JP4449938B2 - Painted steel material excellent in laser cutting property and primary rust prevention property and primer used therefor - Google Patents

Description

The present invention relates to a coated steel material having excellent laser cutting property and primary rust prevention property and a primer used therefor.

  Fabricators such as shipbuilding and construction machinery have high dimensional accuracy (± 0.5mm), have little thermal effect on components, and are relatively easy to unmanned automation. Increasing use of laser cutting as a method. However, laser cutting has a problem that the cutting speed is slow compared to plasma cutting, and the plate thickness that can be cut is limited compared to gas cutting.

  Furthermore, there is a problem that the upper limit of the laser cutting speed and the plate thickness that can be cut is lowered by the primer as the primary rust prevention treatment performed by the fabricator. This mechanism is not clear and is currently being dealt with based on empirically obtained methods for each fabricator. One of them is a pre-treatment called pre-firing with a fabricator, which performs pre-irradiation of the low-power laser onto the coating film at the cutting portion. This pretreatment improves the laser cutting property, but requires two laser irradiations along the actual cutting line, so that there is a large loss both in terms of process and input energy. For this reason, the economic loss is also large.

  So far, Patent Document 1 is known as a pretreatment method for steel materials having excellent laser cutting properties. In this document, the laser cutting performance is improved by limiting the amount of Zn in the coating film added as a rust preventive, but the method of compensating for the decrease in rust resistance by limiting the amount of Zn. Is not described.

  Patent Document 2 describes a high-corrosion-resistant paint using a mixed powder of Zn 65 to 85 wt% and Al 3 to 15 wt% as a heat- and anti-corrosion paint. In the examples, the film thickness during coating is ensured to ensure high corrosion resistance. Therefore, it is set to 75 μm, and since the amount of (Zn + Al) contained in the coating film increases, it is considered that the laser cutting property is low.

Patent Document 3 describes a high-corrosion-resistant paint using a Zn—Al—Mg alloy powder. However, in order to make Zn, Al, and Mg into an alloy powder, a single Zn powder or Al powder is used. Compared with this, the paint manufacturing cost increases. Further, in the examples, the film thickness at the time of coating is set to 60 μm in order to ensure high corrosion resistance, and since the amount of (Zn + Al) contained in the coating film increases, the laser cutting property is considered to be low. .
Japanese Patent Laid-Open No. 10-226846 JP 59-221361 A JP 2001-164194 A

  The invention disclosed in Patent Document 1 does not take any measures for the decrease in rust prevention property due to the decrease in the amount of Zn in the coating film, and there is a possibility that the rust prevention property may be significantly reduced by limiting the amount of Zn. is there. Further, in the inventions disclosed in Patent Document 2 and Patent Document 3, laser cutting properties are not considered, and the amount of (Zn + Al) contained in the coating film that can be estimated from the thickness of the coating film is large and laser cutting is performed. It is thought that it is inferior.

The present invention has been made in view of such circumstances, and provides a coated steel material coated with a primer and a primer used therefor, which has high laser cutting property and excellent rust resistance when cut with a laser. The purpose is to do.

In order to solve the above problems, in the present invention, as a dry coating film on the surface of a steel material , titania powder, zinc powder and aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, Co one or contain as a or compound alone materials of two or more elements, the primer coating of the titania powder is 4.5 g / m ² ≦ titania powder ≦ 26 g / m ² is formed by coating of To provide a coated steel material excellent in laser cutting property and primary rust prevention property.

In this case, it is preferable coating amount of the zinc powder contained in the prior SL primer is 9 g / m ² ≦ zinc powder ≦ 30g / m ^2. Furthermore, the primer contains aluminum powder and / or one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co as a single substance or as a compound. only if to be contained, it is preferable coating amount of the aluminum powder is 0.1 g / ^{m 2} ≦ aluminum powder ≦ 10g / ^{m 2.} Further, when aluminum powder is not contained and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, the total The coating amount is preferably 0.2 to 20 g / m ² in terms of element. When aluminum powder and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, the coating amount of the aluminum powder is 0.1 g / m ² ≦ aluminum powder ≦ 5 g / m ² , and as a single substance or compound of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, Co The total coating amount is preferably 0.05 to 5 g / m ² in terms of element.

In the present invention, the dry coating film is one or more of metal oxide powder, zinc powder, aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, Co. element is contained as the or a compound as sole material, titania powder provides a painted steel primer, characterized in that a 4.5 g / m ² ≦ titania powder ≦ 26g / m ^2.

In this case, the zinc powder contained in the prior Symbol dry coating film, it is preferable to be 9 g / ^{m 2} ≦ zinc powder ≦ 30g / ^{m 2.} Furthermore, the dry coating film contains aluminum powder and / or one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, Co as a single substance or as a compound. When only aluminum powder is contained, the coating amount of aluminum powder is preferably 0.1 g / m ² ≦ aluminum powder ≦ 10 g / m ² . Further, when aluminum powder is not contained and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, the total The coating amount is preferably 0.2 to 20 g / m ^{2 in} terms of element. When aluminum powder is contained and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, application of aluminum powder The amount is 0.1 g / m ² ≦ aluminum powder ≦ 5 g / m ² , and as a single substance of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, Co or The total coating amount as a compound is preferably 0.05 to 5 g / m ^{2 in} terms of element.

According to the present invention, the dry coating film has high laser absorption metal oxide powder and zinc powder and aluminum powder and / or one of Mo, W, Ni, Cu, Cr, P, Mg, V and Co. Or since the primer which contains 2 or more types of elements as a single substance or as a compound was apply | coated to steel materials, the coated steel materials which have the outstanding laser cutting property and rust prevention property can be obtained.

Hereinafter, the present invention will be specifically described.
In general, it is known that when a steel material in which a zinc (Zn) rich primer is applied to the surface of a shot blasted steel material is laser-cut, the cutting speed is reduced. Although the mechanism of the laser cutting speed reduction at this time is not necessarily clear, the present inventors have (1) Laser absorption rate by the primary rust preventive agent by primer coating performed as the primary rust preventive treatment. (2) Scattering / absorption of laser light due to decomposition and evaporation of binder resin and zinc powder in the primary rust preventive agent by heating during cutting, (3) Partial pressure of assist gas (oxygen) by generated gas It was estimated that the decrease in the laser beam was a factor in the laser cutting speed decrease.

  As a result of investigations based on such estimation results, the present inventors have found that (1) is improved in laser cutting property by increasing the laser absorptivity by adding a metal oxide powder having high laser absorption in the primer. I came up with a good idea. In addition, the addition of titania powder reduces the viscosity of the molten slag generated during cutting, and the molten slag is efficiently discharged from the cutting groove to improve the beauty of the cut surface and adhere to the back of the cut portion. It was also found that the occurrence of dross can be suppressed.

  In the initial stage of the laser cutting process, the light energy is absorbed by concentrating the laser beam on the cutting part, and the temperature of the cutting part rises locally and melts. At this time, a laser such as titania powder is used. When the cut portion is covered with a coating film containing a metal oxide powder having high absorbability, light energy is efficiently absorbed by the coating film, so that the laser cutting efficiency can be increased.

  On the other hand, if the amount of zinc (Zn) powder added is reduced in order to solve the above (2) and (3), the primary rust prevention property is lowered, but aluminum (Al) powder and / or Mo, W, Ni, It has been conceived that by adding the elements Cu, Cr, P, Mg, V and Co as a single substance or as a compound, primary rust prevention can be ensured without causing the problems (2) and (3).

  In this case, since the coating film contains metal oxide powder having high laser absorption such as titania powder, in addition to zinc powder, aluminum powder, Mo, W, Ni, Cu, Cr, P, Mg, Even if the elements of V and Co are further added as a single substance or as a compound, the light energy of the laser beam can be efficiently absorbed by the titania powder at the initial stage of laser cutting, and the characteristics excellent in laser cutting performance are maintained. The

  Based on such examination results, in the present invention, on the surface of the steel body, metal oxide powder and zinc powder and aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, Co A primer containing one or more elements as a single substance or a compound is applied.

As a result of studying preferable metal oxide powders, the laser absorptivity of titania (TiO ₂ ) powder and the effect of efficiently discharging the molten slag from the inside of the cutting groove are particularly high. Has been found to improve significantly. Moreover, in order to exhibit such an effect effectively, it is preferable to make the application quantity of titania powder into the range of 4.5-26 g / m < ² >. The coating amount of the titania powder is less effect of improving laser cutting resistance is less than 4.5 g / m ^2, to form a uniform coating film opposite to more than 26 g / m ² is inhibited, it can interfere with rust improvement is there. A more preferable range of the coating amount of the titania powder is 4.5 to 15 g / m ² .

Moreover, from a viewpoint of ensuring laser cutting property, it is preferable that the application quantity of zinc powder shall be 9-30 g / m < ² >. When the coating amount of zinc powder is less than 9 g / m ² , one or more elements of aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are used as a single substance. Alternatively, even when added as a compound, the effect of improving rust prevention is small. Conversely, when it exceeds 30 g / m ² , the effect of improving laser cutting property is small even when titania powder is added. A more preferable range of the coating amount of the zinc powder is 16 to 23 g / m ² .

As mentioned above, adding laser-absorbing metal oxide powder such as titania powder and reducing zinc powder as the primary rust preventive agent as much as possible improves laser cutting performance, but rust prevention performance is inferior. It will be a thing. Therefore, aluminum powder and / or one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are added as a single substance or as a compound, and the above (2) It is preferable to improve rust prevention while reducing the problem (3). When the aluminum powder is added alone, the effect is small if the aluminum powder is less than 0.1 g / m ^{2. On the} other hand, if the aluminum powder exceeds 10 g / m ² , the formation of a uniform coating is inhibited, and the rust prevention property is reduced. There is a risk of causing. For this reason, it is preferable to make the application quantity of the aluminum powder into the range of 0.1-10 g / m < ² > when adding aluminum powder independently. A more preferable range is 0.5 to 2.3 g / m ² .

Instead of aluminum powder, one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are added as single substances or compounds thereof from the viewpoint of material cost and the like. In this case, if the total coating amount is less than 0.2 g / m ^{2 in} terms of element, the effect of improving rust prevention is small, and if it exceeds 20 g / m ² , formation of a uniform coating is inhibited, and rust prevention is achieved. May decrease. For this reason, in place of aluminum powder, when one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are added as a single substance or a compound thereof, The preferable range of the total coating amount is 0.2 to 20 g / m ² , and the more preferable range is 0.6 to 10 g / m ² in terms of elements.

When aluminum powder is contained and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, application of aluminum powder The amount may be 0.1 to 5 g / m ² , and the total application as a single substance or a compound of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co. The amount may be 0.05 to 5 g / m ² in terms of element. A more preferable range is that the aluminum coating amount is 0.5 to 1.5 g / m ² , and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are used. The total coating amount as a single substance or as a compound is 0.6 to 3.0 g / m ² in terms of element.

A particularly suitable example is that the primer (coating film) uses an alkyl silicate resin as a binder, the coating amount of titania powder is 4.5 to 26 g / m ² , and the coating amount of zinc powder is 9 to 30 g / m. m ² , and when adding aluminum powder alone, the coating amount of aluminum powder is 0.1 to 10 g / m ² , and instead of aluminum powder, Mo, W, Ni, Cu, Cr, P, Mg, V In the case where one or more elements of Co are added as a single substance or as a compound, the total coating amount is 0.2 to 20 g / m ^{2 in} terms of element, aluminum powder is contained, and Mo, When one or more elements of W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, the coating amount of aluminum powder is 0.1 to 5 g / m ² , and the total coating amount as a single substance or compound of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co is calculated in terms of elements. It is satisfy | filling all 0.05-5g / m < ² >. As a result, the effect of suppressing the decrease in laser cutting property is extremely high, and the primary rust prevention property can be kept extremely good. The more preferred examples, the coating amount of the titania powder, the coating amount of zinc powder, respectively 4.5~15g ^/ m 2 is more preferable range above a 16~23g / ^{m 2,} the aluminum powder alone When added, 0.5 to 2.3 g / m ² , which is the more preferable range of the coating amount of the aluminum powder, in place of the aluminum powder, Mo, W, Ni, Cu, Cr, P, Mg, V, Co When adding one or two or more elements as a single substance or as a compound, 0.6 to 10 g / m ^{2 in} terms of the element, which is the above-described more preferable range of the total coating amount, contains aluminum powder, Further, when one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, aluminum is used. One or more elements of 0.5 to 1.5 g / m ² , Mo, W, Ni, Cu, Cr, P, Mg, V, and Co, in which the coating amount of the nickel powder is in the above preferable range. The total coating amount as a single substance or as a compound satisfies 0.6 to 3.0 g / m ^{2 in} terms of elements, which is the above-described more preferable range.

  As described above, the coating film (primer) of the present invention containing a metal oxide powder having high laser absorption such as titania powder is a coating film of zinc powder or a conventional coating film in which aluminum powder is added to zinc powder. Can be said to be an essentially different coating film in that a function of efficiently absorbing the light energy of laser light in the laser cutting process and facilitating discharge of molten slag is added.

  As the titania powder, zinc powder, and aluminum powder, those processed by an atomizing method or a mechanical pulverization method can be used, and those having an average particle size controlled to 15 μm or less are desirable. These powders may be subjected to a surface treatment with Al, Zr, polyol or the like for enhancing the dispersibility in the paint, if necessary. As paint additives other than these powders and binder resins, coloring pigments, dispersants, wetting agents, antifoaming agents, suspending agents, thickeners and the like may be added as necessary.

The metal oxide powder is not limited to titania as long as it has a sufficiently high absorption for the laser to be used. For example, by adding zirconia (ZrO ₂ ) powder into the primer, the titania powder The same effect can be obtained. That is, zirconia powder, like titania powder, has a high absorbability of a CO ₂ laser (wavelength λ = 10.6 μm) generally used for laser cutting, and therefore has a high effect of improving laser cutting performance. However, in view of availability and cost, titania is preferable.

  The base steel material of the coated steel material of the present invention is not particularly limited, but is generally used for steel plates having a thickness of up to about 25 mm.

An example of a method for preparing a paint used for the above-described coated steel material and a method for coating the steel material with the paint will be described below.
First, in the coating liquid defined in JIS K 5552, one of metal powder, zinc powder, aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, Co having high laser absorption or Two or more elements are added as a single substance or a compound, and thoroughly mixed and stirred by a shaker machine or the like to prepare a paint. Next, by spraying the prepared paint, for example, by an air spray type coating apparatus, adjusting the spray amount and spray speed so that the weight of the coating film after drying becomes a desired weight, Painted steel is obtained.

  It should be noted that when painting on a steel sheet, it is conceivable to use the paint with a viscosity adjusted by a thinner according to the actual painting environment, for example, room temperature. Even when the viscosity of the paint is adjusted with thinner, it is possible to form a paint film having the above-mentioned desired weight by adjusting the spray conditions so that the weight of the paint film after drying becomes the above-mentioned desired weight. it can.

Using commercially available zinc rich primer (paint liquid and Zn powder) corresponding to JIS K 5552 (2002) zinc rich primer, titania powder is 4.5-26 g / m ² , zinc powder is 9-30 g / m ² , When aluminum powder is added alone to improve primary rust prevention, the coating amount of aluminum powder is 0.1 to 10 g / m ² , and instead of aluminum powder, Mo, W, Ni, Cu, Cr, P, When adding one or more elements of Mg, V, Co as a single substance or as a compound, the total coating amount is 0.2 to 20 g / m ^{2 in} terms of element, and contains aluminum powder. Further, when one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are contained as a single substance or as a compound, The coating amount of the minium powder is 0.1 to 5 g / m ² , as a single substance or a compound of one or more elements among Mo, W, Ni, Cu, Cr, P, Mg, V, and Co. These were mixed with a coating liquid composed of an alkylsilicate-based binder resin and thinner so that the total coating amount was 0.05 to 5 g / m ^{2 in} terms of element, and spray-coated on the steel material surface. The dry resin content of the coating liquid is 5.2 g / m ² . For comparison, the same binder resin with only zinc added or zinc and aluminum added was similarly spray coated on the steel surface. Table 1 shows the blending amount of substances contained in the paint applied to each coated steel material (Invention Examples 1 to 26 and Comparative Examples 1 to 3) and the coating weight of the coated steel material. Table 2 shows the coating amount of each component in the coating film.

  The preparation and coating of the paint at this time were performed based on the method described above. For example, in the case of Invention Example 9 shown in Table 1, first, in 900 g of a paint solution of a commercially available zinc rich primer paint defined in JIS as described above (a paint solution containing an alkylsilicate binder resin and thinner), 620 g of titania powder, 1050 g of zinc powder, and 32 g of aluminum powder were added, and thoroughly mixed and stirred by a shaker machine to prepare a paint. Next, the spray amount and spray speed of the prepared paint are adjusted by an air spray type coating device so that the coating weight after drying is 0.86 g on a steel plate having an area of 200 mm × 100 mm, The invention example 9 which has a coating film of the application quantity shown in Table 2 was obtained by spraying. In addition, although the film thickness of the coating film of each coating steel material was influenced by the coating method and the blast state of the surface of a steel plate, it was in the range of about 5 to 30 μm.

  As the base steel material, a rolled steel material for welded structure, SM490A class, having a size of 200 mm × 100 mm × thickness 12 mm and having a surface subjected to shot blasting was used.

  Moreover, the cutting property test was done by laser cutting about the above coated steel materials. For laser cutting, oxygen was injected at 0.1 MPa as an assist gas with an output of 2.1 kW using a carbon dioxide laser device manufactured by Mitsubishi Electric Corporation. The cutting speed was evaluated at 1000 mm / min. Rust prevention was evaluated by a salt spray test in accordance with JIS K 5552 (2002) zinc rich primer.

  Table 2 shows the evaluation results of the laser cut surface properties and salt spray resistance when the present invention example and the comparative example were cut at a laser cutting speed of 1000 mm / min. In Table 2, the evaluation of the cut surface properties is as follows: ◎ is the best cut surface, shows no occurrence of dross or a very small amount of cut surface, ○ is almost a good cut surface, In some cases, dross has occurred but the cut surface is in place, △ indicates that dross has occurred in more than 50% of the total length of the cutting line, but has been completely cut, and x indicates the cutting line. It shows a state where dross was generated on almost the entire surface and a part of the dross was not cut. Note that dross refers to an adherent formed by cooling and solidifying molten metal containing a gas generated along a cutting line on the surface opposite to the laser irradiation surface during cutting. Moreover, the rust prevention evaluation by the salt spray test was evaluated by the number of days until red rust was generated by the salt spray test defined in JIS K 5552 (2002). These evaluation results are also shown in Table 2.

  Invention Examples 1 to 26 include titania powder and zinc powder in the primer coated on the surface of the steel sheet according to the present invention, and further aluminum powder and / or Mo, W, Ni, Cu, Cr, P, Mg, V, Co. Among them, one or two or more elements were added as a single substance or as a compound, but the laser cut surface properties were ◎ or ◯, and the salt spray red rust occurrence days were 14 days or more.

On the other hand, Comparative Examples 1-3 are outside the scope of the present invention. Among them, Comparative Example 1 was inferior in laser cutting property because only zinc powder was contained in the coating film and the amount thereof was as large as 46 g / m ² . Moreover, although the comparative example 2 is a case where only zinc powder is similarly contained in a coating film, since the quantity is as small as 23 g / m < ² >, it was inferior to rust prevention property. Moreover, Comparative Example 3, zinc powder in the coating is 11.5 g / m ² and an aluminum powder is contained 0.7 g / m ^2, although the case does not contain the titania, does not contain titania For this reason, the effect of improving laser cutting property was not obtained. In addition, the coating film obtained by adding 6.8 g / m ^{2 of} titania powder to the coating film of Comparative Example 3 corresponds to Invention Example 8, but as is clear from Table 2, the laser absorptivity is high, and the molten slag is reduced. The coating film was modified by the effect of titania to enhance the discharge effect, and the laser cutting property was improved.

Next, the zinc powder addition amount is fixed to 11.5 g / m ² , the aluminum powder addition amount is fixed to 0.7 g / m ² , and the titania powder addition amount is 0, 4.5, 6.8, 14 g / m ^2. The cut surface when the steel sheet having the changed coating film was cut twice each at cutting speeds of 900, 950, 1000, 1050, 1100 mm / min was evaluated. The evaluation of the cut surface property is the same as in the above case. The result is shown in FIG. In addition, when titania was not added, since the cutting evaluation at 1050 and 1100 mm / min was x, 800 and 850 mm / min were additionally evaluated. As shown in FIG. 1, it can be seen that as the amount of titania increases, the cutting speed at which the evaluation of the cut surface becomes better increases. From this, it was confirmed that the addition of titania to the primer is effective in improving the laser cutting property.

  The coated steel material excellent in laser cutting property and primary rust prevention property of the present invention can be widely applied to steel plates used in shipbuilding, construction and the like.

The graph which shows the relationship between the titania density | concentration in a primer, and the cutting speed from which a cut surface becomes favorable.

Claims (18)

The steel material is coated with a primer containing titania powder, zinc powder and aluminum powder as a dry coating, and the coating amount of titania powder is 4.5 g / m ² ≦ titania powder ≦ 26 g / m ^2. Painted steel material with excellent laser cutting ability and primary rust prevention. The coated steel material excellent in laser cutting property and primary rust prevention property according to claim 1 , wherein the amount of zinc powder contained in the primer is 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . The laser cutting property and primary rust preventive property according to claim 1 or 2 , wherein an application amount of the aluminum powder contained in the primer is 0.1 g / m ² ≤ aluminum powder ≤ 10 g / m ² . Excellent painted steel. Drying the coating film, containing a titania powder and zinc powder and aluminum powder, titania powder, painted steel primer, characterized in that a 4.5 g / ^{m 2} ≦ titania powder ≦ 26g / ^{m 2.} The primer for coated steel materials according to claim 4 , wherein the zinc powder contained in the dry coating film satisfies 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . The aluminum powder contained in the dried coating film satisfies 0.1 g / m ² ≦ aluminum powder ≦ 10 g / m ^2, and the primer for a coated steel material according to claim 4 or 5 . It contains titania powder and zinc powder as a dry coating on the surface of steel, and further contains one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co as single substances. Or as a compound, and is coated with a primer whose titania powder coating amount is 4.5 g / m ² ≦ titania powder ≦ 26 g / m ² , and has excellent laser cutting property and primary rust prevention property Painted steel. The coated steel material excellent in laser cutting property and primary rust prevention property according to claim 7 , wherein a coating amount of zinc powder contained in the primer is 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . The total coating amount as a single substance or as a compound of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co contained in the primer is 0. It is 2-20 g / m < ² >, The coated steel material excellent in the laser cutting property and primary rust prevention property of Claim 7 or Claim 8 characterized by the above-mentioned. The dried coating film contains titania powder and zinc powder, and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V and Co are used as single substances or compounds thereof. containing, and titania powders, painted steel primer, characterized in that a 4.5 g / ^{m 2} ≦ titania powder ≦ 26g / ^{m 2.} The primer for coated steel materials according to claim 10 , wherein the zinc powder contained in the dry coating film satisfies 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . The total coating amount as a single substance or as a compound of one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co contained in the dry coating film is calculated in terms of elements. It becomes 0.2-20 g / m < ² >, The primer for coated steel materials of Claim 10 or Claim 11 characterized by the above-mentioned. The surface of the steel material contains titania powder, zinc powder, and aluminum powder as a dry coating film, and one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co As a single substance or as a compound, and a primer having a titania powder coating amount of 4.5 g / m ² ≦ titania powder ≦ 26 g / m ² is applied. Painted steel with excellent properties. The coated steel material excellent in laser cutting property and primary rust prevention property according to claim 13 , wherein the amount of zinc powder contained in the primer is 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . The application amount of the aluminum powder contained in the primer is 0.1 g / m ² ≦ aluminum powder ≦ 5 g / m ² and one of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co. The laser cutting according to claim 13 or 14 , wherein the total coating amount as a single substance or a compound of seeds or two or more elements is 0.05 to 5 g / m ² in terms of elements. Painted steel material with excellent properties and primary rust prevention. The dry coating film contains titania powder and zinc powder and aluminum powder, and further, one or more elements of Mo, W, Ni, Cu, Cr, P, Mg, V, and Co are used as a single substance or contains a compound, titania powder, painted steel primer, characterized in that a 4.5 g / ^{m 2} ≦ titania powder ≦ 26g / ^{m 2.} The primer for coated steel materials according to claim 16 , wherein the zinc powder contained in the dry coating film satisfies 9 g / m ² ≦ zinc powder ≦ 30 g / m ² . Aluminum powder contained in the dried coating film is 0.1 g / m ² ≦ aluminum powder ≦ 5 g / m ² , and one or more of Mo, W, Ni, Cu, Cr, P, Mg, V, Co or The primer for coated steel materials according to claim 16 or 17 , wherein a total coating amount as a single substance or a compound of two or more elements is 0.05 to 5 g / m ^{2 in} terms of elements. .

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