CN114657417B - A high-strength plastic titanium alloy suitable for cold deformation processing and its preparation method - Google Patents

Abstract

The invention discloses a high-strength plastic titanium alloy suitable for cold deformation processing and a preparation method thereof, wherein the high-strength plastic titanium alloy comprises the following components in percentage by mass: 3.5 to 4.5 percent of Mo, 2.5 to 3.5 percent of Cr, 0.7 to 1.5 percent of Fe, less than 0.35 percent of O and the balance of Ti; the preparation method comprises the following steps: proportioning raw materials, and preparing a titanium alloy ingot by vacuum melting; hot working at 1150-720 deg.c; carrying out solution treatment at 790-730 ℃ to obtain the finished product of the high-strength plastic titanium alloy, or further carrying out aging treatment at 430-530 ℃ to obtain the finished product of the high-strength plastic titanium alloy, or carrying out cold rolling and aging heat treatment after heat treatment to obtain the finished product of the high-strength plastic titanium alloy. The invention improves the plastic deformation capability of alpha phase at room temperature and high temperature by adding Mo, cr and Fe strong beta stabilizing elements and not adding alpha stabilizing elements, improves the cold deformation processing performance and the matching of strength and plasticity of the titanium alloy by regulating the content and the element distribution of alpha and beta phases through thermal mechanical treatment, and has the characteristics of low cost, easy cold processing and excellent strong plastic matching.

Description

A high-strength plastic titanium alloy suitable for cold deformation processing and its preparation method

technical field

The invention belongs to the technical field of titanium alloy materials, and in particular relates to a high-strength plastic titanium alloy suitable for cold deformation processing and a preparation method thereof.

Background technique

Titanium alloys have the advantages of low density, high specific strength, corrosion resistance, and non-magnetic properties. As structural materials, they are widely used in aerospace, petrochemical, marine engineering, and weaponry. At present, α+β two-phase titanium alloy is the most used type of titanium alloy, but the strength of this type of alloy is usually lower than 1000MPa, such as TC4, TA15, etc., and it is difficult to process cold deformation. Although metastable β titanium alloys can obtain higher strength after solution aging heat treatment, such as TB5, TB6, Ti-15-3, Ti-5553, β21s, etc., these alloys have low plasticity when the strength is greater than 1250MPa. The problem, taking Ti-5553 (Ti-5Al-5Mo-5V-3Cr, US patent) as an example, when its tensile strength is 1500MPa, it has almost no plasticity. In addition, the commonly used metastable β high-strength titanium alloys are added with relatively high content of expensive alloying elements such as V, Nb, and Zr, and most of the alloys need to be plastically processed by thermal deformation, which has long process, large material loss, and high production cost. High, large-scale industrial application is limited. At the same time, compared with the α+β two-phase titanium alloy, the single-phase metastable β titanium alloy has the problem of low yield strength, which makes it difficult to meet the needs of some industrial applications.

Therefore, how to improve the strength and plastic matching of titanium alloys and improve their cold deformation processing capabilities is the main problem facing the expansion of titanium alloy engineering applications.

Contents of the invention

In order to solve the above technical problems, the present invention provides a method for preparing high-strength plastic titanium alloy and its forged and rolled materials; at the same time, the present invention has developed a cold deformation processing method and a subsequent heat treatment method for the alloy. After heat treatment, the strength of the alloy is greater than 1350MPa, and the elongation is greater than 10%, which can greatly expand the application range of the existing high-strength titanium alloy.

The complete technical scheme of the present invention comprises:

A high-strength and high-plasticity titanium alloy, including: Mo 3.5-4.5%, Cr 2.5-3.5%, Fe 0.7-1.5%, O<0.35%, the balance is Ti and unavoidable impurities, and the alloy structure is α and β phase, wherein the alpha phase content is greater than 5%.

A method for preparing a high-strength and high-plasticity titanium alloy forging processing material, comprising the following steps:

A1: According to the mass fraction of Mo 3.5-4.5%, Cr 2.5-3.5%, Fe 0.7-1.5%, O<0.35%, the balance is Ti and unavoidable impurities for raw material ratio;

A2: using vacuum melting equipment to melt the raw materials obtained in step A1 to obtain an alloy ingot with uniform composition;

A3: The alloy ingot obtained in the step A2 is subjected to billet forging and re-forging, and then cooled to room temperature to obtain a forged material;

A4: performing solution treatment on the finished product obtained in step A3, and then cooling to room temperature to obtain a titanium alloy;

A5: performing aging treatment on the titanium alloy obtained in step A4, and cooling to room temperature to obtain a high-strength and high-plasticity titanium alloy;

Further, in step A3, the billet forging process is that the first heat is taken out at 1050-1150°C for heat preservation, and three piers and three pulls are taken out, and the second heat is taken out with heat preservation at 940-980°C for three piers and three pulls;

Further, the forging process in step A3 is changed to five times of piercing and pulling: the first fire is taken out after heat preservation at 730-770°C for one pier and one pull; The third fire is kept warm at 730-770°C and taken out for one pier and one pull. The fourth fire is taken out after 730-770°C for one pier and one pull. Dimensions of forging blank;

Further, the solution treatment temperature in step A4 is 730-780°C, and the holding time is 0.5-3h;

Further, the aging treatment temperature in step A5 is 430-530°C, and the holding time is 1-8h;

A method for preparing a high-strength and high-plasticity titanium alloy rolling material, comprising the following steps:

B1: Machining the billet forging billet obtained in the above step A3 to obtain a rolling billet with qualified quality;

B2: heating and insulating the billet obtained in the step B1, and then performing multi-pass rolling to obtain a rolled alloy;

B3: performing solution treatment on the as-rolled alloy obtained in step B2, and then cooling to room temperature;

B4: performing aging treatment on the solid solution alloy obtained in step B3, and cooling to room temperature to obtain a high-strength and high-plasticity titanium alloy;

Preferably, the rolling temperature in step B2 is 730-770°C, the reheating and holding time after each rolling pass is 5min-10min, and the total deformation is greater than 85%;

Further, the solution treatment temperature in step B3 is 730-780°C, and the holding time is 0.5-3h;

Further, the aging treatment temperature in step B4 is 430-530°C, and the holding time is 1-8h;

A method for cold deformation processing and heat treatment of a high-strength and high-plasticity titanium alloy, comprising the following steps:

C1: Machining the solid solution alloy obtained in the above step A4 or B3 to obtain a qualified billet;

C2: heat-treating the billet obtained in step C1, and then water-cooling and quenching to room temperature;

C3: performing cold deformation on the quenched titanium alloy in the step C2 to obtain a cold deformed alloy; the cold deformation processing method can be cold rolling, cold spinning, or cold extrusion.

C4: heat-treating the cold deformed alloy in step C3, and then air-cooling to obtain a finished product.

Further, the heat treatment temperature in step C2 is 630-700°C, and the heat is kept for 15-60min;

Further, the heat treatment process in step C4 can be directly heat preservation at 430-530°C for 30min-5h;

Further, the heat treatment process of step C4 can also be firstly heat preservation at 730-780°C for 0.5-1h, then air cooling to room temperature, and then heat preservation at 430-530°C for 30min-5h.

The application of the prepared high-strength plastic titanium alloy in the manufacture of parts such as plates, rods, pipes and profiles.

The present invention has the advantage over prior art that:

1) In order to solve the problem of difficult cold deformation processing of titanium alloys in the prior art, the components used in the titanium alloys of the present invention only include five elements: Ti, Mo, Cr, Fe and O, without adding α-stabilizing elements such as Al and Sn, Therefore, the rheological resistance during deformation processing, especially cold deformation processing, is reduced, the plastic processing performance of the alloy is improved while the cost is reduced, and the alloy has excellent strong-plastic matching.

2) At the same time, in order to obtain a good yield strength and avoid the alloy structure from becoming a single-phase metastable β alloy, without adding α stable elements such as Al and Sn, the present invention combines the Heat treatment regulates the content of α phase in the structure and the distribution of alloying elements in α and β phases, and obtains an α+β two-phase titanium alloy with an equiaxed α phase volume fraction greater than 10%, and has excellent cold deformation ability, deformation The amount can reach more than 75%, which overcomes the deficiency that the traditional two-phase titanium alloy is difficult to achieve large deformation amount cold working.

3) The titanium alloy of the present invention can be applied to the production of rods, plates, pipes and further cold processed into parts, etc., and has wide application value in the fields of aviation, aerospace, petrochemical and weaponry.

Description of drawings

Fig. 1 is the optical structure of the solid solution titanium alloy after forging in Example 1 of the present invention.

Fig. 2 is the tensile properties of the heat-treated titanium alloy in Example 1 of the present invention after forging.

Fig. 3 is a scanning electron micrograph of the alloy in solid solution and aging state after rolling in Example 2 of the present invention.

Fig. 4 shows the tensile properties of the cold-rolled heat-treated titanium alloy in Example 3 of the present invention.

Fig. 5 is a comparative view of the appearance and appearance of cold rolling in Example 3 of the present invention.

detailed description

Next, with reference to the accompanying drawings, by describing the accompanying drawings, the specific embodiments of the present invention, such as the mutual position and connection relationship between the designed parts, the function and working principle of each part, the manufacturing process and the operation and use method, etc., will be made. Further detailed descriptions are provided to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concepts and technical solutions of the present invention.

Example 1

The high-strength and high-plasticity titanium alloy of this embodiment is composed of the following components in weight percentage: Mo 4.23%, Cr 2.90%, Fe 0.80%, O<0.18%, and the balance is Ti and unavoidable impurities. In this example, through reasonable component design, only five elements including Ti, Mo, Cr, Fe and O are included, and the addition of α-stabilizing elements such as Al and Sn is avoided. The content of α phase in the medium and the distribution of alloying elements in α and β phases result in the α+β two-phase titanium alloy, which improves the plastic workability of the alloy while reducing the cost, and makes the alloy have excellent strong plasticity matching.

The preparation method of the high-strength and high-plasticity titanium alloy in this embodiment comprises the following steps:

S1 prefabricated electrode: 1.32kg Ti-32Mo master alloy, 0.3kg chromium sheet and 0.09kg iron particles are uniformly mixed, the mixed material is placed in the middle of 8.29kg sponge titanium and pressed to form a block prefabricated electrode; the chromium The mass purity of both the flakes and the iron particles is 99.9%, and the maximum diameter of the iron particles is greater than 3 mm.

S2 ingot casting: connect the prefabricated electrodes obtained in S1 to form electrodes, and perform three smelting in a vacuum consumable electric arc furnace to obtain an ingot.

S3 billet forging: the ingot obtained in S2 is removed from the surface skin and the riser in turn to obtain a 150kg billet with a diameter of 215mm and a length of 440mm. The first fire-opening forging with three piers and three pulls is carried out on the forging machine. The process is to first pier thick to a height of 300mm, then to draw hexagonal rounds to a diameter of 200mm, and then to repeat the pier and pull twice, and air-cool after forging; followed by holding at 950°C for 4 hours The second fire blank forging of three piers and three pulls, the process is to first pier thick to 300mm in height, then draw hexagonal rounding to a diameter of 200mm, repeat the piercing twice, and finally obtain a titanium alloy forging billet; the total deformation of the blank forging is 150%.

S4 modified forging: the titanium alloy forging billet obtained in S3 is subjected to five fires and modified forging: the first fire: put it in a resistance furnace and heat it at 760°C for 3 hours, take it out and perform one pier and one pull forging: first pier the billet thick to 410mm, then turned over 180 degrees, the thickness of the pier to 300mm, and then drawn hexagonally along the axial direction, and rounded to a diameter of 200mm, and then air-cooled; the second fire: heat and hold at 820°C for 3 hours, take it out and carry out two-pier and two-pull forging: first Thicken the billet to 410mm, then turn it over 180 degrees, make the pier thick to 300mm, then draw hexagonal along the axial direction, and roll it to a diameter of 200mm, repeat the pier drawing once, and then air-cool; the third fire: heat and hold at 760°C for 3h , take it out for one pier and one pull forging: firstly pier the billet to 410mm thick, then turn it over 180 degrees, pier thick to 300mm, then pull hexagonal along the axial direction, and then return to the furnace; the fourth fire: hold at 760°C for 1h, take it out for a Pier one pull forging: firstly pier the billet to 410mm thick, then turn it over 180 degrees until the pier is thick to 300mm, then draw hexagonal along the axial direction, and then return to the furnace; fifth fire: keep warm at 760°C for 1 hour, take it out and elongate: the billet Draw a hexagon along the axial direction and roll it to a diameter of 160mm.

S5 solution treatment: the forged billet obtained in S4 is solution treated at 750° C./1 h and cooled to room temperature with water to obtain a solid solution alloy.

S6 aging heat treatment: artificially aging the solid solution alloy obtained in S5 at 470° C. for 6 hours to obtain an aged alloy.

The structure was observed with an optical microscope, and the results showed that the solid solution alloy contained an equiaxed α phase with a volume fraction of about 12%, as shown in Figure 1. A model INSTRON 8801 universal material testing machine was used for the uniaxial tensile performance test, and a typical tensile curve is shown in Figure 2. It can be seen that both solid solution and aging alloys have good matching of strength and plasticity. Among them, the tensile strength of the solid solution alloy is 1031MPa, and the elongation is 34.0%; the tensile strength of the solid solution aging alloy is 1141MPa, and the elongation is 11.1%.

Example 2

The ingot obtained in step S2 in Example 1 was forged into a billet, and then placed in a resistance furnace and heated to 740°C for 1 hour, and then rolled for multiple passes to remove the surface oxide layer and clean it to obtain a rolled titanium alloy. plate; in the multi-pass rolling process, after each pass rolling, the titanium alloy forging billet is put into a resistance furnace and heated to 740°C and kept for 10 minutes; the total deformation of the multi-pass rolling is 80 %.

The as-rolled alloy was subjected to solution treatment at 750°C/30min, and then water-cooled to room temperature. The obtained solid solution structure contained equiaxed α-phase with a volume fraction of about 10%, its tensile strength was 1168MPa, and its elongation was 36.2%. .

Artificially aging the solid solution alloy at 480°C for 4 hours, the obtained aged structure is a two-state structure, as shown in Figure 3, which contains about 15% of the primary equiaxed α phase and a large amount of remaining β phase in the region. ultrafine α phase. Tensile test results show that the tensile strength of the aged alloy is 1326MPa, and the elongation is 16%.

Example 3

The present embodiment is the preparation method of cold-rolled plate, and concrete steps are:

S1: Machining the solid solution forging blank obtained in Step S4 of Example 1 into a slab.

S2: heat the slab in step S1 at 650°C for 30 minutes, adjust the content and element distribution of α and β phases in the structure, and then water-cool and quench to room temperature; rolling is directly heat-treated at 650°C in the forged state.

S3: Remove scale and clean the slab in step S2, and perform multi-pass cold rolling deformation at room temperature, with a total deformation greater than 85%, to obtain a plate with a thickness of 1.5mm; Figure 5a shows the appearance of the cold-rolled plate , it can be seen that the surface quality is good.

S4: The S3 cold-rolled sheet was aged at 460° C. for 1 hour, the tensile strength was 1460 MPa, and the elongation was 8.3%.

S5: The S3 cold-rolled sheet is subjected to solution treatment at 750°C/30min. The obtained structure type is an equiaxed α phase with a volume fraction of about 12% in the β matrix. The tensile strength and elongation of the alloy are 1169MPa and 1169MPa respectively. 36.0%.

S5: The solid solution alloy obtained in S5 was aged at 450°C for 6 hours. It is different from the solid solution structure. A large number of fine equiaxed α phases are precipitated in the structure. The tensile curve is shown in Figure 4. The tensile strength of the alloy is The strength and elongation are 1407MPa and 14.0%, respectively.

In order to compare and illustrate the beneficial effect of step S2, the solid solution plate at 730-780°C was directly cold-rolled, and it was found that the alloy had poor cold-rolling deformation ability and was easy to crack during rolling, as shown in Figure 5b.

Example 4

The high-strength plastic titanium alloy of this embodiment is composed of the following components in weight percentage: Mo 3.8%, Cr 3.30%, Fe 1.22%, O 0.27%, and the balance is Ti and unavoidable impurities. The specific preparation steps of the forging billet are the same as those in Example 1, and will not be repeated here.

The forged billet of Example 4 was solution treated at 780°C for 2 hours, cooled to room temperature with water, and the equiaxed α phase containing 10% volume fraction in the solid solution alloy was obtained, the tensile strength was 1108MPa, and the elongation was 36%; The solid solution alloy was aged at 500℃ for 6h, and the tensile strength and elongation were 1285MPa and 18%, respectively.

Example 5

In this embodiment, the forged billet of embodiment 4 is heated and kept at 750° C. for multiple passes of hot rolling, and the specific steps are the same as those of embodiment 2, and will not be repeated here. The hot-rolled sheet was solution-treated at 770°C for 2 hours, cooled to room temperature with water, and its tensile strength was 1132MPa, and its elongation was 34%. 1387MPa and 13%.

Example 6

In this example, the hot-rolled plate of Example 5 is solution-treated at 770°C for 2 hours, then kept at 680°C for 30 minutes, water-cooled and quenched to room temperature, and then cold-rolled and deformed. The specific steps are the same as in Example 3, and will not be repeated here. repeat. The cold-rolled and deformed plate was solution-treated at 760°C for 2 hours, and its tensile strength and elongation were 1145MPa and 34% respectively; the cold-rolled solid-solution alloy was aged at 460°C for 4 hours, and the tensile strength and elongation were respectively 1415MPa and 12%.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical aspects of the present invention. within the scope of protection of the scheme.

Claims (12)

1. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing, characterized in that, the alloy components are: according to the mass fraction Mo 3.5 ~ 4.5%, Cr 2.5 ~ 3.5%, Fe 0.7 ~ 1.5%, O< 0.35%, the balance is Ti and unavoidable impurities, the alloy structure is two phases of α and β, and the content of α phase is more than 5%; The preparation process comprises the following steps: S1: According to the mass fraction Mo 3.5~4.5%, Cr 2.5~3.5%, Fe 0.7~1.5%, O<0.35%, the balance is Ti and unavoidable impurities for raw material ratio; S2: smelting the raw materials obtained in step S1 to obtain ingots; S3: Heat the titanium alloy ingot obtained in step S2 at 1050-1150°C, take it out and perform the first billet forging for three piers and three pulls; then heat it at 940-980°C, and then take it out for three piers and three pulls The second billet forging; the total deformation of the billet forging is not less than 150%; S4: Carry out the titanium alloy forging billet obtained in step S3 for 5 times of piercing, the first fire: heat and keep at 730~770°C, take it out and carry out forging with one pier and one pull; the second fire: heat and hold at 800~830°C , take it out and carry out two-pier-two-pull forging; the third fire: heat and keep at 730~770°C, take it out and carry out one-pier-one-pull forging; the fourth fire: heat and hold at 730-770°C, take it out and perform one-pier-one-pull forging; The 5th fire: Heat and keep warm at 730~770°C, take out the forging billet forged to the required size, and then air cool. 2. a kind of high-strength plastic titanium alloy preparation method suitable for cold deformation processing according to claim 1, is characterized in that, Also includes S5: performing solid solution treatment on the forged billet obtained in step S4 at 730-790°C, and then air-cooling or water-cooling to room temperature; the volume fraction of α phase in the obtained solid-solution alloy structure is greater than 5%, and its tensile strength is Greater than 1000MPa, elongation greater than 30%. 3. a kind of high-strength plasticity titanium alloy preparation method suitable for cold deformation processing according to claim 2, is characterized in that, Also includes S6: artificially aging the solid solution alloy obtained in step S5 at 430-530°C for 1h-8h; the tensile strength of the obtained aged alloy is greater than 1250MPa, and the elongation is greater than 10%. 4. a kind of high-strength plastic titanium alloy preparation method suitable for cold deformation processing according to claim 1, is characterized in that, It also includes S5: rolling the forged slab obtained in step S4 at 710-780°C for multiple passes; during the multi-pass rolling process, after each pass, put it back into the resistance furnace and heat it to Rolling temperature and heat preservation for 5 minutes to 10 minutes; the total deformation of the multi-pass rolling is greater than 85%. 5. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 4, further comprising S6: performing solid solution treatment on the rolled alloy obtained in step S5 at 730-780°C , followed by water cooling to room temperature; the volume fraction of α phase in the obtained solid solution alloy structure is greater than 10%, the tensile strength is greater than 1050MPa, and the elongation is greater than 35%. 6. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 5, further comprising S7: subjecting the solid solution alloy obtained in step S6 to 430-530°C for 1h-8h Artificial aging; the tensile strength of the obtained aged alloy is greater than 1350MPa, and the elongation is greater than 12%. 7. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 1, 2 or 5, further comprising the steps of: 1) Heat the alloy at 630~700°C for 30min-5h, and quench to room temperature, the volume fraction of α phase in the structure is greater than 15%; 2) Machining the heat-treated alloy in step 1) into a slab, and performing multi-pass cold deformation at room temperature, the total deformation of the multi-pass cold deformation is greater than 85%; 3) The cold deformed alloy in step 2) is directly artificially aged at 430~530°C for 30min~5h, and the tensile strength of the obtained aged alloy is greater than 1450MPa, and the elongation is greater than 10%. 8. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 1, 2 or 5, further comprising the steps of: 1) Heat the alloy at 630~700°C for 30min-5h, and quench to room temperature, the volume fraction of α phase in the structure is greater than 15%; 2) Machining the heat-treated alloy in step 1) into a slab, and performing multi-pass cold deformation at room temperature, the total deformation of the multi-pass cold deformation is greater than 85%; 3) Step 2) The cold deformed alloy is kept at 730~780°C for 0.5~1h, then air cooled to room temperature, and then aged at 430~530°C for 30min~5h. The tensile strength of the obtained aged alloy is greater than 1350MPa , The elongation is greater than 15%. 9. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 1, 2 or 5, further comprising: 1) Heat the alloy at 790-820°C for 30min-2h, cool in the furnace to 620-670°C for 30min-5h, and then air-cool, the volume fraction of α phase in the structure is greater than 15%; 2) Machining the heat-treated alloy in step 1) into a slab, and performing multi-pass cold deformation at room temperature, the total deformation of the multi-pass cold deformation is greater than 85%; 3) The cold deformed alloy in step 2) is directly artificially aged at 430~530°C for 30min~5h, and the tensile strength of the obtained aged alloy is greater than 1300MPa, and the elongation is greater than 8%. 10. A method for preparing a high-strength plastic titanium alloy suitable for cold deformation processing according to claim 1, 2 or 5, further comprising: 1) Heat the alloy at 790-820°C for 30min-2h, cool in the furnace to 620-670°C for 30min-5h, and then air-cool, the volume fraction of α phase in the structure is greater than 15%; 2) Machining the heat-treated alloy in step 1) into a slab, and performing multi-pass cold deformation at room temperature, the total deformation of the multi-pass cold deformation is greater than 85%; 3) The cold deformed alloy in step 2) is kept at 730~780°C for 0.5~1h, then air-cooled to room temperature, and then aged at 430~530°C for 30min~5h. The tensile strength of the aged alloy obtained is greater than 1250MPa, elongation greater than 12%. 11. A high-strength plastic titanium alloy suitable for cold deformation processing obtained according to the preparation method described in any one of claims 1-10. 12. The application of the high-strength plastic titanium alloy according to claim 11 in the manufacture of plates, rods, pipes and profiles.

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