DE102006047929A1 - Process for heat treatment - Google Patents

Abstract

The The invention relates to a method for heat treatment of bores (3) and breakthroughs in workpieces (1), wherein the hole (3) or the breakthrough of a wall (7) is enclosed and has at least two openings, in which first the wall (7) of the bore (3) or the breakthrough to a predetermined Temperature warmed up and subsequently chilled becomes. For cooling becomes a cooling fluid passed through the hole (3) or the breakthrough. The invention further relates to an apparatus for carrying out the method, a supply line (9), through which the cooling fluid of the bore (3) or fed to the breakthrough can be, wherein the supply line (9) is a connection device (11) is assigned, with which this at an opening (13) of the bore (3) or breakthrough and in the supply line (9) a first valve (17) is provided, with which they are closed can be.

Description

State of the art

The The invention relates to a method for heat treatment of bores and breakthroughs in workpieces according to the generic term of claim 1. Furthermore, it relates to a device for carrying out the Process.

To the wear protection and to increase the strength of holes and breakthroughs must this dependent be heat treated by the component material and the loads. There are different ones for this Known method. For example, to harden steel, this will be on a certain temperature at which a structural transformation takes place in austenite, heated and quenched after a predetermined holding period. This forms a martensitic structure, which is a higher one Has hardness and thus increases the life of the bore. An increased life is further achieved in that in the boundary layer of the bore compressive stresses can arise.

For the heat treatment On the one hand, local methods are known from the prior art, for example, inductive heating the component boundary layer and subsequent quenching with water or heating method by radiation, for example by laser or electron beam. To the targeted hardening of holes with large length / diameter ratios or complex internal geometries, these methods are not suitable because the needed accessibility neither for an inductor still for the different types of radiation, for example due to the cone angle or too low radiation adsorption at a flat angle of incidence, given is.

In addition to the local methods there are also through-hardening processes in which the entire component is heated in an oven and then quenched, for example, with cold gas or in a water or oil bath. The disadvantage here is that when drilling generally undesirable tensile residual stresses arise. Nevertheless, in order to obtain residual compressive stresses in the bore, it is necessary to weiterzubear the components with an additional process, for example by shot peening, consuming and costly. Due to the poor deterrence, as the inside of the component cools the slowest, the holes in the core, viewed over the cross section, have lower hardness values for larger components. Another method used for hardening bores is, for example, so-called case hardening. In this, the carbon content in the component surface is increased by adjusting a carbonaceous atmosphere in the furnace. This increases the surface hardness of certain materials. Case hardening is used, for example, for hardening bores in high-pressure injection components. An apparatus for case hardening a bore in a workpiece is for example US 4,208,040 known. For this purpose, the workpiece is clamped with the bore in a device. Through the bore a carbon-containing gas is passed, and the workpiece is heated from the outside.

disadvantage case hardening are the very long process times. In addition, the carburizing of Holes with large Length / diameter ratios Problems arise as a result of limited diffusive mass transport in the gas phase. The above-described unfavorable hardness distribution over the Component cross-section can also exist here after quenching.

Disclosure of the invention

Advantages of the invention

The The invention relates to a method for heat treatment of bores and breakthroughs in workpieces, wherein the bore or breakthrough surrounded by a wall is and at least two openings having. In the method according to the invention will be first the wall of the hole or breakthrough to a predetermined Temperature warmed up and then cooled. To the cooling down becomes a cooling fluid passed through the hole or breakthrough.

By the passage of a cooling fluid through the hole or breakthrough will be a targeted hardening of holes or breakthroughs with a short process duration. Furthermore, a better quenching effect achieved in the bore than that in the known from the prior art method is the case. hereby are also higher hardness values achieved in the hole. additional caused by the inventive method at high quenching intensities high residual compressive stresses in the bore or breakthrough due to temperature and microstructure gradients in the workpiece.

For heating, for example, the entire workpiece can be heated in an oven until the predetermined temperature of the wall is reached. In general, it is then necessary that this temperature is maintained for a predetermined period of time. In an oven, the heating generally takes place from the outside, so that a sufficiently long period of time must be taken into account for heating the workpiece. The heating of the workpiece from the outside, for example, with an electric heater or an induction heating done. When heating the workpiece from the outside, the heater is switched off after the required holding time and a cooling fluid is passed through the bore or the opening. In order to lower the inlet temperature of the cooling fluid further, it is possible that in the supply line for the cooling fluid, a heat exchanger is provided, in which the cooling fluid can be further cooled. Due to the lower temperature of the cooling fluid, the quenching intensity is increased.

Next the heating from the outside it is also possible that the wall of the bore or the breakthrough on the given Temperature is heated by passing a heating fluid through the bore becomes. The heating fluid preferably has a temperature for this purpose, which is equal or greater as the temperature to which the wall is to be heated. The heating up of the heating fluid is generally carried out in a heat exchanger. When the warming drilling or breakthrough with the aid of heating fluid, After the required holding time, the supply of the heating fluid is turned off and the cooling fluid passed through the hole.

In a first embodiment is used for heating and to cool down the same fluid used. Advantage of using only one fluid is that this is not due to a residue second fluid is contaminated.

alternative it is also possible that the heating fluid and the cooling fluid different fluids, wherein the heating fluid to a temperature above the predetermined temperature to which the wall is heated should, heated and the cooling fluid optionally cooled becomes. When using different fluids as heating fluid and as a cooling fluid can be used fluids, either specifically for heating or to cool down are suitable.

If the bore is heated with a heating fluid, this is preferably in a first heat exchanger heated. The heat can thereby for example by an electrical heating or by a second heating fluid. Preferably, the heat is applied by an electric heating. The heat exchanger can be in DC, in countercurrent, cross flow or mixtures of these types of flow operate.

When Heating fluid, for example, gases are used, based on the heating temperature heated were. Furthermore you can as heating fluid and multiphase fluids, for example, gases with it contained solid particles are used. Everyone else, too known in the art fluids that are heated to the heating temperature can, can used become.

Around the quenching intensity to increase, it is preferred that the cooling fluid chilled becomes. For this purpose, a second heat exchanger is preferably used. Of the second heat exchanger This is generally operated with a refrigerant. As cooling fluids to cool down The drilling are all usual Quench fluids. Preferred as a cooling fluid are water, water / salt solutions or oils. The cooling fluids can also be used under pressure to the evaporation temperature and thus the heat transfer to increase. It is also possible the bore with a cooling temperature cooled To cool the gas. In this case, the cooling rate is less than a liquid, for cooling is used, since gases have smaller heat transfer coefficients as liquids.

Next the use of two heat exchangers, wherein heating the heating fluid in a heat exchanger and cooling the cooling fluid in the other heat exchanger it is also possible that heating and cooling in the same heat exchanger carried out becomes. However, for this it is necessary that the heat exchanger first to heat up and then to cool down of the fluid is used. This can be done, for example, by that the heat exchanger flows through both a heating medium and a refrigerant can. Here, tempering coils, through which the heating medium or the refrigerant flows, for example, be traversed alternately by the heating medium or by the refrigerant, or it is possible that both for the heating medium as well the temperature control formed separate temperature control coils in the heat exchanger are. However, the use of two heat exchangers, one heats the heating medium and the other cools the refrigerant.

In order to achieve a rapid heating and cooling of the bore or the breakthrough, the cooling fluid and - if the wall of the bore or the opening is heated with a heating fluid - the heating fluid supplied through a first opening of the bore or the aperture and a second Opening the hole or breakthrough dissipated. As a result, the cooling fluid or the heating fluid can flow through the bore or breakthrough. Depending on the flow rate of the cooling fluid or the heating fluid and the specific heat capacity of the cooling fluid or the heating fluid, the speed at which the wall of the workpiece is cooled or heated, adjustable. Thus, for example, a faster flow through a faster cooling or heating and at a larger specific heat capacity of the heating fluid, the wall of the bore is also heated faster or cooled.

The The invention further relates to a device for carrying out the Method, wherein the device comprises a supply line, through which the cooling fluid the bore or the breakthrough can be supplied. The supply line is associated with a connection device with which this at an opening of the Hole or breakthrough can be attached. Alternatively, you can the supply line against the workpiece in which the breakthrough formed is to be pressed. In the supply line is a first valve provided, with which this can be closed. By the Supply line and the connection device, the cooling fluid can be targeted feed the bore. A targeted cooling of the Hole or breakthrough is possible.

If the heating of the wall of the bore or the breakthrough with takes place a heating fluid, so flows in a preferred embodiment near the connection device, a second supply line for the heating fluid. The first Valve is in this case in the flow direction seen in front of the mouth the second supply line arranged in the supply line. By the first valve leaves so the inflow of the cooling fluid release or close. In the second supply line, a second valve is arranged, with which the second supply line, over which supplied the heating fluid will, can be closed. By the embodiment in which the second supply line for the Heating fluid in the supply line opens It is not necessary after heating the wall of the hole or the breakthrough to change the supply line. It just has to the valve for the heating fluid is closed and the valve for the cooling fluid to be opened.

Around the cooling fluid to continue to cool to a predetermined temperature is in the supply line in one embodiment a first heat exchanger intended. The warming the heating fluid to a predetermined temperature is preferably carried out by an electric heater or a second heat exchanger, which is arranged in the second supply line.

If heating and cooling the wall of the bore or the breakthrough with only one fluid takes place, it is preferred that the second supply line from the Zufuhrlei tion branches off. Also in this case is in the second supply line the second heat exchanger taken, with which the fluid can be heated. The second Supply line forms a bypass, in front of the second heat exchanger branches off from the supply line and after the second heat exchanger returns to the supply line. Also in this embodiment are preferably in the supply line and in the second supply line in front of the mouth the second supply line - in flow direction seen - valves provided with which the supply line and the second supply line can be closed or released. For heating the Wall of the hole or the breakthrough is the supply line closed and the second supply line opened. To finally cool the wall to can, the second supply line is closed and the first supply line is opened.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description closer explained.

It demonstrate

1 an inventively designed device with external heating,

2 an inventively designed device in which the heating and cooling takes place with the same fluid,

3 an inventive device in which different fluids are used for heating and cooling.

Embodiments of the invention

1 shows an inventively designed device in which the workpiece is heated from the outside.

At the in 1 illustrated embodiment of a device for heat treatment of holes and openings in workpieces is a workpiece 1 in which a hole 3 or a breakthrough is formed, heated from the outside. This includes a heater 5 the workpiece 1 , As a heater 5 For example, an electric heater or an induction heater is suitable. Also, any further, known in the art heating, with a workpiece 1 can be heated from the outside, can be used.

The workpiece 1 first with the heater 5 heated to a predetermined temperature. Around the wall 7 the bore 3 To harden, it is necessary that the wall 7 is heated to a predetermined temperature. If the workpiece 1 Made of steel, so must the wall 7 the bore 3 For example, be heated to austenitizing temperature. Furthermore, the wall must be kept at this temperature for a predetermined period of time. After the desired holding time at austenitizing temperature, the heating 5 shut off and a cooling fluid through the hole 3 directed.

The cooling fluid is supplied via a supply line 9 the bore 3 fed. For this purpose, the supply line 9 with a connection device 11 with an opening 13 the bore 3 connected. For example, the cooling fluid flow needed to achieve the desired cooling rate is provided by a pump 15 set. A pump 15 is used when the cooling fluid is a liquid. However, if a gas is used as the cooling fluid, then instead of the pump 15 a blower used.

To avoid cooling fluid during the heating phase in the hole 3 is in the supply line 9 a valve 17 intended. The valve 17 will be closed as long as the workpiece 1 is heated and the heater 5 is turned on. As soon as the cooling process begins, the valve becomes 17 open. The cooling fluid may be from the supply line 9 into the hole 3 flow.

A higher cooling rate can be achieved, for example, by cooling the cooling fluid to a temperature below the ambient temperature. For this purpose, in the embodiment shown here, a heat exchanger 19 used. The cooling fluid flows through the heat exchanger 19 and is brought there to the desired temperature. In addition to a cooling of the cooling fluid, it is of course also possible to heat the cooling fluid. It is only necessary that the temperature of the cooling fluid is lower than the temperature of the wall 7 the bore 3 is, otherwise no cooling can take place. The temperature to which the cooling fluid is heated or cooled is dependent on the desired cooling process.

After completion of the cooling process, the valve 17 closed again and the workpiece 1 can be removed.

In 2 a device designed according to the invention is shown in which the heating and cooling of the bore takes place with a fluid.

For heating or cooling, a fluid through the hole 3 directed. This is the hole 3 with the supply line 9 connected. The connection of the supply line 9 with the hole 3 takes place as well as in the 1 illustrated embodiment with the connection device 11 , So that the fluid, which in the supply line 9 flows, not only to cool but also to heat the wall 7 the bore 3 can be used branches off the supply line 9 a second supply line 21 from. So not two pumps 15 needed is the pump 15 seen in the flow direction before the branch of the second supply line 21 arranged. If the fluid is not a liquid but a gas, then instead of the pump 15 a blower used.

Around the wall 7 the bore 3 to be able to heat, the fluid passing through the second supply line 21 flows, in a second heat exchanger 23 heated. In the second supply line 21 is still a second valve 25 recorded, with which the second supply line 21 can be opened or closed.

Around the wall 7 the bore 3 to warm, is the first valve 17 in the supply line 9 closed and the second valve 25 in the second supply line 21 open. The fluid thus flows through the second supply line 21 , is in the second heat exchanger 23 heated and flows from there further into the hole 3 , In the hole 3 the fluid gives heat to the wall 7 of the workpiece 1 from. The wall 7 is heated. The heated fluid is through the hole as long 3 Run until the required holding time, for which the temperature on the wall 7 must be maintained. After the heating process, the second valve 25 closed. Around the wall 7 the bore 3 To be able to cool down is now the first valve 17 open. The fluid flows through the supply line 9 , In the supply line 9 can optional the heat exchanger 19 be included. If the fluid is to be cooled to a temperature below the ambient temperature, this is done in the heat exchanger 19 , However, it is also possible, the fluid in the heat exchanger 19 as already at 1 described to be heated to a cooling temperature, which is above the ambient temperature. It is only necessary that the temperature of the fluid after flowing through the heat exchanger 19 lower than the temperature of the wall 7 the bore 3 , As soon as the cooling process is finished, the valve becomes 17 also closed. There is no more fluid flowing through the connection device 11 into the hole 3 , The workpiece 1 can be removed.

In 3 a device designed according to the invention is shown in a third embodiment. In the 3 illustrated embodiment differs from the in 2 illustrated embodiment in that for heating the wall 7 the bore 3 and to cool the wall 7 the bore 3 different fluids are used.

For heating the wall 7 the bore 3 a first fluid is used which passes through the second supply line 21 is supplied. Around the wall 7 Being able to heat is the valve 17 closed and the second valve 25 open. With a second pump 27 the heating fluid is through the second supply line 21 directed. The heating fluid is then in the second heat exchanger 23 heated to the heating temperature. In the hole 3 gives the heating fluid heat to the wall 7 and heats up this way. After the wall 7 is heated and optionally has been held at a predetermined holding temperature on the heating temperature, the second valve 25 closed. The heating process is finished. For cooling then the first valve 17 open. The cooling fluid may be from the supply line 9 into the hole 3 stream. The required temperature of the cooling fluid is in the heat exchanger 19 set. If necessary, the cooling fluid can be further cooled or heated here.

The cooling fluid flow required for cooling is supplied by the pump 15 set. If a very fast cooling of the wall 7 the bore 3 should be done, the largest possible cooling fluid flow through the hole 3 stream. Slower cooling is achieved by making the cooling fluid slower through the bore 3 flows. Furthermore, the cooling temperature can also be adjusted by the temperature of the cooling fluid. The colder the cooling fluid, the faster the cooling.

The same applies to the heating, as it according to the embodiment in the 2 and 3 he follows. The faster the wall 7 the bore 3 is to be heated, the greater the fluid flow of the heating fluid to choose. This is according to the embodiment in 2 with the pump 15 and according to the embodiment in FIG 3 with the second pump 27 set. Also, the heating rate can be adjusted by the temperature of the heating fluid. The higher the temperature of the heating fluid is chosen, the faster the wall heats up 7 on. To the temperature of the wall 7 To keep constant, it is preferred that the heating medium with the wall temperature through the hole 3 flows. This means that the temperature of the heating medium is set to the holding temperature as soon as it is reached.

Claims (12)

Method for heat treatment of bores ( 3 ) and breakthroughs in workpieces ( 1 ), whereby the bore ( 3 ) or the breakthrough of a wall ( 7 ) is enclosed and has at least two openings, in which first the wall ( 7 ) of the bore ( 3 ) or the breakthrough is heated to a predetermined temperature and then cooled, characterized in that for cooling a cooling fluid through the bore ( 3 ) or the breakthrough is passed. Method according to claim 1, characterized in that the entire workpiece ( 1 ) for heating by an outside of the workpiece ( 1 ) arranged heating ( 5 ) is heated until the predetermined temperature of the wall ( 7 ) of the bore ( 3 ) or breakthrough is reached. Method according to claim 1, characterized in that for heating the wall ( 7 ) of the bore ( 3 ) or the breakthrough to the predetermined temperature, a heating fluid through the bore ( 3 ), wherein the heating fluid has a temperature which is equal to or greater than the predetermined temperature, to which the wall ( 7 ) should be heated. Method according to claim 3, characterized in that the same fluid is used for heating and cooling, this being used for heating the wall to a temperature above the predetermined temperature to which the wall ( 7 ) is heated, and heated to cool the wall ( 7 ) is optionally heated or cooled to a predetermined temperature, wherein the predetermined temperature is lower than the temperature of the wall ( 7 ). A method according to claim 3, characterized in that the heating fluid and the cooling fluid are different fluids, wherein the heating fluid is heated to a temperature above the predetermined temperature to which the wall is to be heated, and the cooling fluid is optionally cooled or heated to a predetermined temperature , wherein the predetermined temperature is lower than the temperature of the wall ( 7 ). A method according to claim 4 or 5, characterized in that the heating or cooling of the cooling fluid in a first heat exchanger ( 19 ) and the heating of the heating fluid with an electric heater or in a second heat exchanger ( 23 ) he follows. Method according to one of claims 1 to 6, characterized in that the cooling fluid and optionally the heating fluid via a first opening ( 13 ) of the bore ( 3 ) or the breakthrough and via a second opening of the bore ( 3 ) or the breakthrough be dissipated. Device for carrying out the method according to one of claims 1 to 7, a supply line ( 9 ), through which the cooling fluid of the bore ( 3 ) or the breakthrough, wherein the supply line ( 9 ) a connection device ( 11 ) with which this at an opening ( 13 ) of the bore ( 3 ) or the breakthrough or wherein the supply line ( 9 ) against the workpiece ( 1 ) and in the supply line ( 9 ) a first valve ( 17 ) is provided, with which it can be closed. Apparatus according to claim 8, characterized ge indicates that in the supply line ( 9 ) near the connection device ( 11 ) a second supply line ( 21 ) opens for a heating fluid, wherein the first valve ( 17 ) in the flow direction before the mouth of the second supply line ( 21 ) in the supply line ( 9 ) and in the second supply line ( 21 ) a second valve ( 25 ) is arranged, with which the second supply line ( 21 ) can be closed. Apparatus according to claim 8 or 9, characterized in that in the supply line ( 9 ) a first heat exchanger ( 19 ) is provided, in which the cooling fluid can be cooled or heated to a predetermined temperature. Device according to one of claims 8 to 10, characterized in that in the second supply line ( 21 ) a second heat exchanger ( 23 ) or an electric heater is arranged, in which the heating fluid can be heated to a predetermined temperature. Device according to one of claims 8 to 11, characterized in that the second supply line ( 21 ) from the supply line ( 9 ) branches off.