JP2011063862A - Plated steel sheet for producing pipe having corrosion resistance to vapor of fuel, and pipe and oil feed pipe using the plated steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plated steel sheet for producing a pipe having corrosion resistance to the vapor of fuel such as a gasoline, light oil, bioethanol and biodiesel fuel, and to provide a pipe. <P>SOLUTION: The plated steel sheet for producing a pipe is obtained, on the surface of a steel sheet, by forming a plating layer comprising Zn, Co and Mo, an Fe-Ni diffusion layer, and a softened Ni layer therebetween. The pipe and oil feed pipe are obtained, on the inside face of a pipe made of the steel sheet, by forming a plating layer comprising Zn, Co and Mo, an Fe-Ni diffusion layer below the same and a softened Ni layer therebetween. The oil feed pipe made of the steel sheet for feeding fuel to a fuel tank includes: a large-sized pipe part through which fuel passes; and a fine-sized pipe part ventilating the upper part and the lower part in the large-sized pipe part, and at least the inside face of the large-sized pipe part is provided with a plating layer comprising Zn, Co and Mo, and the Fe-Ni diffusion layer is formed at the lower part thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface-treated steel sheet having corrosion resistance against fuel vapor.

In recent years, in order to reduce greenhouse gases, there has been an active movement to use so-called bioethanol-mixed gasoline in which bioethanol, which is carbon neutral, is mixed with gasoline. However, when ethanol is added to gasoline, it becomes easier for the gasoline to absorb moisture, and water may be mixed into the fuel tank.
Furthermore, if the ethanol mixed gasoline is left standing for a long time, the gasoline deteriorates and an organic acid is formed in the gasoline.
In this way, when moisture absorption and gasoline deterioration occur, ethanol can be mixed into both water and gasoline, so water and organic acids are contained inside the gasoline. The mixture may evaporate.
In that case, the inner surface of the pipe, which normally contacts only non-corrosive gasoline vapor, is exposed to a strong corrosive environment.
Therefore, pipes placed under an atmosphere of bioethanol mixed gasoline are also required to have corrosion resistance assuming a corrosive environment.
As a countermeasure to these corrosive environments, for example, Patent Document 1 discloses that the adhesion amount is Cr on a Sn—Zn alloy plated surface having a plating adhesion amount of 10 to 70 g / m ² and Sn-1 to 50% Zn. A steel plate treated with a chromate film made of chromic acid, silica, inorganic phosphoric acid or organic phosphoric acid of 100 mg / m ² or less in terms of conversion, or further treated with a resin chromate film containing an organic resin, and a pair of flanges A fuel container for automobiles having excellent corrosion resistance is described in which the flange portion of the vertical molded body is continuously seam welded.

JP 2000-17450 A

However, the material used for the automobile fuel container described in Patent Document 1 is a corrosion resistance of a portion such as a fuel tank that is immersed in an automobile fuel such as gasoline and directly contacts the automobile fuel, and is not corrosion resistant to steam. .
For example, pipes connected to fuel tanks, such as fuel pipes, are overwhelming in the case of being exposed to highly volatile automotive fuel vapors rather than being directly exposed to automotive fuel. Too many.
In addition, the depletion of fossil fuels has become serious internationally, and the spread of bioethanol and biodiesel fuels has become widespread.
Thus, in addition to conventional automobile fuels such as gasoline and light oil, a material having sufficient characteristics for both bioethanol and biodiesel fuel and its vapor has been demanded.
Accordingly, an object of the present invention is to solve the above-described conventional problems, and a plated steel sheet for pipe production having sufficient corrosion resistance against fuel vapor such as fuel, particularly gasoline, light oil, bioethanol, or biodiesel fuel. Is to provide.
Another object of the present invention is to provide a pipe using the plated steel sheet.

(1) The plated steel sheet for pipe production of the present invention is provided with a plating layer containing Zn, Co, and Mo on at least one surface of the steel sheet, and an Fe-Ni diffusion layer provided therebelow, and has corrosion resistance against fuel vapor. It is characterized by having.
(2) In the plated steel sheet for manufacturing a pipe of the present invention, a softened Ni layer is formed between the plated layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer in (1). It is characterized by being.
(3) The plated steel sheet for manufacturing a pipe of the present invention is characterized in that, in the above (1) or (2), the thickness of the plating layer containing Zn, Co, and Mo is 1.0 to 8.0 μm. And
(4) The plated steel sheet for pipe production according to the present invention is characterized in that, in any one of the above (1) to (3), the fuel contains gasoline, light oil, bioethanol, or biodiesel fuel.
(5) The pipe of the present invention has a plating layer containing Zn, Co, and Mo on the inner surface of a pipe made of a steel plate, and an Fe—Ni diffusion layer is provided therebelow, and is corrosion resistant to fuel vapor. It is characterized by having.
(6) In the oil supply pipe of the present invention, in (5), a softened Ni layer is formed between the plating layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer. It is characterized by.
(7) The pipe of the present invention is characterized in that, in the above (5) or (6), the thickness of the plating layer containing Zn, Co, and Mo is 1.0 to 8.0 μm.
(8) The pipe of the present invention is characterized in that, in any of the above (5) to (7), the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel.
(9) The oil supply pipe of the present invention is an oil supply pipe made of a steel plate for supplying fuel to the fuel tank,
A large-diameter pipe section through which fuel passes;
A small-diameter pipe portion that ventilates the upper and lower portions of the large-diameter pipe portion,
It has a plating layer containing Zn, Co, and Mo at least on the inner surface of the large-diameter pipe portion, and an Fe—Ni diffusion layer is formed thereunder, and has corrosion resistance against fuel vapor. .
(10) In the oil supply pipe of the present invention, in (9), a softened Ni layer is formed between the plating layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer. It is characterized by.
(11) The oil supply pipe of the present invention is characterized in that, in the above (9) or (10), the thickness of the plating layer containing Zn, Co, and Mo is 1.0 to 8.0 μm.
(12) The oil supply pipe of the present invention is characterized in that, in any of the above (9) to (11), the fuel contains gasoline, light oil, bioethanol, or biodiesel fuel.

  The plated steel sheet for pipe production and the pipe using the plated steel sheet of the present invention can suppress rusting even when exposed to fuel vapor such as gasoline, light oil, bioethanol, or biodiesel fuel.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows the structure of the plated steel plate of this invention, (a) is provided with the plating layer containing Zn, Co, and Mo, and the Fe-Ni diffused layer under it on both surfaces of the steel plate used as a board | substrate. In (b), a plated layer containing Zn, Co, and Mo, an Fe—Ni diffusion layer, and a softened Ni layer are formed on both surfaces of a steel plate to be a substrate. . It is a schematic explanatory drawing which shows the method of the corrosion resistance test with respect to the bioethanol mixing gasoline of the plated steel plate of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of the oil supply pipe using the plated steel plate of this invention, (a) is an oil supply which has the large diameter pipe part which a fuel passes, and the thin diameter pipe part which ventilates the upper part and lower part of a large diameter pipe part (B) shows an oil supply pipe in which a large-diameter pipe portion and a small-diameter pipe portion through which fuel passes are formed independently.

Hereinafter, embodiments of the present invention will be described in detail.
<Steel plate>
A low-carbon aluminum killed hot-rolled coil is usually used as an original plate for a plated steel sheet for pipe production.
In addition, a coil produced from non-aged continuous cast steel by adding niobium or titanium to the ultra low carbon steel having a carbon content of 0.003% by weight or less, and further adding niobium or titanium thereto is also used.

<Plating pretreatment>
As the pretreatment for plating described below, the scale (oxide film) on the surface of the cold-rolled steel sheet is removed by performing degreasing by electrolysis or dipping in an alkaline solution usually containing caustic soda. After removal, the product is rolled to the product thickness in a cold rolling process.

<Annealing>
The rolling oil adhered by rolling is electrolytically cleaned and then annealed. The annealing may be either continuous annealing or box annealing and is not particularly particular. After annealing, the shape is corrected.

<Nickel plating>
First, nickel plating is performed on the steel plate after annealing.
In general, a nickel sulfate bath called a watt bath is mainly used as a nickel plating bath, but a sphamic acid bath, a borofluoride bath, a chloride bath, and the like can also be used. The thickness of nickel plating when plating using these baths is preferably in the range of 1 to 3 μm.
In order to obtain the plating thickness, when a typical watt bath is used, the bath composition is nickel sulfate 200 to 350 g / L, nickel chloride 20 to 50 g / L, boric acid 20 to 50 g / L, pH 3.6 to It is obtained by electrolytic conditions of 4.6, bath temperature 50-65 ° C., current density 5-50 A / dm ² , Coulomb number about 900-3000 c / dm ² . The boric acid added as a stabilizer may be citric acid.
Here, the nickel plating formed in the Watt bath is a matte nickel plating in which no organic compound is added in addition to the pit suppressor, and an organic compound called a leveling agent that smooths the deposited crystal plane of the plating layer. There are bright nickel plating and bright nickel plating to which an organic compound containing a sulfur component is added in addition to a leveling agent to make the nickel plating crystal structure finer, but can be used in the present invention. .

<Diffusion>
Next, after nickel plating, heat treatment is performed to form an Fe—Ni diffusion layer.
The purpose of this heat treatment is to soften and recrystallize the finely crystallized state of the nickel plating to improve the adhesion between the steel substrate and the plating layer, and to form pipes on the pipe by the Fe-Ni diffusion layer formed by the heat treatment. It is to improve the film workability (followability) with respect to bending and spooling.
As a method of thermal diffusion, there are a method using a continuous annealing furnace and a method using a box-type annealing furnace. The thermal diffusion temperature is in the range of 400 to 800 ° C., and the diffusion time is usually in the range of 60 seconds to 12 hours for thermal diffusion.
The gas atmosphere at the time of diffusion is a non-oxidizing or reducing protective gas atmosphere.
Furthermore, in the present invention, as a heat treatment method by box-type annealing, heat treatment by a protective gas composed of 75% hydrogen-25% nitrogen generated by an ammonia crack method called hydrogen-enriched annealing with good heat transfer is suitably applied. The This method is advantageous in that the uniformity of the temperature distribution in the steel strip in the longitudinal direction and the width direction of the steel strip is good, so that the variation in the steel strip of the Fe—Ni diffusion layer and between the steel strips is small.
In the diffusion treatment, if the heat treatment is continued even after the iron reaches the outermost surface, the ratio of the iron exposed to the outermost layer increases.
The heat treatment conditions were variously changed for each plating thickness, and the thicknesses of the softened Ni layer and Fe—Ni diffusion layer were calculated from the results obtained by the glow discharge emission analysis, that is, GDS analysis (GDLS-5017 manufactured by Shimadzu). A number of experiments were performed to create a number of samples with varying thicknesses of the softened Ni layer and the Fe—Ni diffusion layer.
GDS analysis is a measurement method for obtaining an analysis chart in the depth direction, and in this patent, Ni and Fe are considered to exist until their respective strengths are 1/10 of the respective maximum strength values.
The thickness of the softened Ni layer can be expressed by the GDS measurement time from the surface layer, that is, the GDS measurement time 0 to the Fe strength becoming 1/10 of the maximum strength value.
The thickness of the Fe—Ni diffusion layer can be expressed by the GDS measurement time from when the strength of Fe becomes 1/10 of the maximum strength value to when the strength of Ni becomes 1/10 of the maximum strength value.
For the Ni plating layer before the heat treatment, the thickness of the Ni plating layer is expressed by the GDS measurement time from the surface layer, that is, the measurement time 0 to the Ni intensity becomes 1/10 of the maximum strength value. The thickness of the plating layer is actually measured with fluorescent X-rays.
The ratio between the GDS measurement time of the Ni plating layer, the GDS measurement time of the softened Ni layer, and the GDS measurement time of the Fe—Ni diffusion layer was calculated, and this ratio and the actual Ni plating layer were calculated. From the thickness, the thickness of the softened Ni layer and the thickness of the Fe—Ni diffusion layer are calculated.

<Plating layer containing Zn, Co, and Mo>
Next, a plating layer containing Zn, Co, and Mo is applied on the Fe—Ni diffusion layer or the softened Ni layer.
The plating thickness of the plating layer containing Zn, Co, and Mo is preferably in the range of 1.0 to 8.0 μm.
In order to obtain a predetermined plating thickness in the plating layer containing Zn, Co, and Mo, zinc sulfate 180-280 g / L, cobalt sulfate 10-70 g / L, ammonium molybdate 0.01-0.4 g / L Electrolytic conditions with a current density of 5 to 50 A / dm ² in a bath composition of ammonium sulfate 10 to 40 g / L, sodium sulfate 20 to 50 g / L, pH 2.7 to 3.7, bath temperature 30 to 50 ° C. Obtained by.
The component ratio of the plated Zn, Co, and Mo-containing layer is preferably Co: 0.1 to 5%, Mo: 0.001 to 1%, and the balance: Zn. Such a component ratio of plating can be realized by adjusting the bath composition, pH, bath temperature, current density, and the like within a suitable range.
FIG. 1 shows a schematic configuration of a steel plate provided with a plating layer containing Zn, Co, and Mo thus formed. (A) is provided with a plated layer containing Zn, Co, and Mo and a Fe—Ni diffusion layer thereunder on both surfaces of the steel plate to be the substrate, and (b) is both surfaces of the steel plate to be the substrate. In addition, a plating layer containing Zn, Co, and Mo, an Fe—Ni diffusion layer, and a softened Ni layer are formed therebetween.

<Evaluation method>
Evaluation test pieces were prepared from steel plates of various plating thicknesses, and corrosion resistance was investigated by immersing them in bioethanol mixed gasoline. Corrosion resistance was confirmed by the presence or absence of rusting.
A corrosive solution simulating bioethanol-mixed gasoline was used as a test.
As the corrosive liquid, 100 ppm formic acid and 200 ppm acetic acid were added to regular gasoline specified in JIS K2202, and 10% bioethanol specified in JASO M361 was added to purify a simulated deteriorated gasoline.
For the purpose of further enhancing the corrosiveness, corrosive water was prepared by adding 1000 ppm formic acid, 2000 ppm acetic acid, and 1000 ppm chlorine to pure water, and 10 wt% was added to the above deteriorated gasoline to obtain a corrosive liquid.
The corrosive liquid is in a state where the upper layer is divided into degraded gasoline and the lower layer is divided into two layers of corrosive water.
It arrange | positioned in an airtight container so that an evaluation test piece (steel plate of this invention) may be immersed in this corrosive solution half, and it passed over time in a 45 degreeC thermostat.
Thereby, as shown in FIG. 2, the evaluation test piece is, from above, the gas phase part 11 in contact with the fuel vapor (gas phase) of the deteriorated gasoline, the liquid phase part 12 in contact with the deteriorated gasoline (liquid phase), and corrosion. It will be separated into the water phase part 13 in contact with water (water phase).
And the corrosion resistance with respect to the fuel vapor | steam of an evaluation test piece was evaluated by investigating the corrosion of the gaseous-phase part 11 of an evaluation test piece.
The evaluation used what bent 90 degree | times by making a plating surface into an inner surface (recessed part). The radius of the trough was 1.0 mm. The rusting of the processed valley was evaluated.
From many experimental results, it was found that rusting in the gas phase portion is suppressed by setting the thickness of the plating layer containing Zn, Co, and Mo to a range of 1.0 to 8.0 μm.
It was also found that rusting in the gas phase portion is further suppressed by forming a softened Ni layer under the plating layer containing Zn, Co, and Mo.
That is, from the experimental results, when the plating thickness of the plating layer containing Zn, Co, and Mo was less than 1.0 μm, sufficient corrosion resistance in the gas phase portion could not be obtained.
Moreover, when the thickness of the plating layer containing Zn, Co, and Mo exceeds 8.0 μm, the surface may be scraped during processing of pipes and the like to generate wear powder, which is not preferable.
Further, by forming a softened Ni layer in the lower layer of the plating layer containing Zn, Co, and Mo, rusting in the gas phase is further suppressed, but the thickness of the softened Ni layer When the thickness exceeds 3.0 μm, the total thickness of the plated layer containing Zn, Co, and Mo and the softened Ni layer increases, and the surface is scraped during processing of pipe pipes and wear powder is generated. It may occur and is not preferable.

<Pipe processing>
Using the above steel plate, correcting the shape with a leveler, slitting to a predetermined outer diameter with a slitter, pipe-forming with a molding machine, and seam welding the end faces in the longitudinal direction by high frequency induction welding Manufacture pipes for fuel.
As shown in FIG. 3A, the fuel supply pipe 20 is attached to the fuel tank 23 so as to extend obliquely upward from the upper part of the fuel tank 23.
In addition, the oil supply pipe 20 is branched from the middle of the large diameter pipe portion 21 through which the fuel passes,
The small diameter pipe part 22 which ventilates the upper part and the lower part of the large diameter pipe part 21 was connected.
The large diameter pipe part 21 is manufactured using the steel plate of the present invention. In addition, you may manufacture a thin diameter pipe part using the steel plate of this invention.
In addition, the oil supply pipe 20 prescribed | regulated by this invention is not restricted to a shape as shown to Fig.3 (a), For example, as shown in FIG.3 (b), with the large diameter pipe part 21 through which fuel passes, Even if the small-diameter pipe portion 22 is attached to the fuel tank 23 in an independent shape, the corrosion resistance against the fuel vapor is still particularly required, and thus those of these forms are also included.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1>
A cold-rolled and annealed low carbon aluminum killed steel plate having a thickness of 0.70 mm was used as a plating base plate.
The components of the steel plate that is the plating original plate are as follows.
C: 0.045%, Mn: 0.23%, Si: 0.02%, P: 0.012%, S: 0.009%, Al: 0.063%, N: 0.0036%, balance : Fe and inevitable impurities.
The steel sheet was subjected to alkaline electrolytic degreasing and pickling with sulfuric acid, and then nickel plating with a plating thickness of 2 μm was performed under conditions of Watt bath matte plating to obtain a nickel-plated steel sheet. The Fe-Ni diffusion layer having a thickness of 1.23 μm was formed on the surface of the steel sheet.
Thereafter, a layer containing Zn, Co, and Mo having a thickness of 1 μm was formed thereon by plating.
The composition ratio of the formed plating layer containing Zn, Co, and Mo was Co: 0.3%, Mo: 0.01%, and the balance: Zn (% is mass). In addition, the thickness and composition ratio of the plating layer containing Zn, Co, and Mo were measured by fluorescent X-ray analysis (ZSX 100e manufactured by Rigaku).

<Examples 2 to 14>
Steel plates of Examples 2 to 14 in Table 1 were obtained by changing the thickness of the plating layer containing Zn, Co, and Mo.
In Examples 2-14, what formed the softened Ni layer between the plating layer containing Zn, Co, and Mo and the Fe-Ni diffusion layer described the numerical value of the thickness. Those that did not form the softened Ni layer were described as having a thickness of zero.
For nickel plating, the plating thickness was changed under the conditions of Watt bath matte plating. The nickel plating thickness was measured by fluorescent X-ray analysis (ZSX 100e, manufactured by Rigaku).
Conditions other than the thickness of the plating layer containing Zn, Co, and Mo, the nickel plating thickness, and the thermal diffusion treatment described in Table 1 were the same as in Example 1.

<Comparative example>
The thickness of the plating layer containing Zn, Co, and Mo, the thickness of the nickel plating, and the thermal diffusion treatment were changed as shown in Table 1, and the other conditions were the same as in the example. 6 plated steel sheets were obtained.

<Evaluation>
Next, an evaluation test piece is prepared from each plated steel sheet of Examples and Comparative Examples, and after aging for 500 hours in a 45 ° C. thermostat, the appearance of the vapor phase portion of the evaluation test piece of each plating thickness is observed. Then, the occurrence of rust was investigated. The results are shown in “Result of generation of red rust in gas phase” in Table 1.

As is apparent from Table 1, the plated steel sheets of Examples 1 to 14 of the present invention were free from rust and excellent as a pipe material having corrosion resistance against fuel vapor.
Since the above corrosive liquid generates steam that is more corrosive than gasoline, light oil, bioethanol, or biodiesel fuel, if there is no rust in this corrosive liquid test, gasoline, light oil, bioethanol, or biodiesel It is considered that there is no rust on the fuel.
On the other hand, the plated steel sheets of Comparative Examples 1 to 6 have red rust and are not practical as a pipe manufacturing material having corrosion resistance against fuel vapor.

The plated steel sheet for pipe production of the present invention can suppress the occurrence of rusting when exposed to fuel vapor such as gasoline, light oil, bioethanol, or biodiesel fuel.
Moreover, the pipe using the plated steel plate for pipe manufacture of this invention and an oil supply pipe are excellent in corrosion resistance with respect to fuel vapor | steam, and its industrial applicability is very high.

11: Gas phase part 12: Liquid phase part 13: Water phase part 20: Oil supply pipe 21: Large diameter pipe part 22: Small diameter pipe part 23: Fuel tank

Claims (12)

A plated steel sheet for pipe production having corrosion resistance to fuel vapor, characterized in that a plated layer containing Zn, Co, and Mo and an Fe-Ni diffusion layer are provided below the plated layer on at least one surface of the steel sheet . 2. The fuel vapor according to claim 1, wherein a softened Ni layer is formed between the plating layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer. Plated steel sheet for pipe production that has corrosion resistance. The plated steel sheet for pipe production having corrosion resistance to fuel vapor according to claim 1 or 2, wherein the thickness of the plating layer containing Zn, Co, and Mo is 1.0 to 8.0 µm. . The said fuel contains gasoline, light oil, bioethanol, or biodiesel fuel, The plated steel plate for pipe manufacture which has the corrosion resistance with respect to fuel vapor | steam in any one of Claims 1-3 characterized by the above-mentioned. It has corrosion resistance against fuel vapor, characterized in that it has a plating layer containing Zn, Co, and Mo on the inner surface of a pipe made of a steel plate, and an Fe-Ni diffusion layer is provided thereunder. pipe. 6. The fuel vapor according to claim 5, wherein a softened Ni layer is formed between the plated layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer. Pipe with corrosion resistance. The pipe having corrosion resistance to fuel vapor according to claim 5 or 6, wherein the plating layer containing Zn, Co, and Mo has a thickness of 1.0 to 8.0 µm. 8. The pipe having corrosion resistance against fuel vapor according to claim 5, wherein the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel. An oil supply pipe made of a steel plate for supplying fuel to a fuel tank,
A large-diameter pipe section through which fuel passes;
A small-diameter pipe portion that ventilates the upper and lower portions of the large-diameter pipe portion,
Corrosion resistance to fuel vapor, characterized in that it has a plating layer containing Zn, Co, and Mo at least on the inner surface of the large-diameter pipe portion, and an Fe-Ni diffusion layer is formed thereunder. Having a refueling pipe. 10. The fuel vapor according to claim 9, wherein a softened Ni layer is formed between the plating layer containing Zn, Co, and Mo and the Fe—Ni diffusion layer. Oiling pipe with corrosion resistance. 11. The oil supply pipe having corrosion resistance against fuel vapor according to claim 9, wherein the plating layer containing Zn, Co, and Mo has a thickness of 1.0 to 8.0 μm. The fuel supply pipe according to any one of claims 9 to 11, wherein the fuel includes gasoline, light oil, bioethanol, or biodiesel fuel.

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