U.S. patent application number 10/521434 was filed with the patent office on 2006-05-25 for vacuum carburizing method and device.
This patent application is currently assigned to Linde Aktiengesellschaft. Invention is credited to Alexander Jurmann, Susanne Jurmann.
Application Number | 20060108719 10/521434 |
Document ID | / |
Family ID | 29796417 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060108719 |
Kind Code |
A1 |
Jurmann; Alexander ; et
al. |
May 25, 2006 |
Vacuum carburizing method and device
Abstract
A method and a device for carburizing at subatmospheric
pressures. According to said method, a treatment gas containing
hydrocarbons is supplied to a treatment chamber and an exhaust
stream exits said chamber. The opacity of the gas atmosphere that
prevails in the treatment chamber and/or the opacity of the exhaust
stream that exits said chamber is/are determined and the supply of
the treatment gas containing hydrocarbons to the treatment chamber
is regulated in accordance with the opacity that has been
determined. If an opacity value that has been set or can be set is
exceeded, the supply of the treatment gas containing hydrocarbons
to the treatment chamber can be interrupted, or the quantity of
treatment gas containing hydrocarbons that is supplied to said
chamber can be reduced.
Inventors: |
Jurmann; Alexander;
(Waakirchen, DE) ; Jurmann; Susanne; (Waakirchen,
DE) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Linde Aktiengesellschaft
Abraham-Lincoln-Strasse 21
Wiesbaden
DE
65189
|
Family ID: |
29796417 |
Appl. No.: |
10/521434 |
Filed: |
July 4, 2003 |
PCT Filed: |
July 4, 2003 |
PCT NO: |
PCT/EP03/07194 |
371 Date: |
October 20, 2005 |
Current U.S.
Class: |
266/81 ;
148/235 |
Current CPC
Class: |
C21D 11/00 20130101;
C21D 1/773 20130101; C23C 8/20 20130101 |
Class at
Publication: |
266/081 ;
148/235 |
International
Class: |
C23C 8/20 20060101
C23C008/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 2002 |
DE |
102324328 |
Claims
1. A method of carburizing carburizing, at subatmospheric
pressures, a treatment gas containing hydrocarbons being supplied
to a treatment chamber and an exhaust stream exiting from the
treatment chamber, comprising the steps of: determining the opacity
of the gaseous atmosphere prevailing in the treatment chamber
and/or the opacity of the exhaust stream exiting from the treatment
chamber and, as a function of the determined opacity, regulating
the feeding of the hydrocarbon-containing treatment gas into the
treatment chamber.
2. A method according to claim 1, further comprising the step of
interrupting the feeding of the hydrocarbon-containing treatment
gas into the treatment chamber when an opacity value, which is set
or can be set, is exceeded.
3. A method according to claim 1, further comprising the steps of
reducing the quantity of the hydrocarbon-containing treatment gas
fed to the treatment chamber when an opacity value, which is set or
can be set, is exceeded.
4. A method according to claim 1, wherein a pressure between 3 and
20 mbar is set in the treatment chamber.
5. A method according to claim 1, wherein alkanes, alkenes, alkines
or derivatives of the afore-mentioned, to which hydrogen can be
admixed, are used as hydrocarbon-containing treatment gas.
6. A device for carburizing at subatmospheric pressures comprising:
at least one treatment chamber, at least one feeding line, by way
of which a treatment gas containing hydrocarbons is fed to the
treatment chamber, and at least one evacuating line by way of which
the exhaust stream is withdrawn from the treatment chamber by means
of an evacuating device, wherein at least one valve is arranged in
the feeding line, at least one device for determining the opacity
of the gaseous atmosphere prevailing in the treatment chamber is
arranged in the treatment chamber, and/or at least one opacity
probe is arranged in the evacuating line, and an analyzing unit is
provided which, as a function of the opacity of the exhaust stream
determined by means of the device for determining the opacity of
the gaseous atmosphere prevailing in the treatment chamber, and/or
by means of the opacity probe, regulates the feeding of the
hydrocarbon-containing treatment gas into the treatment chamber by
means of driving the valve.
7. A device according to claim 6, wherein the valve is a control
valve.
8. A device according to claim 6, wherein the analyzing unit
permits the setting of an opacity limit value.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method of carburizing at
subatmospheric pressures, in the case of which a treatment gas
containing hydrocarbons is supplied to a treatment chamber and an
exhaust stream exits from the treatment chamber.
[0002] In addition, the invention relates to a device for
carburizing at subatmospheric pressures, having at least one
treatment chamber, at least one feeding line, by way of which a
treatment gas containing hydrocarbons is supplied to the treatment
chamber, and at least one evacuating line by way of which the
exhaust stream is withdrawn from the treatment chamber by means of
an evacuating device.
BACKGROUND OF THE INVENTION
[0003] A method of the above-mentioned type for carburizing at
subatmospheric pressures is known, for example, from the technical
article "Influencing the Carbon Transfer When Carburizing at
Subatmospheric Pressures", Technical Journal HTM 54 (1999).
[0004] In the case of the methods and devices for carburizing at
subatmospheric pressures which are part of the prior art--here,
pressures of up to 20 mbar are preferably used--, the problem
arises that a sooting of the system--thus of the treatment chamber
as well as of the evacuating pump--takes place when the soot limit
is exceeded. Furthermore, an undesirable tar formation takes place
in the interior of the treatment chamber.
[0005] The cause of the above is the fact that, when a defined
quantity and composition of hydrocarbon-containing or of a
hydrocarbon-containing treatment gas is supplied into the treatment
chamber, an uncontrolled decomposition of excess hydrocarbons can
take place. Furthermore, the calculated hydrocarbon definition may
be too low which results in faulty calculations in the carbon
transition computation and the carbon behavior computation.
[0006] With respect to the methods which are part of the prior art,
it is also a disadvantage that, when the transferred carbon is
calculated, the theoretical composition of the used
hydrocarbon-containing treatment gas is always used as the basis.
This means, for example, that, when propane is used as the
hydrocarbon-containing treatment gas, the composition
C.sub.3H.sub.8 is used as the basis. However, when technical
propane is used, only the heating value but not the exact
composition is guarantied. The sum of the carbon in the technical
propane is therefore not identical with the theoretical C content
of pure propane which is taken into account when calculating the
transferred amount of carbon. This also leads to inaccuracies in
the computing result.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to indicate a
method of the above-mentioned type as well as a device of the
above-mentioned type for carburizing at subatmospheric pressure,
which avoid the above-mentioned disadvantages.
[0008] With respect to the method, this object is achieved in that
the opacity of the gas atmosphere existing in the treatment chamber
and/or the opacity of the exhaust stream exiting from the treatment
chamber is/are determined and, as a function of the determined
opacity, the feeding of the hydrocarbon-containing treatment gas
into the treatment chamber is regulated.
[0009] With respect to the device, the object is achieved in that
at least one valve is arranged in the feeding line; at least one
device for determining the opacity of the gaseous atmosphere
prevailing in the treatment chamber is arranged in the treatment
chamber; and/or at least one opacity probe is arranged in the
evacuating line; and an analyzing unit is provided which, as a
function of the opacity of the exhaust stream determined by means
of the device for determining the opacity of the gaseous atmosphere
prevailing in the treatment chamber, and/or by means of the opacity
probe, regulates the feeding of the hydrocarbon-containing
treatment gas into the treatment chamber by means of driving the
valve.
[0010] The method according to the invention, the device according
to the invention as well as additional further developments thereof
will be discussed in the following by means of the embodiment
illustrated in the figure.
[0011] The figure shows an only schematically illustrated treatment
chamber 3 to which the hydrocarbon-containing treatment gas is fed
by way of a feeding line 1. The following gases are preferably used
as hydrocarbon-containing treatment gases: Alkanes, alkenes,
alkines, derivatives of the aforementioned, optionally in
combination with hydrogen.
[0012] By way of the evacuating line 4, in which a vacuum pump 6 is
arranged, the desired subatmospheric pressure is set in the
treatment chamber 3. As mentioned above, the work preferably takes
place at pressures of up to 20 mbar, preferably at pressures
between 3 and 20 mbar.
[0013] According to the invention, a valve, particularly a control
valve 2, is now arranged in the feeding line 1. According to the
invention, the evacuating line 4 has an opacity probe 5. The
control valve 2 as well as the opacity probe 5 are connected by way
of data lines 7 or 8 with an analyzing unit 9. Corresponding to an
advantageous further development of the device according to the
invention, the analyzing unit (9) permits the setting of an opacity
limit value.
[0014] According to the invention, the opacity of the exhaust
stream exiting from the treatment chamber 3 by way of the
evacuating line 4 is now determined or measured and, as a function
of the determined opacity, the feeding of the
hydrocarbon-containing treatment gas by way of the feeding line 1
into the treatment chamber 3 is regulated.
[0015] If an opacity value, which was set or can be set, of the
exhaust stream withdrawn from the treatment chamber 3 by way of the
evacuating line 4 is exceeded, the feeding of the
hydrocarbon-containing treatment gas by way of the feeding line 1
into the treatment chamber 3 can be either completely interrupted,
or the quantity of the hydrocarbon-containing treatment gas fed to
the treatment chamber 3 can at least be reduced. When there again
is a falling below the opacity value, which was set or can be set,
the feeding of the hydrocarbon-containing treatment gas into the
treatment chamber 3 can be resumed, or the amount of the fed
hydrocarbon-containing treatment gas can be increased again. The
invention thereby permits a continuous regulating of the
hydrocarbon-containing treatment gas fed to the treatment chamber
3.
[0016] As an alternative or in addition to the opacity probe 5
provided in the evacuating line 4, a device 10 for determining the
opacity of the gaseous atmosphere prevailing in the treatment
chamber 3 may be provided. By way of a data line 11, this device 10
for determining the opacity is also connected with the analyzing
unit 9.
[0017] The above-mentioned device 10 for determining the opacity of
the gaseous atmosphere prevailing in the treatment chamber 3 can
also be constructed as a monitoring connection piece. The device 10
for determining the opacity of the gaseous atmosphere prevailing in
the treatment chamber 3 permits a close-to-the-charge measuring of
the gaseous atmosphere prevailing in the treatment chamber 3.
Falsifying effects, which may occur, for example, during the
cooling of the exhaust stream withdrawn from the treatment chamber
3 are avoided in this variant of the method. However, it is a
disadvantage of this method of operation that the separation of
aerosols, which occurs only when the exhaust stream is cooled, is
not yet visible and therefore determinable in the treatment chamber
3 itself.
[0018] The method according to the invention as well as the device
according to the invention therefore permit a controlled feeding of
the hydrocarbon-containing treatment gas into the treatment
chamber, whereby an uncontrolled decomposition of excessive
hydrocarbons in the treatment chamber as well as in the evacuating
line and thus a soot and tar formation can be effectively avoided.
A large amount of the undesired deposits within the treatment
chamber on the material to be treated in the treatment chamber or
in the evacuating line is reliably avoided by means of the method
according to the invention or by means of the device according to
the invention.
[0019] The foregoing description and examples have been set forth
merely to illustrate the invention and are not intended to be
limiting. Since modifications of the described embodiments
incorporating the spirit and substance of the invention may occur
to persons skilled in the art, the invention should be construed
broadly to include all variations falling within the scope of the
appended claims and equivalents thereof.
* * * * *