CN110592425B

CN110592425B - A kind of high impact toughness titanium alloy and method for preparing seamless pipe using titanium alloy

Info

Publication number: CN110592425B
Application number: CN201910824117.4A
Authority: CN
Inventors: 宋德军; 陶欢; 李冲; 杨胜利
Original assignee: 725th Research Institute of CSIC
Current assignee: 725th Research Institute of CSIC
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2022-03-11
Anticipated expiration: 2039-09-02
Also published as: CN110592425A

Abstract

The invention discloses a high impact toughness titanium alloy, which comprises 4.0-9.0% of Al, 0.5-5.0% of Mo, 1-5% of Zr, 1-5% of Nb, 0.2-2.0% of Fe, and the balance of Ti and impurities. The method for preparing the seamless pipe by utilizing the high-impact-toughness titanium alloy comprises the following steps: weighing an aluminum-niobium intermediate alloy, a molybdenum block, pure sponge zirconium, iron nails and sponge titanium according to the requirements of chemical components, mixing, pressing into an electrode rod, and then putting into a vacuum consumable arc furnace for secondary smelting to obtain a titanium alloy ingot; cogging and forging a titanium alloy ingot at 1150 ℃, and performing forging change at 970-1020 ℃ to obtain a bar blank; heating the bar blank to 950-1200 ℃; the bar billet is subjected to cross rolling and piercing to obtain a tube blank; performing hot rolling on the tube blank by utilizing the waste heat after the oblique rolling perforation, and then performing fixed diameter reduction to obtain a tube; and (4) carrying out heat treatment, straightening, saw cutting, inspection and warehousing on the pipe. The seamless pipe prepared by the titanium alloy has high strength, high plasticity, high low-temperature impact toughness and good corrosion resistance, and meets the application requirements of severe working conditions of oil wells and gas wells.

Description

High-impact-toughness titanium alloy and method for preparing seamless pipe by using titanium alloy

Technical Field

The invention relates to the field of manufacturing of aluminum alloy materials and seamless pipes, in particular to a high-impact-toughness titanium alloy and a method for preparing a seamless pipe by using the titanium alloy.

Background

The titanium and the titanium alloy have small density, high specific strength, excellent corrosion resistance, good medium-high temperature mechanical property, excellent anti-fatigue and creep property and huge application potential in the petrochemical industry. The titanium alloy pipe has good corrosion resistance, particularly seawater corrosion resistance and biological corrosion resistance, and is widely applied to the petrochemical industry. SY/T6896.3-2016 technical Specification No. 3 for Special pipes in the oil and gas industry: the requirements of titanium alloy oil pipe on the manufacturing process of the titanium alloy oil pipe are as follows: the titanium alloy oil pipe is manufactured by adopting a seamless titanium alloy pipe. The low-cost preparation technology of the titanium alloy seamless pipe for the petrochemical industry is always a research hotspot of all countries in the world.

The oil well pipe is subjected to various actions such as underground stress, pulling, twisting and the like, the internal pressure of dozens of megapascals is born, and the stress condition is complex. Generally, the impact energy of a P110 steel oil pipe reaches about 200J, while the impact energy of a P110 steel grade titanium alloy is usually 30-50J, under the condition, an oil field user thinks that the titanium alloy has better corrosion resistance, but the impact toughness is further improved so as to improve the safety and reliability of a pipe column. The domestic research unit improves the commonly used titanium alloy such as TC4, but the impact toughness is not improved. At present, the development mode of the titanium alloy oil pipe in China basically adopts the existing titanium alloy to carry out performance assessment as the main mode, and rarely carries out new material development. Therefore, the titanium alloy oil pipe is slowly applied in China, and the titanium alloy seamless pipe with certain length and wall thickness and excellent mechanical property has certain difficulty in processing because of large room temperature deformation resistance of the titanium alloy.

Therefore, it is necessary to find a titanium alloy with high impact toughness and a method for preparing seamless pipes by using the titanium alloy so as to meet the use requirements of the petrochemical industry.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a high-impact-toughness titanium alloy and a method for preparing a seamless pipe by using the titanium alloy.

In order to achieve the purpose, the invention adopts the specific scheme that:

a high impact toughness titanium alloy, its chemical composition requires to be Al4.0-9.0%, Mo0.5-5.0%, Zr 1-5%, Nb 1-5%, Fe 0.2-2.0%, the rest is Ti and inevitable impurity; wherein the content of impurities satisfies N is less than or equal to 0.05%, C is less than or equal to 0.1%, H is less than or equal to 0.015%, and O is less than or equal to 0.15%.

A method for preparing a seamless pipe by using a high-impact-toughness titanium alloy mainly comprises the following steps:

step one, ingot preparation: weighing an aluminum-niobium intermediate alloy, a molybdenum block, pure sponge zirconium, iron nails and sponge titanium according to the requirements of chemical components, mixing, pressing into an electrode rod, and then putting into a vacuum consumable arc furnace for secondary smelting to obtain a titanium alloy ingot;

step two, preparing a bar blank: cogging and forging the titanium alloy ingot obtained in the step one at 1150 ℃, and forging again at 970-1020 ℃ to obtain a bar blank;

step three, cross piercing: heating the bar blank obtained in the step two in a heating furnace to 950-1200 ℃, and then preserving heat, wherein the heat preservation time is the diameter x (0.5-1.1) min/mm of the bar blank; adopting a molybdenum-based alloy or high alloy top, coating a lubricant on the head, placing the lubricant in the central hole of the heated bar blank, and perforating to obtain a tube blank;

step four, hot rolling and fixed reducing: hot rolling the tube blank obtained in the step three, spraying borax into the tube blank before hot rolling, controlling the deformation to be 50-70%, and then performing fixed diameter reduction to obtain a tube;

step five, heat treatment: placing the pipe obtained in the fourth step into a heat treatment furnace for heat treatment, wherein the heat treatment temperature is 800-980 ℃;

step six, post-treatment: and (4) straightening, sawing, inspecting and warehousing the heat-treated pipe.

Preferably, the requirement of the tube blank produced in the third step is that the outer diameter/wall thickness is 9-12.

Preferably, in the third step, a micro-oxidation atmosphere is kept in the heating furnace in the bar blank heating process, the micro-oxidation atmosphere is a mixed atmosphere of air and natural gas, and the micro-oxidation atmosphere is realized by adjusting the ratio of the air to the natural gas (the ratio of the air to the natural gas can be adjusted according to needs). Maintaining the micro-oxidizing atmosphere in the furnace is beneficial to reducing the possibility of hydrogen absorption of the titanium alloy.

Preferably, in the fourth step, the outer diameter reduction ratio in the diameter reduction process is set to 20 to 30%, and the thickness increase amount is equal to (10% to 15%) wall thickness x after hot rolling.

Preferably, in the sixth step, the pipe is heated to 600-700 ℃ for straightening treatment, and the bending degree of the straightened pipe is less than 1.5 per mill of the total length of the pipe. The pipe prepared by the method is high in strength, and can be straightened only by heating the pipe to 600-700 ℃.

In the third step, the lubricant used for the cross piercing is glass powder lubricant.

Wherein, the hot rolling in the fourth step is carried out by utilizing the residual heat after the cross rolling perforation, and the resources can be saved on the basis of realizing the hot rolling. Spraying borax in the pipe blank before hot rolling, and lubricating the inner wall of the pipe by using the borax to obtain the high-strength seamless pipe.

In the aspect of process adaptability, the surface of the titanium alloy is easy to crack in the heating process and needs to be repeatedly polished, so that the production efficiency is low. The alloy greatly reduces the surface cracking of the alloy and improves the material utilization rate by adding the Fe element. This is because Fe is either substitutionally or interstitially soluble in α -Ti. When Fe is dissolved in the metal interstitials as metal impurity atoms having a relatively small atomic radius, such rapidly diffusing impurities strongly accelerate the diffusion of the matrix material, especially when the temperature is in a certain range below the β -transus temperature. In this temperature range, there are Fe impurity atoms from the high-speed moving impurity-vacancy pairs that are interstitially dissolved in the matrix, which results in a reduction in the matrix diffusion activation energy, promotes diffusion of the matrix material, and increases the effective diffusion capacity of the alloy. When the temperature is close to the phase transition point, dislocation climbing is realized by means of diffusion of vacancies or interstitial atoms, the addition of Fe can generate an impurity-vacancy pair, and meanwhile, the diffusion of the interstitial atoms is enhanced, so that the climbing movement of edge dislocation can be promoted, and the deformation resistance of the titanium alloy is greatly reduced.

Has the advantages that:

1. the invention provides a method for improving the tensile strength and the lasting strength of the alloy by taking Ti as a matrix and Al, Mo, Zr, Nb and Fe as main alloy elements, wherein the Al element is a main strengthening element, so that the tensile strength and the lasting strength of the alloy can be greatly improved; the Mo element is a beta stable element, so that the excellent process plasticity of the alloy is ensured while the room temperature and high temperature performance of the alloy is improved, and the simultaneous addition of two elements is more favorable for improving the comprehensive performance than the addition of only one element; zr is a neutral element, can improve the heat strength of the alloy without influencing the heat stability of the alloy, and refines grains. The Nb element does not greatly contribute to the strength of the titanium alloy, but can greatly improve the thermal stability and the corrosion resistance of the titanium alloy. Fe is a beta stable element, the room temperature strength of the titanium alloy can be greatly improved, the high temperature strength is reduced, the impact toughness and the elongation are not influenced, and the material is ensured to have good processability.

2. The preparation method can realize the mass production of the titanium alloy seamless pipe, and has high efficiency and low cost. And a stable oxide layer is arranged on the surface of the seamless pipe subjected to heat treatment, so that the hardness of the surface of the pipe can be improved while the material is protected, and the wear resistance of the pipe is enhanced. In addition, the oxide layer is an insulating layer, so that the galvanic corrosion problem when the oxide layer is in contact with dissimilar metals can be well solved.

3. The titanium alloy pipe prepared by the invention has high strength, high plasticity, high low-temperature impact toughness and good corrosion resistance, and meets the application requirements of severe working conditions of oil wells and gas wells.

Detailed Description

The high impact toughness titanium alloy prepared by the invention comprises the following chemical components: 4.0 to 9.0 percent of Al, 0.5 to 5.0 percent of Mo, 1 to 5 percent of Zr, 1 to 5 percent of Nb, 0.2 to 2.0 percent of Fe and the balance of Ti. Wherein the content of impurities satisfies N is less than or equal to 0.05%, C is less than or equal to 0.1%, H is less than or equal to 0.015%, and O is less than or equal to 0.15%.

step one, ingot preparation: mixing the aluminum-niobium intermediate alloy, the molybdenum block, the pure sponge zirconium, the iron nail and the sponge titanium according to the chemical component requirements, pressing into an electrode bar, and then putting into a vacuum consumable arc furnace for secondary smelting to obtain a titanium alloy ingot;

step two, preparing a bar blank: cogging and forging a titanium alloy ingot at 1150 ℃, and performing forging change at 970-1020 ℃ to obtain a bar blank;

step three, cross piercing: heating the bar blank in a heating furnace to 950-1200 ℃, and preserving heat after the bar blank is heated to the temperature, wherein the heat preservation time is the diameter x (0.5-1.1) min/mm of the bar blank; adopting a molybdenum-based alloy or high alloy top, coating a lubricant on the head, placing the lubricant in a central hole of a bar blank, and perforating to obtain a tube blank, wherein the outer diameter/wall thickness of the tube blank is 9-12;

step four, hot rolling and fixed reducing: carrying out hot rolling on the tube blank by utilizing the waste heat after the oblique rolling perforation, spraying borax serving as a lubricant into the tube blank before the hot rolling, controlling the deformation to be 50-70%, and then carrying out fixed reducing to obtain a tube, wherein the external diameter reduction proportion in the fixed reducing process is 20-30%, and the wall thickness thickening amount is equal to the wall thickness x (10-15%) after the hot rolling;

step five, heat treatment: placing the pipe in a heat treatment furnace for heat treatment, wherein the heat treatment temperature is 800-980 ℃;

step six, post-treatment: and heating the pipe subjected to heat treatment to 600-700 ℃ for straightening treatment, wherein the bending degree of the straightened pipe is less than 1.5 thousandth of the full length of the pipe, then performing saw cutting, inspection, treatment by adopting a grinding mode on the surface with local defects, and warehousing.

The seamless pipe prepared by the preparation method can be used as a titanium alloy oil well pipe product.

For a further understanding of the present invention, reference will now be made to the following examples and accompanying tables, which, however, should be construed to further illustrate the features and advantages of the present invention and not to limit the scope of the claims thereto.

The following examples use instrumentation conventional in the art. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers. In the following examples, various starting materials were used, and unless otherwise specified, conventional commercially available products were used.

Example 1

Step one, ingot preparation: mixing Al-Nb intermediate alloy, Mo block, pure sponge Zr, iron nail and sponge Ti, pressing electrode bar, and vacuum-pumpingTwice melting with self consumption

The alloy ingot of (3) has an alloy phase transition point of 973 ℃.

Step two, preparing a bar blank: cogging and forging at 1150 ℃, upsetting and pulling at 3-4 times, and forging at 960 ℃ twice, and then machining to prepare a phi 600 bar blank.

Step three, cross piercing: heating the bar to 950 ℃, then preserving heat for 420min, and then performing cross rolling perforation to prepare a tube blank with phi 630.

Step four, hot rolling and diameter fixing and reducing: and (3) hot rolling the tube blank after cross rolling perforation, spraying borax as a lubricant into the tube before hot rolling, and controlling the deformation amount to be 50-70%. And then, performing fixed reducing, wherein the outer diameter is reduced by 20-30% in the fixed reducing process, the wall thickness is thickened by about 10% of that after hot rolling, and the pipe with the diameter of phi 508 multiplied by 21 is prepared, and the maximum length of the pipe can reach 10 m.

Step five, heat treatment: and (3) placing the pipe in an electric furnace, heating to 820 ℃, keeping the temperature for 60 minutes, discharging from the furnace, and air cooling.

Step six, post-treatment: and heating the heat-treated pipe to 720 ℃, straightening on an automatic straightening machine, and sawing, inspecting and warehousing the pipe, wherein the bending degree of the pipe meets the technical requirement of less than or equal to 1.5 thousandth.

Example 2

Step one, ingot preparation: melting aluminum-niobium intermediate alloy, Mo blocks, pure sponge Zr, iron nails and sponge Ti twice through mixing, pressing electrode bars and vacuum self-consumption

The alloy ingot of (2) has an alloy phase transition point of 988 ℃.

Step two, preparing a bar blank: cogging and forging at 1150 ℃, upsetting and pulling at 3-4 times, and forging at 960 ℃ twice, and machining to prepare a phi 350 bar blank.

Step three, cross piercing: heating the bar to 1000 ℃, then preserving heat for 200min, and then performing cross rolling perforation to prepare a tube blank with phi 360.

Step four, hot rolling and fixed reducing: and (3) hot rolling the tube blank after cross rolling perforation, spraying borax as a lubricant into the tube before hot rolling, and controlling the deformation amount to be 50-70%. And then, performing fixed reducing, wherein the outer diameter is reduced by 20-30% in the fixed reducing process, the wall thickness is thickened by about 10% of that after hot rolling, and the pipe with the diameter of phi 219 multiplied by 12.7 is prepared, and the length of the pipe can reach more than 20 m.

Step five, heat treatment: the pipe is placed in a natural gas furnace with micro-oxidation atmosphere (mixed atmosphere of air and natural gas) to be heated to 980 ℃, and is taken out of the furnace for air cooling after being kept for 45 minutes.

Step six, post-treatment: and (3) heating the heat-treated pipe to 750 ℃, straightening the pipe on an automatic straightening machine, wherein the bending degree of the pipe meets the technical requirement of less than or equal to 1.5 thousandth, and then sawing, inspecting and warehousing the pipe.

Example 3

The alloy ingot of (3) has an alloy phase transition point of 983 ℃.

Step two, preparing a bar blank: cogging and forging at 1150 ℃, upsetting and drawing for 3-4 times, and forging for two times at 950 ℃ and then machining to prepare a phi 350 bar blank.

Step three, cross piercing: heating the bar to 1250 ℃, then preserving heat for 90min, and then carrying out cross rolling perforation to prepare a tube blank of phi 159.

Step four, hot rolling and diameter fixing and reducing: and (3) hot rolling the tube blank after cross rolling perforation, spraying borax as a lubricant into the tube before hot rolling, and controlling the deformation amount to be 50-70%. And then, performing fixed reducing, wherein the outer diameter is reduced by 20-30% in the fixed reducing process, the wall thickness is thickened by about 10% of that after hot rolling, and the pipe with the diameter of 42 multiplied by 4.85 is prepared, and the maximum length of the pipe can reach 20 m.

Step five, heat treatment: and (3) placing the pipe in a protective atmosphere furnace, heating to 850 ℃, keeping the temperature for 45 minutes, discharging from the furnace, and air cooling.

Step six, post-treatment: and heating the heat-treated pipe to 610 ℃, straightening on an automatic straightening machine, and sawing, inspecting and warehousing the pipe, wherein the bending degree of the pipe meets the technical requirement of less than or equal to 1.5 thousandth.

Effects of the embodiment

(1) Compositions of titanium alloy ingots prepared in examples 1 to 3 in terms of mass percent

TABLE 1 composition of titanium alloy ingots in terms of mass% (/ wt%) prepared in examples 1 to 3

(2) Mechanical property test of the titanium alloy seamless pipes prepared in examples 1 to 3

The titanium alloy seamless pipes prepared in examples 1 to 3, certain domestic P110 steel grade G3 alloy oil pipes, certain foreign Q125 steel grade G3 pipes and API relevant standard mechanical property requirements are compared, as shown in Table 2.

Table 2 comparison of titanium alloy seamless tubing prepared in examples 1-3 with prior art oil pipe and API-related standards

As can be seen from Table 2, the tensile strength, elongation and impact energy of the titanium alloy seamless pipe all meet the mechanical properties of API SPEC 5CT to P110 steel grade. And the impact energy of the titanium alloy seamless pipes prepared in the examples 1 to 3 is obviously greater than that of domestic G3 pipes of the same grade.

(3) And the corrosion resistance of the titanium alloy seamless pipes prepared in examples 1 to 3

Selecting a more serious corrosion site working condition, carrying out a simulated working condition corrosion evaluation test on the titanium alloy seamless pipe,the method for evaluating the uniform corrosion performance of the titanium alloy seamless pipe under the specific working condition mainly comprises the following two aspects: on the one hand, the evaluation test was carried out with reference to NACE-MR0175 at a temperature of 160 ℃ and H₂S partial pressure of 5MPa and CO₂The partial pressure was 11MPa, the NaCl concentration was 100000ppm Cl, elemental sulfur was 3g/L, the SSCB test period was 720 hours, and the corrosion coupon test period was 168 hours, and the test results obtained according to the above test conditions (including the A method test result, the four-point bending method test result, and the 7-day corrosion condition of the corrosion coupon) are shown in Table 3. Another aspect is to test the annual corrosion rate of seamless pipes, the test results of which are shown in table 3.

TABLE 3 Corrosion resistance test results for titanium alloy seamless tubes prepared in examples 1-3

As can be seen from Table 3, the corrosion resistance test results of the titanium alloy seamless pipes prepared in examples 1 to 3 meet the specification of NACE-MR0175 on the corrosion degree, and no obvious corrosion or pitting phenomenon is found on the surface of the seamless pipe. The annual corrosion rate of the seamless pipe is low, so that the titanium alloy seamless pipe has excellent corrosion resistance.

The seamless pipe prepared by the invention can reduce the weight of the pipe column by 40 percent, thereby improving the tensile safety coefficient of the pipe column; meanwhile, the problem of low safety caused by the conventional P110-grade tubular column can be well solved, and a reliable guarantee is provided for the improvement of the petroleum and natural gas exploitation capability in China.

The present invention provides a high impact toughness titanium alloy and a method for manufacturing seamless pipes using the same, which are described in detail above, and the principle and the specific implementation of the present invention are illustrated herein by using specific examples, which are only used to help understanding the method and the core concept of the present invention. It should be noted that any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are within the protective scope of the present invention to those skilled in the art.

Claims

1. a method of utilizing high impact toughness titanium alloy to prepare seamless pipe is characterized in that, the chemical composition weight percentage range of high impact toughness titanium alloy is: Al 8.9%, Mo 0.5-5.0%, Zr 1-5%, Nb 1-5%, Fe 1.2-2.0%, the balance is Ti and inevitable impurities; the impurity content satisfies N≤0.05%, C≤0.1%, H≤0.015%, O≤0.15%;

The preparation method of the seamless pipe mainly includes the following steps:

Step 1, ingot preparation: according to the above chemical composition requirements, respectively weigh aluminum-niobium master alloy, molybdenum block, pure zirconium sponge, iron nails, and titanium sponge and mix them, press them into electrode rods, and then put them into a vacuum consumable arc. Carry out secondary smelting in the furnace to obtain titanium alloy ingots;

Step 2, preparation of billet: the titanium alloy ingot obtained in step 1 is forged at 1150 ℃, and then forged at 970-1020 ℃ to obtain billet;

Step 3, skew rolling and piercing: place the bar obtained in step 2 in a heating furnace and heat it to 950~1200°C and keep it warm, and the holding time is the diameter of the bar × (0.5~1.1) min/mm; then use molybdenum-based alloy or The high-alloy plug, the head is coated with lubricant, and the lubricant is placed in the center hole of the bar blank after heat preservation, and the tube blank with outer diameter/wall thickness = 9~12 is obtained after perforation;

Step 4. Hot rolling and diameter reduction: hot-rolling the tube blank obtained in step 3. Hot rolling is carried out by using the waste heat after skew rolling and piercing in step 3. Before hot rolling, borax is sprayed inside the tube blank, and the deformation is controlled at 50~70%, and then sizing and reducing the diameter to get the pipe;

Step 5, heat treatment: place the pipe obtained in step 4 in a heat treatment furnace for heat treatment, and the heat treatment temperature is 800-980 ° C;

Step 6. Post-processing: straightening, sawing, inspecting, and storing the heat-treated pipes.

2. a kind of method that utilizes high impact toughness titanium alloy to prepare seamless pipe material according to claim 1, is characterized in that, in step 3, keep heating furnace in the process of billet heating to be a micro-oxidizing atmosphere, and the micro-oxidizing atmosphere is A mixed atmosphere of air and natural gas.

3. A method for preparing seamless pipes by utilizing high impact toughness titanium alloy according to claim 1, wherein in step 4, the reduction ratio of the outer diameter in the process of determining and reducing the diameter is 20-30%, and the Thickening amount = wall thickness after hot rolling × (10%~15%).

4. A method for preparing seamless pipes by utilizing high impact toughness titanium alloys according to claim 1, wherein in step 6, the pipes are heated to 600-700°C for straightening treatment, and the straightened pipes The bending degree is less than 1.5‰ of the full length of the pipe.