JP2011235434A - Steel material excellent in coated film adhesiveness and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a steel material excellent in coated film adhesiveness.SOLUTION: First blasting and second blasting are performed in the order on the surface of the steel material. The first blasting uses projection particles having an average particle size of 0.40 to 1.0 mm, wherein the surface roughness Rzof the surface of the steel material is 40 to 100 μm. Subsequently, onto the surface of the steel material subjected to the first blasting, the treatment using projection particles having an average particle size of 1/2 or less of the particle size of the projection particles used in the first blasting is performed as the second blasting, wherein the surface roughness Rzof the surface of the steel material is 20 to 80 μm. Thereby, such a surface that the surface property of the steel material is effective for improving the coated film adhesiveness is provided and, in particular, in such a case that heavy-duty coating in a thick steel plate or the like is performed, the life of the coated film is markedly improved.

Description

  INDUSTRIAL APPLICABILITY The present invention is coated and used as a material for various steel structures such as civil engineering / architecture, bridges, ships, construction machines, especially marine structures, which are exposed to corrosive environments such as seawater and air. In particular, the present invention relates to the improvement of the adhesion of a coating film formed on the surface of a steel material, and further to the extension of the life of the coating film.

  Steel materials used as materials for various steel structures such as civil engineering / architecture, bridges, ships, construction machines, especially marine structures, are usually made into products of a predetermined size and shape through at least a hot rolling process. in use. An oxide layer called a scale is formed on the surface of the steel material that has been subjected to the hot rolling process. This scale has low adhesion to steel (base metal), and after hot rolling and cooling, if strain is applied by roller straightening or press straightening, it easily peels off or cracks easily Easy to peel. When the steel material to which the scale in such a state is attached is coated for rust prevention, there is a problem that the adhesion of the coating film is low, the coating film is easily peeled off, and the coating film life is short.

For such a problem, for example, Patent Document 1 describes “a method for producing a shape steel having excellent coating film adhesion”. In the technique described in Patent Document 1, a steel slab containing C: 0.03-0.22%, Si: 0.1-0.5%, Mn: 0.2-1.6%, Al: 0.003-0.09%, Mo: 0.01-0.7%, After hot rolling with a rough rolling mill and an intermediate rolling mill, high-pressure water is injected and collided so that the collision pressure is 2.5 kg / cm ² or more and the number of collisions is ^two or more within 5 s in the same location. After descaling, perform hot finish rolling at a rolling temperature of 700 to 1000 ° C and a reduction rate of 15% or less with a finish rolling mill. Immediately after rolling, fine irregularities are formed on the surface of the shaped steel, preferably by mechanical impact. To adjust the surface roughness of the shape steel. Immediately after that, high-pressure water is injected and collided on the surface of the shape steel, and descaling is performed or not, and the cooling rate is 0.5 to 20 ° C / s. Cool to below 500 ° C. In the technique described in Patent Document 1, Si is limited to an appropriate range to improve the adhesion between the scale and the ground iron, and mechanical striking is performed immediately after finish rolling to form fine irregularities, and the thickness is increased on the surface. Is formed with a tight scale having a surface roughness (Rz) of 40 to 100 μm and an excellent coating film adhesion, as well as excellent mechanical properties and weldability.

However, the technique described in Patent Document 1 is based on the premise that coating is performed with the scale remaining, and sufficient coating film adhesion is not necessarily ensured, such as swelling occurring at the heel and end. However, there was a problem that the desired coating film life could not be sufficiently maintained.
Patent Document 2 discloses that a steel plate is subjected to a blasting treatment as a pretreatment, an oxide film on the surface of the steel bar is removed, a chromate treatment for forming a chromate film is performed, and a synthetic resin coating film is further formed. A method for producing a corrosion-resistant steel bar ”is described. Thereby, the adhesion (coating film adhesion) between the steel bar and the synthetic resin coating is improved, and the corrosion resistance is increased.

However, in the technique described in Patent Document 2, in order to handle the chromate treatment solution, it is necessary to treat the treatment solution containing Cr ⁶⁺ , and it is necessary to construct a waste treatment facility and consider the environment. There is a problem of becoming.
Patent Document 3 includes a step of hot-pressing a zinc-based plated steel material to form a hot-pressed product including a zinc-based plated layer containing an iron-zinc solid solution phase and a zinc oxide layer thereon, and A method for producing a hot press-formed product comprising a step of removing a part or all of the zinc oxide layer so that the average film thickness of the outermost zinc oxide layer of the obtained hot press-formed product is 2 μm or less. Are listed. In the technique described in Patent Document 3, it is preferable that the step of removing part or all of the zinc oxide layer is a step of performing shot blasting using a steel ball having an average particle diameter of 100 to 500 μm as a shot bullet. It is said.

JP 09-272951 A JP 2002-220679 A JP 2004-323897

  However, the technique described in Patent Document 3 is effective in removing a thin film (oxide layer) because shot bullets used in the shot blasting process are fine and the unevenness of the steel surface layer formed by the process is reduced. However, there is a problem that the effect is small with respect to the removal of the thick film (oxide layer). Moreover, in this technique, since the unevenness | corrugation formed in steel material surface layer is small, when performing heavy anti-corrosion coating, there exists a problem that coating-film adhesiveness does not come to fully improve.

  The object of the present invention is to solve the problems of the prior art and to provide a method for producing a steel material having excellent coating film adhesion. The “steel material” here includes a steel plate, a steel strip, a thick steel plate, a shaped steel, a bar steel, a steel pipe, and the like.

  In order to achieve the above-mentioned object, the present inventors diligently studied various factors affecting the adhesion of the coating film. As a result, in order to remove the oxide film formed on the surface of the steel material after hot rolling, the adhesion of the coating film is remarkably improved by adding a device to the blasting treatment that has been used conventionally. I found it. Blasting is performed twice using projecting particles having different particle diameters, and the first blasting process is performed using projecting particles having an average particle diameter within a predetermined range, and the subsequent second blasting process is performed. In the heavy-duty anti-corrosion coating in which the surface property of the steel material is optimized by forming using a projecting particle having an average particle size of 1/2 or less of the projecting particle used in the first blast treatment, a thick coating film is formed. In addition, the inventors have found that coating film adhesion is significantly improved.

  As described above, by performing the two-stage blast treatment, the second projection particle is a projection particle having a predetermined particle size finer than the particle size of the first projection particle. The surface appears to have a surface shape in which fine irregularities are formed on the inner surface of the large concave portion formed by the first blasting process, and the convexity formed by the first blasting process is further flattened. become. This surface property is shown in FIG. 1 in comparison with a steel material (conventional material) that has been subjected to blasting only once in cross section. By using a steel material (the steel material of the present invention) having such a cross-sectional shape (surface property), compared with a steel material (conventional material) having a surface property formed by a conventional method (one blast treatment). It was found that the adhesion of the coating film was significantly improved.

Furthermore, after limiting the steel material to be used to a specific composition, it was found that a remarkable improvement in the coating film life was observed by applying the above-described two-stage blast treatment to the steel material surface. .
The present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.

  (1) When the steel material surface is subjected to a blasting treatment to obtain a steel material excellent in coating film adhesion, the blasting treatment is a treatment obtained by sequentially performing a first blasting treatment and a second blasting treatment, The method for producing a steel material having excellent coating film adhesion, characterized in that the second blasting treatment is treatment using projection particles having a particle size smaller than that of the projection particles used in the first blasting treatment. .

(2) In (1), the first blast treatment is performed by causing projected particles having an average particle diameter of 0.40 to 1.0 mm to collide with the steel material surface, and the surface roughness of the steel plate surface is 40 to 100 μm in Rz _JIS. And the second blasting treatment was performed on the projecting particles having an average particle size of 1/2 or less of the average particle size of the projection particles used in the first blasting treatment. A method for producing a steel material having excellent coating film adhesion, characterized in that the steel material is made to collide with the surface of the steel material and the surface roughness of the steel material surface is adjusted to 20 to 80 μm according to Rz _JIS .

(3) In (2), the steel material is in mass%, C: 0.01 to 0.15%, Si: 0.10 to 0.60%, Mn: 0.2 to 1.8%, P: 0.03% or less, S: 0.02% or less, Al : 0.10% or less, N: 0.01% or less, and the composition which consists of remainder Fe and an unavoidable impurity, The manufacturing method of the steel materials characterized by the above-mentioned.
(4) In (3), in addition to the above-mentioned composition, by mass%, Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less Or it is set as the composition containing 2 or more types, The manufacturing method of the steel materials characterized by the above-mentioned.

(5) A steel material excellent in coating film adhesion produced by the method for producing a steel material according to any one of (2) to (4).
(6) A steel material obtained by subjecting a steel material surface to a blasting treatment, wherein the blasting treatment includes a first blasting treatment in which projected particles having an average particle diameter of 0.40 to 1.0 mm collide, and the first blasting treatment. And a second blasting treatment for colliding the projected particles having an average particle size of 1/2 or less of the average particle size of the projected particles used in the treatment, and the surface roughness of the steel material surface is 20 to Rz _JIS Steel with excellent coating film adhesion, characterized by being 80 μm.

(7) In (6), the steel material is mass%, C: 0.01 to 0.15%, Si: 0.10 to 0.60%, Mn: 0.2 to 1.8%, P: 0.03% or less, S: 0.02% or less, Al : Steel material containing 0.10% or less, N: 0.01% or less, and having a composition comprising the balance Fe and inevitable impurities.
(8) In (7), in addition to the above composition, in addition to mass, Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less Or the steel material characterized by setting it as a composition containing 2 or more types.

  According to the present invention, a steel material excellent in coating film adhesion can be easily manufactured at a low cost, and a remarkable industrial effect can be achieved. According to the present invention, the adhesion of the coating film is improved, and there is also an effect that a remarkable improvement in the coating film life is recognized even when a heavy anticorrosion coating such as that in a thick steel plate is applied.

It is explanatory drawing which compares and shows the cross-sectional shape of this invention steel material and a conventional material typically.

  In the present invention, the steel material surface is subjected to a two-stage blasting process including a first blasting process and a second blasting process to obtain a steel material having excellent coating film adhesion. In the two-stage blasting process used in the present invention, the second blasting process is a process using a projecting particle having a particle size smaller than that of the projecting particle used in the first blasting process. As a result, the surface property of the steel material is effective for improving the adhesion of the coating film, the surface having irregularities, that is, the fine irregularities are formed on the inner surface of the large concave portions, and the flatness of the large convex portions has further progressed. It can be a surface exhibiting a shape.

  The first blast treatment is preferably a treatment in which projected particles having an average particle diameter of 0.40 to 1.0 mm collide with the steel material surface. If the average particle size of the projected particles is less than 0.40 mm, the particle size of the projected particles is too small to efficiently remove the surface scale, and the desired surface roughness cannot be secured stably. On the other hand, when the average particle size of the projected particles is larger than 1.0 mm, the unevenness of the steel surface becomes remarkable, the coating film adhesion is lowered, and when the coating film is thin, the occurrence of coating film defects tends to be remarkable. . For this reason, the average particle size of the projection particles used in the first blast treatment was limited to a range of 0.40 to 1.0 mm. In addition, More preferably, it is 0.7-0.9 mm.

Here, as the average particle diameter of the projected particles, a value measured using a test sieve specified in JIS Z 8801 is used. That is, the sieves with large openings are stacked so as to be in the upper stage, and the powder to be measured is put into the uppermost stage to give mechanical vibration. And the weight of the powder which remained on each sieve is measured, and the weight fraction of a particle size is calculated. The particle diameter D _{50 at} which the weight was 50% was taken as the average particle diameter.

  The projected particles used in the blasting treatment of the present invention are not particularly limited, and any conventional particles can be used, but the shape is preferably closer to a sphere, The hardness is preferably harder than the target steel material. For example, cut wires, steel grids, steel shots, slag, alumina, silica sand, glass beads and the like can be exemplified.

As the steel material, it is preferable to use a “metal grinding material for blast treatment” defined in JIS Z 0311. Therefore, the shot particles used are most preferably steel shots in terms of particle shape and hardness.
And it is preferable that the surface roughness of the steel material surface shall be 40-100 micrometers by Rz _JIS by the above-mentioned 1st blasting process. By setting it as such surface roughness, when apply | coating a coating-film liquid, dripping of a coating-film liquid can be prevented and desired thick coating coating can be performed. Here, the surface roughness is displayed using ten-point average roughness Rz _JIS measured in accordance with JIS B 0601-2001.

If the surface roughness of the steel material formed by the first blast treatment is less than 40 μm in Rz _JIS , the unevenness formed by the first treatment is too small, and the second blast treatment applied subsequently The effect of improving the adhesion of the coating film due to the formation of fine irregularities formed on the inner surface of the recess is not sufficiently obtained. On the other hand, when it exceeds 100 μm and becomes rough, the unevenness becomes too large and the coating film adhesion is lowered, and the desired coating film adhesion cannot be ensured. For this reason, the surface roughness of the steel material surface after the first blast treatment was limited to a range of 40 to 100 μm according to Rz _JIS . More preferably, it is 50 to 80 μm in Rz _JIS .

In the first blasting process, the projection (shot) conditions need not be particularly limited. It is preferable that the projecting particles having a particle size (average) in the above-described range are caused to collide with the steel material surface by appropriately adjusting the projecting (shot) conditions so that the steel material surface has the surface roughness described above.
In the second blasting process, it is preferable to use a projecting particle having a small average particle diameter and 1/2 or less of the particle diameter of the projecting particle used in the first blasting process. When the projecting particles to be used are particles having a particle size larger than ½ of the particle size of the projecting particles used in the first blasting treatment, the surface properties in which desired fine irregularities are sufficiently formed on the inner surface of the large concave portion It becomes difficult to obtain a desired coating film anchor effect. In addition, it becomes difficult to achieve smoothing of the large protrusions formed by the first blasting process, and it becomes difficult to obtain a desired coating film anchor effect. Prolonged film life cannot be expected. For this reason, the average particle size of the projection particles used in the second blast treatment is limited to ½ or less of the particle size of the projection particles used in the first blast treatment.
In addition, More preferably, it is 1/3 or less.

In the second blast treatment, it is not necessary to particularly limit the projection (shot) conditions except that the particle size of the projection particles to be used is defined. It is preferable to appropriately adjust the conditions so that the required surface roughness can be obtained.
In the present invention, the surface roughness of the steel material surface is preferably 20 to 80 μm in Rz _JIS by the second blast treatment. By setting it as such surface property, the anchor effect of the coating film by a fine unevenness | corrugation becomes remarkable, and coating-film adhesiveness improves notably. When the surface roughness of the steel material is less than 20 μm in Rz _JIS , the adhesion of the coating film is remarkably lowered. On the other hand, when the surface roughness of the steel material exceeds 80 μm, fine unevenness is not sufficiently formed on the inner surface of the recess, and the effect of improving coating film adhesion is small. For this reason, the surface roughness of the steel material surface by the second blast treatment is limited to the range of 20 to 80 μm by Rz _JIS . More preferably, it is 30-60 μm in Rz _JIS .

In addition, as a projection condition of a projection particle, also in a 1st blast process and a 2nd blast process, from a viewpoint of ensuring desired surface roughness and an improvement in productivity, projection density: 80-200 kg / m < ² >, Preferably, the projection speed is 60 to 100 m / s, and the projection distance is 300 to 1000 mm.
When the projection density is less than 80 kg / m ² , the descaling property decreases. On the other hand, when it exceeds 200 kg / m ² , the desired steel surface roughness cannot be achieved.

On the other hand, if the projection speed is less than 60 m / s, the projection speed is too slow to secure a desired surface roughness stably. On the other hand, if it exceeds 100 m / s, the accumulation of strain on the surface of the steel plate is large, and the surface is hardened and difficult to process.
In addition, when the projection distance is less than 300 mm, the shot (projected particles) is only partially hit, so that the hardness distribution of the surface layer becomes non-uniform. On the other hand, if the length exceeds 1000 mm, shots (projected particles) cannot be efficiently performed, and it takes a long time to remove the scale.

In the present invention, it is preferable that the above-described blast treatment is performed on a steel material having a specific composition from the viewpoint of extending the life of the coating film and further from the viewpoint of improving corrosion resistance.
The steel materials to be subjected to the above blast treatment are in mass%, C: 0.01 to 0.15%, Si: 0.10 to 0.60%, Mn: 0.2 to 1.8%, P: 0.03% or less, S: 0.02% or less, Al: 0.10% In the following, N: 0.01% or less is included, or Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less And it is desirable to make it the steel material which has a composition which consists of remainder Fe and an unavoidable impurity.

Next, the reason for limiting the preferable composition range of the steel material to be used will be described. Hereinafter, unless otherwise specified, mass% is simply expressed as%.
C: 0.01-0.15%
C is an element that increases the strength of the steel material, and is preferably contained in an amount of 0.01% or more in order to ensure a desired strength. On the other hand, the content exceeding 0.15% hardens the steel material and lowers the weldability. For this reason, C is preferably limited to a range of 0.01 to 0.15%. In addition, More preferably, it is 0.02 to 0.10%.

Si: 0.10 to 0.60%
Si is an element that acts as a deoxidizer and increases the strength. In order to secure a desired strength, Si is preferably contained in an amount of 0.10% or more. Si oxidizes during heating and generates firelite at the interface between the scale and the scale, increasing the adhesion between the scale and the scale, but a large content exceeding 0.60% The interface thickness increases too much, and cracking and peeling of the scale become noticeable during roller correction and press correction. For this reason, it is preferable to limit Si to the range of 0.10 to 0.60%. In addition, More preferably, it is 0.20 to 0.40%.

Mn: 0.2-1.8%
Mn is an element having a function of increasing the strength of the steel material by solid solution and improving the toughness. Further, Mn combines with S to form MnS, and has an action of suppressing adverse effects of S on the steel material surface and in steel. In order to acquire such an effect, Mn needs to contain 0.2% or more. On the other hand, if the content exceeds 1.8%, the weldability is lowered and the machinability is lowered. For this reason, it is preferable to limit Mn to the range of 0.2 to 1.8%. In addition, More preferably, it is 0.4 to 1.5%.

P: 0.03% or less P has the effect of increasing the strength of the steel material, but segregates at the grain boundaries, causes secondary work embrittlement, and decreases the workability of the steel material. For this reason, although it is desirable to reduce as much as possible from a viewpoint of workability improvement, excessive reduction raises refining cost. For this reason, it is desirable to set it as about 0.005% or more. Moreover, such a decrease in workability becomes significant when the content exceeds 0.03%. For this reason, it is preferable to limit P to 0.03% or less. In addition, More preferably, it is 0.02% or less.

S: 0.02% or less S is an element that forms FeS at the interface between the ground iron and the scale to reduce the adhesion of the scale, and is desirably reduced as much as possible. Containing a large amount exceeding 0.02% significantly reduces the adhesion of the scale. For this reason, it is preferable to limit S to 0.02% or less.
Al: 0.10% or less
Al is an element that acts as a deoxidizer and refines crystal grains. In order to acquire such an effect, it is preferable to contain 0.01% or more, but if it exceeds 0.10%, oxide inclusions increase and the cleanliness of the steel material decreases. For this reason, it is preferable to limit Al to 0.10% or less.

N: 0.01% or less N increases the strength of the steel material by solid solution, but a large amount reduces weldability. From the viewpoint of weldability, it is desirable to reduce N as much as possible. However, excessive reduction raises the refining cost, so it is preferable to be about 0.001% or more. On the other hand, if the content exceeds 0.01%, the steel material becomes hard, the toughness is lowered, and the weldability is lowered. For this reason, it is preferable to limit N to 0.01% or less.

The above components are basic components, but in addition to the basic composition, Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less Or you may contain 2 or more types.
Cu, Ni, Mo, and W are all elements that contribute effectively to improving corrosion resistance and extending the life of the coating film, and can be selected from one or more as required. Such effects are recognized with Cu: 0.01% or more, Ni: 0.1% or more, Mo: 0.05% or more, W: 0.01% or more, Cu: 0.5%, Ni: 2.0%, Mo : Containing more than 0.5% and W: 0.5% respectively, the steel becomes hard and the toughness is lowered, resulting in a decrease in manufacturability and an increase in steel price. For this reason, when it contains, it is preferable to limit to Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, and W: 0.5% or less, respectively.

The balance other than the components described above consists of Fe and inevitable impurities.
Inevitable impurities include O: 0.005% or less, Mg: 0.005% or less, REM: 0.005% or less, B: 0.005% or less, and Ca: 0.005% or less.
As a method for producing a steel material having the above-described composition, any known method can be applied and is not particularly limited.

  For example, when the steel material is a thick steel plate, the molten steel having the above composition is melted by a generally known melting method such as a converter, and is made into a steel material such as a slab by a conventional method such as a continuous casting method. Then, the steel material is heated, subjected to thick plate rolling (hot rolling), cooled, or further corrected to obtain a thick steel plate having a desired size and shape. In thick plate rolling, characteristics such as desired strength and toughness can be imparted by applying controlled rolling, controlled cooling and the like in addition to normal rolling.

  Further, when the steel material is a shape steel, the molten steel having the above composition is melted by a generally known melting method such as a converter, and is made into a steel material such as bloom by a conventional method such as a continuous casting method. After that, the steel material is heated, subjected to shape steel rolling (hot rolling), cooled, or further straightened to obtain a shape steel such as H-shaped steel or steel sheet pile having a desired dimensional shape. Any of the usual rolling methods can be applied to shape steel rolling. The same applies to the case where the steel material is a steel bar, and a normal steel bar rolling can be applied to obtain a steel bar having a desired size and shape.

  Hereinafter, based on an Example, this invention is demonstrated further in detail.

A steel material having a composition shown in Table 1 (U-shaped steel sheet pile: effective width 600 mm × effective height 180 mm × thickness 13.4 mm) was used as a material. As the material, a steel material (bloom) having the above-described composition was heated and rolled into a U-shaped steel sheet pile having the above-described dimensions by ordinary shape steel rolling (hot rolling). Oxide scale is attached to the surface of the material.
A test material (length: 150 mm) was sampled from the material (steel material), and the test material was sequentially subjected to a blast treatment, a pre-paint treatment, and a paint treatment to obtain a painted steel material (paint test material).

  In the blasting process, the material was preheated (50 to 60 ° C.) and then the blasting process was performed. In the blasting treatment, the first blasting treatment and the subsequent second blasting treatment were sequentially performed on one side of the test material (material) using the projected particles having an average particle size shown in Table 2. In addition, the blast process of the same conditions was given about three test materials, and the result was shown by those arithmetic averages. In addition, the example which performed the blast process only once as a prior art example was also implemented.

The average particle size of the projected particles was obtained by calculating D ₅₀ by the above-described method using a test sieve specified in JIS Z 8801. Moreover, the high carbon cast steel shot prescribed | regulated to JISZ0311 was used for the projection particle | grains.
After the blast treatment, the surface roughness of the surface of the test material (raw material) was measured. The surface roughness is measured in accordance with JIS B 0601-2001 using a stylus type surface roughness meter along the rolling direction (longitudinal direction) of the test material, and the ten-point average roughness Rz. Displayed in _JIS .

  In addition, the coating pretreatment is performed by spraying the chromate treatment liquid (trade name: Cosmer 100 manufactured by Kansai Paint Co., Ltd.) on the surface (one side) of the blasted test material (material) at a plate temperature of 100 ° C. Temperature: A process of baking at 100 ° C. For some test materials, the surface of the blasted test material (material) is spray-coated with a non-chromate treatment solution (trade name: Surfcoat CM 1706 manufactured by Nippon Paint Co., Ltd.), and the plate temperature is 110 ° C. It was set as the baking process.

The coating treatment was a treatment in which polyurethane coating was applied to the surface (one side) of the pretreated test material (material), and the coating thickness was 2.5 mm. The polyurethane coating was a treatment in which a two-component reaction type polyurethane (trade name: Permguard 137 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used and solvent-free spray coating was applied to the test material (material). The painted surface is one side, and the other surface is a non-painted surface.
Subsequently, the obtained coating test material was subjected to an initial adhesion test, an adhesion test, and a peel resistance test to evaluate the adhesion of the coating film. The test method was as follows.
(1) Initial adhesion test As an initial adhesion test, a peel strength test was performed. Bond a rigid rod (iron pin: 10mmφ) to the coating surface of the obtained coating test material, apply a tensile load perpendicular to the coating film, determine the load when the coating film peels, and peel strength (N / mm ² ) was calculated and the initial adhesion of the coating film was evaluated.
(2) Adhesion test A temperature gradient test was performed as an adhesion test. Take a double-sided sample piece from the obtained coating test material, and place the double-sided sample piece in contact with a solution at 80 ° C on one side (painted surface) and in contact with a solution at 70 ° C on the other side (uncoated surface). After dipping in the solution for 60 days, a rigid rod (iron pin: 10mmφ) is adhered to the surface of the coating, and a tensile load is applied perpendicular to the coating to determine the load when the coating peels off. The peel strength (N / mm ² ) was calculated and the adhesion of the coating film was evaluated.
(3) Peel resistance test A cathode peel test was performed as a peel resistance test. A sample piece is taken from the obtained coating test material, an initial hole of 5 mmφ is formed until reaching the metal, and the liquid temperature is 60 ° C. in a 3% NaCl solution, the load voltage is −1.5 V (vs. SCE). ), After immersing for 60 days, the peel width (mm) of a maximum of 5 points was measured, and the arithmetic average value was taken as the peel distance of the coating test material to evaluate the peel resistance of the coating film.

  The results obtained are shown in Table 3.

  The present invention example has high peel strength, excellent initial adhesion of the coating film, has high peel strength even after being immersed in a solution having a temperature difference, and excellent adhesion of the coating film, and It is a steel material with excellent peeling resistance of the coating film. On the other hand, the comparative example outside the scope of the present invention has a low initial adhesion of the coating film, or after being immersed in a solution having a temperature difference, the peel strength decreases and the coating film adhesion decreases. Or the peel resistance of the coating film is reduced.

Claims (8)

  When the steel material surface is subjected to blasting treatment to obtain a steel material having excellent coating film adhesion, the blasting treatment is a treatment obtained by sequentially performing a first blasting treatment and a second blasting treatment, and the second blasting treatment. A method for producing a steel material excellent in coating film adhesion, characterized in that the blast treatment is treatment using projected particles having a particle size smaller than that of the projected particles used in the first blast treatment. The first blast treatment is a treatment in which projected particles having an average particle diameter of 0.40 to 1.0 mm collide with the steel material surface, and the surface roughness of the steel plate surface is set to 40 to 100 μm in Rz _JIS . The blasting treatment is performed by causing the projecting particles having an average particle size equal to or less than ½ of the average particle size of the projecting particles used in the first blasting treatment to collide with the steel material surface subjected to the first blasting treatment, The method for producing a steel material excellent in coating film adhesion according to claim 1, wherein the surface roughness of the steel material is treated to 20 to 80 µm by Rz _JIS . The steel material is mass%,
C: 0.01 to 0.15%, Si: 0.10 to 0.60%,
Mn: 0.2 to 1.8%, P: 0.03% or less,
S: 0.02% or less, Al: 0.10% or less,
N: The manufacturing method of the steel materials of Claim 2 which has a composition which contains 0.01% or less and consists of remainder Fe and an unavoidable impurity.   In addition to the above composition, the composition further contains, by mass%, one or more selected from Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less. The method for producing a steel material according to claim 3.   A steel material excellent in coating film adhesion produced by the method for producing a steel material according to any one of claims 2 to 4. A steel material that is subjected to a blasting process on the surface of the steel material, wherein the blasting process is used in a first blasting process in which projected particles having an average particle diameter of 0.40 to 1.0 mm collide, and the first blasting process. And a second blasting treatment for colliding the projected particles having an average particle size of 1/2 or less of the average particle size of the projected particles, and the surface roughness of the steel material surface is 20 to 80 μm in Rz _JIS. A steel material excellent in coating film adhesion characterized by the above. The steel material is mass%,
C: 0.01 to 0.15%, Si: 0.10 to 0.60%,
Mn: 0.2 to 1.8%, P: 0.03% or less,
S: 0.02% or less, Al: 0.10% or less,
The steel material according to claim 6, wherein N: 0.01% or less, and having a composition composed of the remaining Fe and inevitable impurities.   In addition to the above composition, the composition further contains, by mass%, one or more selected from Cu: 0.5% or less, Ni: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less. The steel material according to claim 7, wherein:

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