| WO/1998/053894 | NON-POROUS GAS PERMEABLE MEMBRANE |
| WO/1986/002766 | ARTICLE WITH REDUCED FRICTION POLYMER SHEET SUPPORT |
| WO/1986/001382 | CURING COATINGS OF A MOISTURE-CURABLE COMPOSITION |
ANDO, Yoshinobu (Sinto SB Tec Company, Ichinomiya-Jigyosyo, 180-1 Komaki, Ogi-cho, Toyokawa-sh, Aichi 05, 44112, JP)
SAKUMAE, Hiroshi (Sinto SB Tec Company, Ichinomiya-Jigyosyo, 180-1 Komaki, Ogi-cho, Toyokawa-sh, Aichi 05, 44112, JP)
ANDO, Yoshinobu (Sinto SB Tec Company, Ichinomiya-Jigyosyo, 180-1 Komaki, Ogi-cho, Toyokawa-sh, Aichi 05, 44112, JP)
| Claims 1. A method for treating rolled steel for a general structure, comprising: a step for spraying dry and high-pressure air onto the rolled steel to remove extraneous substances attached to the rolled steel, a step for heating the rolled steel, from which the extraneous substances are removed, up to a predetermined temperature, a step for shot blasting the rolled steel, which is heated up to a predetermined temperature, a step for spraying dry air onto the rolled steel, which is shot blasted, to remove moisture and fine particles of salt, a step for spraying a coating material onto the rolled steel, from which the moisture and the fine particles of salt are removed, and a step for spraying hot air onto the rolled steel, which is coated by the coating material, to dry the coating material. 2. Facilities for treating rolled steel for the general structure comprising: a first apparatus for spraying dry and high-pressure air onto the rolled steel to remove extraneous substances attached to the rolled steel, an apparatus for heating the rolled steel, from which the extraneous substances are removed, up to a predetermined temperature, an apparatus for shot blasting the rolled steel, which is heated up to a predetermined temperature, a second apparatus for spraying dry air onto the rolled steel, which is shot blasted, to remove moisture and fine particles of salt attached to the rolled steel, an apparatus for spraying a coating material onto the rolled steel, from which the moisture and the fine particles of salt are removed, and an apparatus for drying the coating material on the rolled steel by spraying hot air onto the rolled steel, which is coated by the coating material. 3. The facilities for treating rolled steel for the general structure of claim 2, wherein the apparatus for shot blasting the rolled steel comprises a means for blasting shots that can blast shots in a direction 45~60 degrees from the horizontal plane and that can blast the shots from the upstream side to the downstream side of the direction that the rolled steel moves. 4. The facilities for treating rolled steel for the general structure of claim 2, wherein the second apparatus for spraying dry air onto the rolled steel comprises a nozzle for ejecting dry air that can eject the dry air in the direction 45~60 degrees from the horizontal plane, and can eject the dry air from the downstream side to the upstream side of the direction that the rolled steel moves. 5. The facilities for treating rolled steel for the general structure of any of claims 2 —4, further comprising an apparatus for measuring a thickness of the rolled steel, from which the moisture and the fine particles that are attached to but not firmly fixed to the rolled steel are blown off. 6. The facilities for treating rolled steel for the general structure of any of claims 2 —4, further comprising an apparatus for pre-heating the rolled steel, from which the moisture and the fine particles have been removed. |
A METHOD FOR TREATING ROLLED STEEL FOR A GENERAL STRUCTURE AND FACILITIES THEREFOR
Technical Field
[0001] This invention relates to a method for treating rolled steel for a general structure and facilities therefor. Particularly, it relates to a method for treating rolled steel for a general structure so that the steel can be used for a ship or a large tank, and facilities therefor.
Background of the Invention
[0002]
Conventionally, as such a method, the method for coating a steel plate with a shop primer or chemical conversion coating after treating the surface of the steel plate by shotblasting or pickling is well known. [0003]
Patent document 1 : Japanese Patent Laid-open
Publication No. H8-24781
Disclosures of Invention [0004]
However, in the conventional method, which has the constitution explained in the above paragraph, for treating rolled steel for a general structure, the oxidized scale attached to the rolled steel is entirely removed from its surface by shotblasting. However, since the surface of the rolled steel that is treated by the shotblasting has its base metal exposed, which surface is ground and has a metallic luster, a small amount of a new oxidized layer is immediately formed at the activated surface that is treated by the shotblasting, because of a chemical reaction, such as oxidation. Thus, since the coating of the shop primer, etc., is formed on the new oxidized layer, the coating is likely to be separated from the surface of the rolled steel. Since when the portion where the coating is separated is exposed to rain or an environment containing seawater, it infiltrates the gap between the coating and the base metal, and thus significant corrosion is caused at the surface of the rolled steel. [0005]
This invention has been conceived in the circumstances explained in the above paragraphs. Namely, the purpose of this invention is to provide a method for treating rolled steel for a general structure so that the coating formed on the rolled steel after shotblasting can be prevented from being separated from the rolled steel, and facilities therefor. [0006] To achieve the purpose explained in the above paragraph, the present invention has the following constitution.
Namely, it is a method for treating rolled steel for a general structure, comprising the following: a step for spraying dry and high-pressure air onto the rolled steel to remove extraneous substances attached to the rolled steel, a step for heating the rolled steel, from which the extraneous substances are removed, up to a predetermined temperature, a step for shot blasting the rolled steel, which is heated up to a predetermined temperature, a step for spraying dry air onto the rolled steel, which is shotblasted, to remove moisture and fine particles of salt, a step for spraying a coating material onto the rolled steel, from which the moisture and the fine particles of salt are removed, and a step for spraying hot air onto the rolled steel, which is coated by the coating material, to dry the coating material. [0007]
Since the present invention has the following features: a step for spraying dry and high-pressure air onto the rolled steel to remove extraneous substances attached to the rolled steel, a step for heating the rolled steel, from which the extraneous substances are removed, up to a predetermined temperature, a step for shot blasting the rolled steel, which is heated up to a predetermined temperature, a step for spraying dry air onto the rolled steel, which is shotblasted, to remove moisture and fine particles of salt, a step for spraying a coating material onto the rolled steel, from which the moisture and the fine particles of salt are removed, and a step for spraying hot air onto the rolled steel, which is coated by the coating material, to dry the coating material, the moisture and the fine particles of salt are removed from the surface of the rolled steel, which has its base metal exposed by the shot blasting, which metal has a metallic luster and is likely to be chemically reactive. Thus, the coating can tightly adhere to the surface of the rolled steel, and any possible separation between the coating and the rolled steel can be definitely prevented. Namely, the present invention has significant and excellent effects.
Brief Descriptions of the Drawings
[0008]
Fig. 1 shows an elevational view of facilities for treating rolled steel for a general structure of one embodiment of this invention.
Fig. 2 shows a plane view of the facilities for treating rolled steel for the general structure of Fig. 1.
Fig. 3 shows an enlarged elevational view of a first apparatus for spraying dry air and an apparatus for measuring a thickness, which are primary elements of the facilities for treating rolled steel for the general structure of Fig. 1. Fig. 4 shows an enlarged elevational view of an apparatus for shot blasting. It is the primary element of the facilities for treating rolled steel for the general structure of Fig. 1.
Preferred Embodiments of the Invention
[0009]
Below, based on Figs. 1 —4, one embodiment of the facilities for treating rolled steel for the general structure of the present invention is explained. As shown in Figs. 1 and 2, those facilities include the following: a first apparatus 1 for spraying dry and high-pressure air onto a steel plate W, which corresponds to rolled steel, to spray dry and high-pressure air onto both sides of the steel plate W to remove extraneous substances attached to the steel plate W, an apparatus 2 for measuring the thickness of the steel plate W, an apparatus 3 for heating both sides of the steel plate W, from which the extraneous substances are removed, up to a predetermined temperature, an apparatus 4 for shot blasting both sides of the steel plate W, which is heated up to a predetermined temperature, a second apparatus 5 for spraying dry air onto both sides of the steel plate W, which is shotblasted, to remove moisture and fine particles of salt attached to the steel plate W, an apparatus 6 for spraying a coating material onto the steel plate W, from which the moisture and the fine particles of salt are removed, and an apparatus 7 for drying the coating material on the steel plate W by spraying hot air onto the steel plate W, which is coated by the coating material, wherein these apparatuses are disposed in a line and in sequence from the left to the right of the facilities. [0010]
As shown in Fig. 1, these apparatuses, which are arranged in a line, are connected by roller conveyers 8, which convey the steel plate W and extend from the left side to the right side of the facilities. Further, as shown in Fig. 3, the first apparatus 1 for spraying dry air comprises a nozzle 11 for ejecting compressed air to blow off moisture and fine particles of dust attached to the steel plate W, and a roots blower 13 for providing compressed air for the nozzle 11 through a blower pipe 12. The apparatus 2 for measuring a thickness comprises a laser displacement sensor. The apparatus 3 for heating the steel plate W has a heating source using infrared rays. [0011]
As shown in Fig. 4, the apparatus 4 for shot blasting the steel plate W comprises the following: a cabinet 41, which constitutes a space for shot blasting and includes the roller conveyers 8 and the steel plate W conveyed by the roller conveyers 8, a plurality of centrifugal blasting machines 42 for blasting shots, which machines 42 are disposed on and under the cabinet 41, a lower screw conveyer 43 for recovering the blasted shots, which conveyer 43 is disposed under the cabinet 41, a bucket elevator 44 for carrying the recovered shots upward, which elevator
44 is disposed at the distal end of the lower screw conveyer 43, a wind-type separator 45 for removing fragments of scale or particles contained in the shots, which separator 45 is disposed at the upper portion of the bucket elevator 44, an upper screw conveyer 46 disposed under the separator 45 and a hopper 47 for containing shots, which hopper 47 is disposed above the centrifugal blasting machines 42. [0012]
As shown in Fig. 4, an on-off valve 48 for providing the shots to the centrifugal blasting machines 42 is disposed below the hopper 47. The on-off valve 48 is connected to the centrifugal blasting machines 42 by means of a pipe that provides the shots to the machines 42. The centrifugal blasting machines 42 are arranged above and below the steel plate W so that they can blast the shots in a direction that is 45 — 60 degrees from the longitudinal direction of the steel plate, and so that they can blast from the upstream side to the downstream side of the direction that the steel plate moves. [0013]
As shown in Fig. 4, the second apparatus 5 for spraying dry air onto the steel plate W comprises a duct pipe 52 to connect a roots blower to a nozzle 51 for ejecting dry air, and an adjusting mechanism (not shown) to adjust the height of the nozzle 51 for ejecting dry air, which mechanism can change the vertical position of the nozzle 51 in response to the thickness of the steel plate W. The nozzle 51 for ejecting dry air is tilted 45~60 degrees from the horizontal plane (the longitudinal direction of the steel plate) and can eject the dry air from the downstream side to the upstream side of the direction that the steel plate moves. [0014]
As shown in Fig. 1, the apparatus 6 for spraying a coating material onto the steel plate W is a reciprocating painting machine that is placed horizontally and that uses airless-type nozzle guns 61. Four nozzle guns 61 are disposed above the steel plate W and four below the steel plate W. These guns 61 can be moved in the traverse and longitudinal directions of the steel plate W, and also vertically. The vertical position of the nozzle guns 61 is determined based on the thickness of the steel plate W so as to have the distance between the surface of the steel plate W and the guns 61 be 300 mm. This distance is measured by the apparatus 2 for measuring a thickness. Further, the nozzle guns 61 can spray a coating material while they reciprocate in the traverse direction of the steel plate W based on the speed of the steel plate W. [0015]
As shown in Fig. 1, the apparatus 7 for drying the coating material is a forced-hot-air blowing-type, and comprises a burner for burning LGP gas, and a fan 71 for blowing air. [0016]
For the facilities explained in the above paragraphs, a steel plate W, for example, which is 5500 mm wide, 9000 mm long, and 45 mm thick, is transferred from the first apparatus 1 for spraying dry air to the apparatus 7 for drying the coating material, by the roller conveyers 8. Namely, first, the steel plate W is transferred to the first apparatus 1 for spraying dry air. Then the extraneous substances attached to the steel plate W are removed by spraying high-pressure air onto the surface of the steel plate W. The extraneous substances comprise a liquid, such as rainwater, particles of dust, and fine particles of crystals of sodium chloride derived from seawater, and which substances are attached to the steel plate W when it is stored outdoors. After removing the extraneous substances from the steel plate W, it is transferred to a position where the laser displacement sensor, which acts as the apparatus 2 for measuring the thickness of the steel plate W, is located, and then the thickness of the steel plate W is measured. In the latter, the measured thickness is used for determining the height of the nozzle 51 for ejecting dry air and the vertical position of the nozzle guns 61 of the apparatus 6 for spraying a coating material. [0017]
Next, the steel plate W is transferred to the apparatus 3 for heating the plate W. Then both sides of the plate W are heated so that the temperature of the surface of the plate W increases to 5~20 °C above the temperature of the environment. Then, the heated steel plate W is transferred to the apparatus 4 for shot blasting. By the apparatus 4 for shot blasting, the steel plate W is ground and cleaned by shot blasting at 400 kg/min. of shots from the centrifugal blasting machines 42. As a result, after the shot blasting, the surface roughness (Rmax) of the steel plate W becomes 35^70 / / m. Since the oxidized scale is separated and removed from the surfaces of the steel plate W, the surface of the base metal, which has a metallic luster, is exposed. [0018]
Next, the shotblasted steel plate W is transferred to the second apparatus 5 for spraying dry air. Then the moisture and the fine particles of salt are removed from the steel plate W by spraying dry air onto both sides of the plate W. Namely, the moisture and the fine particles of salt are blown off, and thus removed from, the steel plate W, by ejecting the dry air, which air is generated by the roots blower, from the nozzle 51 to the steel plate W, which plate W has its base metal exposed the metal having a metallic luster, and which base metal is likely to be chemically reactive.
Incidentally, the nozzle 51 ejects the dry air opposite the direction that the steel plate W is moving, so that the removed moisture and fine particles are not blown off the steel plate W toward the apparatus 6 for spraying a coating material that is disposed at the downstream side. As a result, the amount of the sodium chloride before spraying a coating material on the surface of the steel plate W can be reduced to 50 mg or less a square meter. [0019]
Next, the steel plate W, from which the moisture and the fine particles are removed, is transferred to the apparatus 6 for spraying a coating material, and then the nozzle guns 61 spray the coating material onto both sides of the steel plate W. After forming a membrane made from the coating material, the coated steel plate W is transferred to the apparatus 7 for drying the coating material. Then the fan 71 for blowing air ejects the heated air onto the surface of the steel plate W, which air is heated to 70~80 °C by burning LPG gas, to dry the coating material that is on the plate W.
As explained in the above paragraphs, the steps for processing and treating the steel plate W are thus completed. [0020]
For the embodiment explained in the above paragraphs, the centrifugal blasting machines 42 are used as the machines for blasting shots. However, the machines for blasting shots are not limited to such a centrifugal blasting machine. For example, an air-blasting nozzle, which ejects shots by compressed air, can be used. Further, for the embodiment explained in the above paragraphs, airless-type nozzle guns 61 are used as the apparatus 6 for spraying a coating material. However, the apparatus 6 for spraying a coating material is not limited to such an airless-type nozzle gun. For example, a liquid-gas two-phase-type nozzle, which ejects the coating material by compressed air, can be used as the apparatus 6 for spraying a coating material.
Further, an apparatus for pre-heating the steel plate W, from which the moisture and the fine particles are removed, may be used to facilitate drying the coating material on the steel plate W during the following step. Explanation of Denotations
[0021]
1 a first apparatus for spraying dry air
2 an apparatus for measuring a thickness 3 an apparatus for heating the steel plate
4 an apparatus for shot blasting
5 a second apparatus for spraying dry air
6 an apparatus for spraying a coating material
7 an apparatus for drying the coating material
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