WO2012086706A1 - Oil feed pipe and method for producing same - Google Patents

Abstract

The present invention relates to an oil feed pipe, which is advantageous from the viewpoint of the cost and has excellent salt damage/corrosion resistance, and a method for producing the oil feed pipe. The gist of the present invention is an oil feed pipe which is composed of: a steel pipe member (1) that is formed of a steel pipe of a ferritic stainless steel which contains, in mass%, 0.015% or less of C, 0.01-0.50% of Si, 0.01-0.50% of Mn, 0.050% or less of P, 0.010% or less of S, 0.015% of less of N, 0.010-0.100% of Al, 13.0-18.0% of Cr and additionally 0.03-0.30% of Ti and/or 0.03-0.30% of Nb, and if necessary 0.0002-0.0050% of B and/or 0.01-0.50% of Sn; and a binding component (2) that is attached to the steel pipe member (1). The surface between the binding component (2) and the steel pipe member (1), said surface being exposed to a salt damage environment, is provided with a gap structure (3), and a cationic electrodeposition coating film is formed all over the internal surface of the gap structure. Consequently, the oil feed pipe has excellent salt damage/corrosion resistance, while being advantageous from the viewpoint of the cost.

Description

Oil supply pipe and manufacturing method thereof

The present invention relates to an oil supply pipe for an automobile. In particular, the present invention relates to an oil supply pipe made of a material superior in cost to the current SUS436L and having corrosion resistance equivalent to that of the current material.

The oil supply pipe for automobiles is obliged to guarantee the life of 15 years or 150,000 miles by US regulations, and the oil supply pipe made of stainless steel (SUS436L: 17Cr-1.2Mo) has already been put into practical use. Has been.

Since automobiles traveling in the North American region are exposed to a snow melting salt environment, the material applied to the oil supply pipe is required to have excellent salt corrosion resistance. Conventionally, SUS436L has been applied to the oil supply pipe, but there is a demand for a reduction in material cost against the background of the recent rise in resource prices. SUS436L contains about 1% of expensive Mo, and even if it is replaced with AISI 439 steel (17Cr) not containing Mo, a great cost reduction effect can be obtained.

However, the reduction of alloy elements in the material causes deterioration of corrosion resistance. Therefore, it is necessary to compensate for the weakness caused by the lowering of the material by another method.

The portion of the oil supply pipe where corrosion is a concern is the gap structure on the outer surface of the oil supply pipe that is exposed to a salt damage environment. Conventionally, cationic electrodeposition coating has been used as a means for improving the salt corrosion resistance of the gaps.

Patent Document 1 discloses a method of applying cationic electrodeposition coating to an oil supply pipe assembled by using projection welding using a SUS436 pipe as a raw material. However, this technique uses SUS436 as a raw material, and SUS436 is not completely rust-proof. Therefore, a steel using a lower material cannot obtain a sufficient rust prevention effect only by applying this technique.

Patent Document 2 discloses a technique for preventing crevice corrosion by applying electrostatic coating to an oil supply pipe assembled using SUS436 as a raw material.
Patent Document 3 discloses a technique for ensuring anticorrosion even when chipping is applied to a stainless steel oil supply pipe and chipping is applied. However, these techniques are more costly than the electrodeposition coating. On the other hand, since the interior of the gap cannot be painted, there is no guarantee that a sufficient rust prevention effect will be obtained.

Patent Document 4 presents a rust prevention method other than painting. That is, a technique for applying sacrificial corrosion protection by applying zinc to a portion where a passive state film is damaged or a gap portion by welding, brazing, plastic working or the like in assembling a stainless steel oil supply pipe is disclosed. However, it is cumbersome and troublesome to apply zinc to all of the corrosion-prone portions. In addition, since zinc is an expensive metal and is easily consumed in a salt damage environment, there is a problem that the required amount increases. For these reasons, it is difficult to say that sacrificial corrosion protection with zinc in the oil supply pipe is a realistic measure.

Japanese Patent Laid-Open No. 2002-242779 JP 2004-210003 A JP 2006-231207 A Japanese Patent Laid-Open No. 2005-206064

The present invention is based on the premise that a material superior in cost to SUS436L is used without using Mo or Zn, and an object thereof is to secure salt corrosion resistance. In particular, in the case of a structure that supports an automobile oil supply pipe with a binding part, the corrosion resistance of the gap between the binding part and the oil supply pipe becomes a problem. If the anticorrosion coating is performed after the structure is formed as in the prior art, the gap portion cannot be sufficiently coated, resulting in corrosion of the portion and a bottleneck in life. Then, this invention makes it a subject to extend a corrosion life as a whole, even if it uses the material superior in cost by improving the corrosion resistance of the clearance gap part of such a structure.

The present inventors have intensively studied to solve the above problems. Therefore, we focused on cationic electrodeposition coating, which has been proven in the past, as an anticorrosion method with good cost performance (cost effectiveness). That is, it was considered that the anticorrosion property can be improved by devising the electrodeposition coating and its object, and the effect can be applied to a lowering material (ferritic stainless steel) not using Mo or Zn. Therefore, first of all, in the structure, the state of coating film formation in the gap between the electrodeposition-coated SUS436L oil supply pipe and the bundled parts is investigated, and the entire structure is subjected to a salt damage corrosion test to examine the corrosion state in detail. Observed. As a result, it was found that the corrosion of the portion where the coating film was not formed inside the gap was more severe than the portion where the coating film was formed even if the area was a little. In addition, the corrosion resistance of the part where the electrodeposition coating film is formed has no problem in practice, and if the electrodeposition coating film is previously formed in the gap portion, it is found that no corrosion problem occurs. The present invention has been accomplished.

The gist of the present invention is as follows.
(1) In mass%,
C: ≦ 0.015%
Si: 0.01 to 0.50%,
Mn: 0.01 to 0.50%,
N ≦ 0.015%,
Al: 0.010 to 0.100%,
Cr: 13.0 to 18.0%,
Furthermore, it contains one or two of Ti: 0.03-0.30% and Nb: 0.03-0.30%,
P ≦ 0.050% as an impurity,
S ≦ 0.010%,
Limited to
A steel pipe member formed from a ferritic stainless steel made of ferritic stainless steel, the balance of which is Fe and inevitable impurities, and an oil supply pipe made of a binding part attached to the steel pipe member, the binding part attached to the steel pipe member And a steel pipe member having a gap structure on the surface exposed to the salt damage environment, and cation electrodeposition coating on the entire surface of both the binding part and the steel pipe member inside the gap structure or only the steel pipe member An oil supply pipe having a film formed thereon.
(2) The ferritic stainless steel is further mass%,
B: 0.0002 to 0.0050%,
Sn: 0.01 to 0.50%,
Ni: 0.5% or less,
Cu: 0.5% or less,
Mo: 0.5% or less,
V: 0.5% or less,
Co: 0.5% or less,
Mg: 0.005% or less,
Ca: 0.005% or less,
Zr: 0.1% or less,
La: 0.1% or less,
Y: 0.1% or less,
Hf: 0.1% or less,
REM: The oil supply pipe according to (1) above, which contains one or two of 0.1% or less.
(3) The said gap structure part has a cationic electrodeposition coating film on the surface of each of the said steel pipe member and a binding component, The said cationic electrodeposition coating film is contacting each other in a clearance structure part (1) or the oil supply pipe according to (2).
(4) The oil supply pipe according to any one of (1) to (3), wherein the binding part is fastened to a steel pipe member by a bolt and nut.
(5) By mass%, C: ≦ 0.015%, Si: 0.01 to 0.50%, Mn: 0.01 to 0.50%, N: ≦ 0.015%, Al: 0.010 -0.100%, Cr: 13.0-18.0%, and further, one or two of Ti: 0.03-0.30% and Nb: 0.03-0.30% A steel pipe member formed from a steel pipe made of ferritic stainless steel made of ferritic stainless steel with the balance being limited to P ≦ 0.050% and S: ≦ 0.010% as the impurities, the balance being Fe and inevitable impurities, An oil supply pipe composed of a binding part attached to the steel pipe member, wherein the binding method of the binding part to the steel pipe member is mechanical fastening by a bolt and nut, or separately for the binding part and the steel pipe member in advance. Fastening after applying cationic electrodeposition coating to steel pipe members only Method for producing a filler tube, characterized.
(6) The ferritic stainless steel is further mass%, B: 0.0002 to 0.0050%, Sn: 0.01 to 0.50%, Ni: 0.5% or less, Cu: 0.5 % Or less, Mo: 0.5% or less, V: 0.5% or less, Co: 0.5% or less, Mg: 0.005% or less, Ca: 0.005% or less, Zr: 0.1% or less , La: 0.1% or less, Y: 0.1% or less, Hf: 0.1% or less, REM: 0.1% or less, or one or two of the above (5) The manufacturing method of the oil supply pipe of description.
(7) The oil supply pipe according to (5) or (6) above, wherein the cationic electrodeposition coating films on the contact surfaces are in contact with each other at the contact surfaces of the fastened steel pipe member and the bundled parts. Manufacturing method.

According to the present invention, an oil supply pipe that is superior in terms of cost can be provided while stably securing salt corrosion resistance.

FIG. 1 is a diagram illustrating a state in which a binding component is fastened to the oil supply pipe main body by bolts and nuts. FIG. 2 is a view showing a gap sample, (a) is a top view, (b) and (c) are AA arrow partial cross-sectional views, (b) is an example of coating before gap formation, ( c) is a view of a comparative example painted after forming a gap. FIG. 3 is a diagram illustrating an example of a gap structure existing in a conventional oil supply pipe. (A) shows the bird's-eye view of the whole structure, (b) shows the cross-sectional schematic diagram of a binding component attachment part.

Hereinafter, the present invention will be described in detail.
Usually, an automobile oil supply pipe is fixed to a vehicle body by a binding part (metal part). In FIG. 1, the aspect fixed with the binding component with the breather tube is illustrated. In the conventional oil supply pipe, as illustrated in FIG. 3, a bundling part (metal part) for bundling a main pipe, which is a steel pipe member, and a breather tube and fixing it to a vehicle body is attached to the main pipe by welding. . At this time, a state is shown in which a gap is formed in the vicinity of the welded part of the bundled part (metal part) and the main pipe or breather tube. It is usually difficult to form an electrodeposition coating within such a gap. This is because the gap opening amount is too small, so that the electrodeposition coating liquid cannot penetrate into the gap.
In a structure composed of oil supply pipes and bundling parts, salt damage corrosion proceeds if even a slight metal surface is exposed. Therefore, in the present invention, it is important to form an electrodeposition coating film that eliminates the exposure of the metal surface even in such a structure.

In the present invention, as the binding component, either a metal material or a non-metal material may be used as will be described later. When a metal material is used as the binding part, the binding part is also referred to as a metal part.
Hereinafter, the steel main pipe 1 a and the breather tube 1 b are collectively referred to as a steel pipe member 1. However, when the breather tube is not made of steel, the steel pipe member 1 excluding the breather tube is called a steel pipe member.
A space sandwiched between the steel pipe member 1 and the binding component 2 is referred to as a gap structure portion 3.

In the present invention, the gap structure portion 3 has a cationic electrodeposition coating film on the surface of each of the steel pipe member 1 and the binding component (metal fitting component) 2, and the cationic electrodeposition coating films are in contact with each other in the gap structure portion 3. This problem has been solved by adopting a structure (or a structure in which the gap structure is filled with the cationic electrodeposition coating film). When the binding parts are made of a non-metallic material, only the steel pipe member has a cationic electrodeposition coating film in the gap component, and the cationic electrodeposition coating film is not formed on the binding parts that are a non-metallic material. Also good. Hereinafter, description will be made on the assumption that both the steel pipe member and the binding component are metal materials. When the binding part is a non-metallic material, “each of the steel pipe member and the binding part” as having a cationic electrodeposition coating film may be read as “steel pipe member only”.

Before the steel pipe member 1 and the binding part (metal part) 2 are joined to form the gap structure, a cationic electrodeposition coating is formed on the surfaces of the steel pipe member 1 and the binding part (metal part) 2 in advance. . In particular, a cationic electrodeposition coating film is formed on the surface of the steel pipe member 1 and the bundling component (metal component) 2 that forms the gap structure portion 3. Thereafter, the steel pipe member 1 and the binding part (metal part) 2 are joined to form the gap structure part 3, whereby the entire surface of each of the steel pipe member 1 and the binding part (metal part) 2 inside the gap structure part 3. In contrast, a cationic electrodeposition coating film is formed. After forming the cationic electrodeposition coating on the surface of both the steel pipe member 1 and the binding part (metal part) 2 and forming the gap structure part 3, the steel pipe member 1 and the binding part (metal part) 2 are combined. By forming the gap structure portion 3, the gap structure portion 3 has a cationic electrodeposition coating film on each surface of the steel pipe member 1 and the binding component 2, and the cationic electrodeposition coating films are formed in the gap structure portion 3. It will be in contact. When the cationic electrodeposition coating films are in contact with each other, it is possible to prevent the steel pipe member and the coupling component itself from being exposed in the gap structure portion. Thereby, the slight metal surface exposure of the contact part of a coupling component and a steel pipe member which was a bottleneck on corrosion prevention as an oil supply pipe can be avoided, and corrosion resistance can be remarkably improved as an oil supply pipe. .

Further, in the oil supply pipe of the present invention, as shown in FIG. 1, it is preferable that the binding part (metal part) 2 is fastened by a bolt and nut 4. It is because joining may be carried out by welding (FIG. 3), in that case, the cationic electrodeposition coating film may evaporate around the welded portion and the welded portion (heat affected zone by welding). In the case of welding, it is necessary to form a cationic electrodeposition coating again after welding.

Further, in the method of manufacturing the oil supply pipe of the present invention, when the binding part (metal part) 2 is mechanically fastened to the steel pipe member 1 of the oil supply pipe body using a bolt and nut 4 as illustrated in FIG. It is good to fasten after carrying out the cationic electrodeposition coating of the binding part (metal fitting part) 2 and the steel pipe member 1 separately beforehand. By adopting this method, it is possible to reliably form a cationic electrodeposition coating film over the entire surface inside the gap structure portion 3 (all portions forming the inside of the gap structure portion 3). When the binding component is made of a metal material, the binding component and the steel pipe member are separately subjected to cationic electrodeposition coating and then bonded. When the binding member is made of a non-metallic material, the binding may be performed after the cationic electrodeposition coating is applied only to the steel pipe member.

Next, the material of the steel pipe member will be described. The steel pipe member referred to here means a steel pipe constituting the oil supply pipe. For example, a main pipe and a breather tube filled with fuel gas are applicable.

The present inventors have an oil supply pipe that has a stable salt damage corrosion resistance even in a ferritic stainless steel oil supply pipe that has a lower alloy element content than SUS436L and does not contain an expensive corrosion resistance improving element such as Mo, Ni, or Cu. The structure of was found. The stainless steel according to the present invention is inferior in salt corrosion resistance as compared with the conventional SUS436L. However, when combined with a cationic electrodeposition coating film, it has been confirmed that it has corrosion resistance with no practical problems. The component values of the ferritic stainless steel will be described below.

C, N: C and N are elements that cause intergranular corrosion in the weld heat affected zone, and deteriorate the corrosion resistance. Moreover, cold workability is deteriorated. For this reason, the content of C and N should be limited to the lowest possible level. From the viewpoint of corrosion resistance, the upper limit of C and N is preferably 0.015%, and more preferably 0.010%. In addition, although a lower limit is not prescribed | regulated in particular, considering refinement cost, it is good to set it as C: 0.0010% and N: 0.0050%.

Si: Si is useful as a deoxidizing element in the refining process and contains 0.01% or more. However, in order to deteriorate the workability, it should not be contained in a large amount, and the upper limit should be limited to 0.50%. . A preferred range is 0.10 to 0.30%.

Mn: Mn also contains 0.01% or more as a deoxidizing element and S-fixing element, but Mn should not be contained in a large amount in order to deteriorate the workability, and the upper limit should be limited to 0.50%. A preferred range is 0.10 to 0.30%.

P: Since P is an element that significantly deteriorates workability, the P content is preferably as low as possible. The upper limit of the allowable P content as an impurity is 0.050%. A desirable upper limit of P is 0.030%.

S: Since S is an element that deteriorates the corrosion resistance, the content of S is preferably as low as possible. The upper limit of the S content acceptable as an impurity is set to 0.010%. A desirable upper limit of the S content is 0.0050%.

Cr: Cr is a basic element that ensures corrosion resistance, and an appropriate amount is essential, and the lower limit of the Cr content needs to be 13.0%. On the other hand, the upper limit content is preferably set to 18.0% from the viewpoints of being an element that deteriorates workability and suppressing alloy costs. The preferable range of the Cr content is 15.0% to 17.5%, more preferably 16.5% to 17.5%.

Al: Al is useful as a deoxidizing element and contains 0.010% as the minimum amount necessary for deoxidation. However, in order to deteriorate the workability, the upper limit should be limited to 0.100%. It is good to do. Preferably, the upper limit of the content is 0.070%.

In this invention, 1 type or 2 types of Ti and Nb are contained.
Ti: Ti has the action of fixing C and N as carbonitrides and suppressing intergranular corrosion. For this reason, 0.03% is contained as the lower limit, but even if it is contained excessively, the effect is saturated and the workability is impaired, so the upper limit of the content is made 0.30%. In addition, the proper content of Ti is preferably 5 times or more and 30 times or less the total content of C and N. Ti is preferably contained in the range of 10 to 25 times the total amount of C and N.

Nb: Nb, like Ti, Nb fixes C and N as carbonitrides and suppresses intergranular corrosion, so 0.03% is included as the lower limit. Therefore, the upper limit of the content is made 0.30%. The appropriate content of Nb is preferably 5 times or more and 30 times or less the total content of C and N. Nb is preferably contained in a range of 10 to 20 times the total amount of C and N.

B: B is an element useful for preventing secondary work embrittlement and hot workability deterioration, and does not affect corrosion resistance. Therefore, if necessary, 0.0002% is contained as the lower limit. However, if it exceeds 0.0050%, hot workability deteriorates, so the upper limit is preferably made 0.0050%. Preferably, the upper limit of the B content is 0.0020%.

Sn: Sn is an element useful for improving the corrosion resistance with a trace amount, and is contained as necessary. If the content is less than 0.01%, the effect of improving the corrosion resistance is not exhibited. If the content exceeds 0.50%, the cost increases and the workability also decreases. And Preferably it is 0.05 to 0.40%.

Ni, Cu, Mo, V, Co: These elements are elements that improve weather resistance, and may be contained as necessary. The effect becomes more remarkable due to the synergistic effect with Sn. When Ni, Cu, and Mo are contained, the effect is 0.05% or more. A preferable range of Ni and Cu is 0.1 to 0.4%, and a preferable range of Mo is 0.1 to 0.3%. When V and Co are contained, they are each made 0.01% or more at which the effect is manifested. However, excessive addition leads to an increase in alloy costs and a decrease in manufacturability, so the upper limit is made 0.5%.

Mg: Mg forms Mg oxide together with Al in molten steel and acts as a deoxidizer, and also acts as a crystallization nucleus of TiN. TiN becomes a solidification nucleus of the ferrite phase in the solidification process, and by facilitating crystallization of TiN, the ferrite phase can be finely formed during solidification. By miniaturizing the solidified structure, surface defects caused by coarse solidified structures such as ridging and roping of the product can be prevented. Furthermore, in order to bring about improvement of workability, it can be contained as required. When it contains, it is made 0.0001% which expresses these effects. However, if it exceeds 0.005%, manufacturability deteriorates, so the upper limit is made 0.005%. Preferably, considering the manufacturability, the content is made 0.0003 to 0.002%.

Ca: Ca is an element that improves hot workability and cleanliness of steel, and can be contained as necessary. When it contains, it is made into 0.0003% or more which expresses these effects. However, excessive addition leads to a decrease in manufacturability and a decrease in weather resistance due to water-soluble inclusions such as CaS, so the upper limit is made 0.005%. Preferably, considering the manufacturability and weather resistance, the content is made 0.0003 to 0.0015%.

Zr, La, Y, Hf, REM: These elements have the effect of improving hot workability and steel cleanliness, and significantly improving oxidation resistance and hot workability. Can do. When it contains, it makes it 0.001% or more in which the effect expresses, respectively. However, excessive addition leads to an increase in alloy cost and a decrease in manufacturability, so the upper limit is made 0.1%. Preferably, considering the effect, economy and manufacturability, 0.001 to 0.05% is used for one kind or two or more kinds.

Remaining Fe and inevitable impurities: Fe and inevitable impurities other than the elements described above.

Stainless steel having the above composition is manufactured by a normal stainless steel sheet manufacturing method in which a steel piece melted and refined in a converter or electric furnace is subjected to hot rolling, pickling, cold rolling, annealing, finish pickling, and the like. Manufactured as a steel plate. Further, this steel plate is used as a raw material, and it is manufactured as a welded pipe by an ordinary stainless steel pipe manufacturing method such as electric resistance welding, TIG welding, or laser welding.

This stainless steel pipe is usually used for cold plastic working such as bending, pipe expansion, drawing, spot welding, projection welding, MIG welding, TIG welding, brazing, or mounting various metal fittings with bolts and nuts. After being molded and assembled, it is molded into an oil supply pipe.

Bundling parts include metal parts made of ferrous metal materials such as carbon steel, low alloy steel, and stainless steel, and nonferrous metal materials such as aluminum, aluminum alloy, titanium, titanium alloy, copper alloy, and magnesium alloy. In addition, a molded part using FRP reinforced with a resin such as epoxy or polycarbonate, glass fiber, carbon fiber, or the like may be used as a binding part made of a non-metallic material other than a metal fitting.

When using metal fittings for bundling parts, it is desirable that the material is the same material as the steel pipe member. It is often thought that the fuel inside the oil supply pipe does not leak even if the metal fitting is corroded, but the corrosion of the bundling parts makes the environment inside the gap severe, resulting in crevice corrosion on the steel pipe member side. This is because it will accelerate. For this reason, it is important to take corrosion countermeasures for the bound parts as well as the steel pipe members.

The invention is explained in more detail on the basis of examples.
Ferritic stainless steel having the composition shown in Table 1 is melted in a 150 kg vacuum melting furnace, cast into a 50 kg steel ingot, and then subjected to hot rolling, hot rolled sheet annealing, pickling, cold rolling, annealing and finishing pickling processes. A steel plate having a thickness of 0.8 mm was produced.

<Preparation of gap sample>
From the steel plate material, a large plate of t0.8 × 70 × 70 size and a small plate of t0.8 × 40 × 40 size were collected (a large plate was a steel pipe member, and a small plate was a binding component (metal fitting)). ). A hole for fastening a bolt and nut with a diameter of 5 mm was formed in the center of these two sheets, and cationic electrodeposition was applied to each of the large plate and the small plate. As the paint, PN-110 manufactured by Nippon Paint Co., Ltd. was used. The conditions were selected so that the coating temperature was 20 to 25 μm when energized at a bath temperature of 28 ° C. and a coating voltage of 170 V. The baking conditions were 170 ° C. × 20 minutes. Thereafter, the large plate 11 and the small plate 12 are fastened using a bolt 14 and a nut 15 made of polycarbonate of φ4 mm, and a gap structure portion between the large plate 11 and the small plate 12 as shown in FIGS. No. 3 produced gap samples in contact with both cationic electrodeposition coatings 13 (Invention Examples 20 to 55, Comparative Examples 102 and 103).

In addition, a gap sample formed after fastening both plates without forming a cationic electrodeposition coating film in advance was prepared (Comparative Example 101). Before performing electrodeposition coating on the large plate 11 and the small plate 12, two pieces were fastened using bolts 14 and nuts 15, and then cationic electrodeposition coating was performed. As a result, as shown in FIGS. 2A and 2C, a slight gap is formed in the gap structure portion 3, and the large plate 11 and the small plate 12 that do not have a coating film face each other with respect to the gap structure portion 3. It became. In FIG. 2C, a gap larger than the actual gap is drawn for the gap structure portion 3 in order to clarify the difference. Actually, the large plate 11 and the small plate 12 are in contact with each other, and a gap is slightly opened between the large plate 11 in the vicinity of the end surface of the small plate 12 (this is also included in the mode of the gap structure portion 3). . Even in this case, there is a possibility that an extremely slight portion that is not covered with the electrodeposition coating film is generated in the slight gap structure portion 3. Corrosion progresses from the part not covered with the electrodeposition coating.

Next, a gap sample was prepared on the assumption that the joining component is a non-metallic material (Example 56 of the present invention). Only the large plate was made of the steel plate material and was subjected to cationic electrodeposition coating. The plate was made of a non-metallic material (polycarbonate resin). Except for the fact that no electrodeposition coating is applied to the small plate side, the large plate and small plate were fastened using φ4 mm polycarbonate bolts and nuts to create the gap sample so as to have the same structure as in FIG. Invention Example 56). For Comparative Example 104, before applying the cationic electrodeposition coating, two plates, a large plate and a child plate, were fastened using bolts and nuts, and then the cationic electrodeposition coating was applied.

For these gap samples, after sealing the back end face of the large plate, a cycle corrosion test stipulated by JASO-M609-91 simulating a salt damage environment (salt spray: 5% NaCl spray 35 ° C. × 2 Hr, dry: 20% relative humidity) , 60 ° C. × 4 Hr, wet: relative humidity 90%, 50 ° C. × 2 Hr repeated). The test period was 300 cycles. After 300 cycles, the bolts and nuts were removed and immersed in a coating film release agent to peel the coating film, and then the corrosion depth inside the gap was measured by a microscope focal depth method. Ten points were measured and the maximum value was taken as the representative value of the sample. The maximum corrosion depth of 400 μm or less was considered good.

Table 2 shows the sample history, evaluation method, and evaluation results.

Invention No. In Nos. 20 to 55, a coating film equivalent to the portion other than the gap was reliably formed over the entire surface inside the gap. In No. 56, polycarbonate resin was used for the small plate and a coating film equivalent to the portion other than the gap was reliably formed on the large plate side of the gap, so extremely excellent corrosion resistance was obtained.

Comparative Example No. For 101 and 104, the material satisfies the conditions of the present invention, but satisfactory gap corrosion resistance was not obtained because electrodeposition coating was performed after the gap was formed.
Comparative Example No. Reference numeral 102 denotes a test result when the current material X01 (SUS436L) is used. Since SUS436L was used, the crevice corrosion resistance was good, but the cost reduction effect could not be obtained because the material was expensive.
Comparative Example No. 103 is a result of 11Cr steel whose material is outside the scope of the present invention. Even if electrodeposition coating was performed before forming the gap portion to form a coating film, the corrosion resistance of the material was insufficient, and corrosion under the coating film progressed, leading to severe crevice corrosion. Invention Example No. 24 (Material E05) and Comparative Example No. Comparing 103, it can be seen that when a coating film is formed in the gap, the corrosion resistance is drastically improved when the Cr content is between 11% and 13%.

The present invention can be used for an oil supply pipe for automobiles. Moreover, even if it is a use other than that, it can apply to the salt damage corrosion countermeasure of a similar structure.

DESCRIPTION OF SYMBOLS 1 Steel pipe member 1a Main pipe 1b Breather tube 2 Bundling parts 3 Gap structure part 4 Bolt nut 5 Bolt hole 6 Brazing 11 Large plate 12 Small plate 13 Coating film 14 Bolt 15 Nut

Claims (7)

% By mass
C: ≦ 0.015%
Si: 0.01 to 0.50%,
Mn: 0.01 to 0.50%,
N ≦ 0.015%,
Al: 0.010 to 0.100%,
Cr: 13.0 to 18.0%,
Furthermore, it contains one or two of Ti: 0.03-0.30% and Nb: 0.03-0.30%,
P ≦ 0.050% as an impurity,
S ≦ 0.010%,
Limited to
A steel pipe member formed from a ferritic stainless steel made of ferritic stainless steel, the balance of which is Fe and inevitable impurities, and an oil supply pipe made of a binding part attached to the steel pipe member, the binding part attached to the steel pipe member And a steel pipe member having a gap structure on the surface exposed to the salt damage environment, and cation electrodeposition coating on the entire surface of both the binding part and the steel pipe member inside the gap structure or only the steel pipe member An oil supply pipe having a film formed thereon.
The ferritic stainless steel is further mass%,
B: 0.0002 to 0.0050%,
Sn: 0.01 to 0.50%,
Ni: 0.5% or less,
Cu: 0.5% or less,
Mo: 0.5% or less,
V: 0.5% or less,
Co: 0.5% or less,
Mg: 0.005% or less,
Ca: 0.005% or less,
Zr: 0.1% or less,
La: 0.1% or less,
Y: 0.1% or less,
Hf: 0.1% or less,
The oil supply pipe according to claim 1, wherein the oil supply pipe contains one or two types of REM: 0.1% or less.
The gap structure portion has a cationic electrodeposition coating film on the surface of each of the steel pipe member and the binding component, and the cationic electrodeposition coating films are in contact with each other in the gap structure portion. 2. The oil supply pipe according to 2.
The oil supply pipe according to any one of claims 1 to 3, wherein the binding part is fastened to the steel pipe member by a bolt and a nut.
By mass%, C: ≦ 0.015%, Si: 0.01 to 0.50%, Mn: 0.01 to 0.50%, N: ≦ 0.015%, Al: 0.010 to 0. 100%, Cr: 13.0 to 18.0%, and further containing one or two of Ti: 0.03 to 0.30% and Nb: 0.03 to 0.30% A steel pipe member formed from a steel pipe made of ferritic stainless steel made of ferritic stainless steel, the impurities being limited to P ≦ 0.050% and S: ≦ 0.010%, the balance being Fe and inevitable impurities, and the steel pipe member An oil supply pipe comprising a bundled part attached to the steel pipe member, wherein the method of attaching the bundled part to the steel pipe member is mechanical fastening by a bolt and nut, separately in advance for the bundled part and the steel pipe member or only the steel pipe member It is characterized by fastening after applying cationic electrodeposition coating to The production method of the oil supply pipe for.
The ferritic stainless steel is further mass%, B: 0.0002 to 0.0050%, Sn: 0.01 to 0.50%, Ni: 0.5% or less, Cu: 0.5% or less, Mo: 0.5% or less, V: 0.5% or less, Co: 0.5% or less, Mg: 0.005% or less, Ca: 0.005% or less, Zr: 0.1% or less, La: The oil supply according to claim 5, comprising one or two of 0.1% or less, Y: 0.1% or less, Hf: 0.1% or less, and REM: 0.1% or less. A method of manufacturing a tube.
7. The method of manufacturing an oil supply pipe according to claim 5, wherein the cation electrodeposition coating films on the contact surfaces are in contact with each other at the contact surfaces of the steel pipe member and the bundled parts that are fastened.

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