FI107453B - Plant for heat treatment of metallic parts, especially of non-ferrous metals containing zinc - Google Patents

Description

107453

Heat treatment equipment for special parts made of metal, in particular zinc-containing ingots

The invention starts from a heat treatment apparatus for special metal parts according to the features of the preamble of claim 1. Such an apparatus is known from DE utility model DE-GM 9 100 289. The known apparatus comprises a horizontal duct, which is for the most part heated. An endless conveyor belt passes through the channel, for example a metal articulation belt, which is turned downward at the end of the channel and guided back through the cooling bath 10 to the beginning of the channel. The conveyor belt passes a short distance on a horizontal surface before the channel begins; this is where special parts are delivered to the belt. At the end of the cooling duct, special parts fall into a karkai bath in known equipment; however, it is also known to connect to the heated portion of the duct an unheated duct outside the furnace through which the special portions 15 cool more slowly than in the quench bath.

The channel, the heated part of which is also often referred to as a retort, contains a gas space adapted to the purpose of the heat treatment, for example hydrogen or nitrogen. Gloss annealing is preferably carried out using a pure hydrogen gas space to provide a low-oxide surface.

Zinc has a low melting point (420 ° C), a low boiling point (907 ° C) and a relatively high vapor pressure already at the melting point. Parts of non-ferrous metals, which also contain zinc, are thus annealed when annealed; V that zinc is released from the surface of the parts in a vapor form when the temperature of the parts exceeds a certain processing temperature. The zinc vapor is distributed in the gas space of the duct and condenses to: · · · · 25 surfaces that are slightly colder, be they colder parts of the duct surface or colder parts of the non-ferrous metal which are still ahead or at the heated part • · · downstream parts of the duct where the temperature begins to drop again. Zinc vapor seals gradually make the glossy surfaces matt, which is a nuisance, especially when parts are to be glowed bright. Therefore, it is known to chemically etch the faded metal parts in the heat treatment to remove the zinc seals and to give the surface a shiny finish. Aftermarket:. etching of tea is not only a complicated additional step, but it also causes. A further disadvantage is that • · 2 107453 the retorts where the heat treatment takes place need to be cleaned from time to time to remove zinc vapor condensation.

It is an object of the invention to provide a means by which the problems caused by zinc vapor-5 fumes leaving the zinc-containing non-ferrous metals can be reduced.

The problem is solved by equipment according to the features of claim 1. Preferred further developments of the invention are the subject of the claims.

The invention seeks to completely eliminate the problems caused by zinc vapor. Because the zinc-containing materials and heat-treatment temperatures are predetermined, the production of zinc vapor cannot be prevented. Thus, the invention proposes to use a cold trap, where the zinc vapor can condense before it is condensed into special parts to be treated or retort walls. For this purpose, a cold trap is placed outside the heated duct so that cold surfaces close to the special part being treated do not interfere with the heat treatment. The cold trap is in fluid communication with the duct so that zinc vapors are carried along the flow from the hot duct to the cold trap. This results in a strong reduction in the gassing of the zinc vapor channel with the gases, whereby the flow to the cold trap ensures that the zinc vapor is not directed towards the various portions but away from them.

It has turned out that the zinc-containing metal parts come out of the heat treatment equipment in such a glossy state that post-etching with its associated drawbacks (environmental load and cost) can be eliminated, and the heat treatment channel itself still needs to be blast cleaned to remove any residual zinc vapor

: Zinc vapors are primarily sucked from the hottest part of the duct and led through a branched duct to the cold trap outside the duct, respectively. In this way, zinc vapors are accessed where they are most likely to occur. In order to avoid unnecessary consumption of the shielding gas 30, it is advantageous to circulate it, i.e. the shielding gas sucked from the hot section of the duct is routed back through the return line to the duct, but primarily not to the heated section, because:. there it would lower the temperature of the furnace, but in front of it so that it heats up warm ···. with special parts arriving at the mowed section, or to the rear, where the special parts' 1 * 35 are cooled again; when the heated portion of the duct is provided with a cooling duct, if the special parts are cooled in the shielding gas, it is expedient to direct the shielding gas to be recycled to the cooling duct, especially to the beginning thereof.

The effect of the suction is particularly advantageous when the suction takes place at many points in the duct, for example first at the beginning of the duct where the shielding gas 5 can be recycled to the heated part and secondly at the remainder of the heated part.

With the appropriate length of the heated portion of the duct, it may be advisable to conduct the suction conduits to the cold trap also at other points in the conduit, whereby not all conduits need to be led to a different cold trap, but multiple conduits are suitably routed to the same cold trap.

An elongated tank filled with fillers, from which end flow flows, allowing the zinc vapor to condense on the fillers, is particularly suitable as a cold trap. Suitable fillers are those known in the art of chemistry, such as Raschig rings.

The cold trap does not need to be particularly cold. It is sufficient that its temperature differs from the temperature at which the annoying metal vapor condenses and solidifies. It is even undesirable to cool the cold trap too much so that the retort will not experience a drop in temperature and energy consumption. A temperature of 200 to 350 ° C in 20 cold traps is well suited for the removal of zinc vapors.

Cold air is sufficient to cool the trap. In some cases, even exposing a container filled with fillers to ambient air is sufficient. However, the reservoir • ·: primarily leads to the cooling pipe, and in turn to the secondary cooling pipe, which leads to the reservoir of cooling air against the gas flow ·: ··· 25 and ends in the outer cooling pipe near its end, which is closed . In this way, a particularly efficient cooling and cooling process is achieved by the counter-flow principle. . ·. bat zinc vapor separation.

The pads are changed from time to time and can be recycled to recover the crystals from the zinc extracted.

An exemplary embodiment of the invention is schematically illustrated in the accompanying drawing. It shows a longitudinal section through a heat treatment furnace through which special parts to be processed pass. The furnace has a long channel 1 called •; '; also as a retort surrounded for the most part by Insulator 2. Insulator 2 and Duct 1. ···. between them is a heating device 3, which primarily comprises electric heating elements; gas heating could also be used.

4, 107453

An endless conveyor belt 4 passes through the channel 1, on which special portions pass through the channel. The duct 1 leads at both ends out of the furnace insulation 2. The cold section 1a in front of the duct furnace releases special portions. In the rear part 1b of the furnace, controlled cooling of the special parts takes place in a shielding gas which is also used in the heated part 1c of the duct and is therefore surrounded by a cooling jacket 5.

From the heated portion 1c of the duct, two wires 6 and 7 branch upwardly and terminate in retort inserts 8, 9, into which sink elongated cylindrical tanks 10, 11 with a perforated bottom 12 at the bottom end. through the tanks 10.11 have been passed in a gas tight manner.

The containers 14 and 11 are also covered by lids 14 through which tubes 15, 16 are concentric with the containers 10, 11 and are closed at the lower end. Pipes 15 and 16 are led from above by tubular oxygen blowing tubes 17, 18 which terminate just before the lower end of tubes 15, 16. Through the oxygen blowing pipes 15, 17, 18, cooling air is raised which rises upwards in the annular space between the blowing pipe and the pipe 15, 16 and cools the annular space between the pipe 15, 16 and the container 10, 11 filled with fillers, for example Raschig rings. .

The retort insert 8 is associated with the beginning of the heated portion 1c of the duct. Li-20 from sack 8 is led back to the cold section 1a in front of the duct oven by a return line 20 starting from the lid 14 with a pump 21. The second attachment 9 of the retort engages the end of the heated section 1c of the duct. Here, too, the return conduit 22, which starts from the lid 14 and which has a pump 23, is led back to the outlet portion 1b, out of the furnace, to the beginning of the cooling jacket 5.

· ·; Pumps 21 and 23, in the simplest case, suction blowers, may suck the shielding gas channel heater, possibly loaded with zinc vapor. 1c, conduct it to the cooled fillings 19, to which zinc vapor • · ·, · *: *. *. crystallizes and recirculates the purified shielding gas. The heat treated β 4 sections leave the hot portion 1c of the duct shiny and can be cooled in a controlled atmosphere in the shielding gas portion 1b to maintain the shiny surface. A good shielding gas is considered to be hydrogen, which contains only negligible interferences with gloss annealing, such as water vapor or carbon monoxide. To prevent hydrogen from dispersing through the retort wall, the walls are not spherical ···. but preferably metal.

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Claims (15)

Apparatus for heat treatment of special zinc-containing metal parts having a heated passageway (1) and a special parts conveying device (4) extending through the passageway (1), characterized in that the passageway (1) is in fluid communication with the cold trap (8-19) for solidified zinc vapor . Apparatus according to Claim 1, characterized in that the cold trap (8-19) is located outside the duct (1) and communicates with the duct (1) by means of a wire (6, 7) which branches from the heated part (1c) of the duct (1). ). Apparatus according to claim 1 or 2, characterized in that the cold trap (8-19) leaves a return line (20, 22) having a pump (21, 23) and terminating in a channel (1). Apparatus according to claim 3, characterized in that the return line (20) terminates in front of the heated portion (1c) of the duct (1a). Apparatus according to claim 3, characterized in that the heated portion (1c) of the duct (1a) is joined by a cooling portion (1b) of special portions, where the return line (22) terminates. 5 107453 Apparatus according to claim 5, characterized in that the return line (22) terminates at the beginning of the cooled portion (1c) 20 of the channel cooling. Apparatus according to one of Claims 3 to 6, characterized in that the first half of the heated portion (1c) of the duct branches to a cold trap (8, 10), from which a return conduit (20) terminates, terminating in the heated portion of the duct (1a). (1c) in the front, and from the remaining 25 halves of the heated portion (1c) of the duct branching to the second cold trap (9, 11), from which the return conduit (22) terminates behind the heated portion (1c) of the duct (1a) . * · Apparatus according to any one of the preceding claims,. characterized in that the heated duct (1) has several points branching into the same cold trap. . 30 Apparatus according to any one of the preceding claims, characterized in that the cold trap (8-19) comprises an elongated container (10,11) filled with filler caps (19) through which a flow passes. :: 10. Apparatus according to claim 9, characterized in that: ''; the cold trap (8-19) is air-cooled. Apparatus according to claim 10, characterized in that a cooling pipe (15,16) passes within the container (10,11) and a cooling pipe 6,107,453 (17,18) is carried therein, which conveys cooling air in the container (10, 11) against the gas flow. and terminates shortly before the bottom end of the tube (15,16) which is closed. Apparatus according to one of the preceding claims, characterized in that the channel (1) is made of metal. 13. A method for gloss annealing of special zinc-containing metal parts in a heat treatment apparatus having a heated passageway (1) and a conveying device (4) extending through the passageway (1), characterized in that zinc vapors are generated in the passageway (1). suck into the cold trap (8-19) and separate there as a solidified gasket. Method according to Claim 13, characterized in that the zinc vapors are drawn from the hottest part (1c) of the duct (1) and separated outside the duct. Method according to Claim 13 or 14, characterized in that the gloss annealing takes place in the shielding gas and the partial flow of the shielding gas to the cold trap (8- 19) 15 is returned to the duct. • 1 * 1 1 * * • 1 1 * 4 · 7 107453 • 1 • 1 1 * 1 1 * *.