JP2009127081A - Wear resistant and erosion resistant alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve mounting method requiring no welding and also to provide pipes and valves having excellent wear resistance and erosion resistance. <P>SOLUTION: The wear resistant and erosion resistant alloy is a Ti-Ni alloy and contains Cu in an amount at least exceeding 5.0 atomic%. This alloy can be used e.g. for a valve box side valve seat 5 of a globe valve. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a valve, piping, and an action thereof, and more particularly, to a fluid component used in a water supply system such as thermal power and a nuclear power plant.

  Ti—Ni alloys are well known as materials exhibiting corrosion resistance and wear resistance. Further, it is well known that Ti—Ni alloys in the vicinity of the equiatomic ratio exhibit a remarkable shape memory effect and superelasticity with the reverse transformation of the martensitic transformation.

  Practically, Ti—Ni alloys include hot water shower valves, greenhouse window opening / closing devices, coffee makers, and the like as shape memory applications whose shape recovers by heating. In addition, as a super-elastic application having a spring function without heating a Ti—Ni alloy, there are an antenna for a mobile phone, an eyeglass frame, a medical guide wire, and the like.

  In addition, examples of applications to piping include pipe joints that utilize shape recovery characteristics of heating shape memory alloys, and metal packing that can be used repeatedly by heating.

  Here, there is a phenomenon called cavitation as an unavoidable problem in equipment and materials used for fluids. The cavitation is a phenomenon in which when the liquid is subjected to an abrupt pressure change and the static pressure of the liquid is lower than the vapor pressure, air dissolved in the liquid and bubbles are generated due to vaporization of the liquid. When the bubbles are rapidly compressed and collapsed at the high pressure portion, a large impact pressure is generated at that time.

  This occurs near the surface of the material, and when a strong impact of a certain size or more is applied, the portion is damaged (Erosion).

  Regulating valves, drain valves and steam installed in an environment where high-temperature, high-pressure water / steam flows at high speed, where generation and collapse of such bubbles are repeated and material surface damage due to attack by impact pressure is a concern For the blades of the turbine, a Co alloy (Stellite, Cr: about 30 atomic%, C: about 1 atomic%, W: about 4 atomic%, balance: Co) excellent in corrosion resistance and wear resistance is used.

In addition, valves for water supply systems of thermal power and nuclear power plants are used at a pressure of 29.4 MPa (300 kg / cm ² ) or less and at a temperature of 300 ° C. or less. Prime welding has been applied.

  The work process for applying the stellite to the valve seat is first performed in the order of processes such as welding groove processing, overlay welding, post heat treatment, finishing processing, and sliding. For the overlay welding of stellite, gas welding using an oxygen-acetylene flame, TIG welding which is arc welding, and plasma welding are applied.

  Here, gas welding can make use of the characteristics of stellite, but this welding requires highly skilled technicians, and the operation is a high-temperature operation. For this reason, at present, the number of such technicians tends to decrease, and an increasing number of companies adopt TIG or plasma arc welding.

  However, arc welding has a drawback in that the base material is excessively melted to cause dilution of stellite and deteriorate characteristics.

  In addition, when welding the valve seat on the valve box side of a small valve, the arc welding nozzle is larger than the welding hole of the valve and cannot be welded directly to the valve seat. There was a drawback that the process of separating the main body part, firstly overlaying stellite on the valve seat part, and then welding the valve seat part and the packing part or the main body part was necessary.

  Stellite has tungsten carbide (WC) or chromium carbide (CrC) distributed in a Co—Cr matrix.

  For this reason, when stellite is applied to the valve seat of a ball valve, there is a drawback in that when the fluid is throttled, a high differential pressure is generated before and after the valve seat, and the carbide adjacent portion is preferentially eroded and the valve seat is damaged. .

  In addition, when overlaying with stellite, arc welding, which has high practicality, has the disadvantage that it is difficult to weld directly to the valve seat on the valve box side of small valves. When applied, there was a disadvantage that the erosion resistance was inferior.

  In general, erosion damage caused by regulating valves, etc. is mainly caused by "cavitation" and "high-speed shear flow". Stellite is a material that exhibits excellent erosion resistance against cavitation erosion. However, the erosion resistance with respect to the high-speed shear flow has a defect inferior to that of the SUS material.

  Furthermore, there is a concern that Co contained in stellite will flow into the nuclear reactor and be activated in the nuclear power plant's supply / condensation system valves, increasing the work exposure dose. It is desired.

  Non-Patent Document 1 and Non-Patent Document 2 report that Ti—Ni alloys are excellent in erosion resistance and corrosion resistance.

  In addition, the present inventors examined the erosion resistance and wear resistance characteristics of a Ti—Ni—X alloy obtained by adding a third element such as Ag, B, Fe, and Nb to a Ti—Ni alloy. (Refer nonpatent literature 3).

  In the examination, the B and Nb-added alloy showed the work lotion resistance and the Ag-added alloy showed the wear resistance. However, no alloy satisfying both characteristics was obtained.

Mater. Trans. 43-5, 840 (2002) Trans. MRSJ, 26-1, 167 (2001) "Materials and Environment", 52, 643-649 (2003)

  In order to solve these problems, the technical problem of the present invention is to provide a valve mounting method that does not require welding, an alloy having excellent wear resistance and erosion resistance, and fluid parts such as pipes and valves using the alloy. There is to do.

  The present inventors have found that by adding Cu to a Ti—Ni alloy known as a corrosion-resistant and wear-resistant material, excellent wear resistance and erosion resistance are exhibited, and the above problems have been solved.

  That is, according to the present invention, there can be obtained a wear / erosion resistant alloy which is a Ti—Ni based alloy and contains at least 5.0 atomic% of Cu.

  In addition, according to the present invention, in the wear / erosion resistant alloy, the wear / erosion resistant alloy is characterized in that the alloy exhibits a shape memory effect.

  Further, according to the present invention, in the wear / erosion resistant alloy, the alloy is a (100-a) Ti- (ab) Ni-bCu-cX alloy (where a is 45 to 55 atomic%, b is 5-15 atomic%, c is 0-10 atomic%, X is an element composed of at least one selected from Nb, V, Co, Cr, Ag, Ta, and W). A wear- and erosion-resistant alloy characterized by

  Furthermore, according to the present invention, the wear / erosion resistant alloy may be a part of at least one of a high temperature or high pressure pipe joint, a valve seat such as a fluid regulating valve, a drain valve, a valve body, and a steam turbine blade. A fluid component is obtained which is used for the whole and is easily fastened and fixed to the main body.

  In the present invention, it is possible to provide alloys used for pipes, valves and the like, which are excellent in wear resistance and erosion resistance using a valve mounting method that does not require welding, and fluid components thereof.

  Hereinafter, the present invention will be described in more detail.

  The wear and erosion resistant alloy of the present invention is a Ti—Ni alloy or a Ti—Ni alloy having a shape memory effect, and contains at least 5.0 atomic% of Cu. Further, the fluid component of the present invention is made of this wear / erosion resistant alloy using at least one of a high temperature or high pressure pipe joint, a valve seat such as a fluid regulating valve and a drain valve, a valve body and a steam turbine blade. It is used for a part or the whole, and is easily fastened and fixed to the main body part.

  Here, in the present invention, the Ti—Ni-based alloy is an alloy containing Ti and Ni, or one obtained by replacing a part of Ti and Ni of the alloy with a third element (Ti—Ni—X alloy). .

  In the embodiment of the present invention described below, only the Cu-containing Ti—Ni alloy in which x of the (100−x) Ti— (xy) Ni—yCu alloy is 45 to 55 atomic% is shown. Ti-Ni alloys are not limited to these, and Ti-Ni alloys containing Cu of any composition, for example, Ti-Ni-X alloys containing Cu (X = Nb, V, Co Of course, the present invention can be applied to (Cr, Ag).

  However, x = 45 to 55 is preferable in consideration of wear and workability of the alloy. Further, if the Cu content y is 5 atomic% or more, sufficient erosion resistance and abrasion resistance are exhibited, but it is preferable to exceed 5 atomic% in consideration of seizure galling due to repetition. The higher the Cu content, the better the present invention, but the upper limit is preferably about 10% in consideration of workability.

  Further, as the Ti—Ni—X alloy, only X = Nb, V, Co, Cr, and Ag are shown in the example of the present invention, but there is no problem in including elements such as Ta and W. Further, when the present invention is a shape memory alloy, the additive element and content can be limited to a range in which the shape memory effect is not lost, and the upper limit is preferably about 10%.

  Next, a valve device will be described as an example of application of the alloy of the present invention.

  First, the first embodiment will be described.

  FIG. 1 is a cross-sectional view showing an application example to a valve device using a wear-resistant and erosion-resistant alloy according to the first embodiment of the present invention. Referring to FIG. 1, an example of application of a ball valve having a conical valve seat to a valve seat is shown. It is sectional drawing of the ball-shaped valve which has a conical valve seat with a diameter of 25 mm. The ball valve 1 has a valve box side valve seat 3 having an angle of 36 ° in the valve box 2, and a fluid is caused to flow by pulling up the valve body side valve seat 4 having an angle of 35 °. Adjust the flow rate and pressure and shut off the fluid by closing it. These valve seats are made of a Ti-Ni-Cu alloy.

  Next, a second embodiment will be described.

  The ball valve according to the second embodiment is the same as that of the first embodiment except that the shape and mounting method of the valve box side valve seat are different, so only the valve box side valve seat will be described.

  FIG. 2 is a sectional view showing a valve box side valve seat according to a second embodiment of the present invention. The valve box side valve seat 5 according to the second embodiment shown in FIG. It is made of 9 alloys. A circumferential groove 7 for attaching a valve seat was machined in the carbon steel base material 6 of the valve box. The valve box side valve seat 5 is mounted by deforming the valve box side valve seat 5 separately prepared at room temperature after storing the shape at a temperature of 500 ° C. so that the outer diameter of the valve seat is smaller than the groove diameter. The inner diameter of the valve box side valve seat 5 was made larger than the outer diameter of the valve seat mounting groove 7. The valve box side valve seat 5 was fitted into the mounting groove 6 and heated to a temperature of 100 ° C. to recover the shape, and the valve box 6 and the valve box side valve seat 5 were fastened.

A ball valve with a diameter of 25 mm having a valve seat manufactured in this way was attached to the water supply system piping of the power plant and was used at a pressure of 8.624 MPa (88 kg / cm ² ) and a temperature of 288 ° C. The properties, erosion resistance and wear resistance were shown.

  Specific examples of the present invention are shown below, but the present invention is of course not limited thereto.

(Example)
(I) Preparation of Alloy and Test Material Various alloys shown in Table 1 below were prepared by argon arc melting, rapidly cooled after solution treatment at 1000 ° C. for 1 hour, and each test piece was cut out. The erosion test piece was mirror-finished, and the abrasion test piece was # 600 paper finished.

(Ii) Shape memory characteristic evaluation Each strip-shaped test piece was bent and deformed to evaluate the workability. As a result, no. No. 1 to No. 4 containing alloys and Ag that deviate greatly from the chemical theory of No. 16, no. The 19 alloy was brittle and could not be bent.

  The bendable test piece was measured for transformation temperature with a differential scanning calorimeter (DSC) for the evaluation of the presence or absence of shape memory characteristics. As a result, all showed a clear transformation temperature and confirmed the existence of shape memory characteristics.

(Iii) Evaluation of erosion resistance The erosion test was conducted by a method in which a jet obtained by injecting high-temperature / high-pressure compressed water in accordance with JIS R 1645 into the atmosphere from a nozzle having a small pore diameter collides with the surface of the test piece. . Specifically, compressed water having a temperature of 150 ° C. and a pressure of 14.7 MPa was ejected into the atmosphere from a nozzle (SUS304) having a pore diameter of 0.3 mm and a thickness of 1 mm, and was installed at a position 10 mm from the nozzle. Collided with the specimen. The flow rate of the jet is 8 × 10 ⁻⁶ m ³ / s. The test piece has a diameter of 16 mm and a thickness of 3 mm. The jet is a droplet jet that disperses into droplets due to friction with air as the distance from the nozzle increases, but under this test piece condition, it is a continuous jet that does not disperse into droplets.

  Table 2 below shows the results of comparing the degree of damage to each test piece after 2 hours of injection with stellite, and it was found that all of the inventive examples showed erosion resistance equal to or higher than stellite. In the table, circles (◯) indicate less damage than stellite, triangles (Δ) are equivalent, and crosses (x) are inferior.

  FIG. 5 (Ti-Ni), No. 5 19 (Ti-Ni-Ag), No. 19 9 (Ti—Ni—Cu) The relationship between the erosion depth received by each test piece and the injection time was shown, but it can be seen that the present invention example is excellent in erosion resistance.

(Iv) Wear resistance evaluation The wear test was performed by a reciprocating sliding method. The test was performed in pure water at room temperature using the specimen as a fixed test piece and SUS440C as a movable test piece under conditions under a constant load. The fixed test piece was a cylindrical shape having a diameter of 11.3 mm and a length of 15 mm, and the movable test piece was SUS440C, which was a rectangle of 15 × 10 × 120 mm. The test was performed under the conditions of a sliding speed of 167 mm / s and a stroke of 50 mm. The load was started from 98N, and the load was increased by 98N every 50 times of sliding until the seizure galling occurred. The results of comparing the specific wear amount of each fixed piece with Stellite are shown in Table 3 below, and it can be seen that the present invention example is excellent in wear resistance. Here, wear amount = weight before test−weight after test, specific wear amount = wear amount / (sliding distance × final load). In the table, circles (◯) indicate less wear compared to stellite, triangle The mark (Δ) means the same, and the cross mark (×) means many.

  In FIG. 7 (Ti—Ni-5Cu), Stellite, No. 7 19 (Ti-Ni-Ag) and Inventive Example No. The change result of the friction coefficient by the sliding repetition of 9 (Ti-Ni-8.5Cu) alloy was shown. No. No. 7 caused seizure at less than 1000 times, and stellite showed a tendency to increase as the pressing load increased due to repetition. 19 showed almost no change.

  As described above, the wear / erosion resistant alloy according to the present invention is a part or the whole of at least one of a high pressure pipe joint, a valve seat such as a fluid regulating valve and a drain valve, a valve body, and a steam turbine blade. Because it can be easily fastened and fixed to the main body, it is most suitable for fluid parts used in water supply systems such as thermal power and nuclear power plants.

It is sectional drawing which shows the target lens valve by embodiment of this invention. It is sectional drawing which shows the valve box side valve seat of the ball-shaped valve of FIG. In the examples of the present invention, stellite, no. 5 (Ti-Ni), No. 5 19 (Ti-Ni-Ag), No. 19 It is a figure which shows the relationship between the erosion depth of each 9 (Ti-Ni-Cu) test piece, and the injection time. No. in the examples of the present invention. 7 (Ti-Ni-5Ag), Stellite, No. 7 19 (Ti-Ni-Ag) and No. 9 is a diagram showing a change result of a friction coefficient of 9. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball valve 2 Valve box 3 Valve box side valve seat 4 Valve body side valve seat 5 Valve box side valve seat 6 Carbon steel base material 7 Circumferential groove

Claims (4)

  A wear-resistant and erosion-resistant alloy which is a Ti-Ni alloy and contains at least 5.0 atomic% of Cu.   2. The wear / erosion resistant alloy according to claim 1, wherein the alloy has a shape memory effect.   The wear / erosion resistant alloy according to claim 1 or 2, wherein the alloy is a (100-a) Ti- (ab) Ni-bCu-cX alloy (where a is 45 to 55 atomic%, b 5 to 15 atomic%, c is 0 to 10 atomic%, and X is a Cu-containing Ti—Ni alloy of at least one element selected from Nb, V, Co, Cr, Ag, Ta, and W). A wear and erosion resistant alloy characterized by   The wear / erosion resistant alloy according to claim 3 is used for a part or all of at least one of a high temperature or high pressure pipe joint, a valve seat such as a fluid regulating valve and a drain valve, a valve body and a steam turbine blade. A fluid component characterized by facilitating fastening and fixing with a main body.

Images