Patent Application
20240018625
The present invention relates to the technical field of titanium material processing, and specifically, to a method for increasing compositional uniformity of element Al in a titanium-alloy EB ingot.
Titanium alloys are widely used in aerospace, ships, weapons and equipment, chemical industries, etc., due to their high specific strength, light weight, and corrosion resistance. The conventional melting method for titanium alloys is vacuum arc remelting (VAR) with a consumable electrode. Raw materials are formulated and blended together and then pressed into an assembled electrode through welding, the electrode is subjected to double or triple VAR processing to obtain a round ingot, and then the round ingot is forged and polished into a square semi-finished product required for rolling into plates. However, this manufacturing method has a long process, a high loss, and a poor high/low-density inclusion removal. Electron-beam (EB) melting is an advanced melting method for titanium alloys to yield large-size flat ingots for direct rolling through a single melting. The method has the advantages of short production process, high production yield, and low production cost, and can effectively remove high/low-density inclusions due to high degree of vacuum and high degree of superheat of molten titanium, resulting in a refining effect.
Al is the most widely used strengthening element added in titanium alloys. In the process of titanium-alloy EB melting, a melt can reach a temperature of 1800-2200° C. and a degree of vacuum of 10−2 Pa. However, the difference in melting point between Al and Ti is 1000° C., and the difference in saturated vapor pressure between Al and Ti is several times, so Al is very easy to volatilize, causing melting loss. Any discontinuity or fluctuation in the melting process may lead to loss of Al, which makes Al one of the most difficult alloy elements to achieve stable melting loss control and uniformity in the process of titanium-alloy EB melting. In addition, compared with conventional repeated VAR, a method for preparing titanium alloy ingots through a single EB melting with no arc stirring further increases the difficulty of controlling the uniformity of element Al. Therefore, how to increase the uniformity of element Al causes a critical technical bottleneck that urgently needs to be overcome in the current titanium-alloy EB melting. Doing so not only can improve the quality of ingots and materials for subsequent processing, but also have exemplifying and referencing value for increasing compositional uniformity of other alloy elements added in EB ingots.
In the existing melting technology for titanium-alloy EB ingots, briquetting into cylinders and assembling into electrode rod materials through welding that are used in VAR melting are mostly adopted for feeding and melting. In the process of switching to a new electrode rod material that is continuously fed for melting, it is very likely for the tail of the electrode rod material to fall into the molten pool, and the electrode rod material to be fed deviating outside of the melting pattern region, even causing material blockage, which affects the melting rate and the feeding consistency and stability, and further leads to the melting loss of element Al and reduces the compositional uniformity of element Al. Moreover, in the melting process of titanium-alloy EB ingots, there is a certain time interval while an electrode rod material is being switched, which may cause dry burning of the molten pool by electron beams during the switching interval and a sudden flow increase after switching, further affecting the compositional uniformity of element Al in EB ingots. This requires improvement.
In view of deficiencies in the related art, an objective of the present invention is to provide a method for increasing compositional uniformity of element Al in a titanium-alloy EB ingot. This method can effectively resolve such problems as falling, deviation, and blockage of the electrode rod material in the process of switching to a new electrode rod material during melting for EB ingots, and can significantly improve the stability and uniformity of feeding and melting control in the melting process for titanium-alloy EB ingots, thereby increasing the compositional uniformity of element Al in EB ingots.
The technical solutions adopted by the present invention to resolve the above technical problem are as follows. The present invention provides a method for increasing compositional uniformity of element Al in a titanium-alloy EB ingot, including the following preparation steps:
Further, both the upper convex portion and the upper concave portion have rounded corners at a junction, and the rounded corner on the upper concave portion is larger than the rounded corner on the upper convex portion.
Further, the upper convex portion and the upper concave portion have an equal length of 40-120 mm and an equal thickness of 40-200 mm.
Further, in step 4, the briquettes are arranged in the following manner: two adjacent briquette bodies can form a staggered fit together by attaching the upper convex portion to the upper concave portion, the upper convex portion and the upper concave portion are compacted and centered by a clamp at a fitting region, and are welded together on each surface at the joining seam by a plasma welding machine with no less than 3-4 welding spots.
Further, in step 6, the electrode rod material is melted in the following process: the electrode rod material is pushed forward at the constant speed in the automated horizontal feeding mode, when the electrode rod material is pushed from a feeding roller conveyor to a support plate by the pushing rod, the front end of the electrode rod material is melted through the electron beams, and the molten titanium flows into a cooling bed.
Further, in step 7, the electrode rod material is switched by the following manner: the upper convex portion of the next electrode rod material is compacted to the upper concave portion of the molten end of the electrode rod material, and the melting of the electrode rod material is fully and continuously carried out at an electron-beam melting region during the switching of the electrode rod material.
The present invention has the following beneficial effects: In the present invention, by innovating the shape design of the briquette and electrode rod material and optimizing the process of switching the electrode rod material, the stability of the melting process for titanium-alloy EB ingots is improved, thereby effectively increasing the compositional uniformity of element Al in EB ingots. The beneficial effects are specifically shown as follows.
1. The mixed materials are continuously and evenly discharged inchingly in small batches and transported into the cavity of the briquetting mold at a constant speed through the conveyor belt, which avoids segregation and separation of the mixed alloy components caused by discharge in whole and manual transportation and dumping, and improves the uniformity of raw materials in preparation, thereby promoting the compositional uniformity of Al and other elements in EB ingots after melting.
2. Compared with cylindrical briquettes used in conventional VAR melting, the electrode rod material of the present invention is fed straightly and stably as the contact area between the bottom of the electrode rod material and the feeding roller conveyor is greatly increased, which effectively avoids common abnormalities such as deviation and blockage of the electrode rod material, and improves the stability and continuity of feeding and melting of the electrode rod material, thereby making the melting loss of Al uniform and consistent throughout the continuous titanium-alloy EB melting process, and increasing the uniformity of element Al in EB ingots.
3. The briquettes and the assembled electrode rod material through welding are designed innovatively. The longitudinal section of the briquette is Z-shaped as a whole, and two adjacent briquette bodies can form a staggered fit together by attaching the upper convex portion to the upper concave portion. The electrode rod materials are engaged with each other. At a later stage of the melting of an electrode rod material, the tail part of a front electrode rod material will not fall into the molten pool due to the engagement of a next electrode rod material with the tail part of the front electrode rod material, so that even feeding and melting can be ensured in the process of electrode rod material switching and melting, which addresses the common falling issue of conventionally used cylindrical briquettes and electrode rod materials, and overcomes the resulting technical bottleneck of feeding and melting fluctuations, and melting loss of element Al, thereby increasing the uniformity of element Al in EB ingots.
4. In the conventional melting process, the feeding speed remains unchanged when the electrode rod material is switched, while it takes time for the pushing rod to reset and for a next electrode rod material to be transported to the pushing rod, during which electron beams have no material to melt and can only dry-burn the molten pool to maintain the temperature of the molten titanium. After that, the electron beams continue to melt a switched electrode rod material. This leads to inconsistency in the entire melting process, and further causes the melting loss of element Al. In the present invention, by optimizing the process of switching the electrode rod material, the uniformity of melting raw materials can be achieved in the process of switching the electrode rod material, so that the melting loss of Al is uniform and consistent throughout the whole titanium-alloy EB melting process, thereby increasing the uniformity of element Al in ingots.
5. Element Al is one of the most difficult alloy elements to achieve stable melting loss control and uniformity in the process of titanium-alloy EB melting. Therefore, in the present invention, not only the uniformity of Al can be increased, but also the uniformity of other alloy elements common in titanium alloys, such as V, Sn, Mo, Zr, Fe, and Nb, can be increased.
In the accompanying drawings: 1. Cooling bed; 2. Molten titanium; 3. Electron beam; 4. Molten end; 5. Electrode rod material; 501. Briquette body; 502. Upper convex portion; 503. Upper concave portion; 6. Welding spot; 7. Pushing rod; 8. Feeding roller conveyor; and 9. Support plate.
The embodiments of the present invention are described in detail with reference to the accompanying drawings. The embodiments are implemented on the premise of the technical solutions of the present invention, and a detailed implementation and a specific operation process are given. However, the protection scope of the present invention is not limited to the following embodiments.
With reference to the accompanying drawings, a method for increasing compositional uniformity of element Al in a titanium-alloy EB ingot includes the following preparation steps:
Two adjacent briquettes can form a staggered fit together by attaching the upper convex portion to the upper concave portion. The electrode rod materials are engaged with each other. At a later stage of the melting of an electrode rod material, the tail part of a front electrode rod material will not fall into the molten pool due to the engagement of a next electrode rod material with the tail part of the front electrode rod material, so that even feeding and melting can be ensured in the process of electrode rod material switching and melting, which addresses the common falling issue of conventionally used cylindrical briquettes and electrode rod materials, and overcomes the resulting technical bottleneck of feeding and melting fluctuations, and melting loss of element Al, thereby increasing the uniformity of element Al in EB ingots.
The briquette has a total weight up to 200 kg and has a width W, a height H, and a length L. The longitudinal section of the briquette is Z-shaped as a whole. A plurality of briquettes can form a staggered fit together by attaching the upper convex portion 6 to the upper concave portion 7. Both the upper convex portion at a top portion of the front end and the upper concave portion at a top portion of the rear end have a length LO and a thickness h, and have two rounded corners of R1 and R2 respectively at two junctions.
The width W is defined to leave a gap of 20-70 mm on a width of the feeding roller conveyor. The height H is determined according to a height of a feeding inlet and a weight of the briquette. The length L is determined according to the weight of the briquette. The upper convex portion 6 and the upper concave portion 7 have an equal length LO of 40-120 mm. The upper convex portion 6 and the upper concave portion 7 have an equal thickness h of 40-200 mm. The inner concave rounded corner R1 is set to 20-50 mm, and the outer convex rounded corner R2 is 5-10 mm larger than R1.
Comparative Example 1: The same materials were pressed into a cylindrical TC4 titanium-alloy briquette as shown in
In the TC4 titanium-alloy EB ingot obtained in Example 1, the minimum content of Al is 5.97%, and the maximum content of Al is 6.23%, with a compositional deviation of 0.26%. In the TC4 titanium-alloy EB ingot obtained in Comparative Example 1, the minimum content of Al is 5.69%, and the maximum content of Al is 6.46%, with a compositional deviation of 0.77%. Based on this, it indicates that the compositional uniformity of element Al in the EB ingot prepared in Example 1 is significantly higher than that in Comparative Example 1.
As the contact area between the bottom of the electrode rod material and the feeding roller conveyor is greatly increased in Example 1, the electrode rod material is fed straightly and stably, effectively avoiding abnormalities such as deviation and blockage of the electrode rod material; the electrode rod material consisting of Z-shaped briquettes is used in Example 1, which can ensure that the tail part of a front electrode rod material will not fall into the molten pool. In addition, in Example 1, the process of switching the electrode rod material is optimized, avoiding dry burning of the molten titanium by electron beams in the conventional switching process, and achieving the uniformity of melting raw materials in the process of switching the electrode rod material. Based on the improvements in the above aspects, continuous and stable feeding, melting, and switching in the melting process for titanium-alloy EB ingots can be achieved, so that the melting loss of Al in the molten titanium is uniform and consistent throughout the whole melting process, thereby increasing the uniformity of element Al in EB ingots.
In Comparative Example 1, as the used electrode rod material consisting of conventional cylindrical briquettes has a small contact area at the bottom and flat head and tail parts, abnormalities such as deviation, blockage, and falling of the electrode rod material frequently occur in the actual melting process, and the molten titanium is dry-burned by electron beams in the process of switching the electrode rod material, which leads to discontinuous and unstable feeding, melting, and switching throughout the whole melting process for titanium-alloy EB ingots, and large fluctuations in the melting loss of element Al in the molten titanium, resulting in poor uniformity of element Al in titanium-alloy EB ingots.
It is to be noted that, in this specification, the relational terms such as I, II, and III are used only to differentiate an entity or operation from another entity or operation, and do not require or imply any actual relationship or sequence between these entities or operations. Moreover, the terms “include”, “comprise”, and any variation thereof are intended to cover a non-exclusive inclusion. Therefore, in the context of a process, a method, an object, or a device that includes a series of elements, the process, method, object, or device not only includes such elements, but also includes other elements not specified expressly, or may include inherent elements of the process, method, object, or device. Unless otherwise specified, an element limited by “include a/an . . . ” does not exclude other same elements existing in the process, method, object, or device that includes the elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110303151.4 | Mar 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/081925 | 3/21/2022 | WO |
