Creep shape correction method for titanium alloy pipe

Abstract

The invention belongs to the technical field of metal material processing, and particularly relates to a titanium alloy pipe creep deformation shape correction method which comprises the following steps: hoisting the upper end of a titanium alloy pipe to be corrected in a vertical vacuum heat treatment furnace; a heavy object is hung at the lower end of the titanium alloy pipe to be corrected, the gravity center of the heavy object is located on the axis of the titanium alloy pipe, and then heat treatment is conducted. The yield strength of the titanium alloy pipe at the heat treatment temperature is * 10 <-4 > * pipe sectional area-pipe mass < = the mass M of the hung heavy object, the yield strength of the titanium alloy pipe at the heat treatment temperature is * 10 <-4 > * pipe sectional area-pipe mass < = 3 * the yield strength of the titanium alloy pipe at the heat treatment temperature, the unit of the mass of the hung heavy object is kg, the unit of the yield strength is MPa, and the unit of the pipe sectional area is mm < 2 >. Aiming at the pipe which cannot be straightened by a straightening machine, creep deformation shape correction is carried out through the dead weight of the pipe and the pulling force of a hanging heavy object in the heat treatment process in the vertical vacuum furnace, so that the straightness is less than or equal to 1mm / m.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to a creep correction method for a titanium alloy pipe. Background Art

[0002] At present, the titanium alloy tubes that can be cold-rolled are generally medium-low strength titanium alloy equal diameter round tubes. After heat treatment, they are straightened by a multi-roll straightening machine. The principle of straightening is that after the tube is bitten by the roller, it continuously makes linear or rotational motion, so that the product is subjected to deformation such as compression, bending, flattening, etc., and finally achieves the purpose of straightening. However, there are some titanium alloy tubes that cannot achieve high straightness requirements with a straightening machine, including the following types of titanium alloy tubes:

[0003] High-strength titanium alloy cold-rolled and cold-spun tubes, such as TC16, TB2, TB8, TB10, Ti1300, etc., generally require solution treatment and then aging to achieve the required high strength. Due to the high yield strength, the straightening force required for straightening is large, and the rebound after straightening is large. The straightening machine cannot achieve the higher required straightness, such as 1mm / m. The excessive pressure and bending force applied by the pressure roller on the tube during the straightening process will also cause the tube to crack.

[0004] For cold-rolled, cold-spun (such as TC16, TB2, TB8, TB10, Ti1300, etc.), machined (such as TC4, TC11, TA15) titanium alloy thin-walled pipes with large diameter-to-thickness ratio or non-uniform diameter titanium alloy thin-walled pipes, they cannot be straightened by a straightening machine. Straightening of titanium alloy pipes with large diameter-to-thickness ratio is prone to defects such as ovalization and pits. Non-uniform diameter thin-walled pipes cannot be straightened on a multi-roll straightening machine due to inconsistent outer diameters.

[0005] Patent CN 105665468 B "A method for preparing high-precision large-diameter thin-walled titanium tubes" places the finished tube with a long core rod vertically in a heat treatment furnace for vacuum annealing at 650-850°C, thereby achieving the straightening effect on α-type and near-α-type titanium alloy tubes. This method achieves the straightening of large-diameter thin-walled titanium tubes at high temperatures (650-850°C), and is only suitable for the straightening of medium- and low-strength equal-diameter cold-rolled titanium tubes such as α-type and near-α-type. However, for high-strength titanium alloy tubes and non-equal-diameter titanium alloy thin-walled tubes, this method cannot achieve high-precision straightening effects. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a creep correction method for titanium alloy pipes, especially for titanium alloy pipes that cannot achieve high straightness requirements using a straightener. The pipes are subjected to low-temperature aging heat treatment or low-temperature annealing process in a vertical vacuum furnace, and creep correction is performed under the action of the pipe's own weight and the tension of hanging weights, so that their straightness is ≤1mm / m.

[0007] Titanium alloy pipes that cannot achieve high straightness requirements using a straightening machine include: high-strength titanium alloy pipes, titanium alloy thin-walled pipes with a large diameter-to-thickness ratio (prepared by cold rolling, cold spinning or machining processes), and titanium alloy thin-walled pipes with equal or non-equal diameters.

[0008] The present invention is achieved through the following technical solutions.

[0009] The present invention provides a creep correction method for a titanium alloy pipe, comprising the following steps:

[0010] The upper end of the titanium alloy pipe to be corrected is hoisted in a vertical vacuum heat treatment furnace.

[0011] A weight is hung at the lower end of the titanium alloy pipe to be corrected, and the center of gravity of the weight is located on the axis of the titanium alloy pipe. Then, heat treatment is performed to achieve creep correction of the titanium alloy pipe.

[0012] Among them, the yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass ≤ mass of hanging weight M ≤ 3 × yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass, where the mass of the hanging weight is in kg, the unit of yield strength is in MPa, and the unit of pipe cross-sectional area is in mm 2 The mass of the hanging weight is determined through experiments. If the mass is too large, the pipe will be stretched, and if the mass is too small, the straightening effect will not be significant.

[0013] During the heat treatment process, under the action of the pipe's own gravity and the counterweight provided by heavy objects, according to the material mechanics theory, the fixed stress of the metal material reaches a certain critical value and is heated to a certain temperature. Even if the stress does not increase, the plastic deformation of the metal material will continue to occur over time. This is the creep process of the material. After this process, the original elastic deformation of the metal material is replaced by creep deformation, and the stress of the material is gradually released over time, thereby achieving correction.

[0014] It should be noted that the method of the present invention is aimed at high-strength cold-rolled, cold-spun or machined pipes with a yield strength ≥700MPa that cannot achieve high straightness requirements using a straightening machine. It also includes cold-rolled, cold-spun or machined titanium alloy equal-diameter or non-equal-diameter titanium alloy thin-walled pipes with a large diameter-to-thickness ratio that cannot be straightened using a straightening machine.

[0015] When the titanium alloy pipe to be corrected is: a high-strength cold-rolled, cold-spun pipe or machined pipe that cannot achieve high straightness requirements with a straightening machine, it specifically refers to a cold-rolled, cold-spun or machined pipe with a yield strength ≥ 700MPa; due to the high yield strength, the straightening force required for straightening is large, and the rebound after straightening is large, and the straightening machine cannot achieve higher straightness requirements, such as 1mm / m. The pressure and bending force applied by the pressure roller to the pipe during the straightening process are too large and will also cause the pipe to crack. For this type of pipe, when using the method of the present invention, holes are punched at the upper and lower ends of the pipe to be corrected, and a steel rod is inserted into the hole at the upper end. The titanium alloy pipe is hoisted in a vertical vacuum heat treatment furnace using the steel rod at the upper end; a steel rod is inserted into the hole at the lower end, and the weight is hoisted on the steel rod at the lower end. Then close the furnace door, set the heating curve, and heat treatment.

[0016] When the titanium alloy pipe to be straightened is a cold-rolled, cold-spun or machined titanium alloy thin-walled pipe with a large diameter-thickness ratio, the thin-walled pipe is an equal-diameter or non-equal-diameter thin-walled pipe; the large diameter-thickness ratio refers to the outer diameter of the pipe: the wall thickness is ≥ 50. For cold-rolled, cold-spun, machined titanium alloy thin-walled pipes with a large diameter-thickness ratio or non-equal-diameter titanium alloy thin-walled pipes, it is impossible to use a straightening machine for straightening. Straightening titanium alloy pipes with a large diameter-thickness ratio is prone to defects such as ovalization and pits in the pipe, and non-equal-diameter thin-walled pipes cannot be straightened on a multi-roll straightening machine due to inconsistent outer diameters. For this type of pipe, when using the method of the present invention, a steel pipe of equal length is lined inside the titanium alloy pipe (the purpose is to prevent the pipe from becoming elliptical and also to assist in straightening), holes are punched at the upper and lower ends of the titanium pipe and the steel pipe respectively, a steel rod is inserted into the holes at the upper ends of the titanium pipe and the steel pipe in turn, and the titanium alloy pipe is hoisted in a vertical vacuum heat treatment furnace using the steel rod at the upper end; a steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe in turn, and the weight is hoisted on the steel rod at the lower end. Then the furnace door is closed, a heating curve is set, and the temperature is raised for heat treatment.

[0017] Preferably, the heat treatment temperature is 500° C. to 600° C., and the insulation time is 5 h to 8 h.

[0018] Preferably, after the heat treatment is completed, argon gas is filled in the furnace for rapid cooling, and the product is cooled to below 100° C. before being taken out of the furnace.

[0019] Preferably, before heating to 500°C to 600°C, the furnace is first evacuated to a vacuum of less than 1×10 -2 Pa.

[0020] After being processed by the creep correction method of the present invention, the straightness of the titanium alloy pipe is ≤1mm / m, which meets the requirements.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The pipes targeted by the present invention are titanium alloy pipes that cannot achieve high straightness requirements using a straightening machine. For these pipes, a creep straightening method for titanium alloy pipes is proposed. During the heat treatment process in a vertical vacuum furnace, creep straightening is performed under the action of the pipe's own weight and the tension of a hanging weight, so that its straightness is ≤1mm / m. Among them, the mass of the hanging weight meets the following requirements: the yield strength of the titanium alloy pipe at the heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass ≤ mass of hanging weight ≤ 3 × yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass, where the mass of the hanging weight is in kg, the unit of yield strength is in MPa, and the unit of pipe cross-sectional area is in mm 2 The mass of the hanging weight is determined through experiments. If the mass is too large, the pipe will be stretched, and if the mass is too small, the straightening effect will not be significant.

[0023] The above-mentioned titanium alloy pipes include high-strength cold-rolled, cold-spun or machined pipes with a yield strength ≥700MPa, and also include cold-rolled, cold-spun or machined titanium alloy equal-diameter or non-equal-diameter thin-walled pipes with a large diameter-to-thickness ratio that cannot be cold-straightened by a straightening machine.

[0024] The method provided by the present invention is simple to operate and has good effect, which makes up for the defect that the current solution of straightening by using a straightening machine is not suitable for the above-mentioned pipes, and is suitable for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of non-equal diameter thin-walled pipe fittings, where (a) is non-equal diameter thin-walled pipe fitting structure one, (b) is non-equal diameter thin-walled pipe fitting structure two, and (c) is non-equal diameter thin-walled pipe fitting structure three.

[0026] Figure 2 This is the morphology of the titanium tube after heat treatment in Comparative Example 8.

[0027] Figure 3 This is the morphology of the titanium tube after heat treatment in Example 3. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0029] The present invention aims at titanium alloy pipes that cannot achieve high straightness requirements by a straightening machine, including: high-strength cold-rolled, cold-spun or machined pipes with a yield strength of ≥700MPa, and also includes cold-rolled, cold-spun or machined titanium alloy equal-diameter / non-equal-diameter titanium alloy thin-walled pipes with a large diameter-thickness ratio that cannot be straightened by a straightening machine. A creep correction method for titanium alloy pipes is proposed, comprising the following steps:

[0030] The upper end of the titanium alloy pipe to be corrected is hoisted in a vertical vacuum heat treatment furnace.

[0031] A weight is hung at the lower end of the titanium alloy pipe to be corrected, and the center of gravity of the weight is located on the axis of the titanium alloy pipe. Then, heat treatment is performed to achieve creep correction of the titanium alloy pipe.

[0032] Among them, the yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass ≤ mass of hanging weight M ≤ 3 × yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass, where the unit of the mass of the hanging weight is kg, the unit of the pipe mass is kg, the unit of the yield strength is MPa, and the unit of the pipe cross-sectional area is mm 2 .

[0033] The invention performs creep correction under the action of the deadweight of the pipe and the pulling force of the hanging weight during the heat treatment process in a vertical vacuum furnace or an atmospheric furnace, so that the straightness of the pipe is ≤1mm / m.

[0034] When the titanium alloy pipe to be corrected is a high-strength cold-rolled or cold-spun pipe that cannot achieve high straightness requirements using a straightening machine, it specifically refers to a cold-rolled or cold-spun pipe with a yield strength ≥700MPa. For this type of pipe, when using the method of the present invention, holes are punched at the upper and lower ends of the pipe to be corrected, a steel rod is inserted into the upper hole, and the titanium alloy pipe is hoisted in a vertical vacuum heat treatment furnace using the steel rod at the upper end; a steel rod is inserted into the lower hole, and the weight is hoisted on the steel rod at the lower end. Then, the furnace door is closed, a heating curve is set, and the temperature is increased for heat treatment.

[0035] When the titanium alloy tube to be corrected is a cold-rolled, cold-spun or machined titanium alloy thin-walled tube with a large diameter-to-thickness ratio, the thin-walled tube is an equal-diameter or non-equal-diameter thin-walled tube; the large diameter-to-thickness ratio refers to the outer diameter of the tube: the wall thickness ≥ 50. Figure 1As shown, (a) is the non-equal diameter thin-walled pipe structure 1, and the wall thickness of the pipe at A increases, (b) is the non-equal diameter thin-walled pipe structure 2, and the inner diameter of the pipe at B changes, and (c) is the non-equal diameter thin-walled pipe structure 3, and the wall thickness of the pipe at C changes. For this type of pipe, when the method of the present invention is adopted, an equal length steel pipe is lined inside the titanium alloy pipe (the function of inserting the steel pipe is mainly to ensure the roundness and prevent the pipe from becoming elliptical, and it also has the function of straightening), and holes are punched at the upper and lower ends of the titanium pipe and the steel pipe respectively, and a steel rod is inserted into the upper end hole of the titanium pipe and the steel pipe in turn, and the titanium alloy pipe is hoisted in the vertical vacuum heat treatment furnace by using the steel rod at the upper end; a steel rod is inserted into the lower end hole of the titanium pipe and the steel pipe in turn, and the weight is hoisted on the steel rod at the lower end. Then close the furnace door, set the heating curve, and heat treatment is carried out by heating.

[0036] The present invention is specifically described below by the following examples and comparative examples. In each example, the yield strength of the titanium alloy pipe at the heat treatment temperature is ×10 -4 × pipe cross-sectional area - pipe mass ≤ mass of hanging weight M ≤ 3 × yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - pipe mass, where the mass of the hanging weight is in kg, the unit of yield strength is in MPa, and the unit of pipe cross-sectional area is in mm 2 The comparative example includes: increasing the mass of the hanging weight, so that M>3×yield strength of titanium alloy pipe at heat treatment temperature×10 -4 × pipe cross-sectional area - pipe mass. Reduce the mass of the hanging weight, M < yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × Pipe cross-sectional area - Pipe mass. And no hanging heavy objects.

[0037] Example 1

[0038] The specific steps for straightening Φ45×2×2500mmTC16 titanium alloy pipe are as follows:

[0039] Drill Φ8mm holes at the upper and lower ends of the Φ45×2×2500mm TC16 titanium alloy tube at a distance of 20mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 15kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 5h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.7mm / m.

[0040] Comparative Example 1

[0041] Compared with Example 1, the mass of the hanging heavy object is increased, and the specific steps are as follows:

[0042] Drill Φ8mm holes at the upper and lower ends of the Φ45×2×2500mm TC16 titanium alloy tube at a distance of 20mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 50kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 5h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.5mm / m, but the length is elongated, and the outer diameter and wall thickness are unevenly deformed.

[0043] Comparative Example 2

[0044] Compared with Example 1, the mass of the hanging heavy object is reduced, and the specific steps are as follows:

[0045] Drill Φ8mm holes at the upper and lower ends of the Φ45×2×2500mm TC16 titanium alloy tube at a distance of 20mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 3kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 5h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 2.3mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0046] Comparative Example 3

[0047] Compared with Example 1, no heavy objects are hung, and the specific steps are as follows:

[0048] Drill Φ8mm holes at the upper and lower ends of the Φ45×2×2500mm TC16 titanium alloy tube at a distance of 20mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and do not hang any heavy objects on the steel rod. Close the furnace door, set the heating curve, and evacuate to 10 -2Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 5h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 3.2mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0049] Example 2

[0050] The straightening process of Φ50×3.0×2500mmTi-3Al-4Mo-4V-0.5Cr-0.4Fe (Ti-344) titanium alloy pipe is as follows:

[0051] Drill Φ8mm holes at the upper and lower ends of the Φ50×3.0×2500mm Ti-344 titanium alloy tube at a distance of 30mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 28kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door and set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 6h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.9mm / m.

[0052] Comparative Example 4

[0053] Compared with Example 2, the mass of the hanging heavy object is increased, and the specific steps are as follows:

[0054] Drill Φ8mm holes at the upper and lower ends of the Φ50×3.0×2500mm Ti-344 titanium alloy tube at a distance of 30mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 70kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door and set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 6h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.6mm / m, but the length is elongated, and the outer diameter and wall thickness are unevenly deformed.

[0055] Comparative Example 5

[0056] Compared with Example 2, the mass of the hanging heavy object is reduced, and the specific steps are as follows:

[0057] Drill Φ8mm holes at the upper and lower ends of the Φ50×3.0×2500mm Ti-344 titanium alloy tube at a distance of 30mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and hang a 6kg weight on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door and set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 6h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 3.0mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0058] Comparative Example 6

[0059] Compared with Example 2, no heavy objects are hung, and the specific steps are as follows:

[0060] Drill Φ8mm holes at the upper and lower ends of the Φ50×3.0×2500mm Ti-344 titanium alloy tube at a distance of 30mm from the end, and pass a Φ7.8mm steel rod through the hole at the upper end of the titanium tube. Hang the upper end of the titanium tube on the bracket in the vertical heat treatment furnace. Insert a Φ7.8mm steel rod into the hole at the lower end of the titanium tube, and do not hang any heavy objects on the steel rod. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 600℃, start timing heat preservation, heat preservation time is 6h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is 4.2mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0061] Example 3

[0062] Straightening of Φ120 (normal outer diameter) / Φ122 (thickening section outer diameter)×1.5 (normal wall thickness) / 2.5 (thickening section outer diameter)×2000mmTC11 titanium alloy pipe (variable wall thickness pipe with steps), the specific steps are as follows:

[0063] A Φ116.6×8×2000mm steel pipe is lined inside the Φ120 / Φ122×1.5 / 2.5×2000mm TC11 titanium alloy pipe. A Φ10mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 20mm from the end. A Φ9.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ9.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 50kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10-2 Pa, start heating, when the temperature rises to 550 ℃ (aging temperature), start timing insulation, insulation time 7h, then fill with argon gas for rapid cooling, cool to below 100 ℃ out of the furnace. Figure 3 The straightness of the measured pipe is: 0.4mm / m.

[0064] Comparative Example 7

[0065] Compared with Example 3, the mass of the hanging heavy object is increased, and the specific steps are as follows:

[0066] A Φ116.6×8×2000mm steel pipe is lined inside the Φ120 / Φ122×1.5 / 2.5×2000mm TC11 titanium alloy pipe. A Φ10mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 20mm from the end. A Φ9.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ9.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 120kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing heat preservation, heat preservation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.4mm / m, but the length is elongated, and the outer diameter and wall thickness are unevenly deformed.

[0067] Comparative Example 8

[0068] Compared with Example 3, the mass of the hanging heavy object is reduced, and the specific steps are as follows:

[0069] A Φ116.6×8×2000mm steel pipe is lined inside the Φ120 / Φ122×1.5 / 2.5×2000mm TC11 titanium alloy pipe. A Φ10mm hole is drilled in the upper and lower ends of the titanium pipe and the steel pipe at a distance of 20mm from the end. A Φ9.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ9.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 10kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 550 ℃ (aging temperature), start timing heat preservation, heat preservation time 8h, then fill with argon gas for rapid cooling, cool to below 100 ℃ out of the furnace. Figure 2The measured straightness of the pipe is 1.6 mm / m, which is greater than 1 mm / m and does not meet the requirements.

[0070] Comparative Example 9

[0071] Compared with Example 3, no heavy objects are hung, and the specific steps are as follows:

[0072] A Φ116.6×8×2000mm steel pipe is lined inside the Φ120 / Φ122×1.5 / 2.5×2000mm TC11 titanium alloy pipe. A Φ10mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 20mm from the end. A Φ9.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ9.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and no heavy objects are hung on the steel rod. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing insulation, insulation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 2.1mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0073] Example 4

[0074] The specific steps for straightening Φ320×2×1800mmTC21 titanium alloy pipe are as follows:

[0075] A Φ315.6×40×1800mm steel pipe is lined inside the Φ320×2×1800mm TC21 titanium alloy pipe. A Φ20mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 30mm from the end. A Φ19.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ19.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 150kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing and heat preservation, the heat preservation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.5mm / m.

[0076] Comparative Example 10

[0077] Compared with Example 4, the mass of the hanging heavy object is increased, and the specific steps are as follows:

[0078] A Φ315.6×40×1800mm steel pipe is lined inside the Φ320×2×1800mm TC21 titanium alloy pipe. A Φ20mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 30mm from the end. A Φ19.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ19.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 360kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing heat preservation, heat preservation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.5mm / m, but the length is elongated, and the outer diameter and wall thickness are unevenly deformed.

[0079] Comparative Example 11

[0080] Compared with Example 4, the mass of the hanging heavy object is reduced, and the specific steps are as follows:

[0081] A Φ315.6×40×1800mm steel pipe is lined inside the Φ320×2×1800mm TC21 titanium alloy pipe. A Φ20mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 30mm from the end. A Φ19.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ19.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and a 50kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium pipe. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing heat preservation, heat preservation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 1.7mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0082] Comparative Example 12

[0083] Compared with Example 4, no heavy objects are hung, and the specific steps are as follows:

[0084] A Φ315.6×40×1500mm steel pipe is lined inside the Φ320×2×1500mm TC21 titanium alloy pipe. A Φ20mm hole is drilled at the upper and lower ends of the titanium pipe and the steel pipe at a distance of 30mm from the end. A Φ19.8mm steel rod is passed through the holes at the upper ends of the titanium pipe and the steel pipe. The upper end of the titanium pipe lined with the steel pipe is hoisted on the bracket in the vertical heat treatment furnace. A Φ19.8mm steel rod is inserted into the holes at the lower ends of the titanium pipe and the steel pipe, and no heavy objects are hung on the steel rod. Close the furnace door, set the heating curve, and evacuate to 1×10 -2 Pa, start heating, when the temperature rises to 550℃ (aging temperature), start timing heat preservation, heat preservation time is 8h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 2.3mm / m, the straightness is greater than 1mm / m, which does not meet the requirements.

[0085] Example 5

[0086] The specific steps for straightening Φ160×2×1600mmTB10 titanium alloy pipe are as follows:

[0087] A Φ115.6×30×2000mm steel tube is lined inside the Φ160×2×1600mm TB10 titanium alloy tube. A Φ15mm hole is drilled in the upper and lower ends of the titanium tube and the steel tube at a distance of 25mm from the end. A Φ14.8mm steel rod is passed through the holes at the upper ends of the titanium tube and the steel tube. The upper end of the titanium tube lined with the steel tube is hoisted on the bracket in the vertical heat treatment furnace. A Φ14.8mm steel rod is inserted into the holes at the lower ends of the titanium tube and the steel tube, and a 60kg weight is hung on the steel rod. The center of gravity of the weight is in line with the axis of the titanium tube. Close the furnace door and set the heating curve. Vacuum to 1×10 -2 Pa, start heating, when the temperature rises to 500℃ (aging temperature), start timing heat preservation, heat preservation time is 7h, then fill with argon gas for rapid cooling, cool to below 100℃ and take out of the furnace. The straightness of the measured pipe is: 0.6mm / m.

[0088] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.

Claims

1. A creep correction method for titanium alloy pipes, characterized in that: The following steps are involved: The upper end of the titanium alloy pipe to be corrected is hoisted in a vertical vacuum heat treatment furnace; A weight is hung at the lower end of the titanium alloy pipe to be corrected, and the center of gravity of the weight is located on the axis of the titanium alloy pipe, and then heat treatment is performed to achieve creep correction of the titanium alloy pipe; Among them, the yield strength of titanium alloy pipe at heat treatment temperature × 10 -4 × cross-sectional area of ​​the pipe - mass of the titanium alloy pipe ≤ mass of the hanging weight ≤ 3 × yield strength of the titanium alloy pipe at heat treatment temperature × 10 -4 × pipe cross-sectional area - titanium alloy pipe mass, where the unit of the mass of the hanging weight is kg, the unit of the mass of the titanium alloy pipe is kg, the unit of the yield strength is MPa, and the unit of the pipe cross-sectional area is mm 2 ; The titanium alloy pipe to be straightened is a titanium alloy pipe whose straightness cannot be achieved to ≤1mm / m by a straightening machine.

2. The creep correction method of titanium alloy pipe according to claim 1, characterized in that: The titanium alloy tube to be straightened is: a high-strength cold-rolled, cold-spun or machined tube that cannot achieve a straightness of ≤1 mm / m using a straightening machine; The high strength refers to a yield strength ≥ 700 MPa.

3. The creep correction method of titanium alloy pipe according to claim 1, characterized in that: The titanium alloy tube to be corrected is: a cold-rolled, cold-spun or machined titanium alloy thin-walled tube with a large diameter-to-thickness ratio, and the thin-walled tube is an equal-diameter or non-equal-diameter thin-walled tube; The major diameter to thickness ratio refers to the outer diameter of the pipe: wall thickness ≥50.

4. The creep correction method of titanium alloy pipe according to claim 2, characterized in that: When the titanium alloy pipe to be corrected is a high-strength cold-rolled, cold-spun or machined pipe, holes are respectively punched at the upper and lower ends of the pipe to be corrected, a steel rod is inserted into the hole at the upper end, and the titanium alloy pipe is hoisted in a vertical vacuum heat treatment furnace using the steel rod at the upper end; a steel rod is inserted into the hole at the lower end, and the heavy object is hoisted on the steel rod at the lower end.

5. The creep correction method for titanium alloy pipe according to claim 3, characterized in that: When the titanium alloy tube to be corrected is a cold-rolled, cold-spun or machined titanium alloy thin-walled tube with a large diameter-to-thickness ratio, a steel tube of equal length is lined inside the titanium alloy tube, holes are punched at the upper and lower ends of the titanium tube and the steel tube respectively, a steel rod is inserted into the holes at the upper ends of the titanium tube and the steel tube in turn, and the titanium alloy tube is hoisted in a vertical vacuum heat treatment furnace using the steel rod at the upper end; a steel rod is inserted into the holes at the lower ends of the titanium tube and the steel tube in turn, and the weight is hoisted on the steel rod at the lower end.

6. The creep correction method for titanium alloy pipe according to claim 1, characterized in that: The heat treatment temperature is 500°C ~ 600°C, and the insulation time is 5h ~ 8h.

7. The creep correction method for titanium alloy pipe according to claim 1, characterized in that: After the heat treatment is completed, the furnace is filled with argon gas for rapid cooling, and the steel is taken out of the furnace when it is cooled to below 100°C.

8. The creep correction method for titanium alloy pipe according to claim 1, characterized in that: Before heating to 500℃~600℃, evacuate the furnace to a vacuum of less than 1×10 -2 Pa.

9. The creep correction method of titanium alloy pipe according to claim 1, characterized in that: After creep correction of titanium alloy pipe, the straightness is ≤1mm / m.

Images