Preparation method for manufacturing forged and rolled Ti6Al4VELI titanium alloy bar by adding returned scraps

Abstract

The invention discloses a preparation method for forged and rolled combination of Ti6Al4VELI titanium alloy bars added with returned scraps, which specifically includes adding 30% of titanium alloy returned scraps to sponge titanium and master alloy for ingot melting. Subsequently, the ingot is successively subjected to "high-low-high" cogging forging, low-temperature forging improvement, and rolling forming of bars in the two-phase region below the β temperature. Compared with the bars formed by conventional open-die forging, by utilizing the large radial deformation amount of rolling, the number of heating times can be effectively reduced and the production efficiency can be improved. Therefore, the method of the invention combining the reduction of raw material costs and the shortening of the bar preparation process can effectively shorten the preparation cycle of titanium alloy bars, reduce production costs, reduce energy consumption and carbon emissions, can meet mass production, and has important economic and military strategic significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy material processing, and relates to a preparation method for forging and rolling combination of Ti6Al4VELI titanium alloy bars by adding recycled chips. Background Art

[0002] The Ti-6Al-4V alloy is currently the most widely used, most mature and highest-yielding two-phase titanium alloy, with medium strength and moderate plasticity; according to the content of interstitial elements, it can be divided into Ti-6Al-4V alloy and ultra-low interstitial Ti-6Al-4VELI alloy;

[0003] Ti-6Al-4VELI is obtained by adjusting and optimizing alloying elements and their contents on the basis of TC4 alloy, reducing the contents of impurity elements such as C and N, and strictly controlling the O content; then through thermo-mechanical treatment processes such as β-region hot working or β heat treatment, its damage tolerance performance is improved to meet the performance requirements of high fracture toughness (KIC) and low crack growth rate (da / dN) required for high damage tolerance and long life design; Ti-6Al-4VELI is particularly suitable for manufacturing large integral aircraft frames, beams and joints, as well as key load-bearing components with high durability requirements. Its typical application components include mid-rear fuselage load-bearing integral frames, wing beams and welded components, etc., and have been widely used in the structural forgings of fighter aircraft;

[0004] However, due to the still high production and manufacturing costs of titanium alloy materials, the application scope of titanium alloys is restricted, and at the same time, it also affects the rapid commissioning of equipment; therefore, the present invention provides a preparation method for forging and rolling combination of Ti6Al4V ELI titanium alloy bars by adding recycled materials, which can effectively reduce the melting cost of titanium alloy raw materials, reduce the number of forging heats of the bars, thereby shortening the preparation cycle and production cost of titanium alloy bars, reducing energy consumption and carbon emissions, and having important economic and military strategic significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for purifying recycled chips of titanium and titanium alloys, so as to reduce the melting cost of titanium alloy raw materials, reduce the number of forging heats of the bars, and thus effectively shorten the preparation cycle and production cost of titanium alloy bars.

[0006] The technical solution adopted by the present invention is a preparation method for forging and rolling combination of Ti6Al4VELI titanium alloy bars by adding recycled chips, which specifically includes adding 30% of titanium alloy recycled chips to sponge titanium and master alloy for ingot melting, and then the ingot is successively subjected to "high-low-high" cogging forging, low-temperature forging improvement, and rolling into formed bars in the two-phase region below the β temperature.

[0007] The characteristics of the present invention also lie in:

[0008] The preparation method of forged and rolled Ti6Al4VELI titanium alloy bars with returned scraps added is specifically implemented according to the following steps:

[0009] Step 1: Add 30% of Ti6Al4V ELI titanium alloy returned scraps to sponge titanium and master alloy for ingot melting;

[0010] Step 2: "High-low-high" cogging forging: Upset and draw forge the ingot of Ti6Al4V ELI titanium alloy with returned scraps added at 100°C - 300°C above the β transformation temperature, air cool after forging, then upset and draw forge at 30°C - 50°C below the β transformation temperature, and then upset and draw forge again at 30°C - 50°C above the β transformation temperature, and air cool after forging;

[0011] Step 3: Low-temperature secondary forging: Upset and draw forge the billet processed in Step 2 with the heating temperature at 30°C - 50°C below the β transformation temperature, and air cool after upset and draw forging;

[0012] Step 4: Rolling and forming below the β temperature: Roll the billet processed in Step 3 into a round shape with the heating temperature at 30°C - 50°C below the β transformation temperature, and air cool after rolling;

[0013] Among them, the Ti6Al4V ELI titanium alloy returned scraps in Step 1 need to be added after being purified;

[0014] Among them, in Step 2, upset and draw forge the ingot of Ti6Al4V ELI titanium alloy with returned scraps added at 100°C - 300°C above the β transformation temperature for 2 - 3 heating passes, with the deformation per pass controlled between 35% - 50%, upset and draw forge at 30°C - 50°C below the β transformation temperature for 1 - 2 times, with the deformation controlled between 30% - 50%, and then upset and draw forge again at 30°C - 50°C above the β transformation temperature for 1 - 2 heating passes, with the deformation controlled between 30% - 50%;

[0015] Among them, in Step 2, when heating the cold billet for cogging at 100°C - 300°C above the β transformation temperature, first heat the ingot to 800°C and hold for 120 min, then raise the temperature to the required temperature and hold. The heat preservation coefficient for heating cold billets is 0.7, and the heat preservation coefficient for hot billets returning to the furnace is 0.25;

[0016] Among them, in Step 3, the billet is upset and draw forged for 3 - 5 heating passes, with the deformation controlled between 30% - 50%, and air cool after each upset and draw forging;

[0017] Among them, in Step 4, the billet is rolled into a round shape in one pass with the deformation controlled between 40% - 60%;

[0018] Among them, in Steps 2 and 3, the transfer time of the blank from the heating furnace to the quick forging machine is no more than 40 °C, and the final forging temperature is not less than 800 °C.

[0019] The beneficial effects of the present invention are:

[0020] The method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention adds 30% of titanium alloy returned scrap to the sponge titanium and master alloy during ingot melting. On the premise of ensuring metallurgical quality, it reduces the raw material cost of titanium alloy melting, can recycle the national strategic rare and precious metal resources, and at the same time reduces the number of forging heats of the bar and shortens the preparation cycle through the forging-rolling combination method; effectively reduces the production cost of titanium alloy bars, and has important economic and military strategic significance. Description of the Drawings

[0021] Figure 1 is the flow chart of the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention;

[0022] Figure 2 is the macrostructure diagram of the Φ210mm bar of the Ti6Al4V ELI titanium alloy with added returned material in the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention;

[0023] Figure 3 is the macrostructure diagram of the Φ210mm bar of the Ti6Al4V ELI titanium alloy with added returned material in the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention after air burning;

[0024] Figure 4 is the microstructure diagram of the Φ210mm bar of the Ti6Al4V ELI titanium alloy with added returned material in the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention;

[0025] Figure 5 is the room temperature tensile property diagram of the Φ210mm bar of the Ti6Al4V ELI titanium alloy with added returned material in the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention;

[0026] Figure 6 is the 400 °C high temperature tensile property diagram of the Φ210mm bar of the Ti6Al4V ELI titanium alloy with added returned material in the method for preparing the forged and rolled combined Ti6Al4VELI titanium alloy bar with added returned scrap in the present invention. Detailed Embodiments

[0027] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0028] The present invention provides a preparation method for forged and rolled Ti6Al4VELI titanium alloy bars with returned chips added, as follows Figure 1 shown, which can effectively reduce the melting cost of titanium alloy raw materials, reduce the number of forging heats of bars, thereby shortening the preparation cycle and production cost of titanium alloy bars, reducing energy consumption and carbon emissions, and having important economic and military strategic significance;

[0029] Example 1

[0030] The bars are prepared through the process route of ingot melting - cogging forging - rolling forming; specifically, it includes the following steps:

[0031] Step 1, add 30% of Ti6Al4V ELI titanium alloy returned chips to sponge titanium and master alloy for ingot melting;

[0032] Step 2, "high - low - high" cogging forging: Forge the ingot of Ti6Al4V ELI titanium alloy with returned chips added by upsetting and drawing for 3 heats at 100℃ - 300℃ above the β - transformation temperature, with the deformation amount controlled between 35 - 50% for each heat. After forging, air cooling is adopted. Subsequently, conduct upsetting and drawing forging 2 times at 30℃ - 50℃ below the β - transformation temperature, with the deformation amount controlled between 30 - 50%. Then, conduct upsetting and drawing forging 2 times at 30 - 50℃ above the β - transformation temperature, with the deformation amount controlled between 30 - 50%. After forging, air cooling is adopted;

[0033] Step 3, low - temperature re - forging: Conduct upsetting and drawing forging 4 times on the billet processed in Step 2 with the heating temperature at 30℃ - 50℃ below the β - transformation temperature, with the deformation amount controlled between 30 - 50%. After upsetting and drawing forging, air cooling is adopted;

[0034] Step 4, rolling forming below the β temperature: Conduct 1 - time round rolling forming on the billet processed in Step 3 with the heating temperature at 30℃ - 50℃ below the β - transformation temperature, with the deformation amount controlled between 40 - 60%. After rolling, air cooling is adopted.

[0035] Example 2

[0036] Preferably, in Step 1, the added Ti6Al4V ELI titanium alloy returned chips need to be added after professional purification treatment;

[0037] Preferably, in Step 2, when heating the cold billet for cogging at 100℃ - 300℃ above the β - transformation temperature, first heat it to 800℃ and hold for 120 min, then raise the temperature to the required temperature and hold;

[0038] Preferably, in Step 2, the heat - preservation coefficient for heating cold billets during heat treatment is 0.7, and the heat - preservation coefficient for reheating hot billets is 0.25.

[0039] Preferably, in Steps 2 and 3, the transfer time of the blank from the heating furnace to the quick forging machine is ≤40°C, and the final forging temperature is ≥800°C.

[0040] Preferably, in Step 4, the number of rolling and rounding forming fires is no more than 1 fire.

[0041] Example 3

[0042] Experimental results:

[0043] From Figure 2 In the macrostructure diagram of the Φ210mm bar of Ti6Al4V ELI titanium alloy with added return material, it can be seen that the macrostructure of the bar is a uniform and blurred crystal, without shrinkage holes, pores, delamination, segregation, cracks, metal or non-metal inclusions, and other visible defects to the naked eye;

[0044] Figure 3 In the macrostructure diagram of the Φ210mm bar of Ti6Al4V ELI titanium alloy with added return material after air burning, it can be seen that the macrostructure after air burning is a uniform and clear crystal, without delamination;

[0045] Figure 4 In the microstructure diagram of the Φ210mm bar of Ti6Al4V ELI titanium alloy with added return material, it can be seen that the microstructure of the bar is an equiaxed α structure, and the microstructure is uniform;

[0046] Figure 5 And Figure 6 Are the room temperature and 400°C high-temperature tensile property display diagrams. It can be seen from the diagrams that all mechanical properties meet the standard requirements, and the strength-plasticity-toughness matching of the material is relatively reasonable.

[0047] The Ti6Al4V ELI titanium alloy bar with added return material produced by the forging-rolling combination preparation method of the Ti6Al4V ELI titanium alloy bar with added return material of the present invention has low raw material cost for melting, short forging preparation process, can effectively reduce the consumption of rare mineral resources and carbon emissions, and shorten the bar production cycle, and has important economic and military strategic significance.

Claims

1. A method for preparing a forged and rolled Ti6Al4VELI titanium alloy bar with returned scraps added, characterized in that, Specifically, it includes adding 30% of titanium alloy return scrap to sponge titanium and master alloy for ingot melting, and then the ingot is successively subjected to "high-low-high" cogging forging, low-temperature forging improvement, and rolling into bars in the two-phase region below the β temperature; It is specifically implemented according to the following steps: Step 1: Add 30% of Ti6Al4VELI titanium alloy return scrap to sponge titanium and master alloy for ingot melting; Step 2: "High-low-high" cogging forging: Upset and draw forge the ingot of Ti6Al4VELI titanium alloy with added return material at 100°C to 300°C above the β transformation temperature, and use air cooling after forging. Subsequently, upset and draw forge at 30°C to 50°C below the β transformation temperature, and then upset and draw forge at 30°C to 50°C above the β transformation temperature again, and use air cooling after forging; Step 3: Low-temperature forging improvement: Upset and draw forge the billet processed in Step 2 with the heating temperature at 30°C to 50°C below the β transformation temperature, and use air cooling after upset and draw forging; Step 4: Rolling into shape below the β temperature: Roll the billet processed in Step 3 into a round shape with the heating temperature at 30°C to 50°C below the β transformation temperature, and use air cooling after rolling; The Ti6Al4VELI titanium alloy return scrap in Step 1 needs to be added after being purified; In Step 2, the ingot of Ti6Al4VELI titanium alloy with added return material is upset and drawn forged for 2 to 3 heats at 100°C to 300°C above the β transformation temperature, and the deformation per heat is controlled between 35% and 50%. Upset and draw forge 1 to 2 times at 30°C to 50°C below the β transformation temperature, and the deformation is controlled between 30% and 50%. Then, upset and draw forge 1 to 2 heats at 30°C to 50°C above the β transformation temperature, and the deformation is controlled between 30% and 50%; In Step 2, when heating the cogging cold material at 100°C to 300°C above the β transformation temperature, first heat the ingot to 800°C and hold for 120 min, then raise the temperature to the required temperature and hold. The heat preservation coefficient for heating cold material in heat treatment is 0.7, and the heat preservation coefficient for hot material returning to the furnace is 0.25; In Step 3, the billet is upset and drawn forged for 3 to 5 heats, and the deformation is controlled between 30% and 50%. Air cooling is used after each upset and draw forging; In Steps 2 and 3, the transfer time of the billet from the heating furnace to the quick forging machine is not more than 40°C, and the final forging temperature is not less than 800°C; In Step 4, the billet is rolled into a round shape for 1 heat, and the deformation is controlled between 40% and 60%.

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