GB2075557A - Method for the temporary shut down of a carburising installation - Google Patents
Method for the temporary shut down of a carburising installation Download PDFInfo
- Publication number
- GB2075557A GB2075557A GB8114268A GB8114268A GB2075557A GB 2075557 A GB2075557 A GB 2075557A GB 8114268 A GB8114268 A GB 8114268A GB 8114268 A GB8114268 A GB 8114268A GB 2075557 A GB2075557 A GB 2075557A
- Authority
- GB
- United Kingdom
- Prior art keywords
- zone
- carburising
- temperature
- hardening
- installation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000009434 installation Methods 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 9
- 239000011261 inert gas Substances 0.000 claims abstract description 16
- 239000007789 gas Substances 0.000 claims abstract description 14
- 238000010438 heat treatment Methods 0.000 abstract description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000004071 soot Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 230000003442 weekly effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Tunnel Furnaces (AREA)
Abstract
A method for the temporary shutdown of a carburising installation, in which parts to be hardened are conveyed in succession through a heating-up zone, carburising zone, a perlitising zone if present, and a hardening-zone, comprises the following steps: the hardening zone is emptied of products, the conveying mechanism is brought to rest, the temperature in the heating-up, carburising and hardening zones is reduced to 600 DEG C to 800 DEG C and the operating-gas atmosphere is replaced by an inert-gas atmosphere. After the shutdown, the heating- up, carburising and hardening zones are brought to a temperature of 850 to 880 DEG C and the inert-gas atmosphere is replaced by the operating-gas atmosphere as soon as the zones have reached this temperature. When all the zones have reached the said temperature, the hardening zone and carburising zone are brought to the required temperature, whereafter the conveying mechanism is set in operation and the heating up zone is brought to the nominal temperature.
Description
SPECIFICATION
Method for the temporary shut down of a carburising installation
With push-through carburising installations which require to be shut down for periods, for example at week-ends, large losses of capacity result from the circumstance that the installation must run empty before the shut down. The loss of capacity is then dependent upon the time which the parts to be treated require to pass through the installation. The larger the installation, the larger also is the loss of capacity.
In such an installation, the parts to be treated, that is the product, are conveyed quasicontinuously through the installation, i.e. the oven, consisting of a warming-up zone, a carburising zone, possibly a perlitising zone, and a hardening zone. For this purpose, the product is disposed on
plates, pallets, grids or the like which are moved forward in steps of a grid width. At each step, therefore, a grid is introduced into the installation
and a grid whose treatment is finished leaves the
installation. This stepwise conveyance is
employed so that the doors of the installation can
be kept closed in the pauses between steps, as a controlled oven atmosphere cannot otherwise be
maintained.The duration of treatment of the
product-filled grids in the individual zones of the
installation depends upon the required depth of
case hardening, the greatest part of the oven
length being occupied by the carburising zone. The
construction and design of such carburising
installations are well known and have been
described in detail in the literature. With large
installations having 40 grids for example, a freshly
introduced grid leaves the installation again after
40 movements. On the assumption that a period
of time of from 1 5 to 20 minutes is provided for
each step, the last grid to be treated must, with
the previous manner of operation, be entered into
the installation already 10 to 13 hours before a
shut down and, after re-setting of the installation
in operation, a period of 10 to 13 hours will also
be required before the first grid leaves the
installation.
The present invention seeks to reduce these
losses in capacity, that is to provide a method for
temporary shutdown in which the installation can
remain largely filled, with parts to be treated,
during the shut-down period.
According to the invention a method for the
temporary shut down of a carburising installation
in which parts to be hardened are conveyed in
succession through a heat-up zone, carburising
zone, a perlitising zone if present, and a
hardening-zone comprises the following steps:
a) the hardening zone is emptied of products,
b) the conveying mechanism is brought to rest,
the temperature in the heating-up, carburising and
hardening zones is reduced to 6000C to 8000C
and the operating-gas atmosphere is replaced by
an inert-gas atmosphere.
c) after shut down, the heating-up, carburising
and hardening zones are brought to a temperature of 850 to 8800C and the inert-gas atmosphere is replaced by the operating-gas atmosphere as soon as the zones have reached this temperature,
d) as soon as all the zones have reached the intended temperature in accordance with step c, the hardening zone and carburising zone are brought to the nominal temperature, whereafter the conveying mechanism is set in operation and the heating-up zone is brought to the nominal temperature.
Before the shut down, first of all the hardening zone is emptied of the product. This may be effected by introducing into the installation, at a suitable time point, a number of empty grids corresponding to the length of the hardening zone, so that, taking into account the step duration and the oven length, the hardening zone is occupied by these empty grids up to the time of the intended shut down. Inter alia, also, depending upon the nature of the installation (one- two- or three-track) it is necessary to leave the last row or last two rows of grids empty in the heating-up zone behind the entry door, because there is a danger, particularly with not optimally regulatable temperature in this zone, of coarse-grain formation as well as of increased oxidation phenomena on the products upon these grids.For economy of energy, the method is preferably so controlled that the temperature in the carburising and the heating-up zones has already decreased to 8500C to 8800C when the last production grids are positioned in the hardening zone.
Then, after ejection of the last production grid from the hardening zone, the conveying mechanism is set out of operation and the temperature in the heating-up, carburising and hardening zones is reduced to 600 to 8000 C, the temperature of 7000C being preferred. Indeed, no disadvantages result if the temperature is reduced below 6000 C, but the heating-up operation requires considerably longer. Also, at the same time as the temperature decreases, the operatinggas atmosphere is replaced by an inert-gas atmosphere, for which purpose it is generally sufficient to replace the operating-gas supply by the inert-gas supply. The change-over from the operating-gas atmosphere to inert-gas atmosphere will then take place with sufficient speed by flaring out of the installation.In general, care should be taken that, on the change-over from the operating-gas atmosphere to the inertgas atmosphere, there is neither soot or rust formation nor substantial decarburisation of the product. The inter-relationships between operating atmosphere, temperature and carburisation and decarburisation are well known (for example Boudouard equilibrium, iron/carbon diagram) and present no difficulties. While the conveying mechanism is at rest, oven door-locking means prevents the oven atmosphere from being impaired by possible opening of the doors. Thus it is possible for the over pressure in the oven, which amounts to about 1 5 to 20 mm WC (water column) in the operating condition, to decrease to the low value of about 4 mm WC, which results in a considerable saving of inert gas.As inert gas, use may be made of any gases which are inert, under the temperature conditions obtaining, in relation to the materials present in the oven, for example the rare gases or nitrogen. Nitrogen is preferred as inert gas because of ready availability.
At the termination of the condition of rest, the zones of the installation, the heating-up, carburising and hardening zones, are raised to a temperature of 850 to 8800C, preferably 8600C. The warming up is so controlled that the three zones attain this temperature at substantially the same time.
Because of the differing thermal capacities and sizes of the zones (due to constructional requirements), in general the carburising zone will be the last to reach this temperature. The succession in time in the attainment of the temperature is also preferable for methodtechnical reasons. As soon as the zones have attained the predetermined temperature, the inertgas atmosphere is replaced by the operating-gas atmosphere. Generally this will take place at a sufficient rate if the inert-gas supply is cut off and the operating-gas supply in turned on. At the same time, the over-pressure necessary for operation is also re-established.The temperature of 850 to 8800C should be maintained quite precisely, as the operating-gas supply can lead to soot formation in the oven at a temperature below 8500C and, in an inert-gas atmosphere, appreciable decarburising of the product in the oven can occur above 8800 C. A temperature of 8600C is particularly preferred because at this temperature, with the respective atmosphere, no soot formation will occur and also not yet any decarburisation. If the hardening zone is at an operating temperature of less than 850 to 8800 C, or the installation is completed with an additional, perlitising, zone, naturally it will be heated only to this temperature.As soon as all zones have reached the temperature of 8500C to 88O0C or the nominal temperature, if this is lower than the said value, further heating up is effected. First of all the hardening zone and the carburising zone are brought to the nominal temperature, if this is not already the case. As soon as the hardening zone and the carburising zone are at the nominal temperature and the oven atmosphere is in equilibrium, the conveying mechanism is set in operation and production can be continued. At the same time, the heating-up zone is switched to the nominal temperature. It is important that the heating-up zone should be the last to come to the nominal temperature.
The products remaining in the oven during a shut-down period practically do not differ, after their finished treatment, from the products finished in normal operation. The shut-down period can amount to 80 hours. Only after this period are effects upon quaiity to be taken into account.
The advantage attainable by the method according to the invention is remarkable. With an installation comprising 40 grids, the 4 grids comprised in the hardening zone, plus, if necessary for reliability, the last two grids of the heating-up zone are left without production material (empty grids) prior to the shut-down.
Accordingly 34 product-filled grids remain in the installation. The gain in capacity with a step period of 1 8 minutes is thus 10.2 hours, which, for a weekly period of operation of the installation of 1 20 hours, corresponds to a gain of capacity of 8.5%. Installations with a plurality of oven tracks or longer step periods have a corresponding increase of capacity. Apart from the increase in capacity, the savings in energy are naturally also considerabie.
Claims (2)
1. A method for the temporary shut-down of a carburising installation in which parts to be hardened are conveyed in succession through a heating-up zone, carburising zone, a perlitising zone if present, and a hardening-zone comprising the following steps:
a) the hardening zone is emptied of products,
b) the conveying mechanism is brought to rest, the temperature in the heating-up, carburising and hardening zones is reduced to 6000C to 8000C and the operating-gas atmosphere is replaced by an inert-gas atmosphere.
c) after shut down, the heating-up, carburising and hardening zones are brought to a temperature of 850 to 8800C and the inert-gas atmosphere is replaced by the operating-gas atmosphere as soon as the zones have reached this temperature,
d) as soon as all the zones have reached the intended temperature in accordance with step c, the hardening zone and carburising zone are brought to the nominal temperature, whereafter the conveying mechanism is set in operation and the heating-up-zone is brought to the nominal temperature.
2. A method for the temporary shut down of a carburising installation substantially as hereinbefore described.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3017978A DE3017978C2 (en) | 1980-05-10 | 1980-05-10 | Procedure for the temporary shutdown of push-through carburizing plants |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2075557A true GB2075557A (en) | 1981-11-18 |
| GB2075557B GB2075557B (en) | 1983-09-21 |
Family
ID=6102092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8114268A Expired GB2075557B (en) | 1980-05-10 | 1981-05-11 | Method for the temporary shut down of a carburising installation |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE3017978C2 (en) |
| FR (1) | FR2482277A1 (en) |
| GB (1) | GB2075557B (en) |
| IT (1) | IT1142435B (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1489589A (en) * | 1966-08-17 | 1967-07-21 | Electric Furnace Co | Annealing furnace with emergency purge atmosphere |
| US3720546A (en) * | 1969-04-21 | 1973-03-13 | Nippon Steel Corp | Method for preventing destruction of strip metal in annealing furnace connected with direct heating furnace |
| US3827854A (en) * | 1973-10-26 | 1974-08-06 | W Gildersleeve | Automatic metal protecting apparatus and method |
| US4035203A (en) * | 1973-12-21 | 1977-07-12 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Method for the heat-treatment of steel and for the control of said treatment |
| US4049473A (en) * | 1976-03-11 | 1977-09-20 | Airco, Inc. | Methods for carburizing steel parts |
| US4148946A (en) * | 1977-02-14 | 1979-04-10 | Armco Steel Corporation | Method for maintaining a non-oxidizing atmosphere at positive pressure within the metallic strip preparation furnace of a metallic coating line during line stops |
| US4175986A (en) * | 1978-10-19 | 1979-11-27 | Trw Inc. | Inert carrier gas heat treating control process |
-
1980
- 1980-05-10 DE DE3017978A patent/DE3017978C2/en not_active Expired
-
1981
- 1981-05-08 IT IT48424/81A patent/IT1142435B/en active
- 1981-05-08 FR FR8109191A patent/FR2482277A1/en active Granted
- 1981-05-11 GB GB8114268A patent/GB2075557B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2482277B1 (en) | 1983-01-14 |
| DE3017978A1 (en) | 1981-11-19 |
| DE3017978C2 (en) | 1986-03-13 |
| IT1142435B (en) | 1986-10-08 |
| FR2482277A1 (en) | 1981-11-13 |
| IT8148424A0 (en) | 1981-05-08 |
| GB2075557B (en) | 1983-09-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920511 |