Multi-chamber furnace for vacuum carburizing and quenching of gears, shafts, rings and similar workpieces

Abstract

Multi-chamber furnace for vacuum carburizing and quenching of gears, shafts, rings and similar components has at least two process chambers connected in parallel, with a continuous feeding mechanism for individual workpieces. Those chambersthe first one being a heating chamber, the second being a carburizing chamber and the third one diffusion chamberare configured in a vertical arrangement, placed in a shared vacuum space with gas-tight division, whereas at the ends of each chamber there are incorporated heating chambers with thermal insulation, with a graphite heating system and stepping feeding mechanism incorporated in the core for the purpose of continuous feeding of individual workpieces. At the ends of those chambers the construction incorporates transport chambers featuring loading and unloading systems X-Y enabling cooperation with individual process chambers through thermal and gas-tight doors installed in chamber ends, while external access to the transport chambers is ensured through loading and unloading locks.

Claims

1. A multi-chamber furnace for vacuum carburizing and hardening of individual workpieces comprising a set of processing chambers located in a common vacuum housing and equipped with a combined transport system, wherein the set of processing chambers comprise three step pass-through chambers with parallel longitudinal axes, the three pass-through chambers comprising: a heating chamber, a carburizing chamber, and a diffusion chamber, which are arranged vertically over one another in the same order as listed, wherein each of the processing chambers comprises a graphite heating system and a thermal insulation, and a stepping mechanism incorporated in a furnace hearth of each of the processing chambers, and configured for horizontal movement of the individual workpieces, wherein the set of processing chambers is arranged between two vertically-parallel transport chambers and comprises loading and unloading mechanisms for the individual workpieces to and from each one of the respective processing chambers through thermal and gas-tight doors arranged at both ends of each of the processing chambers, and a loading and unloading lock configured to allow external access to the transport chambers, and wherein the unloading lock comprises equipment for quenching of individual workpieces within a furnace operating cycle.

2. The multi-chamber furnace according to claim 1, wherein the stepping mechanism offers between 2 and 100 steps positioning individual workpieces, with a movement timeframe 0.1 to 60 minutes.

3. The multi-chamber furnace according to claim 1, wherein the unloading lock is configured for oil quenching of individual workpieces on a hardening press or in restraining devices.

4. The multi-chamber furnace according to claim 1, wherein the unloading lock comprises a device for individual gas quenching of the individual workpieces.

5. The multi-chamber furnace according to claim 4, wherein the device for individual gas quenching of the individual workpieces comprises a two-part movable nozzle collector with a base, and a system of gas nozzles forcing cooling gas flow at speeds up to 300 m/s, the gas nozzles configured to be adjustable to conform to a desired shape.

6. The multi-chamber furnace according to claim 5, wherein the base has a rotatable drive.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The furnace according to the invention will be described in greater detail on the basis of the enclosed drawing example, in which respective figures represent:

(2) FIG. 1 illustrates a 3D view of the furnace,

(3) FIG. 2A illustrates a cross section side view of the heating chamber,

(4) FIG. 2B illustrates a cross section top view of the heating chamber,

(5) FIG. 3 illustrates a schematic diagram of the stepping mechanism enabling workpiece feeding inside the heating chamber,

(6) FIG. 4 illustrates a cross-section of the gas-cooling chamber for individual items,

(7) FIG. 5 illustrates a schematic diagram of the vacuum pump system and process gas system.

DETAILED DESCRIPTION

(8) The furnace comprises a set of three process chambers sharing a vacuum housing 1, configured in a vertical arrangement (one over another) where the upper one is a heating chamber 2a, the middle one is a carburizing chamber 2b, and the bottom one is a diffusion chamber 2c, while each of those incorporates a heating chamber.

(9) At the level of each process chamber, the vacuum housing is fitted with service and installation door 3 andat heating chamber inlet and outletalso with thermal and gas-tight doors 4, which separate process chambers from vacuum transport chambers 5 and 6 incorporated loading and unloading mechanisms X-Y 7a and 7b workpieces to and from respective chambers 2a, 2b and 2c.

(10) Loading and unloading mechanisms X-Y 7a 7b operate vertically for the three process chambers 2a, 2b and 2c as well as loading lock 8 for chamber 6 and unloading lock 14 from chamber 5. The continuous flow of workpieces through the furnace is effected at pre-defined intervals of e.g. 0.5-2 minutes.

(11) The workpiece intended for processing is placed in the loading position of the loading lock 8 by an external loading device. The lock is fitted with two vacuum valves 10a and 10b, advantageously of a slide straight-run valve type, and it is also connected to the vacuum system with a vacuum valve 11. After the workpiece is loaded as described above, the loading vacuum valve 10b is closed and a pump-out cycle follows until vacuum below 0.1 mbar is reached. Further, after purging vacuum level is reached, the outlet vacuum valve 10a opens and the workpiece is transferred to the vertical transport mechanism 7a in transport chamber 5. After closing valve 10a gas (e.g. nitrogen) is injected to the loading lock through the gas valve 12 and the transport mechanism X-Y 7a. Through the opened thermal and gas-tight doors of the upper heating chamber 2a the workpiece is placed in the start position of this zone. This chamber has e.g. 15 positions for workpiece placement where workpieces are gradually transferred by the stepping mechanism 13a incorporated in the core of the heating chamber.

(12) After the workpiece is transferred to the final position in the heating chamber 2a, the loading and unloading mechanism X-Y 7bplaced in the transport chamber 6collects the workpiece and places it in the first position of the stepping mechanism 13b of the carburizing chamber 2b, where the workpiece is transferred from the initial to the final position during the furnace operating cycle. Having reached the final position, the workpiece is collected by the loading/unloading mechanism 7a of the transport chamber 5 through the thermal and gas-tight doors 4 (opening at that moment) and is placed in the first position of the diffusion chamber 2c.

(13) Having passed the workpiece through the diffusion chamber 2c, using the stepping mechanism 13c incorporated in the heating chamber, the loading/unloading mechanism X-Y 7b of the transport chamber 6 collects the workpiece and places it in the cooling position of the unloading lock 14.

(14) The unloading lock 14 is equipped with two vacuum-pressure valves 15a/15bone connected to the transport chamber 6 and the other ensuring workpiece removal from the furnace after cooling, using an external transport device. In the unloading lock 14fitted with a valve connected to the pump system 17there is equipment for individual gas cooling, operated as follows: the workpiece to be cooled is placed on the base 18, and a two-part nozzle collector is placed around the workpiece, with two movable partsupper 19 and lower 20sliding outwards during transport and closing during the cooling cycle. The collector is interchangeable, adapted individually to the shape of the workpiece. Movable parts 19 and 20 are fitted with a system for cooling gas distribution to the nozzle system 21 directed towards the surface of the workpiece to be cooled, and situated at a short distance from the surface, with a maximum coverage of the workpiece surface and fast line speed of discharged cooling gas. This construction is also characterised by easy outflow of expanded gas after cooling to the area of lock housing 14. During cyclical cooling of workpieces, the cooling gas is supplied to the nozzles 21 from the buffer tank 22 at a defined pressure, where the pressure level is determined by gas consumption and the outflow speed of cooling gas.

(15) After flowing out of the nozzles 21 and hitting the workpiece surface, gas is expanded and next compressedby the incorporated compressor 23to a desired pressure; afterwards it is stored again in the buffer tank 22. The heat from workpiece-gas heat exchange is removed at the fitted heat exchanger 24, advantageously placed between the compressor 23 and the buffer tank 22. With cyclical cooling of individual workpieces and nozzle-based cooling with a high heat-exchange coefficient, a completely closed loop of cooling gas is achieved.

(16) After the workpiece is cooled at a speed enabling quenching, and after valves 25 and 26 of the cooling gas recirculation system are closed (as described above), a vacuum/pressure valve 15b opens. The carburised and quenched workpiece is then removed through a passage, and transferred to finishing operations.

LIST OF DESIGNATIONS

(17) 1vacuum housing 2aheating chamber 2bcarburizing chamber 2cdiffusion chamber 3service and installation door 4thermal and gas-tight door 5, 6transport chambers (with incorporated loading/unloading mechanisms for workpieces to and from individual process chambers) 7a, 7bloading and unloading mechanisms X-Y 8loading lock 10a, 10block vacuum valves 11vacuum valve 12gas valve 13a, 13b, 13cstepping mechanism 14unloading lock 15a, 15bvacuum-pressure valves 17pump system 18nozzle collector base 19, 20movable part of the nozzle collector 21gas nozzles for nozzle collector cooling 22buffer tank 23compressor 24heat exchanger 25, 26valves of the cooling gas recirculation system