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SKZA quenching-tempering lines are predestinated for quenching in a protective atmosphere and tempering small and mid-sized steel workpieces in an automated continuous process. The state-of-the-art design of the lines includes the latest achievements related to this type furnace production. High-quality fibrous insulation ensures good thermal insulation and low energy consumption. The line provides the following operations:
- motorized loading
- heating for quenching in protective atmosphere
- oil quenching
- washing, rinsing and drying
- tempering
The line configuration:
- skip-hoist loading mechanism with motorized dosage of workpieces
- electric muffle furnace to heat workpieces for quenching in protective atmosphere
- oil belt quenching tank
- conveyor washer-dryer
- belt tempering furnace
- automated control system
Technical description:
Heat treatment process starts from the loading of the line.
The loading mechanism is a lifting device driven electromechanically and having clamps for the bay boxing filled with workpieces to be heat-treated. The mechanism takes the bay boxing with workpieces, lifts it to the loading elevation at the top of the furnace and gives a calibrated tilt of the boxing to pour workpieces out onto the conveying belt of the furnace. Workpieces to be heated for quenching are transported by the conveying belt to the electric furnace.
The electric furnace to heat workpieces for quenching has a lined steel casing with a heat-resistant leakproof muffle inside. Removable coiled heaters uniformly heating the muffle are placed in grooves on the internal surfaces of the roof and hearth lining. The muffle is equipped with a vertical unloading tray sealed by a hydraulic lock in oil of the quenching tank and, at the loading zone, by a forechamber with flame curtain preventing air inflow into the working chamber of the muffle filled with a protective gas. The electric furnace conveyor consists of endless conveying belt made of heat-resistant wire cloth, drive and auxiliary devices minimizing tension of the conveying belt in the hot zone of the furnace while bending around the unloading part of the muffle. The loading zone of the conveying belt (loading table), sealing device at the exit of the return side of the belt from the muffle and the conveyor drive are arranged on the anterior frame installed in front of the forechamber.Thermal profile of the electric furnace is controlled within every heat zone using thermoelectric transducers and electronic temperature controllers. Upon achieving the preset temperature, workpieces are quenched in the quenching tank. The quenching tank with conveyor belt is a leakproof container. Inside the tank, a conveyor is mounted with bucket conveying belt moved along the guiding frame by a drive drum and a driven drum of an electric drive mechanism located in the upper part of the conveyor. Its buckets take small details and transload them onto the washer-dryer conveyor. The conveyor in the tank has two parts: one horizontal (in oil) and one inclined (where workpieces drop out of the container). The conveyor makes provision to transport workpieces being quenched during the quench cooling and transload them from the quenching tank into the washer-dryer. The quenching tank is equipped with devices ensuring intensive oil stirring and cooling during the quenching process as well as with tubular heating elements for oil preheating. The washer has 2 zones, one for washing and one for drying. It includes a welded casing, conveyor, tank for washing solution with heaters, pump unit with piping and spraying devices, fan with an air heater and guiding device. The conveyor consists of upper and lower guides, conveying belt, drive and driven shafts, drive mechanism. The conveying belt of a bucket-elevator type is accomplished similarly to that of the quenching tank. There are tubular heating elements to heat washing solution. The pump unit supplies washing solution to spraying devices for washing workpieces. The centrifugal fan blows air heated in the air heater over workpieces in the drying chamber. There are tubular heating elements inside the air heater casing. Amount of air supplied is controlled by a damper. The electric furnace to heat workpieces for tempering has a lined steel casing with an endless conveying belt of heat-resistant wire cloth moving along the guides and a drive inside. The heating system is made similarly to that of the quenching furnace. Agitators are mounted under the roof of the tempering furnace providing a homogeneous temperature distribution during tempering. The automated control system comprises individual cabinets to control line components using Siemens PLCs for temperature profiles regulation and control, operational control of mechanisms, necessary blocking and emergency alarm which may be transmitted to the upper level control system. The line must be fed with natural gas or propane and air for the quenching furnace to produce a protective atmosphere. A gas mixture of the proper composition is formed in the gas panel arranged next to the quenching furnace and is supplied to the butt part of the loading zone where a protective atmosphere (endogas) is produced in the built-in catalytic generator. * supplied without the conveyor tempering furnace (with the shaft furnace)
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