HRP920579A2

HRP920579A2 - Vacuum furnance for the heat treatment of metallic work-pieces

Info

Publication number: HRP920579A2
Application number: HR920579A
Authority: HR
Inventors: Paul Heilmann; Erwin Heumuller; Fritz Kalbfleisch; Friedrich Preisser; Rolf Schuster
Original assignee: Degussa
Priority date: 1987-10-28
Filing date: 1992-09-29
Publication date: 1994-10-31

Description

Područje tehnike The field of technology

Izum je iz područja toplinske obrade metala. The invention is from the field of metal heat treatment.

Izum se odnosi na jednu vakuumsku peć za toplinsku obradu metalnih obradaka sa cilindričnim kućištem pod pritiskom (MKP C21D 1/773, C21D 9/00, C21D 1/767, F27B 5/16) . The invention relates to a vacuum furnace for heat treatment of metal workpieces with a cylindrical casing under pressure (MKP C21D 1/773, C21D 9/00, C21D 1/767, F27B 5/16).

Tehnički problem Technical problem

Tehnički problem koji se rješava ovim izumom je konstrukcija vakuumske peći za toplinsku obradu metala kod koje bi se osiguralo što je moguće brže i ravnomjernije hlađenje šarže, te što je moguće brže zagrijavanje peći, a da pri tome konstrukcija bude što jednostavnija. The technical problem that is solved by this invention is the construction of a vacuum furnace for heat treatment of metals, which would ensure the fastest and most uniform cooling of the batch, and the fastest possible heating of the furnace, while making the construction as simple as possible.

Stanje tehnike State of the art

U patentnim spisima DE-PSen 28 39 807 i 28 44 843 opisane su sve vrste vakuumskih peći. One se uglavnom sastoje od cilindričnog kućišta pod pritiskom u kojem se nalazi šaržni prostor, koji je ograničen toplinski izolacijskim stjenkama i u kojem se nalaze grijaći elementi kao i uređaj za rashladni plin. U šaržnom prostoru alati i razni obratci griju se u vakuumu na temperaturu nastajanja ausenita, a za kaljenje se dovodi rashladni inertni plin koji cirkulira pod pritiskom. Pri tome rashladni plin struji velikom brzinom preko vruće šarže kojoj oduzima toplinsku energiju i odlazi u temperiralo gdje se hladi i ponovo dolazi u šaržnu komoru. Uvođenje rashladnog plina u šaržnu komoru vrši se pomoću mlaznica prema patentnom spisu DE-PS 28 39 807, koje se nalaze na posebnim, aksijalno postavljenim cijevima za dovod plina. Loša strana ove konstrukcije je visoka cijena utroška materijala i izrade cijevi za dovod plina u peć. Cijevi i mlaznice moraju biti od materijala visoke temperaturne postojanosti. Ventilatori primijenjeni prema patentnom spisu DE-PS 28 44 843 imaju lošu stranu da rashladni plin najvećim dijelom usmjeravaju samo na površinu zagrijane šarže, a ne i u njenu unutrašnjost. In the patent documents DE-PSen 28 39 807 and 28 44 843, all types of vacuum furnaces are described. They mainly consist of a cylindrical pressure housing in which there is a batch space, which is limited by thermal insulation walls and in which there are heating elements as well as a cooling gas device. In the batch room, tools and various workpieces are heated in a vacuum to the temperature of ausenite formation, and cooling inert gas circulating under pressure is supplied for hardening. At the same time, the cooling gas flows at high speed over the hot batch from which it takes heat energy and goes to the temperature chamber where it cools and comes back to the batch chamber. The introduction of cooling gas into the batch chamber is performed using nozzles according to patent document DE-PS 28 39 807, which are located on special, axially placed gas supply pipes. The downside of this construction is the high cost of materials and making pipes for gas supply to the furnace. Pipes and nozzles must be made of materials with high temperature stability. The fans applied according to the patent file DE-PS 28 44 843 have the disadvantage that they mostly direct the cooling gas only to the surface of the heated batch, and not to its interior.

Iz patentnog spisa DE-OS 19 19 493 poznato je da se zagrijavanje šarže u temperaturnom području između sobne temperature i oko 750°C ubrzava ako pri tome u peći cirkulira inertan plin, tako da pored zračenja postoji i konvekcija. Pri tome se međutim ne postiže optimalan prijelaz topline između grijača i šarže. From the patent file DE-OS 19 19 493 it is known that the heating of the batch in the temperature range between room temperature and about 750°C is accelerated if an inert gas circulates in the furnace, so that in addition to radiation there is also convection. However, optimal heat transfer between the heater and the batch is not achieved.

Opis rješenja tehničkog problema s popisom i kratkim opisima crteža Description of the solution to the technical problem with a list and brief descriptions of the drawings

Navedeni tehnički problem riješen je tako da je konstruirana vakuumska peć za toplinsku obradu metalnih obradaka sa cilindričnim kućištem pod pritiskom u kojem se nalazi šaržni prostor, kojeg okružuju aksijalno postavljeni grijači, i koji ima toplinsku izolaciju i uređaj za rashladni plin pomoću kojeg se rashladni plin kroz mlaznice uvodi u šaržni prostor te u temperiralo. Ove vakuumske peći trebale bi osigurati što je moguće brže i ravnomjernije hlađenje vruće šarže, da su . što jednostavnije konstrukcije i da se po mogućnosti zagrijavaju što brže. The mentioned technical problem was solved by constructing a vacuum furnace for the heat treatment of metal workpieces with a cylindrical casing under pressure in which there is a batch space, surrounded by axially placed heaters, and which has thermal insulation and a device for cooling gas by means of which the cooling gas through introduces the nozzles into the batch space and into the tempering room. These vacuum furnaces should ensure as fast and even cooling of the hot batch as possible, if they are . as simple constructions as possible and to heat up as quickly as possible.

Prema izumu ovaj problem riješen je tako da su grijači izvedeni kao cijevi koje u unutrašnjosti šaržne komore imaju otvore i koje su pomoću električki izoliranih dijelova povezane s uređajem za razdiobu rashladnog plina. According to the invention, this problem is solved so that the heaters are designed as pipes that have openings in the inside of the batch chamber and which are connected to the cooling gas distribution device by means of electrically insulated parts.

Uređaj za razdiobu rashladnog plina prvenstveno ima ventilator koji rashladni plin puše pod pritiskom kroz grijaće cijevi i ponovo ga isisava iz šaržne komore. The cooling gas distribution device primarily has a fan that blows the cooling gas under pressure through the heating pipes and sucks it back out of the batch chamber.

Dalju prednost predstavlja to da na stjenki toplinske izolacije, u području uređaja za razdiobu rashladnog plina, postoji otvor koji se može otvarati i zatvarati. Na taj način tijekom zagrijavanja šarže održava se strujanje zagrijavanog plina u unutrašnjosti peći uz oplakivanje temperirala. Another advantage is that there is an opening on the wall of the thermal insulation, in the area of the cooling gas distribution device, which can be opened and closed. In this way, during the heating of the batch, the flow of heated gas is maintained in the interior of the furnace, while the temperature control is maintained.

Ako se radi sa skupim rashladnim plinovima prednost ima to da se uz peć raspolaže i s jednim uređajem za ponovno dobivanje rashladnog plina. If you are working with expensive cooling gases, it is an advantage to have a device for recovering the cooling gas in addition to the furnace.

Slike 1 i 2 shemaski prikazuju uzdužne presjeke kroz jedan izvedbeni primjer vakuumske peći prema izumu, pri čemu slika 1 prikazuje peć u fazi zagrijavanja do otprilike 750°C, a slika 2 prikazuje fazu hlađenja (kaljenja u struji rashladnog plina). Figures 1 and 2 schematically show longitudinal sections through one embodiment of a vacuum furnace according to the invention, wherein Figure 1 shows the furnace in the heating phase up to approximately 750°C, and Figure 2 shows the cooling phase (quenching in a cooling gas stream).

Peć se sastoji od cilindričnog kućišta pod pritiskom (1), čija je čeona strana izvedena u obliku vrata (2), kroz koja se peć može puniti i prazniti. Šaržna komora (3) je s vanjske strane omeđena toplinskom izolacijom (4) u obliku cilindrične cijevi od toplinski izolacijskog materijala na čijim se čeonim stranama nalaze odgovarajuće stjenke od kojih je najmanje jedna stjenka (5) pokretna. Ova toplinska izolacija (4) sprečava zračenje u šaržnom prostoru (3) prema van, tako da nastaju samo neznatni gubici energije. Unutar toplinske izolacije (4) naokolo po obodu u šaržnom prostoru (3) aksijalno su postavljeni električni grijači (6) koji su izvedeni u obliku grijaćih cijevi koje u unutrašnjosti šaržnog prostora (3) imaju otvore (7). Ove grijaće cijevi (6) imaju debljinu stjenke od 1 do 3 mm i proizvoljnu dužinu od 40 do 150 mm. Promjer otvora (7) treba odrediti tako da zbroj površina otvora (7) jedne grijaće cijevi odgovara površini proizvoljne dužine cijevi. Grijaće cijevi (6) su pomoću električki izolacijskih dijelova (8) pričvršćene na uređaj za razdiobu rashladnog plina (9), koji se zajedno s pogonskim motorom (10) i ventilatorom (11) nalazi na strani suprotnoj vratima (2) u unutrašnjosti kućišta pod pritiskom. Na stjenki toplinske izolacije (4) koja se nalazi pored uređaja za razdiobu rashladnog plina (9) nalazi se otvor (12) koji je zatvoren pomoću kliznika (13) i koji se može otvoriti. Između kućišta pod pritiskom (1) i toplinske izolacije (4) smještene su cijevi temperirala (14) koje se hlade vodom. The furnace consists of a cylindrical casing under pressure (1), whose front side is made in the form of a door (2), through which the furnace can be filled and emptied. The batch chamber (3) is bounded on the outside by thermal insulation (4) in the form of a cylindrical tube made of heat-insulating material, on the front sides of which there are corresponding walls, at least one wall (5) of which is movable. This thermal insulation (4) prevents radiation in the batch space (3) to the outside, so that only minor energy losses occur. Within the thermal insulation (4) around the perimeter in the batch space (3), electric heaters (6) are axially placed, which are made in the form of heating pipes that have openings (7) in the interior of the batch space (3). These heating pipes (6) have a wall thickness of 1 to 3 mm and an arbitrary length of 40 to 150 mm. The diameter of the opening (7) should be determined so that the sum of the surfaces of the opening (7) of one heating pipe corresponds to the surface of an arbitrary length of pipe. The heating pipes (6) are attached by means of electrically insulating parts (8) to the cooling gas distribution device (9), which together with the drive motor (10) and the fan (11) is located on the side opposite the door (2) inside the housing under by pressing. On the thermal insulation wall (4) located next to the cooling gas distribution device (9) there is an opening (12) which is closed by means of a slide (13) and which can be opened. Between the pressure housing (1) and the thermal insulation (4) there are temperature tubes (14) that are cooled by water.

Nakon punjenja šaržne komore (3) s npr. alatom, ista se puni s nekim inertnim plinom i potom zagrijava. Kliznik (13) oslobađa otvor (12) u toplinskoj izolaciji (slika 1) tako da se inertni plin pomoću ventilatora (11) potiskuje u grijaće cijevi (6) gdje se kroz otvore (7) širi po cijeloj dužini grijaćih cijevi i prodire u šaržnu komoru (3), a kroz otvor (1.2) u toplinskoj izolaciji odvodi ga se ponovo do ventilatora (11). Nakon što se inertni plin dovede pomoću grijaćih cijevi (6), on se u njima brzo zagrije što ima za posljedicu brzo i homogeno zagrijavanje šarže pomoću vrućeg plina u području tamnog zračenja. Izravnim strujanjem vrućeg plina na šaržu, ona se ravnomjerno grije i u svojoj unutrašnjosti. Ovaj proces grijanja uz zaštitni plin koristi se do otprilike 750°C. Pri kaljenju kod kojeg se zagrijavanje mora izvršiti do otprilike 1300°C, inertni plin se uklanja iz peći i dalje se grije samo pomoću topline zračenja, što je u ovom temperaturnom području vrlo učinkovito. After filling the batch chamber (3) with, for example, a tool, it is filled with some inert gas and then heated. The slider (13) releases the opening (12) in the thermal insulation (picture 1) so that the inert gas is forced by the fan (11) into the heating pipes (6) where it spreads through the openings (7) along the entire length of the heating pipes and penetrates into the batch chamber (3), and through the opening (1.2) in the thermal insulation, it is led back to the fan (11). After the inert gas is supplied by means of the heating pipes (6), it is quickly heated in them, which results in a quick and homogeneous heating of the batch by means of hot gas in the region of dark radiation. By direct flow of hot gas to the batch, it is heated evenly in its interior as well. This inert gas heating process is used up to approximately 750°C. In tempering, where heating must be carried out to approximately 1300°C, the inert gas is removed from the furnace and further heated only by radiant heat, which is very efficient in this temperature range.

Za kaljenje zagrijane šarže peć se, pri zatvorenom otvoru (12) ispuni s hladnim inertnim plinom pod pritiskom. Pri tome se stjenka (5) toplinske izolacije (4) podigne tako da nastane procjep i stvara se veza između šaržne komore (3) s prostorom između kućišta pod pritiskom (1) i toplinske izolacije (4) . Rashladni plin potiskuje se ventilatorom (11) preko rashlađenih grijaćih cijevi (6) velikom brzinom u šaržnu komoru (3), odakle se preko cijevnog temperirala (14) vraća u uređaj za razdiobu rashladnog plina (9) i ponovno se vraća u optok. Primjenom odgovarajućih inertnih plinova, a u svezi s visokim pritiscima plinova i brzinama plinova, mogu se s vakuumskom peći prema izumu postići intenzivnosti kaljenja koje se mogu usporediti s kaljenjem u uljnim kupeljima. Na ovaj način mogu se također kaliti i otvrdnjavati i druge vrste čelika, što do sada nije bio slučaj. To temper the heated batch, the furnace is filled with cold inert gas under pressure when the opening (12) is closed. In doing so, the wall (5) of the thermal insulation (4) is raised so that a gap is created and a connection is created between the batch chamber (3) and the space between the pressure housing (1) and the thermal insulation (4). The cooling gas is pushed by the fan (11) through the cooled heating pipes (6) at high speed into the batch chamber (3), from where it returns to the device for distributing the cooling gas (9) through the pipe temperature controller (14) and returns to the circulation again. By using suitable inert gases, and in connection with high gas pressures and gas velocities, with the vacuum furnace according to the invention, tempering intensities comparable to tempering in oil baths can be achieved. In this way, other types of steel can also be tempered and hardened, which was not the case until now.

Grijaće cijevi (6) koje istovremeno služe i kao cijevi za dovod plina, prvenstveno su izrađene od ugljika ojačanog ugljičnim vlaknima. Električki provodljiv poprečni presjek grijaćih cijevi, koji je mjerodavan za stvaranje topline, kao i unutrašnje dimenzije grijaćih cijevi, koje su mjerodavne za volumen struje plina, moraju biti međusobno usklađene. Kombinacija grijaćih elemenata i cijevi za dovod plina doprinosi značajnom pojednostavljenju u tehnici proizvodnje ovih peći. Heating pipes (6), which simultaneously serve as gas supply pipes, are primarily made of carbon reinforced with carbon fibers. The electrically conductive cross-section of the heating pipes, which is relevant for the generation of heat, as well as the internal dimensions of the heating pipes, which are relevant for the volume of the gas flow, must be coordinated with each other. The combination of heating elements and gas supply pipes contributes to a significant simplification in the production technique of these stoves.

Ako se za kaljenje primijeni neki skuplji inertni plin, onda ja svakako korisno ponovno ga dobiti i vratiti u proces. U tu svrhu po završetku kaljenja ispumpa se pomoću kompresora iz unutrašnjosti peći i vodi u spremnik visokog pritiska odakle je raspoloživ za dalju primjenu. If a more expensive inert gas is used for tempering, then it is definitely useful to get it again and return it to the process. For this purpose, at the end of tempering, it is pumped out by means of a compressor from inside the furnace and led to a high-pressure tank, from where it is available for further use.

Navod o najboljem načinu privredne upotrebe izuma Statement on the best way of economic use of the invention

Za primjenu izuma nisu potrebna neka posebna znanja i iskustva već su dovoljna ona kojima raspolaže prosječan stručnjak za ovo područje tehnike, koji izum može primijeniti na osnovu priloženog opisa i crteža. The application of the invention does not require any special knowledge and experience, but those possessed by an average expert in this field of technology, who can apply the invention based on the attached description and drawings, are sufficient.

Od posebnog značaja za praktičnu primjenu izuma je slijedeće: The following is of particular importance for the practical application of the invention:

Grijaće cijevi 6 najsvrhovitije imaju debljinu stjenki od 1 do 3 mm, a proizvoljnu dužinu od 40 do 150 mm. Heating pipes 6 ideally have a wall thickness of 1 to 3 mm, and an arbitrary length of 40 to 150 mm.

Značajno je zatim da promjer otvora 7 bude određen tako da zbroj površina otvora 7 jedne grijaće cijevi 6 odgovara površini proizvoljne dužine cijevi. It is important then that the diameter of the opening 7 is determined so that the sum of the surfaces of the openings 7 of one heating pipe 6 corresponds to the surface of an arbitrary length of pipe.

Grijaće cijevi 6 koje istovremeno služe i kao cijevi za dovod plina moraju prvenstveno biti od ugljika ojačanog ugljičnim vlaknima. The heating pipes 6, which simultaneously serve as gas supply pipes, must primarily be made of carbon reinforced with carbon fibers.

Claims

1. Vacuum furnace for heat treatment of metal workpieces with a cylindrical casing (1) under pressure in which there is a batch chamber (3), which is surrounded by axially placed heaters (6), indicated by the fact that the tubular heaters (6) have in the batch chamber ( 3) openings (7) and that they are connected to the cooling gas distribution device (9) via electrically insulating parts (8).

2. Vacuum furnace according to claim 1, characterized in that the cooling gas distribution device (9) has a fan (11).

3. Vacuum furnace according to claims 1 and 2, characterized in that the thermal insulation (49) in the area of the cooling gas distribution device (9) has an opening (12) that can be closed by a slider (13).