JP2016074953A - Pure titanium plate and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure titanium plate descaled after annealing without salt processing or blasting, and being superior in adhesion of plating coating, oil holding property with lubricant and antiglare property.SOLUTION: A manufacturing method of a pure titanium plate pickling a titanium plate after annealing by dipping in a water solution consisting of fluorinated acid of 5-10 mass% and hydrochloric acid of 12-20 mass% at 35-45°C for 60-300 seconds so that the surface roughness has more than 4 μm in arithmetic mean roughness.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pure titanium plate manufactured under conditions that simultaneously satisfy descaling and surface roughening suitable for coating adhesion such as plating, lubricant application, and antiglare properties, and a method for manufacturing the same.

  Titanium is known as a difficult plating material. Conventionally, a titanium plate is roughened in order to improve the adhesion of the plating coating and the oil retention with a lubricant. As this roughening method, machining such as polishing studied in Patent Document 1, dull roll rolling studied in Patent Document 2, shot peening work studied in Patent Document 3, and studied in Patent Document 4. Laser processing, etching processing studied in Patent Document 5, and the like.

  A mechanical process such as polishing requires a separate polishing process. In the dull roll rolling, manufacturing processes such as a rolling process, a roll surface processing process, and a roll exchange are separately required. In the dull roll rolling, the higher the rolling reduction, the larger the surface roughness. However, since rolling is performed at a rolling rate of several percent, there is a concern that ductility is lowered by work hardening and workability is impaired. In the polishing process or dull roll rolling, there is a concern that the tool or roll to be worn wears with use, and the uniformity is reduced between the coils.

  When finished by shot peening, there is a problem that a large amount of strain is introduced into the surface layer, and hydrogen absorption tends to occur from there. In the case of a thin plate, there is a concern that the shape deteriorates if the surface is too rough. When finished by laser processing, the surface is exposed to a high temperature to reversely transform from the equiaxed α phase to the β phase, and after laser processing returns to room temperature, the microstructure of pure titanium transforms from the β phase to the acicular α phase. There is a problem that the acicular α phase is much more susceptible to corrosion than the equiaxed α phase.

Etching requires a separate step of electrolysis using an electrolytic solution.
In addition, in addition to the general titanium plate manufacturing process, an extra manufacturing process for roughening the surface is required. In other words, it means that extra time and cost are required for manufacturing.

  On the other hand, Patent Document 6 proposes pickling with a mixed acid of hydrofluoric acid and hydrochloric acid for removing scale after annealing. In consideration of surface roughening by pickling, the pickling described in Patent Document 6 has a long processing time according to the embodiment of the same document, and it is the limit to remove the oxide scale in a practical time range. It is difficult to apply to surface roughening.

JP 2007-262470 A JP 2000-015304 A JP 2010-030015 A JP 2009-274345 A JP-A-6-306620 JP 2012-224894 A

  Thus, the conventional surface roughening methods include only methods involving plastic deformation such as shot blasting and dull roll rolling after annealing pickling, and it is difficult to obtain a titanium plate having a rough surface in the annealed state. In addition, work hardening by plastic deformation deteriorates the workability of the titanium material. Furthermore, since distortion due to plastic deformation is added to the titanium material, problems such as hydrogen absorption and shape defects have occurred.

  Therefore, the present invention simultaneously performs the final annealing step and the surface roughening step, suppresses shape defects while maintaining ductility, adhesion of the plating coating, oil retention with a lubricant, and antiglare properties. An object of the present invention is to provide a pure titanium plate excellent in the above.

  The inventors of the present invention have made extensive studies in order to obtain a descaled titanium plate without performing mechanical processing after annealing. Specifically, attention was paid to pickling conditions that have been considered to be unusable for surface roughening in the past, and the pickling conditions were investigated in detail. As a result, it is unexpectedly possible to descal and roughen the surface of the annealed material by dipping it in an aqueous solution containing a predetermined amount of hydrofluoric acid and hydrochloric acid after atmospheric annealing without salt treatment or blast treatment. Got. Table 1 shows an outline of a general surface roughening method after annealing and a surface roughening method in the present invention.

  Thus, the present invention was completed by obtaining a pure titanium plate having a roughened surface only by performing pickling after annealing.

The mechanism of descaling and surface roughening is described as follows.
For example, in pure titanium, it is known that the solid solubility limit of Fe in the α phase is extremely low, and slight segregation to the grain boundary is inevitable, so even if the Fe content is at the impurity level concentration Fe concentrates in the segregation part. When this is eluted by reaction with an acid solution, the internal stress of the scale becomes non-uniform, which becomes the starting point for the generation of microcracks. When the acid solution penetrates into the crack and a part of the metal surface is exposed to elute Ti ⁴⁺ , Cl ⁻ in hydrochloric acid migrates and concentrates to maintain electrical neutrality and pitting corrosion occurs. Then, titanium metal is dissolved by hydrochloric acid and hydrofluoric acid, the scale is peeled off from the base material, and descaling is performed. On this basis, when the hydrochloric acid concentration is increased, the pitting corrosion speed is increased, and the pitting corrosion portion and the non-pitting corrosion portion become large unevenness. That is, the roughness can be increased by increasing the hydrochloric acid concentration. When there is little hydrochloric acid, since pitting corrosion does not generate | occur | produce, an acid liquid does not osmose | permeate a base material easily and a scale remainder tends to arise.

From the surface roughening mechanism, the present inventors have obtained the following knowledge.
(1) As an acid combined with hydrofluoric acid, hydrochloric acid that generates pitting corrosion and has an appropriate dissolution rate is most effective, and the surface can be roughened by increasing its concentration to some extent.

  (2) Patent Document 6 describes that when the hydrochloric acid concentration exceeds 12%, the dissolution reaction of scale and the dissolution reaction of titanium metal do not occur. However, since the amount of titanium dissolved usually increases with respect to the hydrochloric acid concentration, it is unlikely that the dissolution reaction will occur. In Table 1 of Patent Document 6, the sulfuric acid concentration is high at a high hydrochloric acid concentration of 15%. Therefore, as a result of further studies by the present inventors, it was found that in the mixed acid to which sulfuric acid was added, the sulfuric acid had an effect of suppressing the reaction of the mixed acid of hydrochloric acid and hydrofluoric acid. Therefore, in patent document 6, since the sulfuric acid concentration is high, it is thought that the amount of thinning was small. From these findings, it is necessary not to add sulfuric acid to the mixed acid in order to perform efficient surface treatment.

  (3) Further, Patent Document 6 describes that when the amount of hydrofluoric acid exceeds 10%, it becomes a peracid wash state and it becomes difficult to control the pickling reaction. Here, “control” is control of the plate thickness. However, in controlling the surface roughness as in the present invention, the desired roughness can be obtained by setting the treatment time and the temperature of the mixed acid aqueous solution appropriately in addition to the hydrochloric acid / hydrofluoric acid concentration.

The present invention completed based on the above findings is as follows.
(1) The surface roughness after pickling a pure titanium material with an aqueous solution containing a mixed acid composed of 5 to 10 mass% hydrofluoric acid and 12 to 20 mass% hydrochloric acid has an arithmetic average roughness of 4 μm or more. Pure titanium plate characterized by this.

  (2) The pure titanium plate according to (1), wherein the pickling is performed by immersing the pure titanium material in the bath holding the aqueous solution at 35 to 45 ° C. for 60 to 300 seconds. .

  (3) A method for producing a pure titanium plate according to the above (1) or (2), wherein a pure titanium ingot is subjected to hot working, cold rolling and annealing in this order, and a pure titanium material after annealing is produced. A method for producing a pure titanium plate, wherein the pickling is performed.

  According to the present invention, it is possible to provide a pure titanium plate which is descaled by pickling and has a surface roughness of 4 μm or more in terms of arithmetic average roughness. INDUSTRIAL APPLICABILITY The present invention is an excellent invention with high industrial applicability that can provide a pure titanium plate excellent in adhesion of a plating coating, oil retention with a lubricant, and antiglare.

FIG. 1 shows the relationship between the arithmetic average roughness (μm) and hydrochloric acid concentration (mass%) when the annealed titanium plate is immersed in an acid solution at 40 ° C. with adjusted concentrations of hydrofluoric acid and hydrochloric acid for 120 seconds. FIG.

In the following description, “%” represents “mass%” unless otherwise specified.
1. Pure titanium plate (1) Pure titanium In the present invention, pure titanium is used. This is because the β-type titanium alloy significantly absorbs hydrogen, which is a β-stable element, and thus causes hydrogen embrittlement.

  The pure titanium of the present invention is defined by JIS standards 1 to 4 and ASTM standards Grades 1 to 4, and DIN standards 3.7025, 3.7035, 3.7055, 3.7065. It shall contain industrial pure titanium. That is, the industrial pure titanium that is the subject of the present invention is, in mass%, C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less, It can be said that Fe: 0.5% or less and the balance Ti. Further, a small amount of platinum group elements are added to these, and a high corrosion resistance alloy (ASTM Grade 7, 11, 16, 26, 13, 30, 33, or a JIS species corresponding to these is called modified (improved) pure titanium. In addition, titanium materials containing a small amount of various elements are treated as being included in pure titanium in the present invention.

(2) Surface Roughness of Pure Titanium Plate The pure titanium plate of the present invention has a surface roughness of 4 μm or more in terms of arithmetic average roughness. When Ra is 4 μm or more, the contact area with the plating increases, so that the adhesion of the plating is enhanced. In addition, along with this, the oil retention with a lubricant and the like is enhanced, and further the antiglare property is enhanced.

(3) Pickling The pure titanium plate of the present invention is pickled with an aqueous solution containing a mixed acid composed of a predetermined amount of hydrofluoric acid and hydrochloric acid. Each will be described in detail.

(3-1) Content of hydrofluoric acid: 5 to 10%
The hydrofluoric acid is contained in the aqueous solution by 5 to 10% by mass. If it is less than 5%, the dissolving power of the titanium metal base material is weak, and descaling becomes difficult. If it exceeds 10%, sufficient surface roughness can be obtained, but problems with waste acid treatment and cost increase arise. Preferably it is 6 to 9%.

(3-2) Hydrochloric acid content: 12-20%
Hydrochloric acid is contained in the aqueous solution by 12 to 20% by mass. If it is less than 12%, pitting corrosion is unlikely to occur, and the acid solution is less likely to penetrate into the base material. Moreover, when it contains exceeding 20%, the loss by evaporation of hydrochloric acid will become large. Preferably it is 14 to 18%.

2. Manufacturing Method (1) Hot working, cold rolling and annealing are performed on a pure titanium ingot.

  In this invention, the process until pickling can be manufactured with the manufacturing method of a general titanium plate. For example, a process for producing a titanium ingot from sponge titanium or the like, a process for making the ingot hot-rolled by hot working such as forging or hot rolling, a process for shot blasting the hot-rolled steel, and pickling the hot-rolled steel The titanium raw material used for pickling is manufactured by the process of performing, the process of making the hot-rolled sheet descaled by pickling cold-rolled by cold rolling, and the process of annealing the cold-rolled sheet. The conditions in these steps are not particularly limited. For example, in cold rolling, it is preferable to roll to a thickness of 0.1 to 3 mm at a rolling reduction of 30 to 90%, and in annealing, 700 to 820. It is preferable to hold at a temperature of 60 to 180 s.

(2) Pickling.
In the present invention, descaling and provision of irregularities can be completed only by pickling without using a salt bath. In the method of the present invention, in the pickling step of removing scale generated on the surface of the titanium plate by hot rolling or heating during annealing and imparting irregularities to the surface, 12 to 20% hydrochloric acid and 5 to 5 hydrofluoric acid are used. An aqueous solution containing 10% is used.

  It is preferable that the temperature of the acid bath in which the aqueous solution is held is regulated to 35 to 45 ° C. When the temperature is lower than 35 ° C., the reactivity between the acid solution and the titanium plate is poor, and the target surface roughness cannot be obtained. When it exceeds 45 ° C., the reaction becomes excessive and becomes too coarse.

  In such an acid bath, a titanium material having a scale formed after annealing is immersed. It is preferable that the immersion time is defined as 60 to 300 s. If it is less than 60 s, the surface cannot be sufficiently roughened. In addition, a scale residue occurs. If it exceeds 300 s, the surface becomes too rough. Moreover, it is necessary to extremely slow the line speed for pickling over 300 s. Furthermore, if it is not possible to slow down, it is necessary to pass through a continuous line in order to perform pickling again.

  Various titanium ingots having different amounts of oxygen and Fe were produced by vacuum arc melting, and titanium plates were obtained through forging, hot rolling, annealing, surface cutting, cold rolling, final annealing, and pickling.

  Specific cold rolling conditions, final annealing, and pickling conditions are shown in Table 2. In Table 2, “35 to 45 ° C.” is the temperature of the aqueous solution in the bath, and “60 to 300 s” is the immersion time of the titanium plate in the bath after the final annealing.

  Table 3 shows an evaluation method of the oxygen amount, Fe amount, surface roughness (arithmetic average roughness) Ra, and glossiness.

  The results obtained in this way are shown in FIG. According to FIG. 1, all of the titanium plates subjected to pickling using an aqueous solution containing 5% or more hydrofluoric acid and 12% or more hydrochloric acid showed Ra of 4 μm or more. And it became clear that all the titanium plates of the present invention in which Ra is 4 μm or more are excellent in antiglare property. Moreover, these titanium plates are excellent in plating adhesion and oil retention. The scale was not confirmed visually. In addition, it confirmed that the chemical composition of the obtained titanium plate was in the range prescribed | regulated by JIS specification.

On the other hand, when hydrofluoric acid was 4% or less, Ra was inferior to less than 4 μm.
Even if hydrofluoric acid was 5%, Ra was less than 4 μm when hydrochloric acid was less than 12%. Moreover, even if the hydrofluoric acid was 5% or more and the hydrochloric acid was less than 12%, there was also one in which Ra was 4 μm or more. These were poor in descalability because pitting corrosion hardly occurred and the acid solution did not easily penetrate into the base material.

  Even if an aqueous solution containing 5% or more hydrofluoric acid and 20% hydrochloric acid was used, Ra did not increase.

  Moreover, in addition to the conditions of Table 2, it pickled using the mixed acid which added 1-15 mass% of sulfuric acid further, and arithmetic mean roughness was evaluated on the conditions of Table 3. As a result, it was confirmed that when the sulfuric acid content was in the above range, the arithmetic average roughness Ra was less than 4 μm even when the treatment time was 300 s. For this reason, the antiglare property was inferior to the present invention. In addition, the plating adhesion and oil retention are inferior.

Claims (3)

  A surface roughness after pickling a pure titanium material with an aqueous solution containing a mixed acid composed of 5 to 10 mass% hydrofluoric acid and 12 to 20 mass% hydrochloric acid has an arithmetic average roughness of 4 μm or more. Pure titanium plate.   2. The pure titanium plate according to claim 1, wherein the pickling is performed by immersing the pure titanium material in the bath holding the aqueous solution at 35 to 45 ° C. for 60 to 300 s. It is a manufacturing method of the pure titanium board according to claim 1 or 2,
A method for producing a pure titanium plate, comprising: sequentially performing hot working, cold rolling and annealing on a pure titanium ingot, and performing the pickling on the pure titanium material after annealing.