DE102007040858A1 - Vacuum carburizing device for steel, comprises carburizing chamber for material to be processed, vacuum pump, carburizing gas supply for the chamber in stroke operation, return pipe, opening- and closing valves, and control equipment - Google Patents

Abstract

The vacuum carburizing device for steel, comprises a carburizing chamber (3) for a material to be processed, a vacuum pump, which sucks gas from the carburizing chamber to obtain a vacuum, a carburizing gas supply (4) for the carburizing chamber in a stroke operation, a return pipe (15), which connects an inlet side and an outlet side of the vacuum pump, opening- and closing valves (16) arranged in the flow of the return pipe, and a control equipment (20), which opens the opening and closing valve, when a supply of carburizing gas into the carburizing chamber is started. The vacuum carburizing device for steel, comprises a carburizing chamber (3) for a material to be processed, a vacuum pump, which sucks gas from the carburizing chamber to obtain a vacuum, a carburizing gas supply (4) for the carburizing chamber in a stroke operation, a return pipe (15), which connects an inlet side and an outlet side of the vacuum pump, opening- and closing valves (16) arranged in the flow of the return pipe, a control equipment (20), which opens the opening and closing valve, when a supply of carburizing gas into the carburizing chamber is started and closes the opening and closing valve when the carburizing gas supply ends, and a flow-quantity control valve (17), which is arranged in the flow of the return pipe and adjusts a quantity of the carburizing gas returned to the inlet side of the vacuum pump. An independent claim is included for a method for carburizing a material to be processed.

Description

The The invention relates to a carburizing device for steels, and in particular, a carburizing device which is steel subjected to a clock carburizing processing

In the vacuum carburizing processing of steels, in a processing method called pulse carburizing, the processing is performed by alternately repeating a carburizing period (carburizing period) in which carburizing gas is fed into a carburizing chamber which carburizing chamber accommodates in its interior a material (working material) heated to a high temperature, the carburizing chamber being kept in its interior at a predetermined low-vacuum level (ie at a relatively high pressure), and a diffusion period (Diffusion period) in which the carburizing gas is sucked off and diffuses carbon under a high-vacuum level (ie, at a relatively low pressure) from the surface of the material to be processed to the inside of the material to be processed. According to this method, the carburizing can be carried out to a narrow hole inside or a large hole depth into which the carburizing gas is difficult to penetrate, and the carburizing can be carried out uniformly even on an uneven material to be worked. Therefore, the clock carburization is considered as suitable for these materials to carburizing process (it is on the documents JP-A-2000-1765 and JP-A-2002-194526 ).

at the teaching taught in the above patent documents however, the following problems occur: in a vacuum carburizing apparatus as described in each of the above patent documents is in a gas suction line, which is an outlet opening a furnace with a vacuum-Absang-device connects, a adjustable valve for pressure adjustment (comprising a movable shutter mechanism) installed. Continue the pressure control in the carburizing chamber during the Carburizing period and the diffusion period by means of this adjustable Valve, which adjusts the flow rate of the extracted gas. As a result, foreign bodies such as Soot and tar contained in the extracted gas, which flows through the gas suction line to the adjustable Valve and accumulate at the adjustable valve. hereby a bad function of the adjustable valve is easily caused, and the reliability and durability of the device as a whole is lowered. Next must be the size of the adjustable Valve be big, because the gas suction line a big Diameter, which causes an increase in cost.

In addition to that described above, as in the above patent document JP-A-2000-1765 (Paragraph [0016]) also uses a carburizing apparatus in which the above adjustable valve is not provided, but the vacuum-absorbing device is directly connected to the outlet port. This device controls the pressure control briefly a rotational speed of a vacuum pump. However, the range in which this device can control a pressure reached at a suction side (inlet side) is narrow. Therefore, in a case where a vacuum pump having a large suction speed is used as the vacuum suction device, a change (decompression) from a pressure P _{1 '} during the carburizing period after the carburizing gas is introduced is used. to a pressure P ₀ during the diffusion period, executed rapidly as indicated by curve A in FIG 4 shown. However, the pressure during the carburizing period becomes a high-vacuum level pressure P _{1 '} approaching the pressure P ₀ during the diffusion period, so that the carburizing gas enters a tight hole inside during the carburizing period becomes insufficient. Further, in a case where a vacuum pump having a low suction speed is used as the vacuum suction device, the pressure during the carburizing period becomes a desired pressure P _{1 of} a low-vacuum level as it passes through Curve B in 4 is shown. However, after the carburizing gas is introduced, the time until the pressure P ₁ is lowered to the pressure P ₀ during the diffusion period becomes long, and the number of cycles is limited. Thus, problems such as occurrence of uneven carburization, carburizing processing time prolongation and the like may occur.

The This invention was made to solve the above problems of the prior art to solve the art, and it is an object of the invention, at low cost, a vacuum carburizing device ready for which give a desired carburizing period pressure a low-vacuum level during the time of clock carburizing and what a fast switching characteristic (change characteristic) from the carburizing period pressure to the diffusion period pressure and which in terms of their reliability and durability is outstanding.

According to one embodiment of the present invention, there is provided a vacuum carburizing apparatus comprising: a carburizing chamber to be machined Picking up material (processing material) in its interior; a vacuum pump which sucks gas from inside the carburizing chamber to obtain a vacuum; a carburizing gas supply device which supplies carburizing gas to the carburizing chamber in one stroke operation; a return line connecting an inlet side (suction side) of the vacuum pump and an outlet side of the vacuum pump; an open and close valve, which is arranged in the course of the return line; and a controller that opens the open and close valve when a supply of the carburizing gas into the carburizing chamber is started, and which control means closes the open and close valve when the supply ends.

A Embodiment of the present invention will be below described in more detail with reference to the accompanying drawings. It is

1 a mechanical piping of a vacuum Auskohlungs-apparatus, which shows an embodiment of the present invention by way of example;

2 a diagram showing the change in the furnace internal pressure with respect to the number of pump revolutions in the device of 1 shows;

3 a diagram of the furnace internal pressure during the time of clock carburizing by means of the device of 1 ; and

4 a comparative diagram of the furnace internal pressure during the time of clock carburizing between a conventional device and the device according to the invention.

Hereinafter, an embodiment of the present invention will be described with reference to FIG 1 to 3 Example shown. 1 is an overall view of a vacuum carburizing apparatus 1 in which a reference numeral 2 a vacuum carburizing furnace, reference number 2a a furnace housing of the vacuum carburizing furnace, and reference numerals 3 a carburizing chamber, which carburizing chamber receives in its interior a material to be processed (machining material) and comprises a heating device, not shown. reference numeral 4 denotes a carburizing gas supply device that supplies carburizing gas to the inside of this carburizing chamber, and numerals 5 denotes a first opening and closing valve. reference numeral 6 denotes a suction line, which with the oven housing 2a Vacuum Carburizing Furnace 2 connected is. A vacuum pump for suction is with this suction line 6 connected. The vacuum pump includes an oil-sealed rotary pump 7 as well as a mechanical booster pump 8th , which are on the side of the input stage of the pump 7 is provided. reference numeral 9 denotes a second opening and closing valve, and reference numerals 10 denotes an inverter / controller for controlling a rotational speed of the mechanical booster pump 8th ,

reference numeral 15 denotes a return line which the suction line 6 located on an inlet side of the mechanical booster pump 8th is arranged with an outlet pipe 11 the oil-sealed rotary pump 7 connects, reference numerals 16 denotes a third open and close valve, which in the middle course of this return line 15 is arranged, and reference numerals 17 denotes a flow rate control valve which is arranged in a similar manner.

Next denotes reference numeral 20 a control device which at the start time and end time of a complete carburizing operation in accordance with a control program stored in the device open / close signals to the second open and close valve 9 outputs. Next gives the controller 20 When a carburizing period of clock carburizing begins, valve open signals to the first open and close valve 5 the carburizing feed device 4 and the third open and close valve 16 the return line 15 out. In addition, the controller gives 20 Valve clasp signals to both the first and third valves 5 and 16 when the carburization period ends. In addition to the opening and closing operation of these valves, the controller gives 20 based on a reading of the furnace internal pressure in the vacuum carburizing furnace 2 passing through a vacuum gauge 12 and internal furnace pressure set values P _n during the carburizing period and during the diffusion period, a speed control signal to the inverter is detected (hereinafter simply referred to as furnace internal pressure) 10 out. In this way the control device controls 20 the furnace internal pressure.

The vacuum carburizing device 1 has the above vacuum extraction system, which assumes an exemplary operating state, in which operating state, the second open and close valve 9 is open, the third open and close valve 16 the return line 15 is closed, and the oil-sealed rotary pump 7 and the mechanical booster pump 8th be made. When the vacuum carburizing device 1 in this exemplary operating condition, the rotational speed of the mechanical booster pump 8th between its minimum speed and its maximum speed, the furnace internal pressure P changes only over a range m in the region of a high-vacuum level, as it does by a curve M (which approximates a straight line) in 2 is shown.

On the other hand, in an exemplary operating state in which the third open and close valve 16 is open as it is in 1 is shown, a portion of the gas G of the gas, which from the oil-sealed rotary pump 7 is discharged to the inlet side (suction side) of the mechanical booster pump 8th recycled. As a result, the gas-suction amount from the furnace housing decreases 2a Vacuum Carburizing Furnace 2 by the amount of the recirculating gas G, with the result that the furnace internal pressure changes over a range n in the region of a low-vacuum level (pressure near the atmospheric pressure), as indicated by the curve N in FIG 2 is shown. Next, as in this example, in the return line 15 the flow rate control valve 17 is installed, the above curve N and the area n by a flow amount adjustment by means of the flow rate control valve 17 be changed up and down.

Subsequently, the diffusion period pressure P _{0 of} the clock carburizing within the above range m and the carburizing period pressure P ₁ within the above range n are selected (specifically, the above curve N and the range n im change Course of carburizing period slightly due to the introduction of carburizing gas). It is thus, as it is in 3A is shown, it is possible to subject the material to be processed, which has been subjected to a vacuum heating, a clock carburizing. The clock carburizing repeats carburizing at a predetermined interval at a carburizing period pressure P _{1 of} a predetermined low-vacuum level by opening the first and third opening and closing valves 5 and 16 and diffusion at a diffusion period pressure P _{0 of} a predetermined high-vacuum level by closing the first and third opening and closing valves 5 and 16 , In the 3 For example, a numerical value set in parentheses will be explained later. Further, by selecting a pump (oil-sealed rotary pump 7 and mechanical booster pump 8th ) as a vacuum pump having a sufficiently large suction speed, irrespective of the selection of the carburizing period pressure P _1, a quick switching characteristic from the carburizing period pressure P ₁ to the diffusion period pressure P _{0 is} achieved as indicated by the curve C in 4 is shown.

As described above, the opening and closing operation of the third open and close valve 16 driven in synchronization with the supply of the carburizing gas. That in the return line 15 flowing gas G is a comparatively clean mixed gas composed of hydrogen, nitrogen, methane and the like. In this gas were in the from the carburization chamber 3 Foreign object such as soot and tar contained in the exhaust gas flowing out through the vacuum pump. Since the above foreign matter does not conform to the third opening and closing valve 16 create and collect there, the third open and close valve 16 be used without disadvantage over a long period of time. Next, the return line 15 have a smaller pipe diameter than a pipe diameter of the exhaust pipe 6 , and thus also the third opening and closing valve 16 have a small size. As a result, the components which the area of the return line 15 form a small size and can be manufactured at low cost.

Next is in 3B a diagram of the furnace internal pressure for the case that the clock carburizing was performed in a state in which the third open and close valve 16 was closed for the purpose of comparison. 3B shows that the carburizing period pressure P ₁ becomes a pressure of a high-vacuum level, which is limited inside the projected area m. This means that the furnace internal pressure diagram of the curve A in FIG 4 which is a diagram of the furnace internal pressure in the case of a conventional apparatus which does not have a return pipe 15 having.

Next, a concrete case of clock carburizing by the use of the vacuum carburizing apparatus 1 is shown (the volume of the carburizing chamber 3 is 5 m ³ , the suction speed of the vacuum pump is 4 m ³ / min, the carburizing gas supply amount of the carburizing gas supply means 4 is 1 N m ³ / h). Clock carburizing processing of the material to be machined may be accomplished by a synchronized open / close operation of the third open and close valve 16 and the first open and close valve 5 with a desired cycle time (for example, the carburizing period is one minute, the diffusion period 10 Minutes) between a first operation state in which the carburizing period pressure P _{1 is} 1500 Pa, which is suitable in terms of carburizing efficiency and prevention of occurrence of soot and tar and the like, and a second operating state in which the diffusion period pressure P ₀ in 3A , 10 Pa. In contrast, under the condition corresponding to the conventional device, in which the third open and close valve could 16 always closed, as in 3B The carburizing period pressure can only be obtained from a high-vacuum level when the Carburizing period pressure P ₁ 500 Pa with respect to the diffusion period pressure P ₀ of 10 Pa.

The present invention is not limited to the above example. For example, as a vacuum pump, vacuum pumps of other types than the type of the above vacuum pump may optionally be used as a single type or as a combination of plural kinds. For example, if vacuum pumps of several types are installed in the apparatus, their rotational speeds can be controlled simultaneously. Next can on the flow rate control valve 17 be completely dispensed with, or may this be a fixed throttle.

As described above includes a vacuum carburizing device according to the exemplary embodiment a carburizing chamber, which in its interior a material to be processed picks up a vacuum pump which releases gas from inside the carburizing chamber sucks to obtain a vacuum, and a carburizing gas supply device, which feeds the carburizing gas into the carburizing chamber. Further, the carburizing gas supply means is formed the carburizing gas in a cyclic operation in the carburizing chamber to introduce the material to be processed thereby to suspend a vacuum carburizing. Here is the vacuum carburizing device characterized in that an inlet side (suction side) and an outlet side of the vacuum pump with each other in the manner of a bypass are connected by a return line, which return line provided with an opening and closing valve is; and in that a control device is provided, which the opening and closing valve opens, when in clock mode the introduction of the carburizing in the chamber carburizing gas to be introduced is started, and which the opening and closing valve closes, when the introduction of the carburizing gas ends.

at a thus constructed vacuum carburizing device is opened by of the open and close valve while the carburizing gas is introduced into the carburizing chamber is a part of the outlet gas of the vacuum pump (from the vacuum pump discharged gas) is returned to the inlet side of the vacuum pump. As a result, the amount of gas extracted from the vacuum chamber decreases and a furnace internal pressure of the vacuum carburizing apparatus (more specifically, FIG said pressure in the carburizing chamber) increases to a low-vacuum level (Range of atmospheric pressure) towards. With the desired Carburizing period pressure of a low-vacuum level, which by selecting the amount of the backflowing Outlet gas via the above return line can be obtained in combination with a diffusion period pressure in a state in which the open and close valve It is closed, which diffusion period pressure by the suction speed is determined, a clock carburizing be performed. Furthermore, it is also possible to have a fast switching characteristic from the carburizing period pressure to the diffusion period pressure because the vacuum pump is independent of its suction speed the carburizing period pressure determined as described above can choose.

In the gas passing through the above return line are flowing from the flowing from the carburizing chamber Suction gas through the vacuum pump foreign body such as Soot and tar removed. As a result, at the opening and clasp valve no deposit and accumulation of these foreign bodies on, and can the opening and Close valve without the occurrence of malfunction or the like a long period of time can be used.

Further may be the reflux line, in which a part of the outlet gas As described above, a smaller pipe diameter as a pipe diameter of the outlet pipe (gas outlet pipe) of the vacuum carburizing furnace to which the vacuum pump is connected is, have. Thus, the open and close valve This return line also a small size exhibit. As a result, compared to the case, in which the adjustable valve in the above suction line is installed, the components are reduced and the costs are reduced.

As described above, it is according to an exemplary Embodiment possible, at low cost to obtain a vacuum carburizing device which during the clock carburizing period a desired carburizing period pressure from a low-vacuum level, and a fast one Switching characteristic from the carburizing period pressure to a Diffusion period pressure reached, and which in terms of Reliability and durability is excellent.

Also when the foregoing invention is described in detail above with reference to specific embodiments thereof has been described it is obvious to the skilled person that numerous changes and modifications are possible without sacrificing the mind and the scope of protection defined in the claims Deviate from the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2000-1765 A [0002, 0004]
• - JP 2002-194526 A [0002]

Claims (3)

Vacuum carburizing device ( 1 ), which a carburizing gas in a carburizing ( 3 ) to subject a vacuum carburization material to be processed, comprising: a carburizing chamber ( 3 ), which receives in its interior the material to be processed; a vacuum pump containing gas from the carburizing chamber ( 3 ) sucks to obtain a vacuum; a carburizing gas supply device ( 4 ), which carburizing gas in a cycle operation in the carburizing ( 3 ); a return line ( 15 ) connecting an inlet side of the vacuum pump and an outlet side of the vacuum pump; an open and close valve ( 16 ), which in the course of the return line ( 15 ) is arranged; and a control device ( 20 ), which the opening and closing valve ( 16 ) opens when a supply of carburizing gas into the carburizing chamber ( 3 ) and which control device ( 20 ) the open and close valve ( 16 ) closes when the feed ends. Vacuum carburizing device ( 1 ) according to claim 1, further comprising: a flow rate control valve ( 17 ), which in the course of the return line ( 15 ), wherein the flow rate control valve ( 17 ) adjusts an amount of the carburizing gas flowing back to the inlet side of the vacuum pump. A method of carburizing a material to be processed, comprising: a step of carburizing gas into a carburizing chamber (54) in one cycle operation; 3 ) is supplied; a step in which a vacuum pump removes gas from the carburizing chamber ( 3 ) sucks to obtain a vacuum; a step in which an open and close valve ( 16 ), which in the course of a return line ( 15 ), which connects an inlet side of the vacuum pump and an outlet side of the vacuum pump, is actuated when supply of carburizing gas into the carburizing chamber (FIG. 3 ) is started; and a step in which the open and close valve ( 16 ) is closed when the supply of the carburizing gas into the carburizing chamber ( 3 ) ends.