Method for reducing peeling of pure titanium through secondary heating and segmented rolling
By using a secondary heating and segmented rolling method, the problem of peeling during the rolling of titanium ingots smelted in the EB furnace was solved, achieving efficient and economical surface quality improvement and increased yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-03-17
AI Technical Summary
Titanium ingots smelted in EB furnaces suffer from surface stress concentration during rolling due to localized component segregation and high-melting-point impurities, resulting in peeling defects. Existing improvement methods are costly and inefficient.
A two-stage heating segmented rolling method is adopted. The deformation and temperature are controlled during the first rolling, and the second heating promotes the diffusion of segregated elements and stress release. The surface quality is improved by controlling the heating temperature and time.
It significantly reduces the peeling defect of pure titanium plates, improves the yield and surface quality, reduces costs and increases production efficiency.
Smart Images
Figure CN121669697A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hot rolling production technology of pure titanium strip, and in particular to the rolling peeling defect caused by compositional segregation and impurities in vacuum electron beam cold hearth furnace (EB furnace) smelting ingots. It proposes a process optimization method to reduce surface peeling defects by secondary heating and staged rolling. Background Technology
[0002] Titanium possesses advantages such as light weight, high strength, strong corrosion resistance, good high-temperature resistance, and good biocompatibility, making it one of my country's important strategic metal materials. In recent years, my country's titanium consumption has been increasing year by year, while its production has also been growing continuously. Electron beam cold hearth furnaces can directly produce titanium billets (EB billets) with dimensions meeting hot-rolling requirements. The produced EB billets only need milling and grinding before entering the rolling process. This avoids the complex processes of forging, cutting, grinding, and peeling required after producing titanium ingots using conventional methods. Furthermore, electron beam cold hearth furnaces have a refining and purification function, producing high-purity, high-quality EB billets with better properties than forged billets, facilitating subsequent rolling.
[0003] However, although titanium ingots smelted in EB furnaces have high purity, they are prone to surface stress concentration during rolling due to localized component segregation (such as O and N enrichment) and insufficient diffusion of high-melting-point impurities (such as V and Mo). This results in peeling defects after rolling deformation. Traditional hot rolling processes directly roll the titanium billet in a single heating operation. Due to the large difference in plasticity between the segregated zone and the matrix, uneven deformation during the roughing stage easily leads to surface microcracks, which then propagate into macroscopic peeling defects during subsequent rolling. Existing improvement methods, such as improving heating uniformity or adding a grinding process, are costly and inefficient. Therefore, it is necessary to develop an economical and effective process to solve the peeling problem during EB ingot rolling. Summary of the Invention
[0004] The present invention aims to solve the above-mentioned problems and defects by providing a method for reducing the peeling of pure titanium plates through secondary heating and segmented rolling.
[0005] The present invention is implemented using the following technical solution.
[0006] A method for reducing peeling of pure titanium sheets through segmented rolling with secondary heating is disclosed. In the hot rolling process of pure titanium slabs, the rough rolling is performed in two stages with a secondary heating stage inserted in between. By controlling the deformation amount during the first rolling and the reheating temperature, the diffusion of segregated elements is promoted and rolling stress is released, thereby improving the surface quality of the rolled strip.
[0007] A method for reducing peeling of pure titanium plates through secondary heating and segmented rolling includes the following steps:
[0008] Step 1) Primary heating: Place the EB billet that meets the rolling conditions into the heating furnace for primary heating;
[0009] Step 2) First rough rolling: The heated billet undergoes its first rough rolling;
[0010] Step 3) Secondary heating: The billet after the first rough rolling is returned to the heating furnace for secondary heating;
[0011] Step 4) Secondary rolling: The billet, after being heated twice, is rolled to the target thickness.
[0012] Furthermore, the temperature of the first heating in step 1) of the present invention is 880±10℃.
[0013] Furthermore, in step 1) of the present invention, after the first heating, the heat preservation time is 2 to 3 hours.
[0014] Furthermore, the deformation limit during the first rough rolling in step (2) of this invention is 10% to 20%.
[0015] Furthermore, the temperature of the secondary heating in step (3) of the present invention is 850~870℃.
[0016] Furthermore, in step (3) of the present invention, after the secondary heating, the ratio of the heat preservation time to the billet thickness is 1~1.5h / 100mm.
[0017] Furthermore, the heating temperature in step 1) of this invention is the β phase transition point temperature, with a control error of ±10℃.
[0018] Furthermore, the heating temperature in step 1) of the present invention is 880°C.
[0019] Furthermore, the heat preservation time for the first heating in step 1) of the present invention is 2.5 hours.
[0020] Furthermore, the temperature of the secondary heating in step 3) of the present invention is 860°C.
[0021] The technical principle of this invention is as follows:
[0022] 1. Composition segregation control: The first heating to 880℃ (α+β two-phase region) results in a significantly higher diffusion rate of segregated elements than the rolling temperature (e.g., 800℃), but lower than the temperature of the β single-phase region, thus avoiding grain coarsening; the second heating further homogenizes the composition, especially dispersing brittle oxide / nitride particles.
[0023] 2. Stress control mechanism: The deformation amount is limited to ≤20% during the first rolling to avoid the surface stress from exceeding the fracture limit of titanium; the second heating eliminates dislocation accumulation through dynamic recrystallization to prevent the generation of microcracks in subsequent rolling.
[0024] 3. Reduced impact of impurities: High-melting-point impurities are broken down in the first rolling process, and the interface can drive partial dissolution during the second heating, reducing stress concentration sources in subsequent rolling.
[0025] Compared with the prior art, the beneficial effects of this invention are as follows:
[0026] 1. Compared with existing traditional processes, the surface quality of the rolled product is better, saving time and labor costs for subsequent treatment of peeling defects;
[0027] 2. It is easy to operate and highly feasible. It can realize the transformation of process methods without modifying existing equipment, saving costs and improving efficiency at the same time.
[0028] 3. It improves the yield rate and can generate significant economic benefits.
[0029] 4. The present invention reduces the degree of element segregation in the billet and eliminates deformation stress through secondary heating and primary rolling, thus ensuring the stability of secondary rolling.
[0030] 5. The pure titanium plate prepared using the process method of the present invention has significantly improved surface quality, and the peeling defect is reduced by more than 50%.
[0031] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. Attached Figure Description
[0032] Figure 1 This is a process flow diagram of the present invention.
[0033] Figure 2 This is a comparison image of a conventionally rolled product with surface defects, shown in Example TA2.
[0034] Figure 3 This is a SEM image of the defects on the conventionally rolled surface of Example TA2.
[0035] Figure 4 This is a drawing of the surface product rolled by the new process of the present invention TA2.
[0036] Figure 5 This is a SEM image of the surface rolled by the new process of the present invention TA2. Detailed Implementation
[0037] The following embodiments are only a part of the technical solutions of the present invention and are not intended to limit all the technical solutions of the present invention. The embodiments of the present invention are provided to further explain and illustrate the details of the technical solutions of the present invention.
[0038] A method for reducing peeling of pure titanium plates through secondary heating and segmented rolling, the specific steps of which are as follows:
[0039] Step 1) First heating: Place the pure titanium EB billet that meets the rolling conditions into the heating furnace and heat it to 880±10℃, which is close to the β phase transformation point temperature. Hold it for 2~3 hours to make the billet heated at a uniform temperature.
[0040] Step 2) First rough rolling: The heated billet is subjected to the first rough rolling, and the deformation is controlled at 10%~20%. At this time, the surface segregation zone only produces small stress concentrations due to the small deformation, and no macro cracks are formed.
[0041] Step 3) Secondary heating: The pure titanium billet after the first rough rolling is returned to the heating furnace and heated to 850~870℃ for 1~1.5 hours. The purpose is to use low temperature and long-term heating to promote the diffusion of segregated elements (such as O and N) into the matrix, while releasing rolling stress.
[0042] Step 4) Secondary rolling: The billet, after being heated twice, is rolled to the target thickness.
[0043] The following are some embodiments and comparative examples of the present invention.
[0044] See Figure 1 , Figure 4 , Figure 5 As shown.
[0045] Example 1: Taking EB furnace-cast TA2 pure titanium ingots (specifications: 200mm × 1060mm × 7500mm) as an example, hot-rolled titanium coils with a target thickness of 6mm are produced. The specific implementation steps are as follows:
[0046] Step 1) The titanium billet, which has been processed to meet the rolling conditions and has dimensions of 200mm×1060mm×7500mm, is sent into the heating furnace for a first heating, heated to 880℃ and held for 2.5h.
[0047] Step 2) After the first heating is completed, the first rough rolling is performed to roll the 200mm thick billet to 175mm. The billet deformation during this process is 12.5%.
[0048] Step 3) The billet that has undergone the first rough rolling is transferred into a heating furnace for secondary heating, heated to 860℃ and held for 1 hour;
[0049] Step 4) After the second heating is completed, perform rough rolling again for 5 passes to obtain a precision rolled part with a thickness of 40mm;
[0050] Step 5) The finished rolled part is descaled, cut off the head and tail and finished rolled by traditional hot rolling process to obtain titanium strip with a final rolled size of 6*1060*C (mm), which is then wound into coils by a coiler.
[0051] See Figure 2 , Figure 3As shown. The comparative example is the traditional rolling process, which involves heating the billet to 860°C in one pass and performing a single rough rolling.
[0052] A comparison of the uncoiling surface inspection of hot-rolled titanium coils produced using two different methods was conducted. The hot-rolled titanium strip coils produced using the process method described in this invention showed that the surface peeling defects were reduced from 15 per square meter to 3 per square meter, significantly improving the surface quality of the finished product. Furthermore, the intermediate grinding process was eliminated, reducing labor costs.
[0053] Example 2: Taking EB furnace casting of TA1 pure titanium ingot (specifications: 200mm × 1260mm × 6500mm) as an example, hot-rolled titanium coils with a target thickness of 4mm are rolled. The specific implementation steps are as follows:
[0054] Step 1) The titanium billet, which has been processed to meet the rolling conditions and has dimensions of 200mm×1260mm×6500mm, is sent into the heating furnace for a first heating, heated to 880℃ and held for 2.5h.
[0055] Step 2) After the first heating is completed, the first rough rolling is performed to roll the 200mm thick billet to 170mm. The billet deformation during this process is 15%.
[0056] Step 3) The billet that has undergone the first rough rolling is transferred into a heating furnace for secondary heating, heated to 860℃ and held for 1 hour;
[0057] Step 4) After the second heating is completed, perform rough rolling again for 5 passes to obtain a 40mm thick finish rolled part;
[0058] Step 5) The finished rolled part is descaled, cut off the head and tail, and finished rolled by traditional hot rolling process to obtain titanium strip with a final rolled specification of 4*1260*C (mm), which is then wound into coils by a coiler.
[0059] Example 3: Taking EB furnace casting of TA1 pure titanium ingot (specifications: 200mm × 1560mm × 8000mm) as an example, hot-rolled titanium coils with a target thickness of 3mm are rolled. The specific implementation steps are as follows:
[0060] Step 1) The titanium billet, which has been processed to meet the rolling conditions and has dimensions of 200mm×1000mm×8000mm, is sent into the heating furnace for a first heating, heated to 880℃ and held for 2.5h.
[0061] Step 2) After the first heating is completed, the first rough rolling is performed to roll the 200mm thick billet to 170mm. The billet deformation during this process is 15%.
[0062] Step 3) The billet that has undergone the first rough rolling is transferred into a heating furnace for secondary heating, heated to 860℃ and held for 1 hour;
[0063] Step 4) After the second heating is completed, perform rough rolling again for 5 passes to obtain a 40mm thick finish rolled part;
[0064] Step 5) The finished rolled part is descaled, cut off the head and tail, and finished rolled by traditional hot rolling process to obtain titanium strip with a final rolled specification of 4*1560*C (mm), which is then wound into coils by a coiler.
[0065] The above descriptions are merely some specific embodiments of the present invention (since the present invention encompasses numerical ranges, the embodiments cannot be exhaustive; the scope of protection described in the present invention includes the numerical range and other technical aspects of the present invention). Specific content or common knowledge known in the solutions is not described in detail here (including but not limited to abbreviations, acronyms, and units conventionally used in the art). It should be noted that the above embodiments do not limit the present invention in any way. For those skilled in the art, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of protection of the present invention. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling, characterized in that, The method comprises the following steps: Step 1) primary heating: the EB billet meeting the rolling condition is put into a heating furnace for primary heating; Step 2) first rough rolling: the heated billet is subjected to first rough rolling; Step 3) secondary heating: the billet after the first rough rolling is returned to the heating furnace for secondary heating; Step 4) secondary rolling: the billet after the secondary heating is continuously rolled to the target thickness.
2. A method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling according to claim 1, characterized in that, The temperature of the primary heating in step 1) is 880±10℃.
3. A method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, After the primary heating in step 1), the holding time is 2-3 hours.
4. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The deformation limit of the first rough rolling in step (2) is 10%-20%.
5. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The temperature of the secondary heating in step (3) is 850-870℃.
6. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The holding time to billet thickness ratio after the secondary heating in step (3) is 1-1.5h / 100mm.
7. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The temperature of the primary heating in step 1) is the beta phase transformation point temperature, and the control error is ±10℃.
8. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The temperature of the primary heating in step 1) is 880℃.
9. The method of reducing the occurrence of titanium sheeting in pure titanium by means of secondary heating and staged rolling as claimed in claim 1, wherein, The holding time of the primary heating in step 1) is 2.5h.
10. The method of reducing the scaling of pure titanium by means of secondary heating and segmented rolling according to claim 1, characterized in that, The temperature of the secondary heating in step (3) is 860℃.