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Metal plate for laser processing and method for producing stainless steel plate for laser processing

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Metal plate for laser processing and method for producing stainless steel plate for laser processing


A metal plate for laser processing (such as a stainless steel plate or a titanium plate) and preferably an austenitic stainless steel plate suitable for use as a metal mask or the like which undergoes fine processing with a laser has an average grain diameter d (μm) and a plate thickness t (μm) which satisfy the equation d≦0.0448·t−1.28.
Related Terms: Titanium

Browse recent Nippon Steel & Sumitomo Metal Corporation patents - Tokyo, JP
USPTO Applicaton #: #20140060428 - Class: 118500 (USPTO) -
Coating Apparatus > Work Holders, Or Handling Devices

Inventors: Kazuyoshi Fujisawa, Masayuki Shibuya, Kouichi Takeuchi

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The Patent Description & Claims data below is from USPTO Patent Application 20140060428, Metal plate for laser processing and method for producing stainless steel plate for laser processing.

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TECHNICAL FIELD

This invention relates to a metal plate for laser processing such as an austenitic stainless steel plate for laser processing which is suitable for use as a metal mask or the like which undergoes precision processing with a laser and to a method for producing a stainless steel plate for laser processing.

BACKGROUND ART

A laser cut metal mask is a metal plate which has small holes (or slits) in a prescribed patterned image which are formed by melting and boring holes in a portion of a metal plate by irradiating the metal plate with a laser beam. It is primarily used for screen printing of solder paste (solder cream) on a circuit board such as a printed wiring board with a squeegee, but it is also used in other applications such as printing of electrically conductive ink. Plates made of stainless steel, titanium, titanium alloys, aluminum, aluminum alloys, nickel, and the like are used as metal plates. In the past, holes were formed in a metal mask by etching, but with the spread of laser processing machines, laser cut metal masks in which it is possible to form holes with higher precision have come to be much used.

Stainless steel is widely used as a metal plate for metal masks manufactured by etching or laser processing because it has excellent mechanical strength and corrosion resistance. In recent years, as the performance of laser processing machines has improved, not only has there been an increase in processing accuracy but it has also become possible to cope with short deadlines for orders. As a result, the demand for laser cut metal masks made of stainless steel is increasing.

Technical advances in laser processing machines have result in increases in the processing accuracy of small holes in a laser cut metal mask and the ability to prevent warping due to heat. As a result of these advances, the processing accuracy of laser cut metal masks has been further increasing.

Patent Document 1 discloses that when irradiating a metal plate with a laser beam to form a patterned image having small holes in the metal plate, by suppressing the focal spot diameter of the irradiated laser beam to at most 40 μm and setting the distance between the focal point of the laser beam during processing and the surface of the metal plate on the incident side of the laser beam in the range of −200 to +300 μm, the difference between the diameter of small holes which constitute a patterned image on the incident side of the laser beam and the diameter of the holes on the exit side of the laser beam (referred to in this description as hole spreading) is suppressed to at most 10% of the thickness of the metal plate.

Patent Document 2 discloses a method of manufacturing a laser cut metal mask for screen printing by irradiating a metal plate with a laser beam to melt a portion of the metal plate and bore it to create small holes to form a patterned image and then performing grinding by sandblasting of the surface of the metal plate. When a laser cut metal mask is manufactured by this method, no dross remains, so the rear surface of the mask can contact the printed surface of an object to be printed. In addition, since the surface is textured due to sandblasting, the mask easily releases from the object being printed and the speed of printing can be increased.

Patent Document 3 proposes employing chemical polishing to remove dross or the like which is formed on the rear surface by laser processing.

As shown by Patent Documents 1-3, up to now, the performance of laser cut metal masks has been improved by increasing the processing accuracy of small holes by improvements in laser processing methods such as technical advances in processing tools by carrying out mechanical and/or chemical processing of a metal mask after laser processing in order to stabilize the amount of solder which is supplied through the holes.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 9-248976 A

Patent Document 2: JP 6-39988 A

Patent Document 3: JP 2011-148253 A

SUMMARY

OF THE INVENTION

Thus far, there have been almost no disclosures of developments of metal plates which can increase the accuracy of laser processing of small holes in a laser cut metal mask, and there were no metal plates (such as stainless steel plates) which were suited for laser processing of small holes with high accuracy. There were also no metal plates which were suitable for mechanical or chemical processing after laser processing.

For these reasons, as proposed in Patent Document 1, it has been attempted to increase the processing accuracy of laser processing of small holes in a laser cut metal mask by decreasing the focal spot diameter of irradiated laser light or by employing a pulsed laser and suppressing the heat input during laser processing so as to prevent strains due to heat. Alternatively, as proposed in Patent Documents 2 and 3, it has been proposed to increase performance by optimizing the conditions of mechanical or chemical polishing after laser processing.

However, these prior art methods could not avoid decreases in the speed of processing, the processing costs of laser cut metal masks greatly increased, and productivity greatly decreased.

In addition to electrolytic/chemical polishing or mechanical polishing in order to remove dross or burrs which are produced on the rear surface by laser processing, treatment after laser processing has included imparting a mirror finish to the front surface in order to improve squeegee properties (the uniformity of supply of solder by a squeegee). These treatments increased the time required for operations and costs.

An object of the present invention is to provide a metal plate for laser processing and particularly an austenitic stainless steel plate for laser processing suitable for use as a metal mask or the like which undergoes precision processing with a laser, and a method for producing a stainless steel plate for laser processing. Specifically, an object of the present invention is to provide a metal plate and preferably an austenitic stainless steel plate for laser processing which has excellent laser processability and which can be used to manufacture a laser cut metal mask having increased dimensional accuracy of the cross section of openings (for example, hole spreading with respect to a plate thickness of 250 μm of at most 25 μm which is an accuracy of at most 10%) and which is also suitable for forming fine slits, and a method for producing this stainless steel plate.

The main purpose of laser processing in the present invention is laser processing of a metal plate which is utilized in the manufacture of a metal mask having small holes as used in screen printing.

The present inventors found that the above-described objects can be achieved by making the grain diameter of a metal plate at most a certain limit which depends on the plate thickness.

The present invention is a metal plate and preferably an austenitic stainless steel plate for laser processing characterized in that the average grain diameter d (μm) and the thickness t of the plate (μm) satisfy the following Equation (1):

d≦0.0448·t−1.28   (1)

From another standpoint, the present invention is a method of producing an austenitic stainless steel plate for laser processing characterized by carrying out hot rolling, cold rolling, and annealing of an austenitic stainless steel to obtain an austenitic stainless steel plate, carrying out temper rolling of the stainless steel plate with a reduction of at least 20%, and if necessary carrying out stress relief annealing after temper rolling at a temperature of 500-820° C. for 20-150 seconds. There is substantially no change in the average grain diameter of the austenitic stainless steel plate during the temper rolling and stress relief annealing, so the average grain diameter of the cold-rolled steel sheet obtained by carrying out hot rolling, cold rolling, and annealing is made to satisfy above Equation (1). To this end, it is preferable to carry out cold rolling (when cold rolling is carried out two or more times, the final cold rolling before temper rolling) with a reduction of at least 30% and carry out annealing (when annealing is carried out two or more times, the final annealing before temper rolling) by soaking at a temperature of 800-950° C. for 25-70 seconds.

According to the present invention, a metal plate for laser processing which is suitable for use as a metal mask or the like which is manufactured by precision processing with a laser and particularly an austenitic stainless steel plate for laser processing which has a high strength and which can achieve small holes having a high processing accuracy are provided.

Because a metal plate for laser processing according to the present invention decreases the need to suppress heat input by increasing the processing accuracy of laser processing, the speed of laser processing can be increased. As a result, the productivity of laser cut metal masks can be increased and processing costs can be decreased.

Up to now, the processing accuracy of laser processing depended upon the laser apparatus or the processing conditions. According to the present invention, the processing accuracy of laser processing can also be increased by controlling the average grain diameter d (μm) of a metal plate for laser processing and the plate thickness t (μm) so as to satisfy above Equation (1).

With many austenitic stainless steel plates, it was found that refining crystal grains provides the effects that the amount of dross which adheres to the inner surface of the small holes which are formed by laser processing is decreased and the height of burrs which are formed on the peripheral surface of the small holes on the rear surface (the exit side with respect to the laser) is lowered. As a result, processing such as removal of dross and burrs by electrolytic or chemical polishing and smoothing of the inner surface of the holes or the squeegee surface (forming a mirror finish) can be carried out in a shorter length of time, and it is possible to shorten the time for manufacturing a laser cut metal mask (shorten the delivery date) and reduce costs. Therefore, the practical significance of the present invention is extremely great.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is an explanatory view showing a method for producing an austenitic stainless steel plate used in an example.

FIG. 2(A) is an explanatory view schematically showing the state when boring small holes in a stainless steel plate by laser processing, and FIG. 2(B) is an explanatory view showing the state of dross and burrs formed in small holes which are formed by laser processing.

FIG. 3 is a graph showing the relationship between the average grain diameter of a metal plate and the amount of hole spreading.

In FIGS. 2(A) and 2(B), 1: laser, 2: stainless steel plate, 2a: incident surface of laser beam, 2b: exit surface of laser beam, 3: small hole, 3a: width of cutting (cutting diameter) on incident side, 3b: width of cutting (cutting diameter) on exit side, 4: maximum dross thickness, 5: maximum burr height.

MODES FOR CARRYING OUT THE INVENTION

Below, the present invention will be explained more specifically while referring to the accompanying drawings. In the following explanation, an example will be given of the case in which a metal plate which is a material being processed is a stainless steel plate and particularly an austenitic stainless steel plate. However, a metal plate in the present invention is not limited to a stainless steel plate. For example, the present invention can be applied in the same manner to a metal plate other than a stainless steel plate such as a titanium or titanium alloy plate, a pure nickel plate, an aluminum plate, or an aluminum alloy plate, although a method for producing an austenitic stainless steel plate for laser processing according to the present invention and particularly conditions for each step are not applicable to a metal plate other than an austenitic stainless steel plate.

From the standpoints of strength and rust resistance, a stainless steel plate is preferably an austenitic stainless steel plate, but it is also possible to use a ferritic stainless steel. Cold-rolled stainless steel plates including austenitic types are prescribed by JIS G 4305. Among austenitic stainless steel plates, temper rolled materials of SUS 301, SUS 304, SUS 301L, and SUS 304L, and SUS 301-CSP and SUS 304-CSP which are prescribed by JIS G 4313 (stainless steel strip for springs) are preferred because their grains are easily refined.

The chemical compositions of these austenitic stainless steels are given below. In the following explanation, percent with respect to chemical composition means mass percent.

[SUS 301]

C: at most 0.15%, Si: at most 1.00%, Mn: at most 2.00%, P: at most 0.045%, S: at most 0.030%, Ni: 6.00-8.00%, Cr: 16.00-18.00%, remainder of Fe and impurities.

[SUS 301L]

C: at most 0.030%, Si: at most 1.00%, Mn: at most 2.00%, P: at most 0.045%, S: at most 0.030%, Ni: 6.00-8.00%, Cr: 16.00-18.00%, N: at most 0.20%, remainder of Fe and impurities.

[SUS 304]

C: at most 0.08%, Si: at most 1.00%, Mn: at most 2.00%, P: at most 0.045%, S: at most 0.030%, Ni: 8.00-10.50%, Cr: 18.0-20.0%, remainder of Fe and impurities.

[SUS 304L]

C: at most 0.030%, Si: at most 1.00%, Mn: at most 2.00%, P: at most 0.045%, S: at most 0.030%, Ni: 9.00-13.00%, Cr: 18.00-20.00%, remainder of Fe and impurities.

[SUS 301-CSP]

C: at most 0.15%, Si: at most 1.00%, Mn: at most 2.00%, P: at most 0.045%, S: at most 0.030%, Ni: 6.00-8.00%, Cr: 16.00-18.00%, remainder of Fe and impurities.



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stats Patent Info
Application #
US 20140060428 A1
Publish Date
03/06/2014
Document #
14002398
File Date
02/29/2012
USPTO Class
118500
Other USPTO Classes
148610, 428544, 428596, 72201
International Class
/
Drawings
3


Titanium


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