JP2018001249A - Method for producing titanium blank for hot rolling - Google Patents

Abstract

[Problem] To provide a method for manufacturing titanium material for hot rolling that can reduce surface defects that occur during hot rolling. [Solution] This method involves heating a titanium material containing a solidified structure to a temperature of 100°C or higher but lower than 500°C, and plastically deforming the surface of the titanium material to form irregularities. [Selected Figures] None

Description

  The present invention relates to a method for producing a titanium material for hot rolling that can reduce the occurrence of surface defects during hot rolling.

  A typical method for producing a titanium hot rolling material is, for example, as follows. First, an ingot is manufactured by melting and solidifying titanium by a consumable electrode type arc melting method (VAR: Vacuum arc remelting) or an electron beam melting method (EBR: Electron beam remelting). Subsequently, the ingot is broken down by hot working such as slabbing, forging, and rolling to obtain a material for hot rolling such as slab or billet. In recent years, a technique has been developed in which the above breakdown process is omitted by manufacturing a rectangular ingot that can be directly hot-rolled by an electron beam melting method.

  However, large ingots used industrially have coarse crystal grains of several tens mm in the solidified structure. When such an ingot is directly hot-rolled without going through a breakdown process, heterogeneous deformation may occur due to coarse crystal grains, which may develop into large surface defects. In addition, even when a breakdown process or the like is performed, if the processing rate is low or the temperature is not appropriate, the cast structure remains or conversely the structure becomes coarse, and surface flaws occur during hot rolling. May end up.

  If surface flaws occur in this way, the yield in the subsequent descaling process becomes very poor, and therefore a material for hot rolling that does not easily generate hot-rolled surface flaws is desired.

  In Patent Document 1, when a titanium material ingot is directly hot worked, a surface layer is strained and then heated to a recrystallization temperature or higher in order to make the crystal grains near the surface finer. A method of hot working after recrystallization of a depth of 2 mm or more is proposed.

  Patent Document 2 discloses that the surface of a titanium material for hot rolling is plastically deformed cold using a steel tool having a tip radius of curvature of 3 to 30 mm or a steel ball having a radius of 3 to 30 mm. Describes a titanium material for hot rolling in which distortion is applied to the surface layer portion. According to Patent Document 2, it is said that the effect of a coarse solidified structure can be rendered harmless by hot rolling such a titanium material for hot rolling.

  However, in Patent Document 1, shot blasting is cited as a means for imparting strain. However, the depth of strain formed by general shot blasting is about 300 to 500 μm or less, and is coarse with several tens of millimeters. It is very small for a solidified structure and surface defects are not suppressed. On the other hand, there are methods such as rolling and forging as methods for imparting strain other than shot blasting. Rolling and forging can impart distortion not only to the surface layer of the material but also to the entire material.For example, in rolling, there is a region that is not deformed (strained) called dead metal generated by contact with a roll or the like near the surface layer. There is a case. For this reason, in order to appropriately impart distortion to the entire material surface, it is necessary to impart distortion at a considerably large processing rate. Then, the merit of omitting the breakdown process is almost lost, and it does not make sense.

  In Patent Document 2, the strain is imparted by plastic deformation in the cold, but the present inventors have found for the first time that there is a problem that it is particularly difficult to apply to high-strength industrial pure titanium and titanium alloys. It was. In other words, when plastic deformation of high-strength industrial pure titanium or titanium alloy is performed in a cold state, the strain is difficult to enter inside, so it is necessary to apply processing with a large load or to apply processing multiple times. There is. However, it has been newly found that when processing with a large load or processing over a plurality of times is performed, the ductility in the vicinity of the surface layer portion is reduced and cracks are generated on the surface. When a hot rolling material having surface cracks is hot-rolled, the generation of surface defects may increase. Such a problem is not limited to high-strength titanium, and even a titanium material having a relatively low strength can cause minute surface cracks.

Japanese Patent Laid-Open No. 1-156456 International Publication No. 2010/090352

  This invention is made | formed in view of the said situation, and makes it a subject to provide the manufacturing method of the titanium raw material for hot rolling which can reduce the surface flaw which generate | occur | produces at the time of hot rolling.

  When a titanium material is hot-rolled, if cast as it is, large wrinkles may be generated due to coarse crystal grains, which may develop into coarse surface flaws. It is possible to prevent this by applying strain in the cold and forming a fine-grained recrystallized layer. However, when the thickness of the fine recrystallized layer is thin and insufficient, surface unevenness due to the internal coarse cast structure may occur, resulting in hot rolling. In particular, in the case of a titanium material having high strength, the strain may not be introduced to a sufficient depth when the strain is applied in the cold state, and as a result, the recrystallized layer may be thinned and lead to surface defects. Further, in the method described in Patent Document 2, when deep strain is introduced into a titanium material having high strength, there is a possibility that surface cracking occurs in the hot rolling material. Therefore, in the present invention, a surface is generated during hot rolling by forming a deeper recrystallized layer by imparting strain to the titanium material for hot rolling at a temperature of 100 ° C. or more and less than 500 ° C. which is warm to hot. Suppress wrinkles. In such a case, even a material having a certain level of strength can sufficiently impart strain to the surface layer, and surface flaws can be suppressed.

That is, the present invention is as follows.
(1) A method for producing a titanium material for hot rolling, comprising heating a titanium material containing a solidified structure to 100 ° C. or more and less than 500 ° C., and plastically deforming the surface of the titanium material to form irregularities.
(2) A titanium material including a solidified structure is heated to 100 ° C. or higher and lower than 500 ° C., and the surface of the titanium material is hit with a steel tool having a tip shape having a curvature radius of 3 to 30 mm, or the steel is applied to the surface. A method for producing a titanium material for hot rolling, wherein the surface is plastically deformed by pressing a tool.
(3) Heating a titanium material including a solidified structure to 100 ° C. or more and less than 500 ° C., and striking the surface of the titanium material with a steel ball having a radius of 3 to 30 mm, or pressing the steel ball against the surface. The method for producing a titanium material for hot rolling, wherein the surface is plastically deformed.
(4) Forming dimples having an average height (Wc) of the wavy contour curve element of 0.2 to 1.5 mm and an average length (WSm) of 3 to 15 mm by plastic deformation of the surface. The manufacturing method of the titanium raw material for hot rolling as described in any one of (1) thru | or (3) characterized by the above-mentioned.

  According to the present invention, even if it is an as-cast titanium material that omits the breakdown process of the ingot, the surface flaws that occur during hot rolling can be reduced, and an excellent hot rolled and cold rolled product is provided. be able to.

Fig.1 (a) is a figure which shows the example of the steel tool in which a front-end | tip shape has a curvature radius of 3-20 mm (3-30R), FIG.1 (b) has a radius of 3-20 mm (3-30R). It is a figure which shows the example of steel balls. FIG. 2A is a diagram showing the surface properties after applying predetermined plastic deformation to the surface of the titanium material for hot rolling using the tool made of the alloy for impact resistant tools shown in FIG. 2 (b) is a cross-sectional view of the surface layer after applying predetermined plastic deformation to the surface of the titanium material for hot rolling using the tool made of an alloy for impact resistant tools shown in FIG. It is a figure which shows an organization. Fig.3 (a) is a figure which shows the example of the roll used for cold press or cold rolling, FIG.3 (b) is an example of the tool which has the corner R part used for cold press or cold rolling. FIG. FIG. 4 (a) is a view showing the surface of a titanium material for hot rolling that has been plastically deformed after cold pressing with a roll, and FIG. 4 (b) is plastically deformed by cold pressing with a roll. It is a figure which shows the cross-sectional structure of the surface layer of the titanium raw material for hot rolling after further heat processing.

Embodiments of the present invention will be described below with reference to the drawings.
From the viewpoint of reducing surface defects due to hot rolling, the present inventors consider the coarse solidified structure of an ingot whose crystal grains are several tens of millimeters and the influence of the solidified structure remaining after breakdown. As a result of intensive studies on a method for detoxifying the material and a titanium material for hot rolling to which the method is adapted, the following knowledge was obtained and the present invention was achieved.

  In order to refine the coarse solidified structure or to eliminate the part where the influence of the solidified structure remains, the surface layer portion is provided with unevenness to give distortion and then heated during hot rolling. A method of recrystallization by heat treatment is conceivable.

  The present invention is a strain imparting method capable of suppressing surface defects caused by hot rolling. In the present invention, as shown in FIG. 1, the tip shape is a steel tool (FIG. 1 (a)) having a curvature radius of 3 to 30 mm (3 to 30 R), or a steel tool having a radius of 3 to 30 mm (3 to 30 R). A dimple is formed by hitting the surface of a titanium material heated to 100 ° C. or more and less than 500 ° C. with a sphere (FIG. 1B), or pressing a steel tool or a steel sphere by a predetermined amount of plastic deformation. . The titanium raw material for hot rolling obtained by this method has been found to be able to significantly suppress surface defects during hot rolling. In this embodiment, when one dimple is formed, plastic working by hitting or pressing a steel tool or a steel ball may be performed once, or may be performed twice or more. In particular, in the present embodiment, since the plastic working is performed in a state of being heated to 100 ° C. or higher, surface cracks do not occur even if the plastic working is performed a plurality of times.

  In addition, when a heat treatment is performed on the titanium material for hot rolling manufactured by the manufacturing method according to the present invention at a temperature of 820 ° C. that simulates hot rolling for 4 hours, for example, at least depth from the surface. A recrystallized structure having crystal grains smaller than the original solidified structure can be formed in a range exceeding 6 mm. Thus, according to the production method of the present invention, more recrystallization can be formed than in the conventional hot rolling titanium material, and surface defects generated during hot rolling can be greatly reduced.

  In the present embodiment, examples of the titanium material for plastically deforming the surface include the following titanium materials (A) or (B). These titanium materials contain a solidified structure obtained by melting and casting titanium.

(A) An ingot obtained by once melting and solidifying titanium by consumable electrode arc melting (VAR) or electron beam melting (EBR), and further forging and forging Titanium material that has been broken down by hot working such as rolling, and formed into shapes such as slabs and billets.

(B) When the titanium is once melted and then solidified by the electron beam melting method, a rectangular ingot having a size that can be directly hot-rolled is obtained, and the breakdown step (A) is omitted. Titanium material.

  FIGS. 2 (a) and 2 (b) show the tool made of alloy steel for impact-resistant tool shown in FIGS. 1 (a) and 1 (b) (the steel tool or steel ball described above), respectively. The surface cross-sectional structure after performing the heat processing equivalent to the surface after giving the predetermined plastic deformation to the surface of titanium raw material, and also the hot rolling is shown. 2 (a) and 2 (b) are examples using a material having a slab shape of industrial pure titanium JIS type 2 (JIS H 4600).

  On the surface of the titanium material for hot rolling of the present invention, as shown in FIG. 2A, dimples having an uneven shape are formed, and cold pressing is performed using a roll or a tool having a corner R portion described later. Or it has a surface form different from the conventional surface form plastically deformed by cold rolling. The cold-pressed surface has a recess with a corner R transferred linearly in the longitudinal direction of the tool (see FIGS. 4 (a), 4 (b), 5 (a), and 5 (b)). Also, the cold-rolled surface is smooth.

  The surface layer part is recrystallized during the hot rolling due to the strain given by the plastic deformation forming the dimples of FIG. 2 (a), and from 6mm to less than 25mm from the surface as shown in FIG. 2 (b). In the range, recrystallization is formed. That is, the range in which recrystallization is formed is at least a range from the surface to a depth of more than 6 mm, and more preferably a range from the surface to a depth of 7 mm or more. In addition, the range in which recrystallization is formed is a maximum range from the surface to a depth of less than 25 mm. The titanium material for hot rolling of the present embodiment is in such a textured state by hot rolling. When the range in which recrystallization is formed is 6 mm or less from the surface, generation of coarse surface defects of 20 mm or more cannot be suppressed. Moreover, when the range in which recrystallization is formed extends from the surface to a depth of 25 mm or more, the strain is dispersed, and the crystal grain size after hot rolling may be coarsened to cause surface defects. Preferably, it is less than 20 mm. In addition, the range in which recrystallization is formed can be confirmed by observing under a microscope after performing the heat processing equivalent to the heating before hot working on the cross section of the titanium material after giving plastic deformation.

  By the method of the present invention, the surface defects of the titanium material after hot rolling become very minor and are suppressed to a level with no problem. On the other hand, in the case of a titanium material for hot rolling having a coarse solidified structure as cast without applying the method of the present invention without distortion being introduced into the surface layer, a coarse surface defect having a length of 20 mm or more after hot rolling. A lot.

  The tool shape that plastically deforms the surface of the titanium material for hot rolling includes the case where the tip shape of FIG. 1A has a radius of curvature of 3 to 30 mm (3 to 30 R) and a radius of 3 to 30 mm (3 to 3 mm). In the case of 30R) spheres, there is no difference in the effect of suppressing surface defects after hot rolling. From this result, in the present invention, the tip shape is applied to the surface of the material for hot rolling with a steel tool having a radius of curvature of 3 to 50 mm (3 to 30 R) or a steel ball having a radius of 3 to 30 mm (3 to 30 R). The plastic deformation is applied. In the present invention, the surface dimple depth is 0.2 to 1.5 mm, and the recrystallized layer after the heat treatment is formed with a thickness exceeding 6 mm. Since surface defects can be made stable and lighter, a more preferable tool shape has a radius of curvature or a radius of 7 to 20 mm (7 to 20 R).

  In contrast, when the tip shape of the steel tool has a radius of curvature smaller than 3 mm (3R), the amount of strain that can be applied and its range are small and surface defects may not be sufficiently suppressed. Since the convex part of the dimple has a steep shape, it is covered with hot rolling and develops into a surface defect. On the other hand, when R becomes large and the radius of curvature exceeds 30 mm (30 R), the contact surface with the material for hot rolling becomes flat during plastic deformation, and as a result, surface defects after hot rolling are suppressed. The effect may vary depending on the part and may not be sufficiently obtained. Also, in the case of a steel ball, if the radius is less than 3R (radius 3 mm) or exceeds 30R (radius 30 mm), an appropriate effect cannot be obtained as in the influence of the tip shape.

  In the present embodiment, the surface of the surface corresponding to the rolling surface of the titanium material for hot rolling is warped or warmed. In order to reduce the surface defects generated during hot rolling, a recrystallized structure up to a certain depth is required. In particular, for materials with high hardness, it is difficult for strain to enter inside, so processing is applied with a large load or processing is performed multiple times in order to apply strain to the deep position of the surface layer by the method described later. There is a need to. However, it was newly clarified that the ductility in the vicinity of the surface layer portion is reduced due to the applied strain, and the surface is cracked. In order to stably apply strain to a deep position and improve ductility, it is effective to raise the temperature to some extent and lower the strength of the material itself.

  If the temperature is 100 ° C. or higher, the strength is lower than that of cold, and strain can be imparted to a certain depth. On the other hand, when the temperature is higher than 500 ° C., the strain imparted by the processing disappears immediately, and recrystallization may not be possible during subsequent heating. In addition, when an oxide film having a certain thickness is formed on the surface, surface defects may occur due to the indentation of the film, and the surface defects may develop during hot rolling. If it is less than 500 degreeC, the above problems do not occur, so 500 degreeC was made the upper limit.

  It should be noted that the temperature range where the strength and ductility are increased depending on the type of titanium, and therefore, it is not necessarily performed at a higher temperature. For example, in pure titanium for industrial use, twin deformation, which is one of the important deformation mechanisms of titanium, is active near room temperature, but this twin deformation does not occur at temperatures of about 400 to 500 ° C. For this reason, the ductility is lower than at room temperature, and cracks are more likely to occur. On the other hand, in a titanium alloy containing a large amount of Al, this twin deformation hardly occurs even in the vicinity of room temperature. Therefore, ductility can be ensured by increasing the temperature. Also, if the material strength is extremely weakened by increasing the temperature at the time of plastic deformation, the surface undulation will become too large when the surface is plastically deformed, and surface flaws may occur due to the undulation. is there. Therefore, the temperature range for imparting plastic strain is the above temperature range, and does not cause cracking on the surface after plastic deformation, and the temperature range suitable for the material so as to obtain the optimum recrystallization depth and surface state. Just choose.

  On the other hand, conventional conventional shot blasting (shot grain diameter of about 0.5 to 1 mm), cold rolling, cold pressing with a roll or a corner having a radius of curvature of 10 to 20 mm (10 to 20 R). Distortion can also be imparted by (forging).

  However, in general shot blasting, since the diameter of the shot grains is as small as 0.5 to 1 mm, the amount of distortion given is also small. Therefore, as shown in FIG. 400 μm), and surface defects during hot rolling could not be suppressed.

  Further, cold pressing or cold rolling using a roll (FIG. 3 (a)) or a tool having a corner R portion (FIG. 3 (b)) as shown in FIGS. 3 (a) and 3 (b). When distortion is applied in FIG. 4, it is possible to form a recrystallized layer after heating to a depth of 30 mm or more from the surface as shown in FIG. However, the surface defects after hot rolling are still in a harmful level although the size is reduced to about 3 to 10 mm, and the frequency of occurrence is greatly increased.

  Since cold rolling and cold pressing using the tool shown in FIGS. 3 (a) and 3 (b) are reduced from one direction, in the case of cold rolling, a smooth surface is cooled. In the case of the intermediate press, a surface having a recess in which the corner R is transferred linearly as shown in FIG. 4A is formed. This point is greatly different from the present invention in which dimples are formed by plastic deformation at the spherical portion. 4A shows the surface after cold-pressing with a roll having a curvature radius of 15 mm (15R), and FIG. 4B shows the surface cross-sectional structure subjected to heat treatment after the surface is smoothed by cutting. Each is shown.

  When the hot-rolled titanium material has a slab shape, the conventional tool having a roll and a corner R portion is constrained because the surface of the slab contacts in a straight line parallel to the longitudinal direction (see FIG. 4A). The surface of the slab cannot be deformed in the longitudinal direction of the tool, but is mainly plastically deformed in a certain direction (the slab thickness direction). As a result, it is considered that the recrystallized grains after heating form a coarse colony having the same crystal orientation without randomizing the crystal orientation, and the influence of the initial coarse solidified structure remains strong. Moreover, the slab side surface which is not in contact with the roll or the tool may be in a shape unsuitable as a material for hot rolling such as large bulging.

  On the other hand, in the method of the present invention, since the surface is greatly plastically deformed at a spherical portion at a temperature of 100 to 500 ° C., the plastic deformation region is radially expanded from the contact portion of the tool spherical surface in addition to the thickness direction. . Further, the spread of the plastic deformation region overlaps between adjacent dimples. Accordingly, the surface layer portion is subjected to plastic deformation from various directions, unlike the case where the surface layer portion is rolled down by a roll. As a result, it is considered that the recrystallization grains in the surface layer formed after heating promote the randomization of crystal orientation. This point is considered to be the reason why the effect is different from that in the case of being rolled down from one direction by the roll as shown in FIG.

  Next, the shape of the dimple formed on the surface of the titanium material for hot rolling by the above-described method of the present invention will be described.

  The depth (height) and interval of the irregularities of the formed dimples reflect the amount and direction of plastic deformation that the surface has undergone. Of the surface texture parameters described in JIS B0601, the average height (Wc) of the wavy contour curve element is the dimple depth, and the average length (WSm) of the wavy contour curve element is the dimple spacing. Can be used as the indicated value. On the dimple surface formed by plastic deformation in the cold, surface defects after hot rolling were sufficiently suppressed in the range of Wc of 0.2 to 1.5 mm and WSm of 3 to 15 mm. Therefore, in the present invention, it is more preferable to form dimples having a Wc of 0.2 to 1.5 mm and a WSm of 3 to 15 mm by plastic deformation of the surface of the titanium material at a temperature of 100 to 500 ° C. .

  As described above, when Wc exceeds 1.5 mm and WSm is less than 3 mm, the unevenness of the dimple becomes a steep shape, which is covered by hot rolling and develops to a surface defect. On the other hand, if Wc is less than 0.2 mm and WSm exceeds 15 mm, the applied strain amount and its range are small, and surface defects are not sufficiently suppressed, or a sufficient effect cannot be obtained in a planar part. There is a case.

  The above Wc and WSm values are obtained by measuring Wc and WSm at a plurality of locations so that the total number of measured dimples is at least 30 or more, and obtaining the average. The properties of the dimples of the present invention can be obtained by adjusting the amount of plastic deformation by air pressure, projection speed, etc. in addition to the shape of the tool used.

  This embodiment is similarly effective in suppressing wrinkles on the side surfaces and corners when the titanium material for hot rolling has a slab shape. As a result, the edge of the hot-rolled plate (strip-shaped coil), surface defects in the vicinity thereof, and edge cracking due to subsequent cold rolling can be extremely reduced. Furthermore, since wrinkles are suppressed, the seam wrinkles that occur when the side surfaces and the corners wrap around the rolling surface can be reduced at the same time.

  So far, the hot rolling to the plate has been mainly explained, but the same effect can be obtained by the present invention when the cylindrical billet or ingot is hot-rolled to a bar wire, and the bite not in contact with the roll. The surface defects of the product including the protruding part and the free surface part can be extremely reduced.

  The surface defects after hot rolling are remarkably suppressed by the titanium material for hot rolling to which the present invention is applied. In particular, by applying the present invention to a rectangular parallelepiped or columnar ingot (solid structure as cast), it is hot rolled into a plate, strip coil, or bar wire without undergoing a breakdown process such as split rolling. In this case, the effect that the surface defects can be suppressed to a level at which there is no problem.

  In the electron beam melting method, the irradiated electron beam can concentrate the beam by polarization, so that heat can be easily supplied even in a narrow region between the mold and the molten titanium, and therefore the casting surface can be controlled well. In addition, the degree of freedom of the cross-sectional shape of the mold is high. Therefore, it is preferable that a rectangular or cylindrical ingot having a size that can be directly subjected to hot rolling as in (B) is melted using an electron beam melting furnace.

  Prior to hot rolling, the rectangular ingot (slab) melted in the electron beam melting furnace is plastically deformed on the surface in a temperature range of 100 ° C. or higher and lower than 500 ° C. so as to form the dimple shape of the present invention. Applied. Thereafter, it is heated for hot rolling. This heating temperature is preferably in the range of 800 ° C. to 950 ° C. in order to reduce deformation resistance. Furthermore, in order to suppress the scale generated during slab heating, the heating temperature is preferably less than the β transformation point. In addition, the rectangular ingot (slab) for hot rolling which concerns on this invention can be efficiently manufactured to a 2-10 mm strip coil by hot rolling as mentioned above.

  As described above, the rectangular ingot (slab) for hot rolling manufactured according to the present embodiment is not only suitably used for hot rolling, but the titanium plate manufactured by hot rolling has surface defects. Is remarkably suppressed, and a sound thin plate can be produced even if cold rolling is performed thereafter.

  By applying the present invention to a hot-rolled material that has undergone a breakdown process, surface defects that occur during hot rolling are greatly reduced. As a result, it is possible to further increase the descaling process of the hot-rolled plate or bar and the yield of the final product.

  In the present invention, the target hot rolling titanium material is made of either industrial pure titanium or a titanium alloy. The industrial pure titanium referred to here is an industrial pure specified by JIS standards 1 to 4 and ASTM standards Grades 1 to 4 and DIN standards 3, 7025, 3, 7035, and 3,7055. It shall contain titanium. That is, the industrial pure titanium targeted in 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, Fe: 0.5% or less, balance Ti.

On the other hand, in the case of an α-type titanium alloy, the alloy may be appropriately used for the required application.
As the α-type titanium alloy, for example, a high corrosion resistance alloy (ASTM Grade 7, 11, 16, 26, 13, 30, 33 or a titanium material containing a small amount of JIS species corresponding thereto and various elements), Ti— 0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb, Ti-0.5Al-0.45Si, Ti- 0.9Al-0.35Si, Ti-3Al-2.5V, Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2.75Sn-4Zr-0.4Mo-0. 45Si.

  Examples of α + β type titanium alloys include Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-7V, Ti-3Al-5V, Ti-5Al-2Sn-2Zr-4Mo-4Cr, Ti-6Al. -2Sn-4Zr-6Mo, Ti-1Fe-0.35O, Ti-1.5Fe-0.5O, Ti-5Al-1Fe, Ti-5Al-1Fe-0.3Si, Ti-5Al-2Fe, Ti-5Al -2Fe-0.3Si, Ti-5Al-2Fe-3Mo, Ti-4.5Al-2Fe-2V-3Mo, and the like.

  Further, as the β-type titanium alloy, for example, Ti-11.5Mo-6Zr-4.5Sn, Ti-8V-3Al-6Cr-4Mo-4Zr, Ti-10V-2Fe-3Mo, Ti-13V-11Cr-3Al , Ti-15V-3Al-3Cr-3Sn, Ti-6.8Mo-4.5Fe-1.5Al, Ti-20V-4Al-1Sn, Ti-22V-4Al, and the like.

  Examples of the present invention will be described in comparison with comparative examples (comparative examples in which the process of the present invention is not performed at all, and comparative examples in which a process deviating from the conditions of the present invention is performed). In Examples, the thickness of recrystallization is confirmed by confirming the formation region of recrystallization by microscopic observation of the cross section of the material subjected to heat treatment equivalent to heating before hot rolling after plastic deformation. It evaluated by measuring the thickness. As for the surface properties after hot rolling, those having no surface flaws or only fine wrinkles that do not cause a problem in production were evaluated as good, and the evaluation result in that case was “◯”. On the other hand, when coarse surface defects of 20 mm or more occurred, the evaluation result was “x”.

[Test numbers 1-9]
A JIS type 1 pure titanium slab having a cross section of 1050 mm wide × 250 mm thick × 7000 mm long was cast by electron beam melting. The surface of the rolled surface of the titanium slab was plastically deformed. Titanium slab with plastic deformation (titanium material for hot rolling) is inserted into a furnace at 820 ° C., heated for about 240 minutes, and a hot rolled sheet coil having a thickness of 5 mm is manufactured by a continuous hot rolling strip mill. After passing through a continuous pickling line consisting of shot blasting and nitric hydrofluoric acid and cutting about 60 μm per side, both plate surfaces were visually observed to evaluate the occurrence of surface flaws. The results are shown in Table 1.

  No. In the comparative example 1, the slab surface as cast is hot-rolled without plastic deformation. Therefore, coarse surface defects frequently occur on the plate surface after hot rolling and pickling.

  No. In Examples 2 to 5, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is hit using a tool having a tip shape of 3 to 30 R to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Further, the surface layer after the heat treatment corresponding to hot rolling has a recrystallized layer of about 12 to 15 mm. Therefore, there are almost no surface defects on the surface of the plate after hot rolling and pickling, which is good.

  No. In the sixth embodiment, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is struck by hitting 3 to 30 R steel balls to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Further, the surface layer after the heat treatment corresponding to hot rolling has a recrystallized layer of about 12 mm. Therefore, there are almost no surface defects on the surface of the plate after hot rolling and pickling, which is good.

  No. In the comparative example of No. 7, the as-cast slab is heated to 600 ° C., and the surface of the surface corresponding to the rolling surface is hit with a 3-30R steel ball to perform plastic deformation. Therefore, the surface dimple shape is as large as Wc 2.5 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is 25 mm or more. Therefore, most of the large surface defects are generated on the surface of the plate after hot rolling and pickling.

  No. In the comparative example No. 8, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is hit with a 1R steel ball to perform plastic deformation. Therefore, the shape of the dimple on the surface is as shallow as Wc 0.1 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is as shallow as 1.5 mm. Therefore, a partially rough surface flaw is generated on the surface of the plate after hot rolling and pickling.

  No. In Comparative Example 9, the as-cast slab is heated to a temperature of 100 to less than 500 ° C., and the surface of the surface that hits the rolling surface is struck with a tool having a tip shape 40R to perform plastic deformation. Therefore, the surface dimple shape has a WSm as large as 18.2 mm. Therefore, most of the large surface defects are generated on the surface of the plate after hot rolling and pickling.

[Test numbers 10-12]
JIS 2-4 kinds of pure titanium slabs having a cross section of 1050 mm wide × 250 mm thick × 7000 mm long were cast by electron beam melting. The surface of the rolled surface of the titanium slab was plastically deformed. Titanium slab with plastic deformation (titanium material for hot rolling) is inserted into a furnace at 820 ° C., heated for about 240 minutes, and a hot rolled sheet coil having a thickness of 5 mm is manufactured by a continuous hot rolling strip mill. After passing through a continuous pickling line consisting of shot blasting and nitric hydrofluoric acid and cutting about 60 μm per side, both plate surfaces were visually observed to evaluate the occurrence of surface flaws. The results are shown in Table 2.

  No. In Examples 10 to 12, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is hit using a tool having a tip shape of 3 to 30 R to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is about 10 to 15 mm. Therefore, there are almost no surface defects on the surface of the plate after hot rolling and pickling, which is good.

[Test numbers 13 to 16]
A titanium alloy slab having a cross section of 1050 mm wide × 250 mm thick × 5000 mm long was cast by electron beam melting. The surface of the rolled surface of the titanium slab was plastically deformed. No. No. 13 is a Ti-0.05Pd alloy, No. 13 14 is a Ti-0.5Ni-0.05Ru alloy, No. 14; 15 is a Ti-1Fe-0.35O alloy, No. 15; 16 is a Ti-3Al-2.5V alloy. These titanium slabs (titanium materials for hot rolling) are inserted into a furnace at 820 ° C. and then heated for about 240 minutes, and a hot-rolled sheet coil having a thickness of 5 mm is manufactured by a continuous hot rolling strip mill. After passing through a continuous pickling line made of hydrofluoric acid and cutting out about 60 μm per side, both plate surfaces were visually observed to evaluate the occurrence of surface defects.

  No. In Examples 13 to 16, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is struck using a tool with a tip shape of 3 to 30 R to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is about 7.5 to 17 mm. Therefore, there are almost no surface defects on the surface of the plate after hot rolling and pickling, which is good.

[Test numbers 17 to 20 (Table 4)]
Industrial pure titanium slabs and titanium alloy slabs having a cross section of 1050 mm wide × 250 mm thick × 5000 mm long were cast by plasma arc melting. Plastic deformation was applied to the rolling surface of these titanium slabs. No. 17 is an industrial pure titanium JIS class 1, No. 18 is a Ti-1Cu alloy, No. 18; 19 is a Ti-1Cu-0.5Nb alloy, No. 19; 20 is a Ti-1Cu-1Sn-0.3Nb-0.25Si alloy. These titanium slabs (titanium materials for hot rolling) are inserted into a furnace at 820 ° C. and then heated for about 240 minutes, and a hot-rolled sheet coil having a thickness of 5 mm is manufactured by a continuous hot rolling strip mill. After passing through a continuous pickling line made of hydrofluoric acid and cutting out about 60 μm per side, both plate surfaces were visually observed to evaluate the occurrence of surface defects.

  No. In Examples 17 to 20, the as-cast slab is heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is struck using a tool with a tip shape of 3 to 30 R to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is 10 to 18 mm. Therefore, there are almost no surface defects on the surface of the plate after hot rolling and pickling, which is good.

[Test numbers 21 to 25 (Table 5)]
Industrial pure titanium billets and titanium alloy billets having a cross section of a diameter of 100 mm × 1000 mm were cast by electron beam melting. Plastic deformation was applied to the rolled surface of the billet for wire rod. No. 21 to No. 23 is an industrial pure titanium JIS type 2, No. 23. 24 is a Ti-1Fe-0.35O alloy, No. 24. 25 is Ti-3Al-2.5V. These billets (titanium material for hot rolling) were inserted into a furnace at 820 ° C., heated for about 120 minutes, and hot rolled to a diameter of 20 mm. Then, after cutting about 50 μm from the surface with shot blasting and nitric hydrofluoric acid, the surface of the bar was visually observed to evaluate the occurrence of surface flaws.

  No. The comparative example shown in 21 hot-rolls the as-cast billet surface without plastic deformation. Therefore, coarse surface defects frequently occur on the bar surface after hot rolling and pickling.

  No. In Examples 21 to 25, as-cast billets are heated to a temperature of less than 100 to 500 ° C., and the surface of the surface that hits the rolling surface is struck using a tool with a tip shape of 3 to 30 R to perform plastic deformation. The shape of the surface dimples is in the range of Wc 0.2 to 1.5 mm and WSm 3 to 15 mm. Moreover, the thickness of the recrystallized layer of the surface layer after the heat treatment equivalent to hot rolling is 7 to 13 mm. Therefore, the surface of the bar after hot rolling and pickling is good with almost no surface defects.

Claims (4)

  A method for producing a titanium material for hot rolling, comprising heating a titanium material containing a solidified structure to 100 ° C. or more and less than 500 ° C., and plastically deforming the surface of the titanium material to form irregularities.   A titanium material including a solidified structure is heated to 100 ° C. or more and less than 500 ° C., and the surface of the titanium material is hit with a steel tool having a tip shape with a curvature radius of 3 to 30 mm, or the steel tool is applied to the surface. A method for producing a titanium material for hot rolling, wherein the surface is plastically deformed by pressing.   By heating the titanium material containing a solidified structure to 100 ° C. or more and less than 500 ° C., hitting the surface of the titanium material with a steel ball having a radius of 3 to 30 mm or pressing the steel ball against the surface, A method for producing a titanium material for hot rolling, wherein the surface is plastically deformed.   The surface is plastically deformed to form dimples having an average height (Wc) of waviness contour curve elements of 0.2 to 1.5 mm and an average length (WSm) of 3 to 15 mm. The manufacturing method of the titanium raw material for hot rolling as described in any one of Claims 1 thru | or 3.