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Vacuum Heat Treatment Furnace

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Mechanical structure and maintenance of vacuum furnace

Vacuum oil quenching furnace is a multipurpose vacuum heat treatment equipment, which is widely used for vacuum oil quenching of die steel, tool steel, alloy structural steel, gear steel, hard alloy workpieces, as well as high-speed steel, high alloy die steel, and high-temperature alloy vacuum pressure gas quenching. It has the characteristics of no oxidation, decarburization, degassing, degreasing and small deformation. During the operation of the vacuum furnace, a large number of mechanical structures are required to participate in the operation of workpiece feeding, transferring, quenching, etc. In actual production, these components are often faced with a bad use environment, and are prone to various mechanical failures in long-term use, thus affecting the production of vacuum furnaces. Therefore, relevant knowledge is essential.

Taking a large double chamber vacuum oil quenching furnace as an example, the composition, structure and working principle of the vacuum quenching furnace are briefly introduced. The equipment is composed of vacuum furnace host, heating chamber and heating element, vacuum separator, feeding and reclaiming mechanism, oil quenching mechanism, hydraulic (pneumatic) system, vacuum system, gas charging system, water cooling system, electrical control system, external furnace transport vehicle, etc. The structure of vacuum quenching furnace is almost the same. Due to the small weight of workpieces, the workpieces of some small models will be driven by more economical and practical motors, so there is no need for a special hydraulic (pneumatic) system.

The working process of the equipment is as follows:

The workpiece and material frame are placed on the workpiece car of the external furnace car by the forklift, the furnace door is opened, and the workpiece car enters the cold chamber through the rail. Then start the vacuum unit to vacuum the furnace. When the vacuum degree of the cold and hot chamber is balanced, open the vacuum separator, start the hydraulic system, push the workpiece car into the hot chamber, and the workpiece car slowly drops. Put the material frame on the table of the heating chamber, and the workpiece car returns to the cold chamber, and close the vacuum separator. After that, continuously vacuum the hot chamber to the working vacuum and start heating. After heating, open the heat insulation door, the workpiece car enters the hot chamber at a low position, transfers the workpiece to the car, and then returns to the cold chamber. After the hot spot is shut off, the work-piece car drops into the oil tank for quenching treatment. When the oil quenching time is up, the work-piece car rises. Finally, open the cold chamber vent valve to vent the cold chamber, open the furnace door, and the charging car will transfer the workpiece from the furnace to the outside.

In the working process of the vacuum furnace, the charging car transfers the workpieces for many times, and the hydraulic system (pneumatic system) is responsible for driving the charging car and other parts for various transfer operations. In the long-term use, it is inevitable to encounter mechanical structure failures. The following is the analysis and troubleshooting of mechanical structure failures:

1.Hydraulic (pneumatic) mechanism obstacle

The size and quality of workpieces processed by large vacuum quenching furnace are relatively large. The transfer of workpieces is generally driven by hydraulic system, and the hydraulic failure is generally consistent with the failure of general equipment and the treatment method. There are generally three basic factors: pollution, overheating and air entry. The following steps can be taken: (1) Drain the old oil; (2) Clean or replace the filter core and oil filter screen; (3) Clean the oil reservoir and vent (4), disassemble all main assemblies, and clean all parts with diesel oil. (5) Reassemble the washed parts, and tighten each bolt and screw according to the specified torque during assembly; (6) Make the hydraulic system run empty and circulate it for 3 or 4 times, so as to release air; (7) Drain the added oil. After oil drainage, clean the filter and filter screen again; (8) The new oil with the brand recommended by the factory shall be re added into the system according to the specified amount; If necessary, clean the filter again after working for 48 hours.

Pay attention to carefully find the leakage point of the hydraulic system, and adopt the method of replacing the seal or welding to eliminate the vacuum furnace pollution caused by the leakage of hydraulic oil. In order to avoid pollution, some vacuum furnaces will use pneumatic systems instead of hydraulic systems, which is easier to troubleshoot.

2.Troubleshooting of workpiece running mechanism

For large double chamber vacuum oil quenching furnace, the workpiece running mechanism is a difficult point in its design and manufacture. It is equivalent to a cantilever beam structure, and the movement of rising, falling, advancing and retreating must be completed accurately and reliably. The common faults and hazards of the system mainly include the following two aspects:

1) The lifting, descending, forward and backward are not in place

In this case, if the operator does not stop the machine for inspection in time, it will cause serious consequences such as the forklift and the workpieces crashing the heating elements or the worktable. This usually means that the stroke of the hydraulic cylinder is in place, but the stroke switch fails due to the deformation of the workpiece car. At this time, it is necessary to repair and adjust the work-piece running mechanism, and test it repeatedly after alignment to make it work normally.

2) The workpiece trolley is stuck in the furnace and cannot operate

This is usually a problem with the trolley wheels and rails. Because the workpiece trolley is often close to the heating chamber, the wheels and bearings will fall off under high temperature, and the fallen wheels will be stuck in the rails; In addition, due to long-time work, the track itself will produce relatively large deformation and wear. For this kind of fault, it is necessary to machine the track and increase the wheel diameter, otherwise the clearance is too large, which will cause large fork deflection and affect the lifting and landing of the workpiece.

In addition to mastering appropriate maintenance strategies, purchasing high-quality equipment is also the first step to avoid various failures. The VOGQ series vacuum heat treatment furnace produced by SIMUWU Company is well designed to avoid many obstacles in the production process. SIMUWU focuses on the manufacturing of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum gas quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.