JP2008268073A - Material evaluation method, and treatment apparatus for conducting the same evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating properties of material to ultrapure water by using ultrapure water with high electric resistance, and to provide a treatment apparatus usable in such the evaluation. <P>SOLUTION: The treatment apparatus includes a pump 21 for pressure-feeding the ultrapure water, a holder 32 detachably holding a member to be treated, and a nozzle 41 connected to a discharge part of the pump for injecting the ultrapure water delivered from the pump to a surface of the member to be treated. The surface of the member to be treated is treated by injecting the ultrapure water on the member to be treated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for evaluating a material used as a member of a rotary machine such as a pump, a turbine, a compressor, or a blower, and a processing apparatus that can be used for such evaluation, and more particularly, a fluid that handles ultrapure water. The present invention relates to a method for evaluating a material used for a machine or ultrapure water as a lubricant, a seal, a bearing or the like using ultrapure water, and a processing apparatus usable for performing such an evaluation.

Silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ) and the like, which are silicon-based ceramics, are widely used for bearings and shaft seals of rotating machines such as pumps that handle water as a lubricating liquid. These ceramics easily form a gel-like hydroxide or hydrate film on the sliding surface during sliding under water lubrication, and this effect is excellent in low friction and wear resistance. Yes.
A journal bearing and a thrust bearing of a canned motor pump are widely made of SiC on both the rotating side and the fixed side. Moreover, in the pump seal member, it is widely performed that the rotation side is composed of SiC and the stationary side is composed of a carbonaceous molded body, or both are composed of SiC.
Regarding whether or not the above members can be used in an ultrapure water environment, there was no method other than performing a sliding test for evaluating the members in an ultrapure water environment.

In general, tap water has an electric resistance of 0.001 to 0.1 MΩcm, and exhibits excellent characteristics when silicon ceramics are used in such an environment. However, when ultrapure water having an electric resistance of 4 MΩcm or more (the electric resistance of theoretical pure water is 18.25 MΩcm) is used as the handling liquid, since the Si concentration contained in the water is small, Si-based hydroxide or Si The dissolution rate of water-based hydrates in water increases, and silicon ceramics are corroded. Therefore, the surface of the bearing and the seal part breaks and the water film breaks, so the sliding surface comes into direct contact and wears, and the rotational torque rises in an extremely short time compared to tap water, making it unusable. It becomes.
When such a material is actually used as a bearing or a seal member, the period until it becomes unusable becomes a unit of several months. Therefore, if a material evaluation is performed by a sliding test simulating an actual machine, it takes an enormous amount of evaluation time. There is a problem. In addition, although the example of said corrosion generate | occur | produces at 10-20 degreeC of water temperature, since the speed | rate of a chemical reaction will generally become large when water temperature becomes high, a corrosion rate will become large and the lifetime of an apparatus will also be shortened.

The present invention has been made in view of such problems, and provides a method for evaluating a material that can be evaluated in a shorter time than a sliding test simulating an actual machine, and a processing apparatus that can be used for such evaluation. The purpose is to do.
Another object of the present invention is to provide a method for evaluating the characteristics of a material with respect to the ultrapure water using ultrapure water having a large electric resistance, and a treatment apparatus usable for such evaluation.
Another object of the present invention is to measure the erosion depth or volume reduction amount of the treated member by colliding with the surface of the treated member made of the material to be evaluated, and thereby the corrosion resistance of the material. And a processing apparatus usable for the method.

According to the present invention, there is provided a method for evaluating a material, wherein a jet of ultrapure water is collided with a member to be evaluated made of the material to be evaluated, thereby evaluating the corrosion resistance of the material.
In the present invention, ultrapure water refers to water having an electrical resistance of 4 MΩcm to 18.25 MΩcm.
In the above method, the flow velocity of the jet of ultrapure water is preferably 10 m / s or more, more preferably 20 m / s or more. The reason is that if the flow velocity is lower than 10 m / s, the amount of erosion becomes small and it is difficult to evaluate, so it is necessary to lengthen the evaluation time, resulting in an increase in cost. The higher the flow rate, the greater the amount of erosion and the evaluation time can be shortened.
Moreover, the diameter of the jet of ultrapure water is preferably 0.5 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less. The reason for this is that when the diameter is smaller than 0.5 mm, the flow rate decreases, so that control becomes difficult. On the other hand, if the diameter is larger than 5 mm, it is necessary to increase the flow rate in order to ensure a predetermined flow rate. Therefore, a high-grade water pump, ultrapure water production apparatus, etc. are required, and at the same time, the life of the apparatus is shortened and the test cost is increased.
Furthermore, the temperature of the ultrapure water or the test piece, that is, the sample is preferably 10 ° C. or higher and lower than 100 ° C. The reason is that if the water temperature is lowered below 10 ° C., the amount of erosion becomes small and it is difficult to evaluate, so that a long-time test is required and the test cost is increased. On the other hand, as the water temperature is higher, the evaluation time can be shortened. However, if the water temperature is raised to 100 ° C. or higher, the vaporization occurs and the evaluation becomes impossible.
The ultrapure water preferably has an electric resistance of 4 MΩcm to 18.25 MΩcm, more preferably 10 MΩcm to 18.25 MΩcm. The reason for this is that if the electrical resistance of ultrapure water is low, the amount of erosion becomes small and the evaluation becomes difficult, and therefore, if the evaluation time is lengthened, the test cost also increases.
Furthermore, the time for which the ultrapure water collides with the member to be evaluated is preferably 30 hours or more and 200 hours or less, more preferably 50 hours or more and 100 hours or less. The reason is that if the test time is shorter than 30 hours, it is necessary to increase the flow rate of ultrapure water. As described above, the test cost increases, and if the test time is longer than 200 hours, the test time is increased. This is because the cost becomes high.

According to the present invention, a pump for pumping ultrapure water, a holder for detachably holding a member to be treated, and a member to be treated for ultrapure water that is connected to a discharge portion of the pump and sent from the pump. There is provided a processing apparatus characterized in that the surface of the member to be treated is treated by spraying ultrapure water onto the member to be treated.
There may be a temperature control device for the ultrapure water itself or a device for controlling the temperature of the test piece, that is, the sample itself. However, in the case of a test in a high temperature environment, if the temperature of the ultrapure water itself is increased, the amount of outflow from the inner wall of the ultrapure water channel increases, so the temperature of the ultrapure water decreases. Therefore, it is desirable to control the temperature of the sample itself to a high temperature.
In the above invention, the treatment device may be an evaluation device for evaluating the corrosion resistance of the material by measuring the erosion depth or volume reduction amount of the member to be treated due to the collision of ultra pure water, or ultra pure water. The processing apparatus which processes the surface of a to-be-processed member by collision of this may be sufficient.
Moreover, in the said invention, the internal diameter of a nozzle becomes like this. Preferably it is 0.5 mm or more and 5 mm or less, More preferably, it is 1 mm or more and 3 mm or less. The reason is the same as described in [0005].
Moreover, the flow velocity of the jet of ultrapure water is preferably 10 m / s or more, more preferably 20 m / s or more. The reason is the same as the reason described in [0005].
Furthermore, the electrical resistance of the ultrapure water used is preferably 4 MΩcm to 18.25 MΩcm, more preferably 10 MΩcm to 18.25 MΩcm. The reason is the same as the reason described in [0005].

  According to the present invention, the following effects can be obtained. That is, conventionally, silicon-based ceramics that exhibit excellent friction wear characteristics under lubrication with tap water have been widely used as water-lubricated bearings and seals. However, in a sliding environment in ultrapure water with very few impurities, silicon ceramics wear out due to corrosion. To evaluate and select a material with excellent corrosion resistance in ultrapure water, a sliding test may be performed. However, since the erosion rate is very slow, it is necessary to spend a lot of time to evaluate the material. Very inefficient in time and cost. However, according to the present invention, it is performed by colliding with a sample made of a material to be evaluated for the jet of ultrapure water, that is, the material to be evaluated or the material to be processed.

Hereinafter, an evaluation method and an evaluation apparatus according to the present invention will be described with reference to the drawings.
1 and 2, an embodiment of a processing apparatus suitable for carrying out the material evaluation method according to the present invention is shown. The processing apparatus 1 of this embodiment is a sample that holds a pressurized supply unit 2 of ultrapure water disposed on a base plate 10 and a member to be evaluated (hereinafter referred to as a sample) made of a material to be evaluated. A holding unit 3, a nozzle unit 4 that sprays pressurized ultrapure water onto the sample held by the sample holding unit, and a pump control device 5 are provided. The pressure supply unit 2 includes a water supply pump 21 attached to the base plate 10 via the attachment member 11 and a drive motor 25 directly connected to the water supply pump. The water pump 21 and the drive motor 25 directly connected to the water pump 21 may have a known structure, but have the ability to supply ultrapure water at a pressure of 100 kPa to 1000 kPa and a flow rate of 0.5 to 5.0 liters / minute. It is preferable to have. The suction part 22 of the water pump 21 is connected to a supply source of ultrapure water (not shown). Here, ultrapure water refers to water having an electric resistance of 4 MΩcm to 18.25 MΩcm.

  The sample holder 3 includes a holder 31 that is disposed on the base plate 10 and is fixed to the base plate 10 by the support frame 12, and a holder 32 that is disposed at the center of the holder 31. . The holding base 31 is a tray having a quadrangular shape (in this embodiment, a square shape), a drain port 33 is formed at the bottom, and a drain pipe 34 is connected to the drain port 33. A plurality of fixing screws 35 are attached to the head portion 32a of the holder 32, and the sample M can be detachably fixed to the holder 32 with these fixing screws. In this case, the sample M may be fixed to the holder by fixing the sample M to a support member with a screw hole by welding or the like and screwing a fixing screw into the screw hole of the support member. The holder 32 is movable in the tray-like holding table 31 in the front-rear direction (the left-right direction in FIGS. 1 and 2 in the direction of approaching and separating from the nozzle unit described later), and between the nozzle tip and the sample surface. The distance can be adjusted. The holder 32 can be moved and fixed with respect to the holding table 31 by known means, but in this embodiment, a plurality of guide rods 36 are attached to a guide member fixed on the holding table, and the guide rods are attached to the base 32b of the holder 32. The base 32b is fixed by a fixing bolt 38, and the holder is fixed thereby. The sample holder 3 further includes a cover 39 made of a transparent material such as transparent plastic or glass. The lower end of the cover 39 is received in a tray-like holding table, and prevents ultrapure water from splashing outside during operation of the apparatus.

The nozzle unit 4 includes a nozzle 41 attached to a nozzle support plate 42 fixed to the holding table 31 between the water pump 21 and the sample holding unit 3. The discharge part of the water pump is connected to the rear end of the nozzle so that the ultrapure water sent from the water pump can be ejected from the nozzle 41. The nozzle 41 extends in a straight line in the front-rear direction (left-right direction in FIGS. 1 and 2), and the jet of ultrapure water collides with the surface of the sample. The angle formed between the jet and the sample surface is 0 °. It can be set within an arbitrary range of ~ 90 °. The diameter (inner diameter) of the nozzle hole at the tip of the nozzle 41 is preferably 0.5 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less. The structure itself of the nozzle 41 may be a known one, and therefore a detailed description thereof is omitted.
A pump control device 5 having a known structure is disposed and fixed on the base plate 10. This pump control device can control the amount of ultrapure water discharged from the nozzle by controlling the rotational speed of the drive motor for the water pump 22.

  In the evaluation apparatus having the above configuration, the sample M made of the material to be evaluated is fixed to the holder 32 as described above. Next, the holder 32 is moved relative to the holding table so that the distance from the tip of the nozzle 41 to the surface of the sample M becomes a predetermined value, and the holder is fixed to the holding table at that position. Put on. Next, the water pump is actuated by the drive motor 25, ultrapure water is sent to the nozzle 41, ultrapure water is injected from the nozzle, and the jet of ultrapure water collides with the surface of the sample M. This operation is performed for a time determined by the material of the sample, preferably 30 hours or more. When the jet flow collides for a predetermined time, the pump operation is stopped and the sample is taken out of the holder. Thereafter, the corrosion resistance of the material is evaluated by measuring the surface condition of the sample, for example, the erosion depth or the volume reduction.

[Test Example 1]
Using the processing apparatus 1, a jet collision test was performed on the sintered body SiC while changing the purity (electric resistance) of water.
The distance from the tip of the nozzle 41 to the surface of the sample, which is a test piece, is set to 25 mm, and the jet of water from the nozzle collides with the surface of the sample (the angle between the jet and the sample surface is 0 ° to 90 °). Set to any range of). Water was ejected from a nozzle having an inner diameter of 1 mm at a flow rate of 18 m / s for 100 hours to collide with the surface of the sample. Three types of water are used whose electrical resistance is about 0.007 MΩcm (normal tap water as it is), 4.0 MΩcm and 18.0 MΩcm (ultra pure water), and the volume of the test piece, ie, the sample, which collides with each water, is reduced The amount was measured.

  FIG. 2 shows the surface cross-sectional curve of the tested sample. As is clear from FIG. 2, when a jet of ultrapure water having an electric resistance of 18.0 MΩcm is collided, the surface of the used surface is compared to other water (water having an electric resistance of 0.007 MΩcm and 4.0 MΩcm). Is noticeably eroded. FIG. 3 shows the relationship between the electrical resistance of water and the maximum erosion depth based on the test results. In addition, since the product considered to be an oxide adheres to and covers the erosion portion on the sample surface immediately after the test, a cross-sectional curve was measured after removing the deposit with a brush or the like. Erosion begins to progress when the electrical resistance is greater than 4.0 MΩcm, but the maximum erosion depth needs to be increased to some extent for rapid material evaluation. Therefore, the electrical resistance is 4.0 MΩcm as an evaluation method. It is preferable to use the above water.

  Next, when water having an electric resistance of 18.0 MΩcm is used and the jet of the water is collided with the sample (SiC sintered body) for 100 hours, the relationship between the water flow velocity and the maximum erosion depth is shown in FIG. As shown in The water temperature was 10-25 ° C. It can be seen from FIG. 4 that the maximum erosion depth tends to increase as the jet flow velocity increases. In order to perform quick material evaluation, the jet velocity is preferably 10 m / s or more.

  On the other hand, when water having an electric resistance of 18.0 MΩcm is used and the flow velocity of water is made to collide with a sample of the same material as described above, the test time (the time when the jet is made to collide) and the maximum erosion depth FIG. 5 shows the relationship. The water temperature in this case was also 10-25 ° C. Although it is necessary for the maximum erosion depth to be a somewhat large value in order to perform quick material evaluation, it can be seen from FIG. 5 that the test time required for evaluating the material is preferably 30 hours or more.

[Test Example 2]
A thrust bearing member with a spiral groove made of SiC was operated for 500 hours at a bearing surface pressure of 2.2 MPa and a peripheral speed of 12 m / s in water having an electrical resistance of 18.0 MΩcm, which is a condition suitable for an actual pump. The water temperature was 10-25 ° C. FIG. 6 shows an appearance photograph and a cross-sectional curve after the test of the bearing member sliding surface according to this test result. As shown in FIG. 6, the rotating side bearing member is partially worn, but the worn position is near the end of the groove formed on the fixed side bearing member (near the radially inner side of the annular bearing member) ). This is presumed to be due to erosion and corrosion caused by water. The maximum erosion depth was about 3 μm for the bearing member on the fixed side (member with spiral groove), and 2 μm for the bearing member on the rotation side (member without spiral groove). It can be seen that even if the test is performed for 500 hours, the amount of erosion is small and the evaluation time becomes very long if a test according to the actual machine is used as the evaluation method.

In addition, although the said Example and test example demonstrated the case where a processing apparatus was used for the evaluation method of material, a processing apparatus can also be used as processing apparatuses, such as material cutting and surface cutting.
For example, when used as a processing device for cutting, a member to be cut is held by a holder so that a jet of ultrapure water collides vertically with a member to be cut. In this case, when it is necessary to change the position of the member to be cut with respect to the position of the jet, the head portion of the holder is moved in a two-dimensional direction or a three-dimensional direction with respect to another member, for example, a holding table, using a known means. The position of the member to be cut may be automatically moved in a direction perpendicular to the direction of the jet to be movable.

  The present invention can be used for evaluating a material for a bearing member or a seal member of a fluid machine that handles ultrapure water.

(A) is a top view of the processing apparatus which can be used for the material evaluation method of this invention, (B) is an elevation view of the processing apparatus. It is a figure which shows the surface cross-section curve of the test piece after the evaluation test using a SiC sintered compact. It is a figure which shows the relationship between the electrical resistance of the water based on the evaluation test using a SiC sintered compact, and the maximum erosion depth. It is a figure which shows the relationship between the flow velocity of the jet based on the evaluation test using a SiC sintered compact, and the maximum erosion depth. It is a figure which shows the relationship between the test time based on the evaluation test using a SiC sintered compact, and the maximum erosion depth. It is a figure which shows the external appearance photograph and surface cross-section curve of the bearing member after the slip test according to the actual machine of the thrust bearing member with and without a SiC spiral groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Pressurization supply part 3 Sample holding part 4 Nozzle part 5 Pump control apparatus 10 Base plate 21 Water supply pump 25 Drive motor 32 Holding stand 32 Holder 41 Nozzle

Claims (2)

  A method for evaluating a material, characterized in that a jet of ultrapure water is collided with a member to be evaluated made of the material to be evaluated, thereby evaluating the corrosion resistance of the material.   A pump for pumping ultrapure water, a holder for detachably holding the member to be treated, and an ultrapure water sent from the pump connected to the discharge part of the pump and sprayed toward the surface of the member to be treated And a nozzle for processing the surface of the member to be processed by spraying ultrapure water onto the member to be processed.