JPS6191390A - Steel plate for alcohol or alcohol-containing fuel containers - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a container that has corrosion resistance, processability, and
The present invention also relates to a steel plate for fuel containers that exhibits excellent weldability.

With the recent deterioration of the petroleum situation (rise in petroleum costs and decrease in production), alcohol fuels such as methyl alcohol and ethyl alcohol, or alcohol fuels such as methyl alcohol and ethyl alcohol in place of gasoline as automobile fuels, or The use of alcohol-containing fuels (so-called gasohol), such as methyl tertiary-butyl alcohol (MTBA), as an alternative fuel has been proposed and is being put into practice.

Japanese Patent Application Laid-Open No. 1983-1999 is used for automobile fuel container materials for these alcohol fuels or alcohol-added gasoline (gasohol).
-Pb-Sn alloy coated steel sheets, which are published in many patent publications such as ``2''3345 and JP-A-51-115240, are used, but there is a problem that the corrosion resistance of the steel sheets is significantly deteriorated. be. In other words, the cause is that the Pb-Sn alloy steel sheet contains Pb and S, which are mainly composed of Pb.
Since the coating layer is composed of a eutectic alloy of n, for example (1) the pb metal layer is easily corroded because the pb metal is severely corroded by methyl alcohol.

(2) P by acetaldehyde, acetic acid (oxidation product of ethyl alcohol), formaldehyde, formic acid (oxidation product of methyl alcohol) produced by oxidation of alcohol fuel or alcohol-added gasoline.
The b gold metal is severely corroded, and the pb metal layer in the coating layer is easily corroded.

(3) Moisture contained in alcohol or oxidation products of alcohol increase corrosion from pinholes formed in the coating layer.

Due to these reasons, the corrosion resistance of Pb-Sn and alloy plated steel sheets is significantly deteriorated.

For this reason, as a container steel plate for storing such fuel,
A highly corrosion-resistant material is required that has fewer pinholes in the coating layer and has excellent corrosion resistance against alcohol and alcohol oxidation products.

Furthermore, depending on the processing shape or high-speed molding method of the fuel container, the formation of defects that reach the base metal due to enlargement of pinholes in the coating layer, "grease scratches" on the surface, and scratches on the coating layer due to phenomena, and the formation of defects that reach the base metal during handling. As a result, problems such as red rust formation from these defective parts were observed.

In particular, corrosion progressed due to the presence of a large amount of C1- ions, moisture, etc. mixed in from gasoline or from the outside, or moisture separated from the mixed fuel of alcohol and gasoline, and there was a danger of perforation due to perforation corrosion.

On the other hand, the problem of corrosion caused by snow melting salt on the outer surface of the tank has become more severe in recent years, and as mentioned above, defects in the coating layer or collision with road-sprayed salt (so-called chipping phenomenon)
Due to the occurrence of flaws reaching the base steel, there was a concern that corrosion due to C1- ions, in particular, the occurrence of perforation corrosion that leads to perforation.

(Problems to be solved by the invention) 'The present invention has been made in response to these situations, and it
It solves the problem of corrosion resistance against alcohol-containing fuel, gasoline, etc., especially when fuel with poor conditions containing a lot of moisture, CL- ions, etc. that have a negative effect on corrosion is used, and the problem of corrosion resistance of welded parts. ,
Our objective is to provide steel sheets for fuel containers that have excellent formability and weldability.

(Means to solve problems) The gist of the invention is C; oyo 2% or less in heavy duty.

0.0 with one or more of Ti, Nb, and Zr.
Ni, Co, Ni-C on at least one side of the steel plate containing 3 to 0.50% and the remainder being iron and unavoidable impurities.
o Sn, Sn on the alloy diffusion coating layer and the surface of the coating layer
- A steel sheet for alcohol or alcohol-containing fuel containers, characterized by being coated with a Zn alloy plating layer.

(effect) The present invention will be explained in detail below.

Steel sheets containing 3% or more Cr, especially more than 5 Cr, are excellent against alcohol-containing fuels, gasoline, alcohol oxidation products (aldehydes, organic acids such as formic acid, saccharic acid, etc.), and cancer rinsing. It exhibits excellent corrosion resistance.

However, if the Cr content exceeds 20%, the workability and weldability deteriorate, making it difficult to form or weld the fuel container, which is not preferable. Therefore, the Cr content should be 3 to 20%, preferably 5 to 15%, from both the corrosion resistance of the above corrosion products against red rust, workability, and weldability.
Please be sure to specify the range.

As mentioned above, from the point of view of corrosion resistance, Cr has the greatest effect, but in the present invention, from the viewpoint of targeting materials for fuel tanks for storage in automobiles and ponds, C, acid-soluble M, and other steel components are also used. Limit its content.

As the C content increases, chromium carbide is precipitated and the mechanical properties and corrosion resistance of steel deteriorate.

Therefore, the C content is 0.02% or less, preferably 0.000% or less.
5% or less is desirable.

When the amount of acid-soluble M (5olAIk) remaining in the steel is 0 or less than 5% OO, it is difficult to prevent the generation of bubbles due to oxygen gas, and the incidence of surface defects in the steel decreases. This significantly increases the corrosion resistance of steel materials and becomes the starting point for deterioration of the corrosion resistance of steel materials. In addition, excessive acid-soluble M exceeding 0.1% causes M-based oxides to be scattered on the steel surface, resulting in deterioration of corrosion resistance or non-plating in the diffusion treatment layer applied to the steel sheet.
This will cause pinholes etc. and damage the integrity of the diffusion coating layer.

In addition, the second invention of the present invention is to contain one or more of Ti, Nb, Zr, and V in an amount of 0.03 to 0.50% in addition to the above-mentioned steel components to combine with C in the steel. In total, the effectiveness of Cr contained in
This improves corrosion resistance.

The total content of steel components such as Ti, Nb, Zr, and
If the content is less than 0.03%, the effect of preventing precipitation of chromium carbide and improving moldability and corrosion resistance will be small, and if the content exceeds 0.03%, the effect will reach saturation and become uneconomical. Precipitation of these components tends to harden the material and deteriorate moldability. In particular, preferably the content of these elements is Q
, in the range of 075-020%.

In the present invention, if such steel plates are used as they are for fuel containers, the corrosion resistance is insufficient, and therefore, these steel plates are coated with a diffusion coating layer of Ni, Co, and Ni-Co alloy and a coating layer is added to the surface of the coating layer. , a plating coating layer of Sn or Sn-Zn alloy is applied.

Sn, Sn-
Although the Zn alloy plating layer exhibits excellent corrosion resistance against alcohol and alcohol-containing fuel, it does not necessarily have sufficient corrosion resistance due to the influence of moisture, Cj- ions, etc. contained in the fuel. The welded parts do not have sufficient corrosion resistance against moisture, C1- ions, etc., which are corrosion factors in fuel.

Therefore, in the present invention, alcohol, alcohol-containing fuel, alcohol oxidation products, water, gasoline C1-
By providing a coating layer of a metal or alloy that has good corrosion resistance against ions, etc., and a diffusion coating layer of Ni or CO1Ni-Co alloy that has good corrosion resistance against the above, between this coating layer and the steel plate, these corrosions can be prevented. In addition to ensuring corrosion resistance due to factors, it also suppresses corrosion of the base steel that occurs from defects (pinholes) in the coating layer, the bottom part during molding, etc.

In particular, an, Sn' of the outermost coating layer in the welded part
- the plated coating layer of Zn alloy is melted by welding,
Since the diffusion coating layer remains even in areas where the coating layer has partially disappeared, the effect of maintaining corrosion resistance in the welded part is extremely large. Therefore, even if the welded portion is installed at the bottom of the fuel container depending on the arrangement of the automobile body, an excellent corrosion-resistant life can be ensured.

Therefore, Ni, Co and Ni used for providing the diffusion coating layer applied to the steel plate used in the present invention
-Co alloy metals include alcohols, alcohol-containing fuels, alcohol oxidation products (aldehydes, organic acids),
Sn, Sn-Zn has good corrosion resistance against gasoline, moisture, and C1- ions, and at the same time brings the potential difference between the plated coating layer provided as an upper layer of the diffusion coating layer and the steel plate close to each other.
This metal was selected as a metal that would cause potential damage to the steel plate if it was diffused into a steel plate with a Cr content of more than 30% to the coating layer.

The processing method and processing conditions for providing the diffusion coating layer are not particularly specified.
For example, by the following electroplating method, Ni, C0
1Ni-Co alloy plating is performed.

(1) Ni plating; Current density 1 to 150 A/dm" (2) Co plating; Current density 1 to 15 oA/dm" (3) Ni-c
o Alloy plating; For example, in the case of Ni-50% CO, the current density is 1 to 150 A/drr? Next, after electroplating, washing with water and drying, heat treatment is performed in a reducing or non-oxidizing atmosphere to provide a diffusion treatment layer.

This diffusion treatment layer can be formed by using, for example, nickel acetate (1 o y/l)-surfactant (1
? /l), N1 metal ions such as systems, Co metal ions,
Alternatively, an aqueous solution containing a mixture of N1 and CO metal ions may be applied and heat treated.

Therefore, Ni, C01Ni, which undergoes these diffusion treatments,
The thickness of the -Co alloy is preferably 001μ or more, preferably 01μ or more. This thickness is within a range where pinhole formation is extremely low and a uniform diffusion coating layer is applied. In addition, diffusion treatment is performed in a reducing or non-oxidizing atmosphere, but Cr-containing steel sheets are relatively easily oxidized due to the influence of trace amounts of moisture, oxygen, etc. contained in this heating atmosphere, and Cr-containing steel sheets become oxidized due to oxidation. If such oxides are formed, the uniform formation of the subsequent plated coating layer will be inhibited. Therefore, in order to prevent this oxidation, it is preferable that the coating treatment be performed to a thickness of 0.01 μm or more.

The diffusion treatment is carried out using a continuous annealing furnace or a batch type box-type annealing furnace in a reducing atmosphere or non-oxidizing atmosphere, and the temperature is 600 to 1000°C, preferably 650 to 95°C.
It is carried out at a temperature of 0°C.

At temperatures below 600°C, it takes a long time for the diffusion process to be carried out sufficiently, making it unsuitable for industrial production, and also
Diffusion treatment conditions exceeding 000° C. are not preferable because when the obtained product is molded, roughness (so-called ridging phenomenon) occurs due to the influence of coarsening of crystal grains.

In addition, the diffusion treatment time varies from several tens of seconds to several hundreds of seconds for continuous annealing, and several hours to several tens of hours for batch annealing, depending on the heating method and control method to ensure the soaking temperature of the annealing furnace used. Although not particularly specified, in particular Cr as cold rolled (As Co1d material)
Using a continuous annealing furnace for both annealing and diffusion treatment of the steel plate containing the steel plate, the process strain of the cold-rolled material promotes mutual diffusion between the pre-coating layer and the steel plate. A diffusion coating layer that achieves the objective of the present invention can be obtained by heating diffusion treatment for 20 to 180 seconds, which is economically and industrially advantageous.

Next, after the diffusion treatment and cooling in the above atmosphere, in the present invention, H
After activation treatment using an acid solution such as CL, H2SO4, a plated coating layer of Sn, Sn-Zn alloy is provided.

The plating method, plating conditions, etc. of this plating coating layer are not particularly specified, but for example, (1) Sn plating current density 1 to 30 A/dtt? (2) Sn-Zn alloy plating current density 10 to 30 A/dm' In the present invention, such a coating plating layer has a current density of 0.1
A thickness of ~lOμ, particularly preferably 05-5μ, is preferred. This is because if the thickness is less than 0.1μ, the uniform coverage of the coating layer is extremely insufficient, a large amount of pinholes are generated, and the effect of improving corrosion resistance that can be obtained by applying a coating layer may not be obtained. If the layer thickness exceeds 10 μm, the effect of improving corrosion resistance may be saturated and the adhesion and moldability of the coating layer may deteriorate.

In addition, if the amount of Zn added to the Sn-Zn alloy increases, the corrosion resistance against alcohol-containing fuel will deteriorate due to the increased Zn content, and white rust, which is a corrosion product, will clog the pipes connected to the fuel container. , less than 30 inches, preferably 20
% or less is better.

Furthermore, after providing a plating coating layer of Sn or Sn-Zn alloy, a phenol sulfonic acid bath or a flux such as a phytic acid aqueous solution containing Sn ions is applied to seal the pinholes in these coating layers. Or,
The melting point of Sn (231℃) ~ 30℃ is still in a non-oxidizing atmosphere.
The corrosion-resistant life may be further extended by performing a heat melting treatment at a temperature of 0°C, preferably 240 to 280°C.

Furthermore, the surface of the coating layer of the present invention may be subjected to a chromate-based treatment for the purpose of improving the corrosion resistance or painting performance of these coating layers, and in particular extending the corrosion-resistant life of the coating on the outer surface of the fuel container. good.

Therefore, as this chromate-based treatment, CrO3 aqueous solution or CrO3-5o which is CrO3 with anion added is used.
4-2, CrO3-PO4-2, Cr○-F-based bath, immersion treatment, electrolytic treatment, etc.

In this case, a relatively stable oxide film is formed on the surface of Sn and Sn-Zn alloys, so in order to remove this oxide film and at the same time stably obtain a uniform romate film, CrO3
CrO3-5o4-” containing anions.

Cr was deposited by cathodic electrolytic treatment using a Cr03-F-based bath, with an amount of 10-150 m9/lr? It is preferable to apply the coating (on one side) because it provides excellent effects (improved corrosion resistance and paintability).

As described above, the coating treatment for Cr-added steel of the present invention can provide excellent effects even when applied to both sides corresponding to the inner and outer surfaces of the fuel container. The coating treatment of the present invention is applied to ensure corrosion resistance against the contained fuel, and the outer surface of the fuel container is coated with a Zn or Zn-based alloy plating layer to prevent corrosion from occurring from the outer surface. It's okay.

That is, Zn or Zn- (8 to 20%) Nu, Z has relatively excellent corrosion resistance against Cl- ions etc. from road spray salt, etc., and has a sacrificial anti-corrosion effect on steel materials.
n-' (8-20%) Co.

Zn-(8~20%) (Ni+Co), Zn-(8
~20%) A Fe-based alloy coating layer of 0.5 to 10μ may be applied to extend the corrosion resistance life against corrosion from the outer surface.

Similarly, the coating treatment of the present invention may be applied to both sides, and the outer surface may be subjected to a chromate treatment as described above to provide a coating treatment that serves both as anticorrosion and decoration. Alternatively, the treatment of the present invention may be applied only to the inner surface of the fuel container, and the outer surface may be used as it is made of steel.

Although the steel components of the present invention are defined as described above, these steels contain Ni as impurities from the converter etc.
, Mo, etc. contained in amounts of 1% or less and 0.3% or less, respectively, have little effect on performance.

Further, at the same time, the present invention has been described with respect to alcohol or a fuel tank containing alcohol, but the present invention has good corrosion resistance and there is no problem even if it is applied or shared with a fuel tank intended for ordinary gasoline.

(Example) Examples of the present invention will be described below.

As shown in Table 1, using steel sheets with copper compositions mainly varying in Cr content, after surface cleaning and activation treatment in normal surface treatment processes such as degreasing and pickling, at least one side of the steel sheets was Coating with Ni, Co, Ni-Co alloy,
A steel sheet according to the present invention and a comparative example steel sheet are shown which have been further subjected to each plating treatment after the diffusion treatment, and (1) square tube drawing 9 was performed assuming the shape of the fuel container, and the inner surface of the fuel container and the outer surface of the fuel container were targeted, respectively. Performance evaluation and (1) The results of an evaluation test of the copper plate seam welding material of the present invention assuming a welded part of a fuel container are shown.

As a result, the product of the present invention has extremely superior properties as a steel sheet for alcohol or alcohol-containing fuel containers, compared to comparative materials.

The evaluation test was conducted in the following manner.

! Evaluation test for the inner surface of the fuel container (A) Test for gasohol (84 cm gasoline + 14.5 cm ethanol + 5% N, C
J aqueous solution containing 15%) system solution (B) gasohol target test (79.8% Ganrin + 19% ethanol + 0.02 polyformaldehyde + 1% NaCJ, aqueous solution 1.18%
(containing) system solution (C) Gasohol target test (82,49% gasoline + 7.5% methanol + 0,0
l% formaldehyde) system solution CD) 100 thialcohol target test (97% methanol + 0.03% formaldehyde + 3
A rectangular tube drawing test with a fighting height of 200 x 200 WuRX 80 shown in Fig. 2 was prepared from a blank size of 500 x 500 mm using each aqueous solution of the LCJ (containing 2.97% aqueous solution) system, and the inside of the test piece was The container was filled with a corrosive solution and sealed, and was subjected to repeated vibration and standing for approximately one year to determine the state of corrosion inside.

■Evaluation test for the outer surface of the fuel container (E) Cycle corrosion test ■Salt water injection (5% N, (435℃ x 4 hours) → ■Dry (70℃, humidity 60%, 2 hours) → ■Wet ( 49℃ Humidity 9 days Chi 2 hours) → ■ Cooling (-20℃ x 2 hours) → ■
The above cycle was repeated 60 times for 1 cycle of salt spray ■ to ■, and the reduction in plate thickness in the corroded area and the occurrence of rust were comprehensively evaluated, and the corrosion resistance performance was evaluated.

Incidentally, the surface corresponding to the outer surface of the fuel container of the present invention has a weight of 100 t.
/l Cry, -0,6f/rr? The performance was evaluated using a chromate treatment of 15 to 1T? by cathodic electrolytic treatment at 80 A/d for 0.1 second using a 5o4-'' system bath.

(F) Erosion resistance test after painting Using the chromate-treated evaluation material of the evaluation test (E) above, after squeezing a square tube and applying 25μ of epoxy-phenol paint, fine stones with a diameter of about 7.5U were pressed. 3.5
After chipping was performed for 10 seconds at my/art so that 22 particles per lca collided, a 50 cycle test was conducted under the cycle test conditions of (E) above, and the occurrence of red rust from the chipped part and the plate thickness at that part were evaluated. The post-painting corrosion resistance was evaluated by measuring the reduction and the occurrence of blisters on the painted surface other than the chipping area.

■Moldability evaluation test Blank size 0.8X 500X 500IIa, 150X15 under the condition of wrinkle pressing pressure 30T after applying lubricant
0. A square tube was drawn with a corner punch, and its formability was evaluated based on the limit of drawing depth, the occurrence of burrs on the outer surface of the square tube drawing material, and the powdery peeling of the coating layer (powdering phenomenon). .

(Effects of the Invention) As described above, according to the present invention, as a steel sheet for alcohol or alcohol-containing fuel tank for automobiles, due to the mutual effects of the steel composition of the present invention, the diffusion coating layer, and the plating coating layer, corrosion resistance and forming processability are improved. It is possible to provide a steel plate for a fuel container that has extremely excellent properties and can also ensure corrosion resistance in welded parts.

Claims (2)

[Claims] (1) C in weight%; 0.02% or less Cr; more than 3% to 20% Acid-soluble Al; 0.005 to 0.10% The balance is unavoidable impurities and at least one side of the steel plate made of iron is coated with Ni, Co A steel sheet for use in alcohol or alcohol-containing fuel melters, comprising a Ni--Co alloy diffusion coating layer and a Sn, Sn--Zn alloy plating coating layer on the surface of the coating layer. (2) C in weight%: 0.02% or less, Cr: more than 3% to 20%, acid-soluble Al: 0.005 to 010%, 0 in one or more of Ti, Nb, Zr, and V .03～
A diffusion coating layer of Ni, Co, and Ni-Co alloy is applied to at least one side of a steel plate made of iron and 0.5% remaining unavoidable impurities, and a Sn, Sn-Zn alloy plating coating layer is applied to the surface of the diffusion coating layer. A steel plate for alcohol or alcohol-containing twisted container, characterized by: