Preparation method of dental medical titanium alloy thin bar

Abstract

The invention belongs to the technical field of medical implant materials, and particularly relates to a preparation method of a dental medical titanium alloy thin bar. Comprising the following steps: heating a titanium alloy forging stock to a beta phase transformation point temperature, preserving heat, forging to obtain a bar blank, and rolling the bar blank to obtain a titanium bar; sequentially carrying out peeling treatment and hot continuous rolling on the titanium rod to obtain a wire rod blank; n multi-pass orthogonal cold rolling is conducted on the wire rod blank, the total deformation of each multi-pass rolling pass is smaller than or equal to 40%, each multi-pass orthogonal cold rolling comprises 3-6 passes, and a cold-rolled wire blank is obtained; and the cold-rolled wire blank is sequentially subjected to cold straightening, cutting and coping, and the dental medical titanium alloy thin bar is obtained. According to the method, the crystal grains are dislocated through the high-deformation orthogonal cold rolling technology, dislocation entanglement and cellular structures are formed, the microstructure is greatly refined, coarse and large crystal grains left in the hot working process are eliminated, the purpose of refining the crystal grains is achieved, and the standard requirement of the dental medical GR4B titanium thin bar is met.

Description

Technical Field

[0001] This invention belongs to the field of medical implant materials technology, specifically relating to a method for preparing dental medical titanium alloy thin rods. Background Technology

[0002] GR4 titanium alloy (Grade 4, pure titanium) is a high-purity, high-strength titanium material, belonging to the highest grade of commercially pure titanium (CP-Ti). Compared to GR1-GR3 pure titanium, GR4 significantly improves mechanical properties through its higher oxygen content, while maintaining excellent biocompatibility, corrosion resistance, and lightweight characteristics (density 4.5 g / cm³). This makes it an important material in the medical field, widely used in orthodontics, dentistry, cardiovascular medicine, and surgical instruments. Particularly in dentistry, when used as a dental implant, it can be directly implanted into the jawbone, providing long-term stable support. When used for orthodontic archwires and brackets, it is more rigid than nickel-titanium alloys, making it more suitable for specific orthodontic needs. As a metal frame for removable partial dentures, it is both resistant to saliva corrosion and lightweight. Due to the special service environment of GR4, not only is a good surface quality required, but higher demands are also placed on its mechanical properties.

[0003] The ISO 5832-2 standard requires that the mechanical properties of GR4B for surgical implants meet the following requirements: tensile strength: ≥680MPa; yield strength: ≥520MPa; elongation after fracture: ≥10%, with no requirement for reduction of area. However, current production methods for GR4 fine rods involve cold drawing combined with intermediate annealing. During cold drawing, the wire surface experiences intense friction with the die and is subjected to radial extrusion, leading to plastic deformation of the surface metal, grain compression, and residual compressive stress. Due to the accumulation of multiple small deformations, the stress gradient is gentle, resulting in a shallow surface compressive stress layer. This layer is removed through subsequent straightening and polishing. However, the residual compressive stress layer can increase the tensile strength of the fine rod. Therefore, the mechanical properties of the GR4 fine rod semi-finished product after straightening and polishing are reduced, thus failing to meet the requirements for high-strength GR4B fine rods used in dental applications. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing dental GR4B thin rods. High-deformation orthogonal cold rolling induces dislocations in the grains, introducing a high dislocation density and forming complex dislocation entanglements and cellular structures. This hinders dislocation movement, resulting in high-strength GR4B thin rods. Furthermore, cold rolling significantly refines the microstructure, eliminating coarse grains left over from hot working, thus achieving grain refinement. No intermediate annealing is required for the GR4B thin rods; the entire process is cold-formed, greatly shortening the processing time. The resulting dental GR4B titanium thin rods meet the standard requirements: σ m ≥680MPa; σ 0.2 : ≥520MPa; A: ≥10%.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] The purpose of this invention is to provide a method for preparing dental medical titanium alloy thin rods, comprising the following steps: S1. After heating the titanium alloy forging billet to the β phase region forging temperature and holding it at that temperature, a bar billet is forged, and the bar billet is rolled to obtain a titanium bar.

[0007] S2. The titanium rod is subjected to peeling and hot rolling in sequence to obtain a coiled billet.

[0008] S3. Perform N multi-pass orthogonal cold rolling on the coiled billet until the total deformation of the rolling passes is ≤40%. Each multi-pass orthogonal cold rolling includes 3 to 6 passes. Through orthogonal cold rolling, dislocations are generated in the grains, forming dislocation entanglements and cellular structures to obtain cold-rolled wire blanks.

[0009] S4. The cold-rolled wire blank is sequentially cold-straightened, cut and ground to obtain dental medical titanium alloy thin rods.

[0010] Furthermore, N is 1 to 2, and the rolling speed for each pass is 30 m / min to 40 m / min.

[0011] Furthermore, the hot rolling temperature is 820℃~850℃.

[0012] Furthermore, the rolling temperature is 750℃~850℃, and the holding time is 2h~3h.

[0013] Furthermore, the forging temperature for the β phase region is 1000℃~1100℃, and the holding time is 4h~6h.

[0014] Furthermore, the diameter of the dental medical titanium alloy thin rod is Φ5.0~Φ6.0mm.

[0015] Furthermore, the diameter of the titanium rod is Φ100mm~Φ105mm, and the diameter of the disc blank is Φ8.0mm~Φ9.5mm.

[0016] Furthermore, the amount of skin removed during the peeling process is 3mm to 7mm.

[0017] Furthermore, the titanium alloy is GR4 titanium alloy.

[0018] Compared with the prior art, the present invention has the following advantages: The preparation method provided by this invention utilizes an orthogonal cold rolling process. Cold rolling can apply a larger deformation than single-pass drawing. This high-deformation orthogonal cold rolling induces dislocations in the grains, introducing a higher dislocation density and forming complex dislocation entanglements and cellular structures. This hinders dislocation movement, resulting in high-strength GR4B fine rods. Furthermore, cold rolling significantly refines the microstructure, eliminating coarse grains left over from hot working, thus achieving grain refinement. No intermediate annealing is required for the GR4B fine rods; the entire process is cold-formed, greatly shortening the processing time. The resulting dental GR4B titanium fine rods meet the standard requirements: σ m ≥680MPa; σ 0.2 : ≥520MPa; A: ≥10%.

[0019] This invention introduces a higher dislocation density through high-deformation cold rolling, forming complex dislocation entanglements and cellular structures that strongly hinder dislocation movement, thereby improving the strength of GR4B fine bars. Compared to conventional processes, the GR4B fine bars obtained by this invention exhibit a 10.96% increase in tensile strength and a 19.1% increase in yield strength. Attached Figure Description

[0020] Figure 1 This is a physical image of the dental medical titanium alloy thin rod prepared in Example 1 of the present invention.

[0021] Figure 2 This is a physical image of the dental medical titanium alloy thin rod prepared in Example 2 of the present invention.

[0022] Figure 3 This is a physical image of the dental medical titanium alloy thin rod prepared in Example 3 of the present invention.

[0023] Figure 4 The image shows the metallographic structure of the dental medical titanium alloy thin rod prepared in Example 1 of this invention.

[0024] Figure 5 The tensile strength and yield strength properties of the titanium alloy thin rods prepared in Examples 1 to 3 and Comparative Example 1 of this invention are shown in the diagram.

[0025] Figure 6The graphs show the elongation and reduction of area properties of the titanium alloy thin bars prepared in Examples 1 to 3 and Comparative Example 1 of this invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0028] Currently, the existing processing methods for producing GR4 thin rods involve cold drawing combined with intermediate annealing. During cold drawing, the wire surface experiences intense friction with the die and is subjected to radial extrusion, leading to plastic deformation of the surface metal, grain compression, and residual compressive stress. Due to the accumulation of multiple small deformations, the stress gradient becomes gentle, resulting in a shallow surface compressive stress layer. This layer is removed through subsequent straightening and grinding. However, the residual compressive stress layer can increase the tensile strength of the thin rod. Therefore, the mechanical properties of the GR4 thin rod semi-finished product after straightening and grinding are reduced, thus failing to meet the requirements for high-strength GR4B thin rods used in dental applications.

[0029] Therefore, to solve the above problems, this invention uses orthogonal cold rolling instead of the traditional roll drawing process to prepare dental GR4B thin rods with medium to high strength and plasticity. This achieves good comprehensive mechanical properties while also improving the surface cleanliness and reducing defects in the thin rods. Specifically:

[0030] A method for preparing a dental medical titanium alloy thin rod includes the following steps: S1. After heating the titanium alloy forging billet to the β phase region forging temperature and holding it at that temperature, a bar billet is forged, and then the bar billet is rolled to obtain a titanium bar.

[0031] In this invention, the β-phase region forging temperature is the β-phase transformation point temperature + (50℃~150℃), the β-phase region forging temperature is 1000℃~1100℃, and the holding time is 4h~6h. The titanium alloy forging billet is a GR4 ingot. The chemical composition of the GR4 titanium ingot is: Fe: ≤0.03%; C: ≤0.020%; H: ≤0.0010%; N: ≤0.010%; O: ≤0.40%, with the balance being Ti and unavoidable impurities. The GR4 ingot is placed in a resistance furnace and heated above the β-phase transformation point, held for 4h~6h to forge a billet. Then, it is held at 750℃~850℃ for 2h~3h before rolling. The purpose is to gradually reduce the diameter of the titanium alloy forging billet to produce a high-precision bar. The diameter of the rolled titanium bar is Φ100mm~Φ105mm.

[0032] S2. The titanium rod is subjected to peeling and hot rolling in sequence to obtain a coiled billet.

[0033] In this invention, the surface of the rolled titanium rod has an oxide scale, so it needs to be peeled off to avoid the formation of a contamination layer on the surface of the titanium rod. The amount of peeling off is 3mm to 7mm. After peeling off, a semi-finished titanium rod is obtained. The semi-finished titanium rod is hot-rolled at 820℃ to 850℃ to obtain a coiled billet with a diameter of Φ8.0mm to Φ9.5mm.

[0034] S3. Perform 1 to 2 multi-pass orthogonal cold rolling on the coiled billet until the total deformation of the rolling passes is ≤40%. Each multi-pass orthogonal cold rolling includes 3 to 6 passes. Through orthogonal cold rolling, dislocations are introduced into the grains, forming dislocation entanglement and cellular structure, to obtain cold-rolled wire blank.

[0035] In this invention, an orthogonal cold rolling process is used, with each pass rolling at a speed of 30 m / min to 40 m / min. Cold rolling can apply a greater deformation than single-pass drawing. This high-deformation orthogonal cold rolling induces dislocations in the grains, introducing a higher dislocation density and forming complex dislocation entanglements and cellular structures. This hinders dislocation movement, resulting in high-strength GR4B fine bars. Furthermore, cold rolling significantly refines the microstructure, eliminating coarse grains left over from hot working, thus achieving grain refinement. No intermediate annealing treatment is required for the GR4B fine bars; the entire process is cold-formed, greatly shortening the processing time.

[0036] S4. The cold-rolled wire blank is sequentially cold-straightened, cut and ground to obtain dental medical titanium alloy thin rods.

[0037] In this invention, after room temperature straightening, the cold-rolled wire blank is cut to length and then surface-ground, with a grinding allowance of 0.2mm to 0.5mm, to obtain dental titanium alloy thin rods. These rods possess medium to high strength and plasticity, achieving good comprehensive mechanical properties while improving surface cleanliness and reducing defects. The resulting dental GR4B titanium thin rods meet the standard requirements: σ m ≥680MPa; σ 0.2 : ≥520MPa; A: ≥10%.

[0038] The following specific examples will provide further explanation.

[0039] Example 1 A method for preparing a dental medical titanium alloy thin rod includes the following steps: The raw material is GR4 titanium ingot, with the following chemical composition: iron (Fe): 0.024%; carbon (C): 0.011%; hydrogen (H): 0.0006%; nitrogen (N): 0.004%; oxygen (O): 0.360%, with the balance being titanium and unavoidable impurities.

[0040] S1. Forging and rolling: The GR4 ingot is placed in a box-type resistance furnace and heated to 1050℃ in the β single-phase region. After holding for 4 hours, the ingot is forged to obtain a billet. Then, the billet is placed in a resistance furnace and held at 830℃ for 3 hours before rolling to obtain a GR4 billet with a diameter of Φ103mm.

[0041] S2. Peeling and Grinding: Peel and grind the oxide scale on the surface of the rolled bar. The amount of peeling is 3mm, and a semi-finished bar with a diameter of Φ100mm is obtained.

[0042] S3. Wire rod preparation: The semi-finished GR4 titanium rod obtained after peeling is hot rolled at a rolling temperature of 830℃ to finally obtain a wire rod blank with a diameter of Φ8.5mm.

[0043] S4. Cold rolling: Completed through two multi-pass cold rolling cycles. Each multi-pass rolling cycle consists of four passes, with a total deformation of ≤40% for each rolling pass and a rolling speed of 40m / min. The diameter of the wire blank after the first multi-pass rolling cycle is Φ6.7mm, and the diameter of the cold-rolled wire blank after the second rolling cycle is Φ5.3mm.

[0044] S5. Cold straightening, cutting, and grinding: After straightening the cold-rolled wire blank, it is cut to length and then ground. The surface grinding amount is 0.3mm, resulting in a finished GR4B medical-grade thin rod with a diameter of Φ5.0mm. Figure 1 As shown.

[0045] Example 2 A method for preparing a dental medical titanium alloy thin rod includes the following steps: The raw material is GR4 titanium ingot, with the following chemical composition: iron (Fe): 0.026%; carbon (C): 0.008%; hydrogen (H): 0.0006%; nitrogen (N): 0.003%; oxygen (O): 0.317%, with the balance being titanium and unavoidable impurities.

[0046] S1. Forging and rolling: The GR4 ingot is placed in a box-type resistance furnace and heated to 1050℃ in the β single-phase region. After holding for 4 hours, the ingot is forged to obtain a billet. Then, the billet is placed in a resistance furnace and held at 850℃ for 2.5 hours before rolling to obtain a GR4 billet with a diameter of Φ105mm.

[0047] S2. Peeling and Grinding: Peel and grind the oxide scale on the surface of the rolled bar. The amount of peeling is 5mm, and a semi-finished bar with a diameter of Φ100mm is obtained.

[0048] S3. Wire rod preparation: The semi-finished GR4 titanium rod obtained after peeling is hot rolled at a rolling temperature of 830℃ to finally obtain a wire rod blank with a diameter of Φ8.00mm.

[0049] S4. Cold rolling: Completed by two multi-pass cold rolling cycles. One multi-pass cold rolling cycle includes four passes, and the total deformation of the rolling passes is ≤40%. The rolling speed is 35m / min. The diameter of the wire blank after the first multi-pass cold rolling cycle is Φ6.5mm. After the second cold rolling cycle, a cold-rolled wire blank with a diameter of Φ5.2mm is obtained.

[0050] S5. Cold straightening, cutting, and grinding: After straightening the cold-rolled wire blank, it is cut to length and then ground. The surface grinding amount is 0.2mm, resulting in a finished GR4B medical-grade thin rod with a diameter of Φ5.0mm. Figure 2 As shown.

[0051] Example 3 A method for preparing a dental medical titanium alloy thin rod includes the following steps: The raw material is GR4 titanium ingot, with the following chemical composition: iron (Fe): 0.026%; carbon (C): 0.008%; hydrogen (H): 0.0006%; nitrogen (N): 0.003%; oxygen (O): 0.317%, with the balance being titanium and unavoidable impurities.

[0052] S1. Forging and rolling: The GR4 ingot is placed in a box-type resistance furnace and heated to 1050℃ in the β single-phase region. After holding for 4 hours, the ingot is forged to obtain a billet. Then, the billet is placed in a resistance furnace and held at 850℃ for 2.5 hours before rolling to obtain a GR4 billet with a diameter of Φ105mm.

[0053] S2. Peeling and Grinding: Peel and grind the oxide scale on the surface of the rolled bar. The amount of peeling is 5mm, and a semi-finished bar with a diameter of Φ100mm is obtained.

[0054] S3. Wire rod preparation: The semi-finished GR4 titanium rod obtained after peeling is hot rolled at a rolling temperature of 830℃ to finally obtain a wire rod blank with a diameter of Φ8.00mm.

[0055] S4. Cold rolling: Completed by one multi-pass cold continuous rolling, which includes 4 passes, with a total deformation of ≤40% for each rolling pass and a rolling speed of 38m / min. The cold rolled wire blank has a diameter of Φ6.2mm.

[0056] S5. Cold straightening, cutting, and grinding: After straightening the cold-rolled wire blank, it is cut to length and then ground. The surface grinding amount is 0.2mm, resulting in a finished GR4B medical-grade thin rod with a diameter of Φ6.0mm. Figure 3 As shown.

[0057] Comparative Example 1 A method for preparing a dental medical titanium alloy thin rod includes the following steps: The raw material is GR4 titanium ingot, with the following chemical composition: iron (Fe): 0.024%; carbon (C): 0.011%; hydrogen (H): 0.0006%; nitrogen (N): 0.004%; oxygen (O): 0.360%, with the balance being titanium and unavoidable impurities.

[0058] S1. Forging and rolling: The GR4 ingot is placed in a box-type resistance furnace and heated to 1050℃ in the β single-phase region. After holding for 4 hours, the ingot is forged to obtain a billet. Then, the billet is placed in a resistance furnace and held at 850℃ for 3 hours before rolling to obtain a GR4 billet with a diameter of Φ103mm.

[0059] S2. Peeling and Grinding: Peel and grind the oxide scale on the surface of the rolled bar. The amount of peeling is 3mm, and a semi-finished bar with a diameter of Φ100mm is obtained.

[0060] S3. Wire rod preparation: The semi-finished GR4 titanium rod obtained after peeling is hot rolled at a rolling temperature of 830℃ to finally obtain a wire rod blank with a diameter of Φ8.00mm.

[0061] S4. Perform multiple cold drawing operations on the Φ8.00mm coil blank until the diameter of the intermediate wire blank is Φ6.2mm.

[0062] S5. Intermediate annealing: After holding the intermediate wire blank at 680℃ for 1.5h in a box-type resistance furnace, remove it from the furnace and air cool it to room temperature.

[0063] S6. Multi-pass cold drawing: The deformation per pass is ≤13%, and the drawing speed is 24m / min. The process involves four passes of cold drawing to obtain a semi-finished wire blank with a diameter of 5.2mm.

[0064] S7. Cold straightening, cutting, and grinding: The semi-finished wire blank after multiple drawing passes is straightened, cut to length, and ground. The surface grinding amount is 0.2mm, and the final product is GR4B medical thin rod with a diameter of Φ5.0mm.

[0065] The mechanical properties of the GR4B medical thin rods prepared in Examples 1 to 3 and Comparative Example 1 were tested, including the following steps: The results are shown in Table 1.

[0066] Table 1 Mechanical properties of GR4B medical thin rods prepared in Examples 1-3 and Comparative Example 1 Through Table 1 and Figures 5-6 It can be observed that, compared to Comparative Example 1, as shown in Example 1, the GR4B thin rods obtained by the process of the present invention have a tensile strength increased by 10.96%, a yield strength increased by 19.1%, and an elongation increased by 18.12%.

[0067] Figure 4 This is a metallographic image of the dental titanium alloy thin rod prepared in Example 1 of the present invention. Figure 1 As shown, its average grain size is 8.2 μm, and the average grain size is greater than 10.0.

[0068] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a dental medical titanium alloy thin rod, characterized in that, Includes the following steps: After heating the titanium alloy forging billet to the β phase region forging temperature and holding it, a bar billet is forged, and the bar billet is rolled to obtain a titanium bar. The titanium rods were sequentially peeled and hot-rolled to obtain coiled billets. The circular billet is subjected to N multi-pass orthogonal cold rolling, with the total deformation of each multi-pass rolling pass ≤40%. Each multi-pass orthogonal cold rolling includes 3 to 6 passes. Through orthogonal cold rolling, dislocations are generated in the grains, forming dislocation entanglements and cellular structures to obtain cold-rolled wire blanks. The cold-rolled wire blank is sequentially cold-straightened, cut, and ground to obtain dental medical titanium alloy thin rods.

2. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, N is 1 to 2, and the rolling speed for each pass is 30 m / min to 40 m / min.

3. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The temperature of hot continuous rolling is 820℃~850℃.

4. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The rolling temperature is 750℃~850℃, and the holding time is 2h~3h.

5. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The forging temperature for the β phase region is 1000℃~1100℃, and the holding time is 4h~6h.

6. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The diameter of dental medical titanium alloy thin rods is Φ5.0mm~Φ6.0mm.

7. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The diameter of the titanium rod is Φ100mm~Φ105mm, and the diameter of the disc blank is Φ8.0mm~Φ9.5mm.

8. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The amount of skin removed during the peeling process is 3mm to 7mm.

9. The method for preparing dental medical titanium alloy thin rods according to claim 1, characterized in that, The titanium alloy is GR4 titanium alloy.

Images