JPH0520165B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a method for manufacturing pure titanium and titanium alloy seamless pipes in which a hot finished product is obtained only by an inclined rolling mill group using inclined rolls. (Prior Art) Pure titanium and titanium alloy seamless pipes (hereinafter simply referred to as "titanium pipes" or "titanium seamless pipes") have conventionally been manufactured by a hot extrusion method.
The Eugene-Ségiurnet method, which is a typical example of such a hot extrusion method, involves heating a blank tube that has been perforated by processing or pressing in an induction heating furnace, and then applying glass powder, which is a lubricant, to the inner and outer surfaces of the tube. This method involves inserting it into a container and extruding it through a ring-shaped gap formed by a die and mandrel to make a seamless tube. By the way, when producing titanium seamless tubes by hot extrusion, Fe extrusion dies are used as shown in Japanese Patent Application Laid-open No. 54-56924 in order to prevent defects on the inner surface of the tube caused by seizure with tools. Content 15
There is a method of preventing external flaws on extruded pipes using a Ni-based superalloy of less than %. In addition, a method has been devised to prevent flaws on the inner surface of the extruded tube by isolating the inner circumferential surface of the blank tube from the extrusion mandrel via a lubricant and a sleeve (Japanese Patent Publication No. 15726/1983). On the other hand, steel pipes, which are considered to be much easier to process than titanium or the like, are already well known as seamless pipes, and typical methods for producing seamless steel pipes include the following methods. (1) Mannesmann-Pragmill method: According to this method, as shown in FIG. It is stretched by an elongation rolling mill 14, then sent to a sizer 19 via a plug mill 16 and a polishing mill 18 called a reeler, which is also a type of inclined rolling mill, into a finished product. (2) Mannesmann-mandrel mill method: In this case, as shown in FIG.
It is perforated at 22, stretched and rolled at a mandrel mill (elongator) 24, reheated at a reheating furnace 26, and passed through a stretch reducer 28 to become a finished product. However, unlike in the case of steel pipes, when manufacturing difficult-to-process materials such as titanium, the above-mentioned hot extrusion method is generally used instead of the Mannesmann pipe manufacturing method. Inner surface flaws occur due to rice cracking due to the rotary forging effect of the inclined boring machine, and defects occur on the inner and outer surfaces of rolled pipes due to surface torsional shear deformation and circumferential shear deformation that occur during the perforating and rolling process. The above process was not adopted because of the risks involved. However, the reduction in production costs by the inclined rolling method is remarkable, and its practical application is strongly required to expand the use of titanium seamless pipes, especially in today's situation where significant production cost reductions are required. There is. (Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and its purpose is a method for manufacturing titanium and titanium alloy seamless pipes using an inclined rolling method, which eliminates the conventional defects. The goal is to provide the following. (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors have conducted various studies and have abolished the two-roll type mandrel mill, plug mill, and furthermore the sizer and reducer that are reducing mills. However, by specifying the rolling conditions, we learned that titanium seamless pipes could be manufactured by hot rolling using only an inclined rolling mill.
The invention has been completed. That is, first, in order to manufacture a titanium or titanium alloy seamless pipe, we reexamined the conventional seamless pipe manufacturing method and found the following points. (1) Limitations of the conventional hot extrusion method for titanium tubes: It is actually impossible to apply lubricant uniformly over the entire length of the raw tube to reduce friction between the tool and the material, and it is difficult to apply lubrication during drilling. The lubrication effect is 100% due to cuts and temperature changes of tools such as dies and mandrels.
This results in seizure with the tool, and this seizure creates vertical streaks (in the extrusion direction) inside the pipe.
This may occur over the entire length of the outer surface, and the machining required to remove this flaw reduces yield and increases the number of maintenance steps. Moreover, the extrusion method has low production efficiency and is not suitable for mass production. In recent years, press capacity has increased in order to improve production efficiency, but it is still not comparable to the Mannesmann pipe manufacturing method. In addition, in the extrusion method, the deflection of the mandrel bar,
The unevenness of thickness may worsen due to unevenness in the temperature of the raw pipe. (2) Problems when adopting the Mannesmann-plug mill method and the Mannesmann-mandrel mill method for manufacturing titanium seamless tubes: In two-roll rolling mills such as mandrel mills and plug mills that have regulating tools on the inner surface, the tools Streaks may occur due to seizure, poor biting may occur due to slipping between the roll and the material, and slip defects may occur. Also, for example, α such as Ti-6Al-4V alloy
When attempting to roll a +β alloy at a temperature in the α+β range using the two-roll mandrel mill or plug mill described above, if the temperature drop is taken into account, it is necessary to raise the perforation temperature with the inclined perforator in the previous process to a considerably high temperature. In some cases, the heating temperature becomes so high that the desired mechanical properties of the product cannot be obtained. On the other hand, even if it is possible to perforate in a low temperature range with an inclined perforator, it will be difficult to roll in the downstream process, and even if rolling is possible, there will be problems with seizure flaws and streaks. For reducers etc., t/d (thickness/
There is a problem of internal angularity depending on the size (outer diameter ratio). However, for example, pure titanium or Ti-6Al-
As a result of numerous experiments conducted by the present inventors, when perforating or elongating 4V alloy etc. using an inclined rolling mill,
Problematic rotary forging effects, surface torsional shear deformation,
It was discovered that the occurrence of defects on the inside and outside of the tube due to shear deformation in the circumferential direction does not become a problem if proper temperature conditions and roll setting conditions are set, and that the problems with inclined rolling mills in particular can be solved, and the present invention has been made. completed. Rather, as in the case of conventional steel pipes, tilt rolling alone makes it possible to perform thick wall processing with a high degree of workability, without using a plug mill or mandrel mill. Moreover, since the amount of cooling at that time is small, hot rolling is possible even if inclined rolling is continued thereafter. Here, the gist of the present invention is a method for manufacturing a hollow tube from a solid billet using an inclined punching machine equipped with a plurality of inclined rolls arranged oppositely across a pass line, the method comprising: Drilling is performed under conditions that satisfy the following relational expression, where T ₀ is the heating temperature of the titanium or titanium alloy billet to be drilled, the drilling ratio El in the inclined drilling machine, and the number of reelings Rn between the plug and the roll used for drilling. This is a method for manufacturing titanium and titanium alloy seamless pipes, characterized in that the steps of hot rolling are completed. 800℃≦T ₀ ≦1050℃ 1.3≦El≦3.5 However, when 1.3≦El≦2.5, Rn≧1.2 When 2.5<El≦3.5, Rn≧1.4 Furthermore, from another aspect, the gist of the present invention is The solid billet is perforated by an inclined perforator equipped with a plurality of inclined rolls arranged oppositely across a pass line, and then passed through at least one of an inclined elongation mill, an inclined tube polishing mill, and an inclined reduction rolling mill. A method for manufacturing a hollow tube using a heating temperature T ₀ of a titanium or titanium alloy billet sent to the inclined drilling machine, a drilling ratio El in the inclined drilling machine,
When the number of reelings between the plug and the roll used for perforation is Rn, perforation is performed under conditions that satisfy the same relational expression as described above, and the final This is a method for manufacturing titanium and titanium alloy seamless pipes, characterized in that hot rolling is completed in a rolling mill. As described above, the present invention is characterized in that a titanium seamless tube is manufactured from a solid billet by hot rolling using only an inclined rolling mill. Thus, the method according to the present invention simplifies the manufacturing process of seamless titanium pipes and provides products with good tensile properties and inner surface properties. (Function) Next, in order to gain a better understanding of the present invention, the circumstances that led to the production of titanium tubes using only an inclined rolling mill will be explained. As already mentioned, in the case of steel pipes, the solid billet is heated to a high temperature (usually 1200°C to 1270°C).
There are a pipe making method using the Mannesmann-mandrel mill line shown in the figure and a pipe making method using the Mannesmann plug mill line shown in FIG. However, in the case of titanium seamless pipes whose heating temperature is low, even if it is possible to perforate with a piercer, it takes time to transport the material to the next process, so the material temperature becomes too low and the deformation resistance increases. Therefore, rolling may become impossible in the next step due to seizure with the tool, poor biting, or tripping of the motor due to increased mill load. Therefore, in the above manufacturing process, it is necessary to raise the heating temperature so that the subsequent rolling process can be carried out smoothly. However, when the present inventors investigated the tensile properties of the perforated material with a piercer by varying the heating temperature, it was found that heating at high temperatures did not result in satisfactory ductility values due to coarsening of the crystal grains. . Therefore, the heating temperature of the billet cannot be increased unnecessarily. Considering the above, it is a good idea to simplify the manufacturing process in order to manufacture pipes by heating at low temperatures. Therefore, manufacturing a titanium tube using only a piercer as in the present invention makes it easier to control the tensile properties, so that a simple and high-quality product can be obtained. However, in order to improve the inner surface properties of the tube, it is necessary to suppress the spiral step that occurs during inclined rolling. It is necessary to take this point into consideration when designing the plug. In addition, the advantage of using only an inclined rolling mill as in the present invention is that thick wall processing with a high degree of processing can be performed with one roll.
Since it is not necessary to use many rolls like a mandrel mill, the cooling temperature of the rolled material is also lower, which is advantageous for rolling in subsequent steps. In addition, when rolling with an inclined rolling mill, wall thickness processing is performed using plugs and rolls, but this processing is not done all at once; in the case of a two-roll system, the wall thickness is increased every half rotation of the material. Since the process is carried out gradually while undergoing external diameter processing, it is also more advantageous than a plug mill in terms of plug seizure properties. Next, the reasons for limiting the drilling conditions for the inclined drilling machine will be described. In the present invention, the heating temperature (T ₀ ) of the titanium or titanium alloy billet is limited to 800℃≦T ₀ ≦1050℃, but this is because if T ₀ is less than 800℃, the deformation resistance will increase, resulting in poor biting or bottoming. This is because misrolls such as slippage failure occur. In addition, the lower limit of T ₀ was set to 800°C because the surface pressure of tools such as rolls, guides, and plugs becomes high, causing seizure, and a decrease in deformability causes internal and external surface flaws. On the other hand, if T ₀ exceeds 1050°C, the ductility of tensile properties decreases due to coarsening of crystal grains in such high-temperature heating, so the upper limit was set at 1050°C. The drilling ratio (El) is limited to 1.3≦El≦3.5, but
If the perforation ratio is less than 1.3, stable perforation is required because the so-called tail-off failure is likely to occur, where the plug does not come out from the bottom of the rolled material or the rolled material does not separate from the roll when it comes off. Therefore, the lower limit value was set as El=1.3. However, if the perforation ratio exceeds 3.5, the bottom part may be torn off by the guide edge part due to flaring during tail drop (a condition in which the circumference of the bottom part of the rolled material is larger than the steady part), resulting in misrolling. becomes. Furthermore, if there is no guide such as in a three-roll system, buckling occurs between the rolls, resulting in poor tailing, so the upper limit was set as El = 3.5. By the way, the number of reeling (Rn) is 1.3≦El
Rn≧1.2 when ≦2.5, Rn≧1.4 when 2.5＜El≦3.5
However, this is due to the following reasons. First, the number of reelings (Rn) is the number of times the plug is lightly rolled between the reeling part and the rolls (Rn).
and is expressed as below. Rn=L/n×π×d×tanβ×η _l /η _r L: Plug reeling length n: Number of inclined rolls d: Material diameter after drilling β: Roll inclination angle η _l : Advance efficiency (0.4 ~0.95) η _r : Rotational efficiency (0.8 to 1.1) The plug has a substantially conical shape, and as shown in Fig. 8, it has a curvature in the rolled part with a length Lr and an inclined arrangement. tilted rolls 31, 31'
The reeling part has a predetermined angle α ₃ so as to be approximately parallel to the exit surface of the In the part), the light reduction rate serves to eliminate variations in the wall thickness of the rolled material. If the number of times of reeling during thickness reduction between the plug and the roll is small, spiral undulations (spiral steps) will occur on the inner surface of the rolled material. In order to finish with one inclined drilling machine, it is necessary to reduce this spiral step, and therefore, the above-mentioned
The Rn value was limited. Even when further hot rolling is performed using an inclined rolling mill subsequent to the inclined perforating machine, it is sufficient to carry out the perforating and rolling under the same conditions. Further, as the drilling conditions of the inclined drilling machine, it is more desirable that the inclination angle β and the intersecting angle γ of this inclination angle β
The sum γ+β may be performed under the condition of the following formula. In such a case, the effect of improving the quality of the inner and outer surfaces of the tube after perforation can be obtained. 8°≦β≦16, γ+β≧15° Hereinafter, a specific example of the method for manufacturing a seamless titanium tube according to the present invention will be described in detail based on the drawings. FIG. 3 is a schematic plan view showing the state of piercing rolling in an inclined rolling mill equipped with cone-shaped rolls used in the implementation of the present invention, FIG. 4 is a side view, and FIG.
The figure is a front view. That is, the inclined rolls 31 and 31' have a cone shape with an inlet face angle α ₁ on the inlet side and an outlet face angle α ₂ on the outlet side, and the position where the roll face on the inlet side and the roll face on the exit side intersect is as follows. It is a gorge part and has an inclination angle β equal to the opposite direction with respect to the horizontal plane (or vertical plane) of the pass line through which the billet 33 passes.
The plug 34 is inclined so that it crosses the vertical plane (or horizontal plane) of the pass line at a symmetrical intersection angle γ, and furthermore, the plug 34 has its axis line The plug 3 is installed and disposed on the mandrel bar 35 so as to match the path center x-x, and as shown in FIG.
4 includes a rolling part 341 having a length Lr and a reeling part 342 having a length L. Further, the guides 32, 32' are arranged vertically (or horizontally) with the pass line in between. Note that when γ=0° or its value is small, a barrel-shaped roll shape is obtained. The present invention is to manufacture a seamless pipe from a solid billet using only the above-mentioned inclined rolling mill, and the method is as shown in FIGS.
The solid billet 33, which has been heated to a predetermined temperature at
The hollow tube 42 is obtained by hot rolling. Manufacturing is completed with only this perforation step, and the hollow tube is made into a hot-finished tube. In another aspect of the present invention, the form and reason for arranging one or more inclined rolling mills such as an inclined stretching mill, an inclined tube polishing mill, and an inclined reducing mill in the downstream process of a piercing rolling mill are not necessarily limited. Examples include, but are not limited to, the following: (1) Inclined perforation machine (piercer) → inclined rolling milling machine (reeler): If it is necessary to improve the waviness of the inner and outer surfaces of the piercer perforated material, it is rolled with a reeler. (2) Inclined drilling machine (Piercer) → Inclined elongation rolling mill (Elongator): If the specified thinness cannot be obtained with one piercer,
Stretch with elongator. (3) Inclined drilling machine (Piercer) → Inclined elongation rolling machine (Elongator) → Inclined rolling polishing machine (Reeler): If the waviness of the inner and outer surfaces of the tube made thin with the Elongator becomes a major problem, roll it with a reeler. death,
Remove undulations. (4) Inclined perforator (piercer) → inclined elongation rolling machine (elongator) → inclined rolling polishing machine (reeler) → inclined reduction rolling mill (rotalisizer): The outer diameter of each tube rolled by the reeler, Alternatively, if there are variations within a tube and it is necessary to finish it to a constant size, use a rotary sizer to finish the tube to a constant outside diameter. (5) Inclined drilling machine (piercer) → inclined reduction rolling mill (rotary sizer): When the outer diameter of the perforated material in the piercer varies from one piece to another or within one piece and needs to be finished to a constant size, a rotary sizer is used. Use. Next, Fig. 7 A to E respectively show a heating process, a perforation process, a stretching process, a polishing process, and a drawing process.
The hollow tube 42 obtained in step 0 is transferred to the inclined stretching rolling mill 4.
3, the tube 44 is obtained by elongation rolling, and if necessary, the tube 44 is passed through an inclined rolling polishing machine (reeler) 45.
Reeling rolling (polishing) is performed to obtain a tube 46. Further, if necessary, only reduction rolling is performed using an inclined reduction rolling mill (rotary sizer) 47 without using an inner surface regulating tool to obtain a final finished tube 48. Next, the present invention will be explained in more detail with reference to Examples. Example 1 The present invention was carried out using the equipment shown in FIG. Processing conditions are shown in Table 1.

[Table] (Note) *: See Table 6.
The results are summarized in Table 2. In the table, among the tool seizure conditions, an x mark indicates that the guide, plug, or roll was seized. ○ mark indicates no burn-in. Furthermore, among the occurrences of misroll, an x mark indicates that either a biting defect or a bottom slipping defect has occurred. The ○ mark indicates that it was possible to perforate.

[Table] Example 2 In this example, Example 1 was repeated, but a Ti-6Al-4V alloy was used instead of pure titanium. Processing conditions are shown in Table 3.

[Table] (Note) *: See Table 6.

【table】

[Table] Example 3 This example shows an experimental example in which a small-diameter product is obtained through the process of heating furnace → piercer (inclined drilling machine). Processing conditions are summarized in Table 5.

[Table] (Note) *: See Table 6.

【table】

【table】

[Table] From the above, according to the method according to the present invention: With the piercer alone, misrolls and tubes,
Manufacture is possible without causing external defects. It also has good tensile properties, and as for pure titanium,
It satisfies JISH4630. The tensile properties of the Ti alloy were also comparable to those of the extruded material and had no particular problems. Since the manufacturing process is simplified, countermeasures can be taken immediately when defects occur. Comparative Example 1 This example shows a method in which the process goes through a heating furnace → piercer → mandrel mill → reheating furnace → stretch reducer. Processing conditions are shown in Table 9. The results are shown in Table 10.

【table】

[Table] From the above, when using a mandrel mill as seen in the conventional manufacturing method of steel pipes: With low-temperature heating, the rolled material becomes quite low temperature, so rolling with a mandrel mill is impossible (flaws occur)
It is. It is difficult to set the temperature setting conditions and roll installation conditions (including the rolling reduction rate during rolling) in the square mill. Example 4 In this example, a case will be described in which a large-diameter product is obtained by the method of the present invention through a heating furnace, a piercer, an elongator, and a reeler. Processing conditions are summarized in Table 11.

【table】 The results are shown in Table 12.

[Table] A tube of good quality was obtained that could be rolled up to the reeler and had good tensile properties. Comparative Example 2 In this example, a tube was manufactured through the following steps: heating furnace → piercer → elongator → plug mill → reeler. Processing conditions are summarized in Table 13.

【table】

[Table] Inner and outer surface flaws occurred in the plug mill, and poor engagement occurred in the reeler, making it impossible to obtain a good product. (Effects of the Invention) As detailed above, according to the present invention, titanium seamless pipes can be manufactured by hot rolling using an inclined rolling method, so the productivity is significantly improved compared to the conventional hot extrusion method. The advantages of this method are large, as it enables the production of long tubes, and the quality is also superior to that obtained by the conventional hot extrusion method. Moreover, such benefits are achieved simply by limiting the operating conditions of the inclined drilling machine to a specific range, and considering that it is relatively easy to achieve such conditions, the benefits of the present invention are even more significant. I know it's big.

[Brief explanation of the drawing]

Figures 1 and 2 are flowcharts showing the conventional seamless steel pipe manufacturing process; Figures 3 to 5
The figure is an explanatory diagram of the action of the inclined roll used in the inclined perforation rolling in the present invention; Figure 6 A and B are a flowchart of one embodiment of the method according to the present invention; Flowchart of another embodiment of the method according to the invention; and FIG. 8 is an explanatory diagram of reeling length and reeling number. 31, 31'... Inclined roll, 33... Billet, 34... Plug, 40... Inclined drilling machine, 43
... Inclined drawing and rolling mill, 45... Inclined rolling polished tube machine,
47... Inclined reducing rolling mill.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a hollow tube from a solid billet using an inclined drilling machine equipped with a plurality of inclined rolls arranged oppositely across a pass line, the method comprising: titanium fed to the inclined drilling machine; Or the heating temperature T ₀ of the titanium alloy billet, the drilling ratio El of the inclined drilling machine,
Titanium and titanium alloy seamless pipes are characterized in that the hot rolling is completed after drilling under conditions that satisfy the following relational expression, where Rn is the number of times of reeling between the plug and the rolls used for drilling. Production method. 800℃≦T ₀ ≦1050℃ 1.3≦El≦3.5 However, when 1.3≦El≦2.5, Rn≧1.2 When 2.5<El≦3.5, Rn≧1.4 2. A method for manufacturing a hollow tube from a solid billet through at least one of an inclined elongation rolling mill, an inclined tube milling machine, and an inclined reduction rolling mill, the method comprising: heating temperature T ₀ of the billet of titanium or titanium alloy sent to the drilling machine, the drilling ratio El of the inclined drilling machine, the number of reelings between the plug and the roll used for drilling.
When Rn, perforation is performed under conditions that satisfy the following relational expression,
Alternatively, a method for producing titanium and titanium alloy seamless pipes, characterized in that hot rolling is completed in a final rolling mill of an inclined reduction rolling mill. 800℃≦T ₀ ≦1050℃ 1.3≦El≦3.5 However, when 1.3≦El≦2.5, Rn≧1.2 When 2.5<El≦3.5, Rn≧1.4