KR20050017007A - Parts for fluid - Google Patents

Abstract

Predetermined metal members constituting fluid parts such as valves and joints used in piping and fluid control devices include: C: 0.001 to 0.1 wt%, Si: 5 wt% or less, Mn: 2 wt% or less, P: 0.03 weight% or less, S: 100 ppm or less, O: 50 ppm or less, Cr: 18-25 weight%, Ni: 15-25 weight%, Mo: 4.5-7.0 weight%, Cu: 0.5-3.O weight %, N: 0.1 to 0.3% by weight, the balance is substantially alloy of Fe and other unavoidable impurities, and expressed in weight% to secure the gap corrosion resistance based on the complex addition of each component of the alloy The CRI (gap corrosion resistance index) value determined by CRI = [Cr] + 4 × [Mo] + 30 × [N] is set in the range of 40 ≦ CRI ≦ 55.

Description

Fluid Part {PARTS FOR FLUID}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fluid components such as fluid control devices, such as joints used in piping systems, valves used in fluid control devices, and more particularly, to fluid parts suitable for use in the manufacture of pharmaceuticals or food products.

Joints, valves and the like (collectively referred to as fluid parts) are frequently used as general-purpose parts in fluid control devices and various piping.

For example, metal valves are used in reaction vessels used in the manufacture of medicines and foods, and tanks used for storing and transporting medicines and foods themselves, for the purpose of bringing in and taking out raw materials and products. Metal valves are classified into carbon steel, low alloy steel, stainless steel, Ni-based alloys, titanium, and Ni / Cu alloys according to chemicals, food ingredients, purity, and temperature. In the metal valve used at the time of manufacture, storage, and transportation, stainless steel, such as SUS304 steel and SUS 316L steel, which generally have good corrosion resistance, is often used. However, most of the corrosion damages that metal valves receive are due to crevice corrosion caused by chloride ions contained in drugs and foods. In most cases, in order to prevent corrosion of the valves and increase of germs, it is common to perform maintenance such as washing / sterilizing the inside of the valve.However, if the washing, sterilizing or drying process is incomplete, Since chloride ions often remain, crevice corrosion is likely to occur frequently at the valve body and the fastening portion or packing portion of the flange, and excessive time and effort are required for repair, and metal ions generated by the crevice corrosion are products. Very important problems such as deterioration of quality have arisen.

Therefore, when it is desired to improve the corrosion resistance of a member made of SUS 316 so as not to cause corrosion problems even when used in a food or pharmaceutical manufacturing apparatus that handles a high salt solution, other problems such as a decrease in strength and hardness may arise. For this reason, it was almost impossible to improve only the crevice corrosion resistance while maintaining other characteristics with respect to the conventional fluid parts that meet the required specifications.

It is an object of the present invention to provide a fluid component capable of improving gap corrosion resistance while maintaining other performance.

1 is a cross-sectional view showing a valve as a first embodiment of a fluid component according to the present invention.

2 is a cross-sectional view showing a flow path closed state of a diaphragm valve as a second embodiment of a fluid component according to the present invention.

3 is a longitudinal sectional view showing a flow path opening state of the valve of FIG. 2;

4 is an exploded longitudinal sectional view showing a pipe joint as a third embodiment of a fluid component according to the present invention;

Fig. 5 is a longitudinal sectional view showing the assembled state of the pipe joint of Fig. 4.

Fig. 6 is an exploded longitudinal sectional view showing a pipe joint as a fourth embodiment of a fluid part according to the present invention.

The present invention provides a fluid component for solving the above problems, and from the above point of view, a chemical or food environment in which a fluid corrosion such as a valve or a joint is exposed and a crevice corrosion occurs is investigated. As a result, in most cases, it has been found that the place where crevice corrosion damage occurs contains a small amount of chloride ions in medicine or food. As a corrosion environment for evaluating these crevice corrosions, it is possible to obtain the fact that it can be simulated in a seawater environment. Against this background, exposure tests of various stainless steel valves in natural seawater were conducted. Specifically, the natural seawater at room temperature continued to flow in the valve for about half a year to observe the corrosion situation and to investigate the presence of crevice corrosion damage. As a result of the intensive efforts in this way, the present invention has been made to specify the fluid flow path opening and closing of the fluid flow opening and closing of the fluid flow control valve, the fluid flow control valve, and the pipe joint for the production, storage, and transport, which do not cause the gap corrosion, which has conventionally been a problem. As a result, the gist is as follows.

The fluid component according to the present invention is a fluid component such as a valve or a joint used in a pipe and a fluid control device, and is constituted by a plurality of constituent members, and has a contact surface that contacts any one of the other constituent members. A predetermined metal member is formed such that the end of the contact surface is exposed to the outer surface of the fluid part, C: 0.001 to 0.01 wt%, Si: 5 wt% or less, Mn: 2 wt% or less, P: 0.03 wt% or less, S: 100 ppm or less, O: 50 ppm or less, Cr: 18-25 wt%, Ni: 15-25 wt%, Mo: 4.5-7.0 wt%, Cu: 0.5-3.0 wt%, N: 0.1-0.3 wt% In addition, the remainder is an alloy consisting essentially of Fe and other unavoidable impurities, and is expressed in weight percent to secure crevice corrosion resistance based on the complex addition of each component of the alloy. Corrosion Resistance Index To characterized in that the 40≤CRI≤55.

CRI = [Cr] + 4 × [Mo] + 30 × [N]

Furthermore, it is preferable to contain 1 type (s) or 2 or more types of W: 2 weight% or less and V: 2 weight% or less, respectively.

According to the fluid component of the present invention, a predetermined metal member, ie, crevice corrosion, having a contact surface in contact with any one of the other component members of a plurality of constituent members of the fluid component, the end of the contact surface being exposed to the outer surface of the fluid component. C: 0.001 to 0.01% by weight, Si: 5% by weight or less, Mn: 2% by weight or less, P: 0.03% by weight or less, S: 100 ppm or less, O: 50 ppm or less, Cr : 18 to 25 wt%, Ni: 15 to 25 wt%, Mo: 4.5 to 7.0 wt%, Cu: 0.5 to 3.0 wt%, N: 0.1 to 0.3 wt%, and the balance is substantially In order to obtain an alloy of inevitable impurities, and to secure crack corrosion resistance based on the complex addition of each component of the alloy, CRI = [Cr] + 4 × [Mo] + 30 × [N] expressed in weight%. Since the obtained CRI value is set in the range of 40≤CRI≤55, there is a disadvantage in that the gap corrosion resistance is improved. Without causing a reduction in strength and hardness and which was considered degraded, it is possible to improve the crevice corrosion resistance.

It is preferable that the surface roughness of a metal member becomes Ra1 or less, More preferably, it is Ra 0.2 or less.

Examples of the fluid component include joints, valves, and the like, but the present invention is not limited thereto, and various kinds of them are possible.

For example, the fluid component is a valve having a body, an actuator, and a screw member, and at least one of the body, the actuator, and the screw member is made of a predetermined metal (ie, the alloy) member in some cases. The fluid component is a diaphragm valve in which a non-metal diaphragm is sandwiched by a metal body and a metal bonnet, and both the body and the bonnet may be made of a predetermined metal (ie, the alloy) member. In the latter case, the diaphragm clamping portions of the body and the bonnet are in a state where crevice corrosion is very likely to occur, and the durability of the diaphragm valve as a whole can be remarkably improved by improving the crevice corrosion resistance of this portion.

In addition, the fluid component is a tubular joint which can be assembled by fastening a cap nut to a male screw provided on an outer circumference of the tubular joint member, and at least one of the joint member and the cap nut is made of a predetermined metal (ie, the alloy) member. There may be it.

Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the drawing shown here.

1 shows a first embodiment of a fluid component of the invention. In the description of the first embodiment, the left and right sides of the drawing shall be left and right.

The fluid component 1 of this embodiment is a needle stop valve, which has a bottomed cylindrical body 2 having a tubular left protrusion 8 and a tubular right protrusion 9 at the bottom thereof, and the body. (2) a cylindrical stem (3) inserted to be movable up and down, a cylindrical guide (4) inserted in the upper inside of the body (2) to guide the vertical movement of the stem (3), and the body (2) A panel nut (5) screwed to the lower end of the male threaded portion (10) installed on the upper outer circumferential surface thereof, a cap nut (6) screwed to the top of the male threaded portion, and an upper end of the stem (3). The handle 7 is provided.

The stem 3, the guide 4, the cap nut 6, and the handle 7 constitute the actuator of the fluid part 1.

The lower portion of the body 2 extends slightly from the vicinity of the center portion to the left side and extends from the position above the central inlet portion of the fluid inflow passage 2a to the passage in the left projection 8 and the central side end of the fluid inflow passage 2a. A fluid outflow passage 2b extending slightly to the right to lead to the passage in the right protrusion 9 and a communication passage 2c extending in the vertical direction so as to communicate the two passages 2a and 2b are provided. The communication path 2c has a stepped shape in which the lower portion is smaller in diameter than the upper portion. The inner circumferential surface of the body 2 above the communication path 2c is a stem guide path 11 extending in the vertical direction. A female threaded portion 11a is provided in the lower part of the stem guide path 11 so as to be slightly caught in the communication path 2c, and an upper portion of the step guide path has a larger diameter than the female threaded portion 11a. 4) is inserted.

The stem 3 has a conical shape with a lower end portion 3a, and is screwed to the female threaded portion 11a of the body 2 with a larger diameter than the other portion of the upper portion of the conical portion 3a. The male screw part 3b is provided.

The guide 4 is supported by the end part of the female screw part 11a upper end so that the upper end part may protrude more than the upper end surface of a body. The top wall of the cap nut 6 is provided with a through hole through which the upper end of the stem 3 is inserted, and the cap nut 6 is screwed into the male screw portion 10 of the body 2 to guide. (4) is fixed to the body (2). The upper end of the stem 3 protrudes above the cap nut 6, and the handle 7 is attached thereto.

A tubular joint part is formed in the tubular left protrusion 8 and the right protrusion 9 of the lower part of the body 2, respectively, and the front ring 12 fitted around the tube protruding from each of the protrusions 8, 9 and The cap nut 14 which fastens the back ring 13, these front rings 12, and the back ring 13, and fixes a pipe | tube to each protrusion 8 and 9 is arrange | positioned at each protrusion 8 and 9.

Regarding the material of each member 2, 3, 4, 5, 6, 7, the guide 4 is made of PTFE + PFA, the handle 7 is made of ADC 12, the body 2, the stem 3 ), Panel nut 5 and cap nut 6 are C: 0.001 to 0.01 wt%, Si: 5 wt% or less, Mn: 2 wt% or less, P: 0.03 wt% or less, S: 100 ppm or less, O : 50 ppm or less, Cr: 18-25 wt%, Ni: 15-25 wt%, Mo: 4.5-7.0 wt%, Cu: 0.5-3.0 wt%, N: 0.1-0.3 wt% The addition consists essentially of an alloy of Fe and other unavoidable impurities, while the weight percent CRI = [Cr] + 4 × [Mo] + 30 to ensure the crevice corrosion resistance based on the complex addition of each component of the alloy. The CRI value determined by × [N] is set in a range of 40 ≦ CRI ≦ 55.

That is, the contact portion between the body 2 and the tips of the nuts 5 and 6, the contact portion between the circumferential surface of the top wall through hole of the cap nut 6 and the stem 3, and the like are positions where gap corrosion is likely to occur. The metal members 2, 3, 5, and 6 which are in the use state where gap corrosion easily occurs are made of the alloy. Moreover, the surface of the contact part of each metal member 2, 3, 6 is finished by the surface roughness of Ra = 0.1, and the clearance corrosion resistance is improving by the synergistic effect with the adoption of the stainless steel of the said composition.

In addition, the back ring 13 and the cap nut 14 of the pipe joint portion formed in the tubular left protrusion 8 and the right protrusion 9 of the lower part of the body 2 are made of the above alloy to improve the clearance corrosion. desirable.

2 and 3 show a second embodiment of the fluid component of the present invention. 2 shows a passage closed state, and FIG. 3 shows a passage open state, respectively.

The fluid part 21 of this embodiment is a diaphragm valve, which opens and closes the body 22 having the fluid inflow passage 22a and the fluid outlet passage 22b and the fluid passages 22a and 22b of the body 22. The diaphragm 23 and the actuator 24 which move the diaphragm 23 to an open position and a closed position are provided.

The body 22 has an upward circular recess 22c in the center portion, and each inner end of the fluid inflow passage 22a and the fluid outlet passage 22b opens through the recess 22c.

The diaphragm 23 consists of the rectangular diaphragm 23a in which the front end of the suspension bracket 23c was embedded, and the circular diaphragm 23b provided in close contact with the upper surface of this rectangular diaphragm 23a. The diaphragm 23 is shaped so that the center part protrudes downward, and in the channel | path closed state shown in FIG. 2, the center part contacts the bottom face of the recessed part 22c of the body 22, and the fluid inflow path 22a is carried out. And a passage leading from the fluid outlet passage 22b. As a result, no protrusion (wear portion) supporting the diaphragm 23 exists on the recess 22c side of the body 22, and the passage in the body 22 is straight.

The actuator 24 has a bonnet 25 formed in a cylindrical shape having a top wall, a casing 26 covered on the top wall of the bonnet 25, and a lower end thereof is coupled to a hanging bracket 23c of the diaphragm 23, and an upper end thereof. The piston 27 protruding upward from the casing 26, the piston 28 disposed in the casing 26 so as to be movable upward and downward and fixed to an intermediate portion of the stem 27, and the lower end of the stem 27. The diaphragm pressing member 29 provided in this is provided. And the body 22 and the diaphragm 23 so that the outer peripheral edge of the rectangular diaphragm 23a of the diaphragm 23 may be pinched by the flange part 25a of the bonnet 25 and the opening edge 22d of the body 22. And the actuator 24 are overlapped, and the diaphragm valve 21 is assembled by being joined by the screw member which is not shown in figure.

In the passage closed state shown in FIG. 2, when compressed air is introduced into the casing 26 below the piston 28, the piston 28 and the stem 27 move upward as shown in FIG. 3. In addition, the diaphragm 23 located in the recess 22c of the body 22 also moves upward to open the passage, and in the body 22, from the fluid inflow passage 22a to the fluid outlet passage 22b. A straight flow path leading to it, that is, a flow path without a fluid retention portion, is formed. In the passage opening state, the diaphragm 23 is convex upward from the annular portion between the center portion and the outer peripheral edge which is sandwiched by the flange portion 25a of the bonnet 25 and the opening edge 22d of the body 22 by elastic deformation. Deformed to terminate.

Regarding the material of each member 22, 23, 25, 26, 27, 28, the piston 28 is made of SUS F316L, the diaphragm 23 is rectangular diaphragm 3a made of PTFE, and the circular diaphragm 3b. ) Is made of butyl rubber, the body 22, the bonnet 25, the casing 26 and the stem 27 are C: 0.001 to 0.01 wt%, Si: 5 wt% or less, Mn: 2 wt% or less, P : 0.03 wt% or less, S: 100 ppm or less, O: 50 ppm or less, Cr: 18-25 wt%, Ni: 15-25 wt%, Mo: 4.5-7.0 wt%, Cu: 0.5-3.0 wt% , N: 0.1 to 0.3% by weight, and the balance is substantially alloy of Fe and other unavoidable impurities, and expressed in weight% to secure the gap corrosion resistance based on the complex addition of each component of the alloy. The CRI value determined by CRI = [Cr] + 4 x [Mo] + 30 x [N] is set in the range of 40≤CRI≤55.

That is, the butt portion through the diaphragm 23 of the body 22 and the bonnet 25, the engaging portion of the bonnet 25 and the casing 26, the circumferential surface of the through hole of the top wall of the casing 26 and the stem 27 The contact portion and the like are places where crevice corrosion is likely to occur, and the metal members 22, 25, 26, and 27 in the use state where crevice corrosion is likely to occur are made of the alloy. Moreover, the surface of the contact part of each metal member 22, 25, 26, 27 is finished by the surface roughness of about Ra = 0.1, and the clearance corrosion resistance improves by the synergistic effect with the adoption of the stainless steel of the said composition. have.

4 and 5 show a third embodiment of the fluid component of the invention. In the description of the third embodiment, the left side of the figure will be before the right side and the right side.

The fluid component 30 of this embodiment is a pipe joint, and is formed of a tubular body (joint member 31) into which the tube 32 is inserted at the rear end side and a tube 32 protruding from the rear end side of the body 31. It is provided with the front ring 33 and the back ring 34 fitted in the circumference, and the cap nut 35 which fastens the front ring 33 and the back ring 34, and fixes the pipe | tube 32 to the body 31, have.

Outward flanges 36 are formed on the outer periphery of the intermediate portion of the body 31, and male screw portions 37 and 38 are formed on the outer periphery of the front and rear ends thereof, respectively. On the inner circumference of the rear end portion, a large diameter portion 31a having a larger inner diameter than the front portion is formed, and a tapered surface 31b having a forward shape is formed on the inner circumference of the rear end portion.

A female screw 35a is formed on the inner circumference of the front end of the cap nut 35, and this screw is screwed into the male screw 38 on the rear end of the body 31. An inward flange 35b is formed at the rear end of the cap nut 35.

On the outer circumference of the front ring 33, a tapered surface 33a is formed, which coincides with the tapered surface 31b at the rear end of the body 31, and a tapered annular recess 33b having a thin front is formed on the inner circumference of the rear end thereof. It is. At the front end of the back ring 34, the tapered annular convex part 34a of the front part which fits into the recessed part 33b of the front ring 33 is formed.

In the pipe joint 30, when the cap nut 35 is fastened, the front surface of the inward flange 35b of the cap nut 35 contacts the rear surface of the back ring 34 to advance the back ring. In this way, the convex part 34a of the back ring 34 is inserted in the recessed part 33b of the front ring 33, and the front ring 33 is advanced with the back ring 34, and the front ring 33 is carried out. The front end of the impingement collides with the tapered surface 31b of the body 31. In addition, when fastened, the respective front end portions of the front ring 33 and the back ring 34 are deformed inward and embedded in the pipe 32 so that the pipe 32 is strongly fastened.

Regarding the material of each member 31, 33, 34, 35, the front ring 33 is made of SUS 316, and the body 31, the back ring 34 and the cap nut 35 have a C: 0.001 to 0.01 weight. %, Si: 5 wt% or less, Mn: 2 wt% or less, P: 0.03 wt% or less, S: 100 ppm or less, O: 50 ppm or less, Cr: 18-25 wt%, Ni: 15-25 wt% %, Mo: 4.5-7.0% by weight, Cu: 0.5-3.0% by weight, N: 0.1-0.3% by weight, and the balance is substantially composed of Fe and other unavoidable impurities. In order to secure crevice corrosion resistance on the basis of complex addition, the CRI value calculated by weight CRI = [Cr] + 4 × [Mo] + 30 × [N] is set within the range of 40≤CRI≤55. It is.

That is, the screw coupling portion of the body 31 and the cap nut 35, the contact portion of the cap nut 35 and the back ring 34, and the like are places where crevice corrosion is likely to occur, and in a use state where crevice corrosion is likely to occur. The metallic members 31, 34, 35 which are present are made of the above alloy.

6 shows a fourth embodiment of the fluid component of the invention. The fluid component 40 of this embodiment is a tubular joint, which is a tubular first joint member 41 and a second joint member 42 having fluid passages 41b and 42b communicating with each other, and both joint members. The first joint member 41 and the second joint member are provided with a gasket 43 interposed between the end faces to which the 41 and 42 abut, and a screw means for engaging both joint members 41 and 42. Gasket pressing annular projections 41a and 42a are provided on the end face to which 42 abuts, and the flange part 42c is provided in the vicinity of the edge part of the 2nd joint member 42. As shown in FIG. The screw means is fitted to the second joint member 42 such that the male screw portion 46 provided on the first joint member 41 and the top wall inner surface contact the flange portion 42c via the thrust ring 45. 1 consists of a cap nut 44 screwed to the male threaded portion 46 of the joint member 41.

In this pipe joint 40, the gasket 43 is deformed and the appropriate sealing force can be obtained by fastening the cap nut 44 fastened to the 1st joint member 41 by screwing.

Regarding the material of each member 41, 42, 43, 44, the gasket 43 is made of SUS 316, and the first joint member 41, the second joint member 43 and the cap nut 44 are C : 0.001-0.01 wt%, Si: 5 wt% or less, Mn: 2 wt% or less, P: 0.03 wt% or less, S: 100 ppm or less, O: 50 ppm or less, Cr: 18-25 wt%, Ni : 15 to 25% by weight, Mo: 4.5 to 7.0% by weight, Cu: 0.5 to 3.0% by weight, N: 0.1 to 0.3% by weight, and the balance is substantially made of an alloy consisting of Fe and other unavoidable impurities, CRI = [Cr] + 4 × [Mo] + 30 × [N], expressed in weight percent, in order to ensure crevice corrosion resistance based on the complex addition of each component of the alloy, 40≤CRI≤ It is set in the range of 55.

That is, the screw joint part of the 1st joint member 31 and the cap nut 44, the contact part of the cap nut 44 top wall through-hole peripheral surface, and the 2nd joint member 43 are easy to produce gap corrosion. The metal member 41, 43, 44 in the use state which is easy to generate | occur | produce gap corrosion is made of the said alloy.

The present invention achieves excellent durability by strictly limiting the chemical composition of the fluid component and the crevice corrosion resistance index CRI value particularly against crevice corrosion damage occurring in the fluid component used in the manufacture, storage and transport of medicines and foods. For this purpose, the present inventors have defined the crevice corrosion resistance index CRI value in a limited range of Cr, Ni, Mo, Cu, N, W, and V, which are the main alloying components of stainless steel, which are materials of fluid parts. If it limits to more than a lower limit, it discovered that the outstanding durability was obtained in the said environment.

Below, the reason for limitation of the structural requirements of the alloy (stainless steel) which comprises the fluid component which concerns on this invention is demonstrated.

[C amount: 0.001-0.01 wt%]

C is generally detrimental to the corrosion resistance of stainless steel, but a certain amount of content is required from the viewpoint of strength. Very low C amount of less than 0.001% by weight is expensive to manufacture. In addition, if it exceeds 0.01% by weight, the corrosion resistance is greatly degraded, so it is set to 0.01% by weight or more and 0.01% by weight or less.

[Si content: 5 wt% or less]

Si is an effective element for improving the oxidation resistance of stainless steel. If it exceeds 5% by weight, hot workability is significantly degraded. Therefore, the amount of Si was limited to 5.0 weight% or less.

[Mn content: 2 wt% or less]

Mn is an austenite stabilizing element and can be added as a substitute for expensive Ni, but the corrosion resistance in the brine targeted by the present invention is not effective at more than 2.0% by weight, and the upper limit of the amount of Mn that does not affect the corrosion resistance. As 2.0 wt% or less.

[P amount: 0.03 wt% or less]

It is preferable that P is small in terms of corrosion resistance and hot workability. If it exceeds 0.03% by weight, hot workability is extremely degraded. Therefore, the amount of P was made into 0.03 weight% or less.

[S amount: 100 ppm or less]

S is an element that significantly affects not only corrosion resistance but also hot workability. The lower the amount, the better. Therefore, the amount of S was made into 100 ppm (0.01 weight%) or less.

[O content 50 ppm or less]

O, like S, is an element that significantly affects hot workability, and the lower the better. O was limited to 50 ppm or less obtained by the usual stainless steel steelmaking method.

[Cr amount: 18 wt% or more and 25 wt% or less]

Cr is a basic component of the present invention. It is added in the form of coexistence with Ni, Mo, Cu, N. In order to obtain good corrosion resistance, it is necessary to add 18% by weight or more. Corrosion resistance improves with more Cr, but when it exceeds 25 weight%, manufacturability becomes slightly difficult and it becomes economically expensive. Therefore, the range of Cr amount was limited to 18 weight% or more and 25 weight% or less.

[Ni amount: 15 wt% or more and 25 wt% or less]

Ni, together with Cr, Mo, Cu, and N, is a basic component of the stainless steel of the present invention. In addition, in order to make the manufacture of the thick plate of stainless steel easy, it is necessary to make a metal structure into austenite form, and therefore, addition of Ni is essential. The minimum amount of Ni for making the steel of this invention into an austenite phase is 15 weight%. If the amount of Ni is too large, not only the price is expensive but also the manufacturability is difficult. It was economically inexpensive and made it 25 weight% as an upper limit of the amount of Ni which maintains an austenite phase.

[Mo amount: 4.5 wt% or more and 7.0 wt% or less]

Mo, together with Cr, Ni, Cu, and N, is a basic component of the stainless steel of the present invention. It is an essential element to obtain high corrosion resistance in salt water environment. It becomes effective by coexisting with Cr and N in the range of 4.5 to 7.0 weight%. If it is less than 4.5 weight%, corrosion resistance will become inadequate, but even if it exceeds 7.0 weight%, the improvement effect of corrosion resistance will be saturated, and manufacturability will become difficult and expensive.

[Cu amount: 0.5 wt% or more and 3.0 wt% or less]

Cu is an essential element in order to obtain high corrosion resistance in the brine environment in the form of coexistence with Cr, Ni, Mo, N. With the addition of 0.5% by weight or more, the coexistence effect is remarkable, while when it exceeds 3.0% by weight, the corrosion resistance is saturated and the hot workability is deteriorated. Therefore, the amount of Cu was limited to 0.5 to 3.0 weight%.

[N amount 0.1 weight% or more and 0.3 weight% or less]

N is added as a base component in the form of coexistence with Cr, Ni, Mo, Cu. N is a strong austenite forming element and an element that inhibits the progress of crevice corrosion occurring in stainless steel. In order to obtain stable corrosion resistance, an amount of N of at least 0.1% by weight or more is required. In addition, addition of 0.3 wt% or more is very difficult in steelmaking, and deteriorates the hot workability of stainless steel. Therefore, the range of N amount was limited to 0.1 weight% or more and 0.3 weight% or less.

[W amount: 2 wt% or less]

When W is added in the form of coexistence with Cr, Mo, N, and V, the passivation film is further stabilized, thereby improving the corrosion resistance of crevice corrosion of stainless steel in seawater. The addition of 2 wt% or less depending on the environment is because the addition of more than 2 wt% significantly impairs hot workability.

[V amount: 2 wt% or less]

The addition of V in the form of coexistence with Cr, Mo, N, and W further stabilizes the passivation film, improving the resistance to crevice corrosion in seawater. Add up to 2% by weight, depending on the environment. The larger the amount of V, the higher the corrosion resistance of the gap, but when added in excess of 2% by weight, the hot workability of stainless steel is significantly degraded, making steel production difficult and economically expensive. Therefore, the upper limit of the amount of V was limited to 2 weight%.

[CRI value 40 or more and 55 or less]

If the CRI value calculated by [Cr] + 4 x [Mo] + 30 x [N] is 40 or more, the gap corrosion does not substantially occur in stainless steel. In addition, if it exceeds 55, the steel manufacturing cost is high, the problem of versatility, or the valve manufacturing cost increases. Therefore, the CRI value is in the range of 40 or more and 55 or less from the viewpoint of securing excellent crevice corrosion resistance and reducing the cost.

In the first to fourth embodiments, the contact portion of each metal member 2, 3, 6, 22, 25, 26, 27, 31, 34, 35, 41, 43, 44 made of the alloy The surface is finished with surface roughness of about Ra = 0.1. As a result, the gap corrosion resistance is made less likely to occur.

Example

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated based on an Example.

Table 1 compares the chemical composition of the fluid component and the comparative product of the present invention, and the result of performing a comprehensive evaluation and the presence or absence of crevice corrosion damage after continuously flowing natural seawater at room temperature for about half a year.

The material for fluid parts was solvented by the electric furnace-AOD method and the electric furnace-VAC method, respectively. These molten steels were cast on the continuous slab under normal conditions. Furthermore, the soaking process of 30 minutes-1 hour was performed at 1150 degreeC-1250 degreeC. After surface trimming, the valve shown in FIG. 2 and FIG. 3 was produced, the solution process was performed, and it used for each test. About surface roughness, all were set to Ra = 0.1.

Comprehensive evaluation was performed as follows based on the exposure test result and CRI value in natural seawater.

◎ Table: Valve which has no gap corrosion damage and satisfies CRI value between 40 and 55.

X table | surface: The valve which does not satisfy | fill either or both of the said conditions.

In Table 1, all the CRI values less than 35 have crevice corrosion, and the valve number 5 having a CRI value of 42.93 has a small amount of Ni, Mo, and Cu, and only a large amount of Cr increases the CRI value. Even that alone means that it is impossible to prevent crevice corrosion. The CRI value was 40 or more while keeping the ranges of Cr: 18 to 25% by weight, Ni: 15 to 25% by weight, Mo: 4.5 to 7.0% by weight, Cu: 0.5 to 3.0% by weight, and N: 0.1 to 0.3% by weight. In all cases, crevice corrosion does not occur.

The results of Table 1 show that the fluid component according to the present invention has very good crevice corrosion resistance.

As described above, the use of the valve of the present invention reduces the gap corrosion damage caused by chemicals and foods, and it is possible to ensure the durability of the valve for a long time without repairing or replacing the corrosion damage portion. Therefore, the value of the present invention is very high.

The fluid component according to the present invention has excellent crevice corrosion resistance, and can be applied to applications such as joints used in piping systems, valves used in fluid control devices, and the like, and are particularly suitable for use in medicine and food manufacturing equipment. Do.

Claims (5)

A fluid component such as a valve or a joint used in a pipe and a fluid control device, the fluid component including a plurality of constituent members, the contact surface being in contact with any one of the other constituent members, and the end of the contact surface being the fluid component. The predetermined metal member made to be exposed to the outer surface of C: 0.001-0.01 weight%, Si: 5 weight% or less, Mn: 2 weight% or less, P: 0.03 weight% or less, S: 100 ppm or less, O: 50 It is ppm or less, Cr: 18-25 weight%, Ni: 15-25 weight%, Mo: 4.5-7.0 weight%, Cu: 0.5-3.0 weight%, N: 0.1-0.3 weight%, and remainder is substantial In order to obtain an alloy of Fe and other unavoidable impurities, it is expressed in weight percent to secure crevice corrosion resistance based on the complex addition of each component of the alloy, CRI = [Cr] + 4 × [Mo] + 30 CRI (Crevice Corrosion Resistance Index) value of × [N] is 40 ≤ CRI ≤ 55 Fluid part, characterized in that. The fluid component according to claim 1, which contains one or more of W: 2 wt% or less and V: 2 wt% or less, respectively. The fluid component according to claim 1 or 2, wherein the fluid component is a valve having a body, an actuator, and a screw member, wherein at least one of the body, the actuator, and the screw member is a predetermined metal member. The fluid component according to claim 1 or 2, wherein the fluid component is a diaphragm valve in which a nonmetal diaphragm is sandwiched by a metal body and a metal bonnet, wherein both the body and the bonnet are made of a predetermined metal member. The tubular joint according to claim 1 or 2, wherein the fluid component can be assembled by fastening a cap nut to a male screw provided on an outer circumference of the tubular joint member, wherein at least one of the joint member and the cap nut is formed of a predetermined metal member. The fluid part which is done.