformed.
Welding sequence: The northern part of surface C is a convex surface, and welding starts from surface C.
Determine the welding benchmark. The outermost two sides of the shaft have slight wear within the range of about 800mm. Use this as a benchmark to align the entire shaft body cable to ensure that the hexagonal dimension after surfacing is 700mm. 16 round rods are marked segmentally according to the alignment line. Weld four welding benchmarks on each side. The fillets are not welded, and about 1 mm is left unsoldered in the middle.
After the selection of welding rods, after sampling and testing at the designated bicycle parts, the chemical composition is as follows: The reason for selecting D112 for No. c is as follows: Yuansuo other chemical compositions 2 Welding process: Use rollers to set up both ends of the inspected shaft and adjust it to the level.
Cover the shaft body (except the shaft head) with an electric blanket, preheat it to 10C, and keep it warm for 4 hours with the temperature controlled to be above 24CTC.
The shaft body is divided into sections every 450mm, and welding is carried out symmetrically in sections. The welding specifications should be as small as possible and the welding should be carried out evenly. The surfacing part should be within ±2mm of the thickness of the reference plane.
Monitor the entire welding process and use a level to pay close attention to the deformation of the shaft body. The overall deformation of the shaft is controlled within 1mm. As shown in Table 2: hours, slow cooling. The physical inspection of the shaft after welding and annealing is shown in Table 3 and Table 4: Table 2 North shaft head after welding, Middle south shaft head Table 3 North shaft head after welding, Middle south shaft head Table 4 North shaft head after welding and annealing The machining of the 3.3 star wheel shaft of the Zhongnan shaft head is used as the datum plane, and the universal milling head is used to turn the angle to process six aspects.
3.4 Problems and Solutions After machining, it was found that there was a circle of transverse cracks at the non-surfacing part of the original shaft body 200mm away from the starting position of the hexagonal size, with a length of 30mm70mm; there were several longitudinal cracks on the processing surface. The analysis of the cracks concluded that: transverse cracks It comes with the parent body. Since a layer of wear-resistant layer is overlayed on the surface of the original parent body (the weld bead can be seen), the composition is similar to 38Cr2MnMV. The cold welding operation during use produced transverse cracks, and the cracks were distributed in the weld seam (width 25mm) Within the ring range, the deepest is 15mm and the shallowest is 2mm. The longitudinal cracks are fatigue cracks.
Disposal advice: The treatment plan for cracks is as follows. Use a polisher to remove the cracks and perform a colorant display inspection. Heating repair welding. The heating temperature is 30CTC, and J506 welding rod is used for repair welding. After welding, it is kept at 350C for 3 hours, slowly cooled, polished, and inspected for coloring to ensure that there are no new cracks.
4. Theoretical calculations and practical tests of the process plan for repairing the star wheel 1 prove that the structure of inserting and welding the six inner sides of the star wheel is simple and feasible. For the star wheel teeth, use 75 thick, 16Mn steel plates according to the shape of the missing teeth, butt welding, and full penetration welds. Use welding rods similar to the parent material to weld the spoke plates and star wheel claws, and then overlay the wear-resistant alloy layer.
2. Process implementation plan: Place the star wheel on the platform based on the relatively flat surface, cut the material according to the missing tooth shape, butt weld, and fully penetrate the weld. Use D112 welding rod to underlay welding the spoke plates and star wheel claws.
The inner hole machining is based on the three teeth of the star wheel. The inner hole is processed to the specified size, and the end face is exposed to light as the assembly reference.
Hot-fitting: Hot-fit the processed inner sleeve of the star wheel and the star wheel to determine the interference. 44mm~0.15mm. Weld the axial positioning block and angle marking line on the star wheel before assembly. After assembly, the end face of the inner sleeve must not protrude from the end face of the star wheel, and the three teeth of the star wheel and the inner hexagon must be in a consistent position with each other.
Circumferential welding is performed by spot welding the completed star wheel weld and welding the circumferential welds on both sides. The welds are subjected to non-destructive testing, and the JB/T11345 temperature is applied for 4 hours, followed by cooling in the furnace.
Wear-resistant layer surfacing. Weld with alloy electrode 856. After surfacing, the alloy layer thickness of the star wheel claw is not less than 10mm, and the alloy layer thickness of the spoke assembly plate is not less than 5mm. Pay attention to the deformation of the star wheel claw. The symmetrical deflection of the star wheel claw in the direction of the rotation axis is less than 2mnu 5.1 Ken wheel inner hexagonal SW bolt table 1 Inspection table of the actual assembly width of the 2ft wheel 2 width number 12345678259.5 3 group assembly (the assembly diagram is shown below fl wheel assembly diagram (1) According to the data in Table 1 and the actual work of the star wheel In the process, take the minimum data in each number and group the star wheels according to the minimum gap formed. The grouping situation is as follows: SW tolerance minimum gap 3*.64 SW tolerance minimum gap 3*.43 SW tolerance minimum gap 3-0.1 SW tolerance 696, minimum clearance 6 (2) The assembly process is as follows:
① Map the center line of the star wheel shaft and install the spacer sleeves. Start from the middle and assemble to both ends at the same time. The minimum distance between the star wheel and ffi sleeves is 3mm. The direction of each set of star wheel teeth The difference is 60%. If the gap is too small, add spacers at both ends to adjust.
② During the assembly process, the tooth pitch is checked, and the tooth pitch deviation is controlled within 30mm. The distance between the plates is 200mm, and the interference with the grate plate during the rotation of the star wheel is simulated. Adjust the thickness of the spacer according to the actual space size after assembly to ensure a gap of 70mm or 85mm.
③ After the inspection is correct, assemble the bearing and the gear coupling with a tensioning sleeve.
(1) The hexagonal dimension of the star wheel shaft is 690mm across the sides, and the repaired part meets various mechanical performance requirements and usage requirements.
(2) The geometric dimensions of each part of the star wheel are as shown in the figure, the alloy layer is firmly bonded, and there are no defects such as cracks and pores. The tooth rotation plane is within 10mm.
(3) After assembly, the total gap within the 6-meter-long range is 7. The first single-roller crusher used on site has been online since September 2003. The star wheel shaft is in normal condition. The second one has passed the hot apricot load in July 2005. Test drive inspection.
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