JP5314396B2 - Aluminum alloy plate for lithographic printing plates - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for a lithographic printing plate, which is manufactured by cold-rolling a hot-rolled plate into the final thickness while skipping an intermediate annealing step, has a surface layer in which Ga and Mg are concentrated, makes uniform pits formed in electrolysis treatment, and does not form a streak thereon when having been processed as a printing plate. <P>SOLUTION: The aluminum alloy sheet has a composition including 0.03 to 0.15% Si, 0.2 to 0.7% Fe, 0.05 to 0.5% Mg, 0.003 to 0.05% Ti, 30 to 300 ppm Ga and the balance aluminum with unavoidable impurities, has recrystallized grains with an average grain size of 50 &mu;m or smaller in a direction perpendicular to the rolling direction, in the surface layer, contains Mg of 5 to 50 times higher concentration in the surface layer of 0.2 &mu;m deep from the surface than the average Mg concentration, and contains Ga of 2 to 20 times higher concentration in the surface layer of 0.2 &mu;m deep from the surface than the average Ga concentration. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an aluminum alloy plate for a lithographic printing plate, and more particularly to an aluminum alloy plate for a lithographic printing plate that is suitable for roughening by electrochemical etching and has excellent productivity during production.

  In general, an aluminum alloy plate is used as a support for lithographic printing plates (including offset printing plates), and the support is rough from the viewpoint of improving the adhesion of the photosensitive film and improving the water retention of the non-image area. In recent years, the surface of the aluminum alloy plate for the support is roughened by electrochemical etching because of its excellent plate-making suitability and printing performance, and continuous processing with coil materials. The approach to surface is developing rapidly.

  As an aluminum alloy plate capable of obtaining a relatively uniform electrolytic surface roughening by electrochemical etching treatment, a material equivalent to A1050 (aluminum purity 99.5%) or a material added with a small amount of alloy components based on A1050 equivalent material is used. Some proposals have been made on alloy components (see, for example, Patent Document 1).

  In order to improve the printing durability of the printing plate, the printing plate with an aluminum alloy plate as a support is exposed and developed by normal methods, and then heat-treated (burning) at high temperatures to reinforce the image area. To be done. Since the burning treatment is usually performed under the conditions of a heating temperature of 200 to 290 ° C. and a heating time of 3 to 9 minutes, heat resistance (burning resistance) is required so that the strength of the support does not decrease during the burning treatment. It has been.

  In addition, recently, with the advance of printing technology, the printing speed has increased and the strength against the support has increased in response to the increased stress applied to the printing plates that are mechanically fixed to both sides of the printing press cylinder. When the demand is increasing and the support strength is insufficient, the fixed portion is deformed or damaged, resulting in troubles such as printing misalignment. Therefore, it is indispensable to improve the strength of the support along with the above-mentioned burning resistance. .

  In order to satisfy the above requirements, an attempt was made to adjust the additive component based on the A1050 equivalent material (see Patent Document 2). The additive component was adjusted based on the A1050 equivalent material and the oil pit depth on the plate surface was adjusted. Attempts have also been made to adjust the thickness (see Patent Document 3).

  Conventionally, these aluminum alloy materials for lithographic printing plates are homogenized, hot-rolled ingots, cold-rolled, and subjected to intermediate annealing in the middle of cold-rolling to recrystallize the rolled plate surface. After forming the structure, by performing secondary cold rolling, the generation of pits during the electrochemical etching process is made uniform, and the occurrence of streaks when the process as a printing plate is performed is prevented. A decrease in productivity and an increase in manufacturing costs due to annealing are inevitable, and improvements are desired.

  As a method of obtaining an aluminum alloy plate for lithographic printing plates by performing cold rolling without performing annealing treatment after hot rolling, in hot rolling consisting of hot rough rolling and hot finish rolling, The starting temperature is set to 450 ° C. or more, rolling is performed at a rolling speed of 50 m / min or more from the starting pass, a reduction amount of 30 mm or more, or a one-pass reduction ratio of 30%, and the end temperature of hot rough rolling is set to 300 to A method has been proposed in which the recrystallization of the plate surface is controlled by setting it to 370 ° C., and then setting the end temperature of hot finish rolling to be 280 ° C. or higher and winding it as a coil (see Patent Document 4).

In this case, in order to omit intermediate annealing, it is necessary to recrystallize at the stage of winding as a coil after completion of hot finish rolling, but in order to obtain uniform electrolytic surface roughening characteristics It is important that the recrystallized grain size to be formed is fine and uniform as in the material subjected to the intermediate annealing without coarsening, and that the degree of recrystallization of the plate surface layer part is uniform.
JP 2000-108534 A JP 2005-15912 A JP 2004-35936 A Japanese Patent Laid-Open No. 11-335761

  For the purpose of obtaining an aluminum alloy material for a lithographic printing plate capable of achieving more uniform and fine pit formation in electrolytic treatment, the inventors have re-examined the component composition and structure properties based on the conventionally proposed materials. As a result of investigation, it has been found that a material containing Mg and Ga and having a Mg and Ga concentration in the surface layer portion higher than the Mg and Ga concentration in a region deeper than the surface layer portion is effective. Moreover, in order to manufacture such an aluminum alloy sheet having a textured property without intermediate annealing, in particular, the starting temperature of hot rough rolling, the holding time of the material from the end of hot rough rolling to hot finish rolling It was found that controlling the finishing temperature of hot finish rolling is important.

  The present invention has been made as a result of further tests and examinations based on the above knowledge, and the purpose of the present invention is to restore the surface layer portion of the plate at the stage of winding as a coil after the hot finish rolling. The degree of crystal is uniform, the recrystallized grains are fine and uniform, can be cold-rolled to the final thickness without intermediate annealing after hot rolling, and moderate Mg and Ga in the surface layer part An aluminum alloy for a lithographic printing plate that has a high degree of strength characteristics, has a high degree of concentration, has uniform and fine pit generation during electrochemical etching, has no streak when processed as a printing plate To provide a board.

The aluminum alloy plate for a lithographic printing plate according to claim 1 for achieving the above object comprises: Si: 0.03 to 0.15% (mass%, hereinafter the same) , Fe: 0.2 to 0.7%, Mg: 0.05 to 0.5%, Ti: 0.003 to 0.05%, Ga: 30 to 300 ppm , allowable Zn content is 50 ppm or less, and consists of the balance aluminum and inevitable impurities An aluminum alloy plate having a composition, wherein the average recrystallized grain size in the direction orthogonal to the rolling direction of the surface layer portion is 50 μm or less, and the Mg concentration of the surface layer portion from the surface to a depth of 0.2 μm is 5 to 50 of the average Mg concentration The surface layer portion from the surface to a depth of 0.2 μm has a Ga concentration of 2 to 20 times the average Ga concentration.

  An aluminum alloy plate for a lithographic printing plate according to claim 2 is characterized in that, in claim 1, the aluminum alloy plate contains Cu: 0.05% or less.

  The aluminum alloy plate for a lithographic printing plate according to claim 3 is characterized in that, in claim 1 or 2, the amount of Mg precipitated in the matrix of the aluminum alloy plate is 50% or less of the average Mg concentration. .

  An aluminum alloy plate for a lithographic printing plate according to claim 4 is characterized in that in any one of claims 1 to 3, it has a tensile strength of 190 MPa or more.

  According to the present invention, after completion of hot finish rolling, at the stage of winding as a coil, the degree of recrystallization of the plate surface layer portion is uniform, the recrystallized grains are fine and uniform, and intermediate annealing after hot rolling is performed. Can be cold-rolled to the final thickness without performing the process, moderate Mg and Ga enrichment can be obtained in the surface layer of the plate, and the generation of pits during the electrochemical etching process is uniform and fine. Thus, there is provided an aluminum alloy plate for a lithographic printing plate which does not generate streaks and has excellent strength characteristics.

  The significance and reasons for limitation of the components contained in the aluminum alloy plate for lithographic printing plates of the present invention will be described. Si coexists with Fe to produce an Al—Fe—Si intermetallic compound, The crystal structure is refined, and these compounds serve as starting points for pit generation, making the formation of pits uniform during electrolytic treatment and finely distributing the pits. The preferable content of Si is in the range of 0.03 to 0.15%. If it is less than 0.03%, the distribution of the compound becomes non-uniform, and unetched portions are generated during the electrolytic treatment, thus preventing the formation of pits. Make uniform. If it exceeds 0.15%, a coarse compound is produced, and precipitation of simple Si is likely to occur, and the uniformity of the roughened structure is lowered.

  Fe produces an Al—Fe-based intermetallic compound, and coexists with Si to produce an Al—Fe—Si-based intermetallic compound. The dispersion of these compounds refines the recrystallized structure. The compound serves as a starting point of pit generation, uniformizing pit formation during the electrolytic treatment, and finely distributing the pits. A preferable content of Fe is in the range of 0.2 to 0.7%. If the content is less than 0.2%, the distribution of the compound becomes non-uniform, and unetched portions are generated during the electrolytic treatment, thus preventing formation of pits. Make uniform. If it exceeds 0.7%, a coarse compound is produced, and the uniformity of the roughened structure is lowered.

Most of Mg functions as a solid solution in aluminum to improve strength and heat softening resistance. Further, Mg acts to suppress the precipitation of simple Si, which reduces the uniformity of the roughened structure by forming a Mg—Si compound (Mg ₂ Si). Strength is the tensile strength at normal temperature as a printing plate support, and heat softening resistance is also called burning resistance, and is 0.2% proof stress after heating at a temperature of about 280 ° C. 90 MPa or more is a practically desirable range. The preferable content of Mg is in the range of 0.05 to 0.5%. If the content is less than 0.05%, the effect is not sufficient. If the content exceeds 0.5%, the precipitation of Mg ₂ Si increases. Quality declines. A more preferable content range of Mg is 0.06% or more and less than 0.10%.

  In an aluminum alloy containing Mg, an oxide film mainly composed of Mg oxide (MgO-based oxide) is easily formed by a heat treatment such as homogenization treatment or heating during hot rolling. Since it is porous, wettability with the treatment liquid is improved in the electrolytic surface roughening treatment, and the surface roughening is promoted. In order to obtain this effect, it is desirable that the Mg concentration in the surface layer portion from the aluminum alloy plate surface to a depth of 0.2 μm is 5 to 50 times the average Mg concentration. If it exceeds 50 times, the roughening proceeds excessively and the pits tend to be non-uniform.

Further, Mg in solid solution promotes roughening, and the precipitation of Mg—Si compound (Mg ₂ Si) suppresses the precipitation of simple Si that reduces the uniformity of the roughened structure. The amount of Mg precipitated in the matrix of the aluminum alloy plate is preferably 50% or less of the average Mg concentration, and when the solid solution and precipitation of Mg are in this ratio, a preferable roughening can be achieved. It becomes.

  Ti refines the ingot structure and refines the crystal grains. As a result, pit formation during the electrolytic treatment is made uniform, and streaks are prevented when processing as a printing plate is performed. The preferable content of Ti is in the range of 0.003 to 0.05%. If the content is less than 0.003%, the effect is small, and if it exceeds 0.05%, a coarse Al-Ti compound is formed. As a result, the roughened structure tends to be uneven. In addition, when adding B with Ti for refinement | miniaturization of an ingot structure | tissue, it is preferable to contain Ti in 0.01% or less of range.

  By concentrating Ga in the surface layer portion, the pits at the time of electrolytic treatment are refined and function to improve the uniformity of pit formation, and a desired pit pattern can be obtained. The preferable content of Ga is in the range of 30 to 300 ppm. When the content is less than 30 ppm, the effect is small, and when the content exceeds 300 ppm, the roughened structure tends to be uneven. As for the degree of concentration, it is desirable that the Ga concentration in the surface layer portion from the surface to a depth of 0.2 μm is 2 to 20 times the average Ga concentration.

  Cu easily dissolves in aluminum, and has an effect of refining pits with a content of 0.05% or less. If it exceeds 0.05%, the pits at the time of electrolytic treatment are likely to be coarse and non-uniform, and unetched portions are likely to occur. In addition, in this invention, the amount of Cu mixed from the metal | base metal employ | adopted in order to obtain content of the said Fe and Si is about 5-100 ppm (0.0005-0.01%).

  As for inevitable impurities, the effects of the present invention are not impaired as long as they are in the range of inevitable impurities contained in a commercially available aluminum ingot. For example, Ni: about 50 ppm, V: about 200 ppm, Cr: about 50 ppm, Zr: about 40 ppm, Mn: about 50 ppm, B: about 10 ppm, Zn: about 50 ppm are allowed.

  The production of an aluminum alloy plate for a lithographic printing plate according to the present invention involves ingot-making an ingot of an aluminum alloy having the above component composition by continuous casting or the like, and homogenizing the obtained ingot, followed by hot rolling, Although it is performed by hot rolling, the feature is in the hot rolling process consisting of hot rough rolling and hot finish rolling, rolling start temperature in hot rough rolling, rolling end temperature, rough rolling to finish rolling. After the hot finish rolling, intermediate annealing is performed by controlling the recrystallization grains when the coil is wound as a coil after the hot finish rolling is specified. There exists in the point made into the board | plate material of predetermined thickness only by cold rolling, without performing.

  First, the surface of the rolled surface of the ingot of the aluminum alloy having the above composition is chamfered to remove a non-uniform structure causing streaks, and then homogenized for 1 hour or more in a temperature range of 500 to 610 ° C. Process. By this homogenization treatment, Fe and Si dissolved in supersaturation are uniformly deposited, and the etching pits formed during the electrolytic treatment become fine circles, and the printing durability is improved. When the homogenization temperature is less than 500 ° C., the precipitation of Fe and Si is not sufficient, and the pit pattern tends to be non-uniform. When the homogenization treatment is performed at a temperature exceeding 610 ° C., the amount of Fe dissolved increases, and as a result, fine precipitates that are the starting point of pit generation are reduced. If the holding time of the homogenization treatment is less than 1 hr, the precipitation of Fe and Si is insufficient and the pit pattern tends to be non-uniform.

  Hot rolling is usually performed in a hot rolling line after hot rough rolling in a rough rolling stand, and then the rolled material is transferred to a finishing rolling stand and hot finishing rolling is performed in a finishing rolling stand. In the present invention, the hot rough rolling starts at 400 to 520 ° C., ends at a temperature of 400 ° C. or higher, and finishes the hot rough rolling. The hot rough rolled material is held for 60 to 300 seconds and the surface of the hot rough rolled material is recrystallized before the hot finish rolling is started. Moreover, the said enrichment of Mg and Ga can be obtained by the holding | maintenance before the hot finish rolling start after completion | finish of the said hot rough rolling. That is, the Mg and Ga concentrations in the surface layer portion from the plate surface to a depth of 0.2 μm can be adjusted to 5 to 50 times and 2 to 20 times the average Mg and Ga concentrations, respectively.

  If the starting temperature of hot rough rolling is less than 400 ° C., the deformation resistance of the material is large, and the number of rolling passes is increased, thereby reducing productivity. When the temperature exceeds 520 ° C., coarse recrystallized grains are generated during rolling, and a streak-like non-uniform structure tends to be formed. When the end temperature of hot rough rolling is less than 400 ° C., recrystallization due to holding after the end of hot rough rolling becomes insufficient, and it becomes difficult to obtain a uniform surface layer structure and it is difficult to obtain the concentration of Mg and Ga. . Further, if the holding time after the hot rough rolling is completed and before the hot finish rolling is started is less than 60 seconds, the recrystallization is insufficient and it is difficult to obtain a uniform surface structure. Further, the difference between the Mg and Ga concentration in the surface layer part and the average Mg and Ga concentration is small, and it becomes difficult to obtain a predetermined concentration. If the time exceeding 300 seconds is maintained, recrystallized grains grow and partially coarse recrystallized grains are generated, and it becomes difficult to obtain fine recrystallized grains at the end of hot rolling, and the concentration of Mg and Ga The degree becomes difficult to obtain.

Next, hot finish rolling is performed, and the hot finish rolling is finished at a temperature of 330 ° C. or higher and wound as a coil. When the finish temperature of hot finish rolling is less than 330 ° C., recrystallization occurs only partially, causing streaks. The finish temperature of hot finish rolling is preferably 370 ° C. or less. When the finish temperature of hot finish rolling exceeds 370 ° C., recrystallized grains become coarse and streaks are likely to occur.

  After performing the above hot rolling, the average recrystallized grain size in the direction orthogonal to the rolling direction of the surface layer portion of the hot finish rolled material can be reduced to 50 μm or less by winding up as a coil. After rolling, it becomes possible to make a plate material of a predetermined thickness only by cold rolling without performing intermediate annealing, and it is possible to achieve improvement in productivity and concomitant reduction in manufacturing cost, and the final after cold rolling In the rolled material, the average recrystallized grain size in the direction orthogonal to the rolling direction of the rolled material in the surface layer portion can be set to 50 μm or less to prevent unevenness in the surface quality of the printing plate.

  The lithographic printing plate needs to have appropriate strength characteristics so that it can withstand deformation during transportation, tension when set in a printing machine, plate breakage during printing, and the like. In order to impart such strength characteristics, in addition to the alloy composition, the reduction ratio of cold rolling after hot rolling is important, and it is desirable that the workability during cold rolling be 80% or more. If the degree of processing during cold rolling is less than 80%, sufficient strength is not given to the printing plate (printing plate support), and deformation and plate breakage are likely to occur. In order to impart the necessary strength characteristics to the printing plate, it is desirable that the tensile strength of the printing plate after cold rolling is 190 MPa or more.

  Moreover, in the final rolled material after cold rolling, the effect of improving ink stain resistance is obtained by setting the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the plate surface to 0.03 to 0.5 μm. Can do. When Ra is less than 0.03 μm, when applied as a printing plate, the amount of dampening water retained may be drastically reduced, and the ink in the image area can easily move onto the non-image area, resulting in ink stain resistance. descend. If Ra exceeds 0.5 μm, the blanket cylinder may become dirty. In order to improve the ink stain resistance, it is necessary to have a surface roughness capable of maintaining a sufficient water retention amount. For this reason, the arithmetic average roughness of the roughened finished surface is 0.03 to 0. The thickness is preferably in the range of 0.5 μm, more preferably 0.2 to 0.4 μm.

  In order to set the arithmetic average roughness Ra in the direction perpendicular to the rolling direction of the plate surface to 0.03 to 0.5 μm, the surface roughness Ra in the direction perpendicular to the rolling direction is 0.03 to 0 with an outer diameter of 250 to 700 mm. It is necessary to perform final cold rolling using a 6 μm work roll (WR) and adjust the final cold work degree, rolling speed, rolling oil properties, and rolling oil supply amount according to the alloy composition. is there.

In the aluminum alloy sheet of the present invention, the amount of aluminum powder on the surface of the rolled sheet after the final cold rolling is preferably adjusted to 0.1 to 3.0 mg / m ² . The aluminum powder is a powder of an aluminum alloy remaining on the surface of the rolled sheet generated from the aluminum alloy rolled material during the final cold rolling, and in the case of the aluminum alloy of the present invention containing Mg, the amount of aluminum powder If it is less than 0.1 mg / m ² , when wound as a coil after the final cold rolling, the effect of preventing scratches in the coil is insufficient, and if it exceeds 3.0 mg / m ² , aluminum powder is used in the degreasing process. Is not sufficiently removed and remains on the plate surface, and during the electrolytic surface roughening treatment, the pit formation is insufficient or uneven in the portion where the aluminum powder remains, and the appearance due to unetched parts and uneven patterns after electrolytic graining It causes a defect. Excessive aluminum powder can also cause line contamination.

  In order to adjust the amount of aluminum powder on the surface of the plate after the final cold rolling to the above range, in addition to adjustment to the above components, the final cold rolling degree of processing, the properties of the rolling oil, the supply of the rolling oil according to the composition It is necessary to adjust the amount. In particular, the viscosity of the rolling oil in the final cold rolling is important, and it is preferable to use a rolling oil having a viscosity of 1 to 6 cSt. If the viscosity is less than 1 cSt, the amount of rolling oil introduced between the rolling roll and the rolled material is reduced, resulting in poor lubrication, and excessive aluminum powder is likely to occur. When the viscosity exceeds 6 cSt, the amount of rolling oil introduced between the rolling roll and the rolled material becomes excessive, and the generation of aluminum powder tends to be reduced. In addition, the amount of aluminum powder can be measured as a quantitative analysis of residual wear powder on the surface of the plate by wiping with a cotton wool dipped in a certain area of the surface of the plate and measuring the aluminum content in the cotton wool.

In addition, as rolling oil in the final cold rolling, Mg content in the aluminum alloy (Mg
%) And the viscosity ρ of the rolling oil used in the final cold rolling is preferably a rolling oil satisfying ρ ≦ 2 × Mg% + 4. When ρ> (2 × Mg + 4), the deformation resistance is small, and the amount of rolling oil introduced between the rolling roll and the rolled material increases, so that coarse pits are easily formed excessively.

In the present invention, on the surface of the aluminum alloy sheet after the final cold rolling, the number of oil pits having a diameter (equivalent circle diameter) of 30 μm or more is adjusted to 50 pieces / mm ² or less, whereby an electrolytic surface roughening treatment is performed. The etching pits formed in the step can be made more uniform. Since the aluminum alloy of the present invention contains Mg, large oil pits having a diameter of 30 μm or more tend to remain as coarse pits even after electrolytic graining. When such coarse pits exceed 50 pieces / mm ² , Etching pits formed by the electrolytic surface roughening treatment tend to be non-uniform.

In order to adjust the number of oil pits having a diameter (equivalent circle diameter) of 30 μm or more to 50 / mm ² or less, the final cold rolling degree, the form of the rolling roll surface, the properties of the rolling oil, the supply of the rolling oil It is necessary to adjust the amount. In the case of an aluminum alloy containing Mg and having a relatively large deformation resistance as in the present invention, a roll having a roll surface roughness of arithmetic average roughness Ra: 0.2 to 0.5 μm in the final cold rolling. It is desirable to perform cold rolling using a rolling oil having a viscosity of 1 to 6 cSt.

  When the roll surface roughness exceeds 0.5 μm in arithmetic average roughness Ra, the local surface pressure within the contact arc length increases, the oil film is cut and the metal contact area increases, and lubrication failure is likely to occur. . If Ra is less than 0.2 μm, the amount of rolling oil introduced between the rolling roll and the rolled material becomes excessive, and the number of large oil pits increases. If the viscosity of the rolling oil is less than 1 cSt, the amount of rolling oil introduced between the rolling roll and the rolled material is reduced, and lubrication is likely to occur. If the viscosity exceeds 6 cSt, the rolling oil is introduced between the rolling roll and the rolled material. The amount of rolling oil becomes excessive and the number of large oil pits increases. For the oil pits, the surface of the aluminum alloy plate is degreased and cleaned, and then the surface is observed at a magnification of 500 times using a scanning electron microscope (SEM), and the number and distribution of oil pits are measured by a cutting method. be able to.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects of the present invention. These examples show one preferred embodiment of the present invention, and the present invention is not limited thereto.

Example 1 and Comparative Example 1
Aluminum alloy having the composition shown in Table 1 is melted and cast, and the rolled surface of the obtained ingot is chamfered by 5 mm / one side to a thickness of 500 mm, and each ingot is homogenized under the conditions shown in Table 2. It processed and hot-rolled, and it wound up by the coil as predetermined plate | board thickness by hot finish rolling. After the hot rolling, cold rolling was performed without performing intermediate annealing to obtain a cold rolled material having a plate thickness of 0.3 mm. In Tables 1 and 2, those outside the conditions of the present invention are underlined.

  Using the cold rolled material as a test material, the average recrystallized grain size in the direction perpendicular to the rolling direction of the surface layer portion of the rolled material is measured by the following method, and the concentration of Ga and Mg in the surface layer portion and the Mg precipitation rate are measured. evaluated. The results are shown in Table 3. In Table 3, those outside the conditions of the present invention are underlined.

  Measurement of the average recrystallized grain size: After degreasing and cleaning the surface of the test material, mirror polishing, anodizing with Parker's solution, observing crystal grains in the polarization mode of an optical microscope, The crystal grain size was determined by a cutting method.

Measurement of the concentration of Ga and Mg in the surface layer part: Comparison of Ga and Mg concentration in the surface layer part and Ga and Mg concentration in the inner part is based on depth analysis of Ga and Mg (depth profile measurement by secondary ion mass spectrometry (SIMS)). ) And the ratio of the count number of the highest Ga and Mg concentration on the surface to the count number from the inner aluminum substrate was obtained.
Measurement of Mg precipitation rate: The amount of Mg in the total intermetallic compound was examined by a phenol residue analysis method as shown in FIG. 1, and {(Mg amount in total intermetallic compound (wt%)) / (average Mg amount (wt %))} × 100 (%).

  In addition, the tensile strength of the test material (cold rolled material) is measured, and the following methods are used to observe the presence or absence of uneven patterns and streaks, to evaluate the occurrence of unetched parts, and to evaluate the uniformity of etch pits. Went. The results are shown in Table 4. In Table 4, those outside the conditions of the present invention are underlined.

Degrease the cold rolled material (solution: 5% sodium hydroxide, temperature: 60 ° C., time: 10 seconds) -neutralization treatment (solution: 10% nitric acid, temperature: 20 ° C., time: 30 seconds) -AC electrolysis Roughening treatment (solution: 2.0% hydrochloric acid, temperature: 25 ° C., frequency: 50 Hz, current density: 60 A / dm ² , time: 20 seconds) -desmut treatment (solution: 5% sodium hydroxide, temperature: 60 (° C., time: 5 seconds) -anodic oxidation treatment (solution: 30% sulfuric acid-temperature: 20 ° C., time: 60 seconds), washed with water, dried, cut into a certain size to obtain a test piece.

About each test piece, the presence or absence of a nonuniform pattern and streak was observed. In addition, using a scanning electron microscope (SEM), the surface was observed at a magnification of 500 times, and a photograph was taken so that the area of the visual field was 0.04 mm ^2. Pit uniformity was evaluated.

Observation of presence / absence of uneven pattern: A case where the uneven pattern was visually observed on the surface of the test piece was evaluated as bad (×), and a case where the uneven pattern was not observed was evaluated as (◯).
Observation of the presence or absence of streak: A case where the streak was visually observed on the surface of the test piece was evaluated as bad (x), and a case where no streak was observed was evaluated as (◯).
Evaluation of occurrence of unetched (unetched) portion: unetched portion exceeding 20% is defective (x), 10% exceeding 20% (◯), 10% or less (◎ ).
Evaluation of uniformity of etch pits (pits): Large pits with an equivalent circle diameter exceeding 10 μm are defective (×) when the area ratio exceeds 10% of all pits, and those exceeding 5% and less than 10% (◯) 5% or less is (◎).

Tensile strength: A JIS-5 test piece was taken from the cold-rolled material and subjected to a tensile test. A sample having a tensile strength exceeding 200 MPa (◎), a component exceeding 190 MPa and less than 200 MPa (◯), 190 MPa Those less than were evaluated as bad (x).

  As can be seen from Table 4, all of the test materials 1 to 4 and the test materials 12 and 13 according to the present invention are free from uneven patterns and streaks, have excellent etching properties after electrolytic treatment, and are uniformly etched over the entire surface. A pit is formed.

  On the other hand, since the test material 5 has a large amount of Mg, the surface quality of the plate material is inferior, and the test material 6 has a small amount of Ga, so that sufficient roughening cannot be obtained and the uniformity of the pits is also lowered. Since the test material 7 had a large amount of Ga, an unetched portion was generated in the surface roughening treatment.

  Since the test material 8 has a long holding time from the end of hot rough rolling to the start of hot finish rolling, the recrystallized grains grow to generate partially coarse recrystallized grains. Fine recrystallized grains cannot be obtained, and a predetermined concentration of Ga and Mg cannot be obtained, and the test material 9 has a short holding time from the end of hot rough rolling to the start of hot finish rolling. Insufficient recrystallization resulted in failure to obtain a uniform recrystallized structure in the surface layer portion of the plate material, and failure to obtain a predetermined concentration of Ga and Mg, resulting in uneven patterns and streaks.

  The test material 10 had a low finish temperature of hot finish rolling, and since recrystallization was not sufficiently performed and non-recrystallized portions were generated, uneven patterns and streaks occurred, and the uniformity of pits during electrolytic treatment was poor. . Since the test material 11 had a low homogenization temperature, the precipitation of Fe and Si was not sufficient, the pit pattern during the electrolytic treatment became non-uniform, and an unetched part also occurred.

  Since the test material 14 has a low degree of cold work, the tensile strength is less than 190 MPa, the strength necessary for a printing plate is not imparted, and deformation and plate breakage are expected.

It is a flowchart which shows the measuring method of a measurement of Mg precipitation rate.

Claims (4)

Si: 0.03-0.15% (mass%, the same applies hereinafter), Fe: 0.2-0.7%, Mg: 0.05-0.5%, Ti: 0.003-0.05% , Ga: 30 to 300 ppm , an allowable Zn content of 50 ppm or less , an aluminum alloy plate having a composition composed of the balance aluminum and unavoidable impurities, the average in the direction orthogonal to the rolling direction of the surface layer portion The recrystallized grain size is 50 μm or less, the Mg concentration in the surface layer portion from the surface to a depth of 0.2 μm is 5 to 50 times the average Mg concentration, and the Ga concentration in the surface layer portion from the surface to a depth of 0.2 μm is 2 times the average Ga concentration. An aluminum alloy plate for a lithographic printing plate characterized by being -20 times. The aluminum alloy plate for a lithographic printing plate according to claim 1, wherein Cu: 0.05% or less (not including 0%, the same shall apply hereinafter) is contained. The aluminum alloy plate for a lithographic printing plate according to claim 1 or 2, wherein the amount of Mg precipitated in the matrix is 50% or less of the average Mg concentration. The aluminum alloy plate for a lithographic printing plate according to any one of claims 1 to 3, which has a tensile strength of 190 MPa or more.

Images