Method of treating workpiece for fluid energy machine

Abstract

The invention relates to a method for treating a workpiece (100) suitable for a fluid energy machine, in particular a shaft (100) for a fluid energy machine, comprising the following steps: carrying out a first heat treatment process on the entire workpiece (100), the first heat treatment process comprises a first solution treatment process at a first preset temperature, a first quenching process and at least one first tempering process at a second preset temperature; and performing a second heat treatment process on one or more sections (110) of the workpiece (100), wherein the sum of these sections is less than the entire workpiece; the second heat treatment process comprises at least one second tempering process at a fourth preset temperature, or the second heat treatment process comprises a second solution treatment process at a third preset temperature, a second quenching process and at least one second tempering process at the fourth preset temperature; wherein the first heat treatment process and the second heat treatment process are carried out such that the impact toughness in one or more sections (110) of the workpiece (100) lies within a first predetermined value range and such that the magnetic induction in at least one other second section (120) of the workpiece (100) lies within a second predetermined value range.

Description

[0001] The present invention relates to a method for processing a workpiece for a fluid energy machine and a workpiece for a fluid energy machine. Background Technology

[0002] A fluid energy machine is a machine or device in which mechanical work is exchanged with a fluid (i.e., a gas and / or liquid). A fluid energy machine thus transfers work from the outside to the fluid (the working machine) or extracts energy from the fluid (the prime mover), which is then delivered to the outside as mechanical work. A turbomachine is a working machine that transfers energy between a rotor and a fluid. A turbomachine can be a turbine or a compressor. While a turbine transfers energy from the fluid to the rotor, a compressor transfers energy from the rotor to the fluid.

[0003] In such fluid energy machines, impellers can be arranged on a rotating shaft. For example, in a compressor like a cryogenic radial turbo compressor, the expander impeller and the compressor impeller can be fixed to both ends of a steel shaft. This shaft must withstand the high torque generated by the fluid flowing through the impellers. For example, in cryogenic applications, the process fluid flowing through the impellers can reach temperatures as low as 50 K at the expander outlet and / or the compressor inlet. Shaft rotation can be guided by magnetic bearings, which may include a pair of radial bearings, a pair of auxiliary bearings, and an axial bearing. The axial bearings can interact directly with an axial thrust disc, which can be part of the shaft, wherein the shaft is ferromagnetic. A (high-speed) motor or generator can also be mounted, for example, in the central portion of the shaft, in conjunction with magnetic or oil bearings. A high level of ferromagnetism can then also be required in the central portion of the shaft. Temperature gradients can occur along the shaft axis. The temperatures experienced can depend on the motor's limiting conditions.

[0004] In some cryogenic applications, shaft materials may need to combine high impact toughness at one or both ends and at the coldest temperature they experience (which could be 77K, i.e., -196°C or even lower), and secondarily, high magnetic induction to maintain high axial thrust and / or to allow the operation of high-speed motors or generators. This combination of high impact toughness and high magnetic induction can be difficult to achieve because high-speed magnetic steels are generally unsuitable for very cold cryogenic temperatures, while cryogenic steels exhibit poor ferromagnetism and are typically soft magnetic materials. Alloys for shafts used in cryogenic applications down to 77K and below can be optimized for impact toughness, but are typically poorly ferromagnetic because ferromagnetism and impact toughness are negatively correlated. Therefore, the axial thrust of extremely cold expanders or compressors may have to be limited, potentially preventing them from operating at maximum efficiency. Furthermore, high-speed motors or generators may not be usable. Conversely, if high axial thrust should be maintained, or if a high-speed motor or generator should be used, the minimum temperature of the corresponding process gas may be limited due to the use of hard magnetic materials, potentially restricting applications to mildly cold conditions.

[0005] Therefore, there is a desire to improve the workpieces used in fluid energy machines, especially the shafts used in fluid energy machines. Summary of the Invention

[0006] This invention relates to a method for processing a workpiece for a fluid energy machine, and a workpiece for a fluid energy machine having the features of the independent claim. Embodiments and advantages form the subject matter of the dependent claims and the subject matter of the following description.

[0007] The corresponding fluid energy machine can be suitably configured for cryogenic applications, particularly for temperatures as low as 77 K or even lower. The workpiece is, in particular, a shaft, preferably a shaft for the rotor of the corresponding fluid energy machine, on which one or more impellers can be arranged, for example, at one or both axial ends of the shaft. Specifically, the workpiece is made of a material with a single chemical composition. The workpiece is particularly manufactured in one piece. The workpiece can suitably be (especially relative to the main axis or axis of rotation) axisymmetric. The length of the workpiece in the axial direction can be particularly greater than the maximum diameter of the workpiece in the radial direction.

[0008] According to the invention, a first heat treatment process is performed on the entire workpiece, wherein the first heat treatment process includes a first solution treatment process at a first predetermined temperature, a subsequent first quenching process, and a subsequent first tempering process at a second predetermined temperature. Each of the at least one first tempering process can be performed at a different, separately predetermined second temperature. Suitably, these first tempering processes can be separated by air cooling.

[0009] The second heat treatment process is performed on one or more sections or segments of a workpiece, particularly on one or more axial sections having a predetermined length in the axial direction. This section or these sections should also be referred to hereinafter as one or more first sections (i.e., at least one first section). Specifically, all these (first) sections together suitably form only a part of the entire workpiece. Therefore, the sum of all these first sections on which the second heat treatment is performed does not correspond to or aggregate the entire workpiece. The sum of all these sections is less than the entire workpiece. The second heat treatment process is therefore not performed on the entire workpiece, but only on a part of the workpiece.

[0010] The second heat treatment process includes at least one second tempering process at a fourth predetermined temperature. Alternatively, the second heat treatment process includes a second solution treatment process at a third predetermined temperature, a subsequent second quenching process, and then at least one second tempering process at the fourth predetermined temperature. Each of the at least one second tempering process may be performed at a different, separately predetermined fourth temperature. The second tempering processes may be separated by air cooling.

[0011] The corresponding first and second solution treatment processes should be specifically understood as heating the workpiece material to a predetermined temperature, in particular causing one or more components of the workpiece material to enter the solid solution.

[0012] The corresponding first and second quenching processes should be specifically understood as rapid cooling of the workpiece material, especially in air, following the corresponding solution treatment process. Through this quenching process, the corresponding material composition retains the properties of the melt.

[0013] The corresponding first and second tempering processes should specifically be understood as heating the workpiece material to a corresponding temperature, which is suitably below the critical point in the phase equilibrium curve of the corresponding material. Subsequently, the workpiece material is allowed to cool, for example, in still air.

[0014] Because the first heat treatment process is performed on the entire workpiece, the mechanical, physical, or magnetic properties can be uniformly affected throughout the entire workpiece. In the case where the second heat treatment process is not performed on the entire workpiece, but only on specific one or more first sections of the workpiece, the mechanical, physical, or magnetic properties in these first sections can be affected individually, particularly independently of the remaining sections of the workpiece. With the aid of this space-constrained second heat treatment process, the workpiece can therefore be selectively heat-treated, especially selectively tempered. Therefore, the properties in different sections of the workpiece can be adjusted individually and independently of each other, and can be suitably optimized for the specific application of the corresponding fluid energy machine. If, in that specific application, there are different requirements for different kinds of properties such as impact toughness and magnetic induction, for example in cryogenic applications, selective tempering of the workpiece suitably allows these requirements to be met. The present invention therefore allows for significant improvements to workpieces for desired applications in fluid energy machines.

[0015] The present invention also relates to a workpiece for a fluid energy machine, particularly a shaft of a fluid energy machine, which is processed according to an embodiment of the method according to the invention. The workpiece according to the invention and the embodiments and advantages of the method according to the invention should arise in a similar manner from this description.

[0016] According to the invention, a first heat treatment process and a second heat treatment process are performed such that the impact toughness in one or more (first) segments of the workpiece is within a first predetermined value range, and the magnetic induction in at least one other second segment of the workpiece is within a second predetermined value range. Suitably, the at least one second segment corresponds to that portion of the workpiece on which the second heat treatment process is not performed. Each of the first segments is also, in particular, an axial segment having a predetermined length in the axial direction. The first and second segments may be axially adjacent to each other. Suitably, the first and second segments do not overlap in the axial direction. An axial transition segment may exist between adjacent first and second segments.

[0017] Specifically, by means of a second heat treatment process performed only on the first segment, the impact toughness in the first segment can be affected, and a specific value of the impact toughness can be adjusted to be within a first value range. By means of a first heat treatment process performed on the entire workpiece (i.e., also on the second segment), the magnetic induction in the second segment is particularly affected, and a specific value of the magnetic induction is suitably adjusted to be within a corresponding second value range. Therefore, after the workpiece is treated by means of the first and second heat treatment processes, the different axial segments of the workpiece have different, individual mechanical, physical, and / or magnetic properties. In particular, in these different first and second segments of the workpiece, the impact toughness and magnetic induction can be individually adjusted and optimized for the specific application of the corresponding fluid energy machine. The corresponding impact toughness and the corresponding magnetic induction can be suitably uniform in the radial direction in the corresponding first or second segment (i.e., particularly uniform from the surface to the center of the corresponding first or second segment).

[0018] Impact toughness and magnetic induction are always negatively correlated with the temperature of the heat treatment process. That is, the lower the temperature of the heat treatment process, the higher the magnetic induction that can be achieved. Conversely, the higher the temperature of the heat treatment process, the higher the impact toughness achieved. However, by performing a first heat treatment process and a second heat treatment process, impact toughness and magnetic induction can be adjusted individually and independently in different sections of the workpiece. In particular, by means of the first heat treatment process, the magnetic induction in the second section can be adjusted to be within a second predetermined value range. By means of the second heat treatment process, the impact toughness in the first section can be adjusted to be within a corresponding first predetermined value range. Suitablely, high impact toughness and high ferromagnetism can be combined in the same workpiece, which is specifically made of a single chemical composition and is manufactured in one piece. Selective tempering of the workpiece during the second heat treatment process particularly allows for the combination of high impact toughness or ductility and ferromagnetism in the workpiece.

[0019] Suitably, one or more final tempering processes of the second heat treatment process modify the final mechanical properties of the first section. If several second tempering processes are performed during the second heat treatment process, these subsequent second tempering processes are specifically performed at a reduced tempering temperature (i.e., at a reduced fourth temperature). The higher the tempering temperature, the lower the strength of the workpiece material achieved, and in addition, the higher the ductility and impact toughness. That is, after a tempering process at a higher temperature, the workpiece material is, for example, softer than after a tempering process at a lower temperature. In particular, to achieve optimal impact toughness characteristics, the first section of the workpiece may be double-tempered in the second heat treatment process (i.e., two second tempering processes may subsequently be performed at a reduced fourth temperature).

[0020] Suitably, if the workpiece being processed is arranged as a shaft, the shaft is particularly capable of withstanding high torque due to its strength, suitably due to its yield stress and ultimate tensile strength, even at cryogenic temperatures as low as 77K or lower. High impact toughness suitably prevents brittle failure of the shaft in the event of impacts during operation. In cryogenic applications, the material should exhibit sufficient impact toughness to prevent catastrophic failure, independent of its actual strength. The impeller can be suitably arranged in a corresponding first section of the shaft with high impact toughness. Furthermore, high magnetic induction allows the use of magnetic bearings to guide the shaft in a corresponding second section. High magnetic induction also allows the mounting of a (high-speed) motor or generator in the corresponding second section. In particular, the shaft can be treated to have high impact toughness at one or both of its axial ends and at its coldest temperature experienced (e.g., 77K or lower), and is treated to have high magnetic induction to maintain high axial thrust and / or to allow the operation of a high-speed motor or generator. Therefore, the axial thrust on the shaft is suitably not limited, and the fluid energy machine can operate particularly efficiently or even at maximum efficiency. Furthermore, the minimum temperature of the corresponding process gas is not necessarily limited.

[0021] According to one embodiment, a first heat treatment process and a second heat treatment process are performed such that the residual austenite level of the workpiece material is within a first predetermined austenite level range in one or more first segments of the workpiece, in order to control the impact toughness to be within a first predetermined value range in one or more segments of the workpiece. Furthermore, the first heat treatment process and the second heat treatment process are performed such that the residual austenite level of the workpiece material is within a second predetermined austenite level range in at least one other second segment of the workpiece, in order to control the magnetic induction to be within a second predetermined value range in at least one other second segment of the workpiece, wherein the first predetermined austenite level range and the second predetermined austenite level range are different from each other. Specifically, a specific level of austenite in the workpiece material causes both impact toughness and magnetic properties to increase or decrease. By means of different heat treatment processes and their corresponding temperatures, the austenite in the workpiece material can be at least partially transformed into martensite. Specifically, by means of the first and second heat treatment processes, the level of retained austenite (i.e., the amount of austenite that has not been converted into martensite) in the corresponding sections of the workpiece can be controlled to be within the corresponding austenite level range, and thus at different levels within the same workpiece. Therefore, by adjusting the corresponding austenite level in the corresponding workpiece sections, the impact toughness and material inductance can be adjusted accordingly.

[0022] According to one embodiment, the first, second, third, and fourth predetermined temperatures are each determined based on the material of the workpiece. The first to fourth temperatures are specifically determined according to the specific workpiece material, such that impact toughness and magnetic induction can be adjusted to within corresponding predetermined value ranges by means of appropriate heat treatment processes. The first to fourth temperatures can be specifically determined to individually control specific levels of retained austenite at different locations within the workpiece. Suitably, two degrees of freedom exist for adjusting impact toughness and magnetic induction. In particular, by selecting a specific chemical composition of the workpiece material and / or by selecting specific first to fourth temperatures for the first and second heat treatment processes, impact toughness and magnetic induction can be adjusted to within corresponding value ranges. Specifically, the first to fourth predetermined temperatures are each determined based on the chromium equivalent (Cr) of the workpiece material. eq ) and nickel equivalent (Ni eq The ratio of chromium equivalent to nickel equivalent is used to determine this. The specific ratio of chromium equivalent to nickel equivalent (Cr...) eq / Ni eq In particular, it allows for the formation of retained austenite to be more or less readily. The lower the ratio, the more retained austenite can be formed.

[0023] Other degrees of freedom exist for adjusting impact toughness or magnetic induction. The parameters of carbon, nitrogen, silicon, and molybdenum content (provided by the chemical composition) and grain size (provided by the tempering duration) do not affect the retained austenite ratio, which itself affects impact toughness and magnetism, but they only affect impact toughness and the DBTT (ductile-brittle transition temperature). The elements listed in the chemical composition play a role in the formation of intermetallic precipitates. By adjusting these parameters, impact toughness can be altered without changing the magnetic induction.

[0024] According to one embodiment, the first predetermined range of impact toughness is between 10 J and 20 J at 77 K, particularly between 10 J and 20 J at 20 K. Specifically, the impact toughness in the first segment is adjusted to be essentially 15 J at 77 K. For example, the impact toughness of the workpiece can be assessed by means of the so-called "Charpy impact test" or "Charpy V-notch test," a standardized high strain rate test to determine the amount of energy absorbed by the workpiece material during fracture. Alternatively or additionally, the lower limit of the second predetermined range of magnetic induction is 1.48 T at a magnetic field of 20 kA / m. Alternatively or additionally, the upper limit of the second predetermined range is 5.00 T at a magnetic field of 20 kA / m.

[0025] According to one embodiment, during the second heat treatment process, a cooling process is performed on at least one transition section to a predetermined fifth temperature (e.g., 200°C or lower). This at least one transition section is located between one or more first sections and at least one second section. Suitably, such a transition section is located between axially adjacent first and second sections. The cooling process can be performed, for example, by means of an airflow or by means of a spiral coil containing a water flow. This cooling process, in particular, prevents the characteristics of the second section (which are adjusted during the first heat treatment process) from being affected during the second heat treatment process. The intensity of the corresponding cooling during the cooling process can, in particular, allow for minimizing the axial length of the corresponding transition section and further allow for suitably increasing the axial length of the first and second sections. For example, the lengths of the individual sections can be adjusted to accommodate a high-speed motor or generator mounted in the middle of the shaft. When the shaft is designed for use with a magnetic axial thrust bearing, a cooling process may not be necessary; in this case, only the center disc should be strongly magnetic. Furthermore, if the shaft ends are smaller in diameter than the middle portion of the shaft, temperature rise will also be limited due to conductive heat transfer.

[0026] According to one embodiment, at least one temperature sensor is provided at a predetermined location on the surface and / or inside the workpiece. During the first and / or second heat treatment processes, the temperature at the corresponding predetermined location is monitored by means of at least one temperature sensor. For example, the corresponding temperature sensor may be welded to the workpiece surface at the corresponding location. To provide the corresponding temperature sensor inside the workpiece, these sensors may be inserted, for example, through a hole drilled from the surface of the workpiece toward the corresponding location. The temperature at the corresponding location can be specifically monitored to ensure proper execution of the second heat treatment process. During the second heat treatment process, the temperatures at different locations on the surface of the workpiece in the first section should, in particular, have the same value or at least substantially the same value within a predetermined tolerance margin. During the development or calibration phase, the temperature sensor inside the workpiece can be used, in particular, to calibrate the corresponding apparatus used to perform the second heat treatment process. After the second heat treatment process, the temperature sensor can be removed from the workpiece. For example, a type K thermocouple can be used as the temperature sensor. A type K thermocouple is a temperature sensor having conductors made of chromium-nickel alloy and aluminum-nickel alloy. The requirements for these type K thermocouples are defined in standards ANSI / ASTM E230 or IEC 60584.

[0027] Specifically, temperature sensors can be placed along the entire length of the workpiece. During the second heat treatment process, only the corresponding first section of the workpiece should be heat-treated, while the rest of the workpiece should be kept cool by means of a cooling process. The corresponding temperature sensors placed in these cooled sections can particularly allow for control of the cooling level. The cooling process can be regulated, for example, using a loop regulator or a closed-loop regulator. The temperature sensors can generate corresponding measurements for this closed-loop regulation. The comparison between the measurements and the corresponding setpoint can determine the cooling power to be provided, for example, by means of water or air flow. The temperature sensors and the cooling process can suitably allow for control of the temperature gradient between the cold section and the heat-treated section. The number of temperature sensors is specifically selected to allow closed-loop control to keep the sections not receiving the second heat treatment cooled. Loop control can suitably allow for avoiding an excessively strong cooling process, which could negatively affect the second heat treatment process.

[0028] According to one embodiment, at least one set of temperature sensors is disposed at a predetermined axial position (i.e., a predetermined position in the axial direction) of the workpiece, each set of temperature sensors comprising at least two temperature sensors disposed on the surface of the workpiece at a predetermined, particularly equidistant, distance in the circumferential direction. Each set of temperature sensors is thus suitably distributed uniformly around the circumference of the workpiece at a particular axial position, for example, to monitor whether the temperature of the workpiece surface remains constant along the circumference during a second heat treatment process. For example, each set of temperature sensors may particularly include four temperature sensors, which allows for efficient and accurate monitoring of the surface temperature at the corresponding axial position.

[0029] Alternatively or additionally, at least one temperature sensor is disposed inside the workpiece on the main axis or rotation axis of the workpiece at a predetermined axial position. These sensors may be disposed, in particular, by means of insertion into a fine hole drilled radially from the surface toward the axis. During the development or calibration phase, these temperature sensors on the workpiece axis may be used, in particular, to calibrate the corresponding apparatus for performing the second heat treatment process.

[0030] According to one embodiment, a first set of temperature sensors is disposed at a first axial position corresponding to a first axial end of one or more first segments in the axial direction. Alternatively or additionally, a second set of temperature sensors is disposed at a second axial position corresponding to a second axial end of one or more first segments in the axial direction. This second end is therefore particularly opposite to the first end in the axial direction. This second axial end specifically corresponds to the interface between the corresponding first segment and the corresponding transition segment, which is located between the corresponding first segment and the adjacent second segment. A third set of temperature sensors is suitably disposed at a third axial position between the first and second axial positions, particularly in the middle between the first and second axial positions. During the second heat treatment process, all these temperature sensors in the first, second, and third sets of sensors should specifically show the same temperature value or at least substantially the same temperature value within a predetermined tolerance margin. Alternatively or additionally, a fourth set of temperature sensors may be disposed at the interface between at least one transition segment and at least one second segment. The temperature measured by the sensors in this fourth set should be particularly lower than the aforementioned fifth predetermined temperature, for example, lower than 200°C.

[0031] According to one embodiment, the second heat treatment process is performed on one or more end segments of the workpiece, particularly on one or more end segments extending axially from the axial end of the workpiece for a predetermined length. In this case, the workpiece particularly includes a second segment. This second segment may extend axially, for example, between two end segments. If only one end segment is treated during the second heat treatment process, the second segment may be adjacent to the corresponding first segment and may extend axially to another axial end of the shaft. In the case of a shaft, these end segments may be suitably treated in the second heat treatment process to have high impact toughness and high strength, such that one or more impellers can be arranged in these end segments, and such that the shaft can withstand the high torque generated by the impellers and prevent brittle failure. The two end segments may be treated identically, for example, during the second heat treatment process. The corresponding third and fourth temperatures of the corresponding second heat treatment processes performed on different axial end segments may also be changed. Thus, the two axial end segments may be treated individually to have separate impact toughness.

[0032] According to one embodiment, the third predetermined temperature is the same as or at least substantially the same as the first predetermined temperature. Therefore, the first and second solution treatment processes are performed, particularly at the same or at least substantially the same temperature. For example, the first and third predetermined temperatures differ from each other by no more than 10°C, particularly no more than 5°C, and especially no more than 1°C.

[0033] According to one embodiment, the first heat treatment process is performed using a heat treatment furnace. The workpiece can be fully arranged inside the heat treatment furnace such that the entire workpiece can be uniformly heated during the first solution treatment process and at least one first tempering process.

[0034] According to one embodiment, the second heat treatment process is performed using an induction furnace and / or an induction local heating device and / or a radiant furnace and / or a cooling device. The radiant furnace may, in particular, include a predetermined number of light bulbs, such as four or six bulbs. With the aid of the induction furnace, the induction local heating device, and / or the radiant furnace, the first section can be locally heated, especially without heating the second section. With the aid of the cooling device, at least one transition section between the first and second sections can be particularly cooled during the second heat treatment process.

[0035] According to one embodiment, the workpiece is made of martensitic stainless steel (MSS) or precipitation-hardening stainless steel (PHSS). Martensitic stainless steel is a stainless steel alloy having a martensitic crystal structure. Precipitation-hardening stainless steel is a corrosion-resistant stainless steel alloy that may include copper, molybdenum, aluminum, titanium, or combinations thereof. These types of materials are heat-treatable alloys, and their final properties depend particularly on the solution treatment temperature and the (single or double) tempering temperature. In particular, the level of retained austenite in the workpiece material (i.e., the level of austenite that has not been transformed into martensite) can be controlled so that the impact toughness and material inductance are within corresponding value ranges.

[0036] According to one embodiment, a fluid energy machine is a working machine (i.e., a machine that transfers work from the outside to a fluid). Specifically, the fluid energy machine is a rotating turbine machine, particularly a compressor or turbo compressor or cryogenic turbo compressor, especially for transferring energy from a rotor to a fluid. The fluid energy machine specifically includes a rotor, wherein a shaft may be configured for the rotor of the fluid energy machine. The fluid energy machine is particularly designed for cryogenic applications, particularly for temperatures as low as 77K or even lower. The fluid energy machine may particularly be a turbo compressor having at least one cryogenic turbine side operating at a process temperature of 77K or lower, or having both a cryogenic turbine and a compressor, equipped with axial magnetic bearings and / or a high-speed motor or generator. Processing workpieces according to embodiments of the invention particularly allows operation of the corresponding fluid energy machine with process fluids in deep cryogenic conditions as low as 77K or even as low as 20K and utilizes the advantage of high ferromagnetism in the central portion of the shaft. This allows for the possibility of compensating for high axial thrust with magnetic bearings and / or adding a high-speed motor or high-speed generator to the fluid energy machine.

[0037] Further advantages and developments of the invention are specified in the description and associated drawings.

[0038] Of course, the features mentioned above and explained below can be used not only in the indicated combinations, but also in other combinations or independently, without departing from the scope of the invention.

[0039] The present invention is schematically illustrated in the accompanying drawings according to exemplary embodiments, and will be described in detail below with reference to the drawings. Attached Figure Description

[0040] Figure 1 A workpiece that can be processed according to an embodiment of the method according to the invention is shown schematically in a side view.

[0041] Figure 2 shows a side view ( Figure 2a ) and front view ( Figure 2b The diagram schematically illustrates a workpiece that can be processed according to an embodiment of the method according to the invention.

[0042] Figure 3 An embodiment of the method according to the present invention is illustrated schematically in block diagram form. Detailed Implementation

[0043] Figure 1 The workpiece 100 is schematically shown in a side view, specifically as a shaft to be used as a rotor in a fluid energy machine, such as a turbomachine, such as a compressor for cryogenic applications, such as a cryogenic turbocompressor.

[0044] Shaft 100 is symmetrical about the principal axis or axis of rotation 105. The length of shaft 100 in the axial direction is greater than its maximum diameter in the radial direction. Shaft 100 is made of a material with a single chemical composition and is manufactured in one piece.

[0045] The shaft includes a first axial end 101 and an opposing second axial end 102. An impeller should be arranged on a first section 110 of the shaft 100, particularly at an end section extending axially from the first axial end 101 for a predetermined length. In this axial end section 110, the shaft 100 should have high impact toughness and high strength to prevent brittle failure and withstand the high torque generated by the impeller.

[0046] In the second section 120, which is axially adjacent to the first section 110, the shaft 100 should have high magnetic induction, for example, to enable the use of magnetic bearings and / or to add a high-speed motor or high-speed generator. The first section 110 and the second section 120 do not overlap, but are separated by a transition section 130.

[0047] Shaft 100 should be treated according to an embodiment of the method according to the invention in order to adjust its mechanical and magnetic properties. In particular, shaft 100 should be treated to have high impact toughness in the first section 110 and high magnetic induction in the second section 120 at low temperatures as low as 77K, especially as low as 20K.

[0048] Before processing shaft 100 accordingly, multiple temperature sensors (e.g., type K thermocouples) are placed at predetermined locations on the surface and inside the workpiece, as should now be explained with reference to Figure 2.

[0049] Figure 2a A portion of axis 100 is shown in a side view. Figure 2b The previous view shows the first segment 110 of shaft 100.

[0050] like Figure 2a and Figure 2b As shown, several sets of temperature sensors 210, 220, 230, and 240 are provided at predetermined axial positions on the workpiece, wherein each set of temperature sensors includes several temperature sensors disposed on the surface of the shaft at predetermined equidistant distances in the circumferential direction.

[0051] Specifically, a first set 210 comprising four temperature sensors 211, 212, 213, and 214 is disposed at a first axial position 201, which corresponds to the first axial end of the first segment 110 (i.e., the first axial end 101 of the shaft). For example, it can be... Figure 2b As seen in the image, these four temperature sensors 211, 212, 213, and 214 are evenly distributed around the circumference of axis 100.

[0052] The second set 220 of temperature sensors also includes four temperature sensors. Figure 2a In the image, only three sensors from sensors 221, 222, and 223 of the second sensor set 220 can be seen. This second set 220 is located at a second axial position 202, which corresponds to the second axial end of the first segment 110, and this second axial end corresponds to the interface between the first segment 110 and the transition segment 130. According to... Figure 2b The four sensors of the first sensor set 210 and the second sensor set 220 shown are evenly distributed around the circumference of axis 100.

[0053] The third set of temperature sensors 230 also includes four temperature sensors, although only three of these sensors 231, 232, and 233 are available. Figure 2a As seen in the image. The third sensor assembly 230 is positioned at a third axial position 203 between the first axial position 201 and the second axial position 202, particularly in the middle between the first axial position 201 and the second axial position 202, and therefore particularly in the middle of the first segment 110. According to... Figure 2b The four sensors of the first sensor set 210 and the third sensor set 230 shown are evenly distributed around the circumference of axis 100.

[0054] The fourth set of temperature sensors 240 also includes four temperature sensors, of which only three of these sensors 241, 242, and 243 are available. Figure 2a As seen in the image, the fourth sensor assembly 240 is positioned at a fourth axial position 204, which corresponds to the interface between the transition section 130 and the second section 120. According to... Figure 2b The four sensors of the first sensor set 210 and the fourth sensor set 240 shown are evenly distributed around the circumference of axis 100.

[0055] In addition, multiple temperature sensors are installed inside the shaft 100 on the main axis 105 at a predetermined axial position.

[0056] Figure 2b A temperature sensor 250 is shown, which is disposed on the main axis 105 at a first axial position 201. Correspondingly, one such temperature sensor is disposed on the main axis 205 at each of the second axial positions 202, the third position 203, and the fourth axial position 204. These sensors are disposed by insertion into holes drilled radially from the surface toward the axis 105.

[0057] By means of all these temperature sensors disposed on the surface of the shaft 100 and on the main axis 105, the corresponding temperature is monitored during the processing of the shaft according to an embodiment of the invention.

[0058] The processing of shaft 100 will now refer to Figure 3 The figure illustrates, schematically, an embodiment of the method according to the present invention.

[0059] In the first step 301, various temperature sensors are provided to the shaft, as explained above. In step 302, calibration of the furnace and apparatus for shaft processing is performed based on the temperature values ​​measured by temperature sensors 250 disposed inside the shaft 100 on the main shaft 105.

[0060] In step 310, a first heat treatment process is performed on the entire shaft 100, for example, using a heat treatment furnace. During this first heat treatment process 310, a first solution treatment process is performed in step 311 at a first predetermined temperature T1 (i.e., heating the entire shaft 100 to the first predetermined temperature T1). Subsequently, after the first solution treatment process 311, a first quenching process is performed in step 312, for example, in air, wherein the shaft 100 is rapidly cooled.

[0061] Subsequently, in step 313, a first tempering process is performed on the entire shaft 100 at a predetermined second temperature T2, wherein the shaft 100 is heated to the corresponding second temperature T2, which is below the critical point in the phase equilibrium curve of the workpiece material. Several such first tempering processes can also be performed during the cooling cycles in between, wherein during each of these several first tempering processes, the shaft 100 is heated to a separate second temperature T2.

[0062] By means of the first heat treatment process 310, the magnetic induction in the second section 120 is adjusted to be within a predetermined range (e.g., between 1.48T and 5.00T at a magnetic field of 20 kA / m). Suitably, the lower the second predetermined temperature T2, the higher the magnetic induction that can be achieved in the second section 120.

[0063] Specifically, by means of the first heat treatment process 310, the level of residual austenite in the second section 120 is adjusted to be within the corresponding predetermined austenite level range, so that the magnetic induction can be adjusted to be within the corresponding value range.

[0064] For example, the material of shaft 100 can be precipitation hardening stainless steel (PHSS), such as stainless steel 1.4542 (i.e., X5CrNiCuNb16-4). In this case, the first predetermined temperature T1 of the first solution treatment process 311 can be between 1030°C and 1050°C. The predetermined second temperature T2 of the first tempering process 313 can be, for example, 620°C, 590°C, or 550°C.

[0065] Alternatively, the material of shaft 100 may be, for example, martensitic stainless steel (MSS), such as stainless steel 1.4313 (i.e., X3CrNiMo13-4). In this case, the first predetermined temperature T1 of the first solution treatment process 311 may be between 950°C and 1050°C. The predetermined second temperature T2 of the first tempering process 313 may be, for example, 550°C or 520°C.

[0066] Following the first heat treatment process 310, a second heat treatment process 320 is performed on the first segment 110 of the shaft 100, for example, using an induction furnace, an induction local heating device, or a radiation furnace. During this second heat treatment process 320, in step 321, a second solution treatment process is performed at a third predetermined temperature T3, wherein the first segment 110 is heated to the third predetermined temperature T3. Following the second solution treatment process 321, in step 322, a second quenching process is performed, wherein the first segment 110 is rapidly cooled in air.

[0067] Subsequently, in step 323, at least one second tempering process is performed on the first segment 110 at a predetermined fourth temperature T4, wherein the first segment 110 is heated to a corresponding fourth temperature below the critical point of the shaft material. Suitably, several such second tempering processes are performed with cooling cycles in between, wherein during each of these second tempering processes, the first segment 110 is heated to a separate fourth temperature T4. Alternatively, the second solution treatment process 321 and the second quenching process 322 may also be omitted, such that only one or more second tempering processes 323 are performed.

[0068] By means of a second heat treatment process 320, and especially by means of one or more second tempering processes 323, the impact toughness in the first section 110 is adjusted to be within a corresponding value range (e.g., between 10 J at 77 K and 20 J at 77 K, especially between 10 J at 20 K and 20 J at 20 K). In particular, the higher the tempering temperature T4, the lower the achieved strength, the higher the achieved ductility, and the higher the achieved impact toughness.

[0069] Specifically, by means of the second heat treatment process 320, the corresponding residual austenite level in the first section 110 is adjusted to be within the corresponding predetermined austenite level range, so that the impact toughness can be adjusted to be within the corresponding value range.

[0070] For example, if the shaft material is precipitation-hardening stainless steel 1.4542 (i.e., X5CrNiCuNb16-4), then the third predetermined temperature T3 of the second solution treatment process 221 can be between 1030°C and 1050°C, corresponding to the first predetermined temperature T1. In this case, the first segment 110 can be double-tempered by two subsequent second tempering processes 323. The first tempering process in these double tempering processes 323 can be performed at a corresponding fourth temperature T4, for example, 760°C. Then, the subsequent second tempering process in these double tempering processes 323 can be performed at a corresponding fourth temperature T4, for example, 620°C.

[0071] If the shaft material is, for example, martensitic stainless steel 1.4313 (i.e., X3CrNiMo13-4), then the third predetermined temperature T3 of the second solution treatment process 221 can be between 950°C and 1050°C, corresponding to the first temperature T1. Furthermore, in this case, the first segment 110 can be double-tempered by two subsequent second tempering processes 323. The first tempering process in these double tempering processes 323 can be performed at a corresponding fourth temperature T4 (e.g., between 650°C and 670°C). Then, the subsequent second tempering process in these double tempering processes 323 can be performed at a corresponding fourth temperature T4 (e.g., between 600°C and 620°C).

[0072] During the second heat treatment process 320, particularly during the second solution treatment process 321 and the second tempering process 323, a cooling process is performed on the transition section 130 to keep the temperature of the transition section 130 below a predetermined fifth temperature T5, for example, 200°C. This cooling process can be performed, for example, by means of an airflow or by means of a spiral coil containing a water flow. By means of this cooling process, the magnetic induction of the second section 130 (as adjusted during the first heat treatment process 310) is prevented from being affected by the second heat treatment process 320.

[0073] During the second heat treatment process 320, the temperature is monitored by temperature sensors from the first sensor set 210, the second sensor set 220, the third sensor set 230, and the fourth sensor set 240. Suitably, all temperature sensors from the first sensor set 210, the second sensor set 220, and the third sensor set 230 should show the same temperature value or at least substantially the same temperature value within a predetermined tolerance margin. That is, during the second heat treatment process 320, the first section 110 should be heated uniformly and evenly. The temperature measured by the sensors in the fourth sensor set 240 should be below a fifth predetermined temperature T5, for example, below 200°C.

[0074] Following the second heat treatment process 320, the treated shaft can be used as a rotor in a corresponding turbomachinery. This invention therefore allows for individual and independent adjustment of impact toughness and magnetic induction in different sections of the shaft 100, which is made from a single chemical composition and is integrally manufactured. The shaft 100 can thus be optimized for specific cryogenic applications in the corresponding turbomachinery.

[0075] List of reference numerals

[0076] 100 shafts

[0077] 101 First Axial End

[0078] 102 Second Axial End

[0079] 105 main axis, rotation axis

[0080] 110 First Section

[0081] 120 Part 2

[0082] 130 Middle Section

[0083] 201 First Axial Position

[0084] 202 Second Axial Position

[0085] 203 Third Axial Position

[0086] 204 Fourth Axial Position

[0087] The first set of 210 temperature sensors

[0088] 211 First set of temperature sensors

[0089] 212 First set of temperature sensors

[0090] 213 First set of temperature sensors

[0091] 214 First set of temperature sensors

[0092] The second set of 220 temperature sensors

[0093] 221 Second set of temperature sensors

[0094] 222 Second set of temperature sensors

[0095] 223 Second set of temperature sensors

[0096] The third set of 230 temperature sensors

[0097] 231 Temperature Sensors in the Third Set

[0098] 232 third set of temperature sensors

[0099] 233 Third set of temperature sensors

[0100] The fourth set of 240 temperature sensors

[0101] 241 Temperature Sensors in the Fourth Set

[0102] 242 fourth set of temperature sensors

[0103] 243 Temperature Sensors in Set 4

[0104] 250 temperature sensor mounted on the main axis

[0105] 301 Temperature sensor is installed

[0106] Calibration of 302 furnace and equipment

[0107] 310 First Heat Treatment Process

[0108] 311 First Solution Treatment Process

[0109] 312 First Quenching Process

[0110] 313 At least one first tempering process

[0111] 320 Second Heat Treatment Process

[0112] 321 Second Solution Treatment Process

[0113] 322 Second Quenching Process

[0114] 323 At least one second tempering process

Claims

1. A method for processing a workpiece (100) suitable for a fluid energy machine, particularly a shaft (100) for a fluid energy machine, the method comprising the following steps: A first heat treatment process (310) is performed on the entire workpiece (100), the first heat treatment process (310) including a first solution treatment process (311) at a first predetermined temperature, a first quenching process (312), and at least one first tempering process (313) at a second predetermined temperature; and A second heat treatment process (320) is performed on one or more segments (110) of the workpiece (100), wherein the sum of these segments is less than the entire workpiece; the second heat treatment process (320) includes at least one second tempering process (323) at a fourth predetermined temperature, or the second heat treatment process (320) includes a second solution treatment process (321) at a third predetermined temperature, a second quenching process (322) and the at least one second tempering process (323) at the fourth predetermined temperature. The first heat treatment process (310) and the second heat treatment process (320) are performed such that the impact toughness in one or more segments (110) of the workpiece (100) is within a first predetermined value range, and the magnetic induction in at least one other second segment (120) of the workpiece (100) is within a second predetermined value range.

2. The method according to claim 1, further comprising: Perform the first heat treatment process (310) and the second heat treatment process (320) such that the residual austenite level of the material of the workpiece (100) is within a first predetermined austenite level range in the one or more segments (110) of the workpiece (100) in order to control the impact toughness to be within the first predetermined value range in the one or more segments (110) of the workpiece (100). as well as Perform the first heat treatment process (310) and the second heat treatment process (320) such that the level of residual austenite in the material of the workpiece (100) is within a second predetermined austenite level range in the at least one other second segment (120) of the workpiece (100) in order to control the magnetic induction to be within the second predetermined value range in the at least one other second segment (120) of the workpiece (100).

3. The method according to claim 1 or 2, wherein the first predetermined temperature, the second predetermined temperature, the third predetermined temperature, and the fourth predetermined temperature are each determined based on the material of the workpiece (100), particularly based on the ratio of the chromium equivalent to the nickel equivalent of the material of the workpiece (100), and particularly wherein One or more of the parameters are adjusted to affect the impact toughness, and the parameters include the carbon, nitrogen, silicon, and molybdenum content and grain size of the workpiece composition.

4. The method according to any one of the preceding claims, wherein the first predetermined value range of the impact toughness is between 10 J at 77 K and 20 J at 77 K, particularly between 10 J at 20 K and 20 J at 20 K, and / or wherein the lower limit of the second predetermined value range of the magnetic induction is 1.48 T at a magnetic field of 20 kA / m, and / or wherein the upper limit of the second predetermined value range of the magnetic induction is 5.00 T at a magnetic field of 20 kA / m.

5. The method according to any one of the preceding claims, further comprising: During the second heat treatment process (320), a cooling process is performed on at least one transition section (130) to a fifth predetermined temperature, the at least one transition section being located between the one or more sections (110) and the at least one other second section (120).

6. The method according to any one of the preceding claims, further comprising: At least one temperature sensor (211, 212, 213, 214, 221, 222, 223, 231, 232, 233, 241, 242, 243, 250) is disposed at a predetermined position (201, 202, 203, 204) on the surface of the workpiece (100) and / or inside the workpiece (100). During the first heat treatment process (310) and / or the second heat treatment process (320), the temperature at the corresponding predetermined position (201, 202, 203, 204) is monitored by means of the at least one temperature sensor (211, 212, 213, 214, 221, 222, 223, 231, 232, 233, 241, 242, 243, 250).

7. The method according to claim 6, wherein setting the at least one temperature sensor (211, 212, 213, 214, 221, 222, 223, 231, 232, 233, 241, 242, 243, 250) comprises: At least one set (210, 220, 230, 240) of temperature sensors is disposed at predetermined axial positions (201, 202, 203, 204) on the workpiece (100), each set (210, 220, 230, 240) comprising at least two temperature sensors disposed on the surface of the workpiece at predetermined, particularly equidistant, distances in the circumferential direction; and / or At least one temperature sensor (250) is provided inside the workpiece (100) at a predetermined axial position (201, 202, 203, 204) on the main axis (105) or rotation axis (105) of the workpiece (100).

8. The method according to claim 7, wherein A first set (210) of temperature sensors (211, 212, 213, 214) is disposed at a first axial position (201), the first axial position corresponding to a first axial end of the one or more segments (110) in the axial direction; and / or A second set (220) of temperature sensors (221, 222, 223) is disposed at a second axial position (202), the second axial position corresponding to the second axial end of the one or more segments (110) in the axial direction; and / or A third set (230) of temperature sensors (231, 232, 233) is disposed at a third axial position (203) between the first axial position (201) and the second axial position (202), particularly at the midpoint between the first axial position (201) and the second axial position (202); and / or The fourth set (240) of temperature sensors (241, 242, 243) is disposed at the interface between the at least one transition section (130) and the at least one second section (120).

9. The method according to any one of the preceding claims, wherein the second heat treatment process (230) is performed on one or more end segments (110) of the workpiece (100), particularly on one or more end segments extending axially in a predetermined length from the axial end (101) of the workpiece.

10. The method according to any one of the preceding claims, wherein the third predetermined temperature is the same as the first predetermined temperature, or wherein the first predetermined temperature and the third predetermined temperature differ from each other by no more than 10°C.

11. The method according to any one of the preceding claims, wherein the first heat treatment process (310) is performed using a heat treatment furnace.

12. The method according to any one of the preceding claims, wherein the second heat treatment process (320) is performed using an induction furnace and / or an induction local heating device and / or a radiation furnace and / or a cooling device.

13. The method according to any one of the preceding claims, wherein the workpiece (100) is made of martensitic stainless steel or precipitation hardening stainless steel.

14. The method according to any one of the preceding claims, wherein the fluid energy machine is a working machine, particularly a turbomachinery, particularly a rotating turbomachinery, particularly a compressor or turbo compressor or cryogenic turbo compressor.

15. A workpiece (100) suitable for a fluid energy machine, in particular a shaft (100) of a fluid energy machine, processed by the method according to any one of the preceding claims, wherein the impact toughness in one or more segments (110) of the workpiece (100) is within a first predetermined value range, and such that the magnetic induction in at least one other second segment (120) of the workpiece (100) is within a second predetermined value range.

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