Preparation method of high-shear-strength Nb55Ti wire

Abstract

The invention provides a preparation method of a high-shear-strength Nb55Ti wire. The preparation method comprises the steps of ingot casting preparation, intermediate blank forging, machining, rolling, rounding and drawing, scaling and overhauling, vacuum annealing, finished product roller drawing, finished product polishing, detecting and rewinding, rivet manufacturing of a finished product, shearing and stamping, and annealing at 800-900 DEG C; a cast ingot is prepared through a vacuum consumable melting method, then an intermediate blank with a fine and uniform structure is prepared through six-heating-number upsetting and drawing, then the cast ingot is subjected to one-heating-number rolling, cold drawing and two-heating-number vacuum annealing to prepare the small-specification wire, and finally the Nb55Ti wire is high in precision, uniform in structure and consistent in force matching.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy preparation, and in particular to a method for preparing a high shear strength Nb55Ti wire. Background Art

[0002] There is a large market demand for niobium-titanium wire for aviation fasteners in China, but the following problems exist in the preparation process of niobium-titanium alloy wire: (1) Partial component segregation during smelting. Since niobium has a high melting point, solving the problem of niobium infusible blocks becomes a difficult problem in the preparation of niobium-titanium ingots; (2) During the hot / cold deformation process, niobium-titanium alloy will undergo an extremely large deformation across scales, and it is difficult to ensure the uniformity of the structure and mechanical consistency of the entire roll of wire; (3) The shear strength of the existing niobium-titanium wire preparation technology is relatively low, and there is an urgent need to break through the existing shear strength and ensure that the strength and toughness of the wire match.

[0003] Chinese patent CN117483473A discloses a processing method for Ti45Nb titanium alloy straight wire, which comprises the following steps: forging a Ti45Nb titanium alloy ingot that has passed the composition inspection; repeatedly deforming the forged billet; hot rolling the billet; cold drawing with a roller die; intermediate annealing; cold drawing with a roller die; online continuous annealing with argon filling; and vertical electrical straightening. The Ti45Nb titanium alloy straight wire prepared by the method of the present invention is simple to operate, has a stable and controllable process, a straightness of ≤2.0mm / m, an ellipticity of ≤0.02mm, a surface roughness Ra≤1.0μm, a uniform and fine microstructure, and a qualified eddy current flaw detection. The mechanical properties of the annealed state at room temperature are consistent and stable, and meet the requirements of relevant standards. The tensile strength of the wire prepared by this patent is 552MPa, the yield strength is 515MPa, the elongation is 22.8%, the cross-sectional shrinkage is 77.4%, and the shear strength is 378MPa. Its performance is relatively low and cannot meet the increasingly high strength requirements.

[0004] Chinese patent CN107282688B discloses a method for preparing Ti45Nb alloy coil wire, which comprises: 1. Cold rolling of rod hole: Select Ti45Nb smooth rod with uniform composition and uniform longitudinal and transverse structure, and use two-roller reversible cold rolling mill, square hole type roller cold rolling into square rod blank; 2. Roller die drawing: Use wire drawing machine, two-joint square to round hole roller die to draw it into round billet, and then use roller die to draw the round billet to obtain a certain specification and dimensional tolerance. Round wire; 3. Vacuum annealing of intermediate specifications: anneal the round wire in a vacuum furnace to obtain annealed round wire with a bright surface; 4. Cold rolling: cold rolling the bright round wire with rollers installed horizontally and vertically in a cold rolling mill, the rollers use a twelve-square hole type to roll the wire from a larger size to a smaller size, and the last two frames of the cold rolling mill are alternately installed with round hole rollers to obtain round wire with a certain size accuracy; 5. Rounding: degreasing the round wire and rounding it. This patent uses continuous rolling to round the intermediate billet, and its production investment cost is extremely high, and it is difficult to produce in small batches. In addition, the shear strength of the wire prepared by this patent is 350-400MPa, which cannot meet the increasingly high strength requirements.

[0005] Chinese patent CN111705279A discloses a heat treatment method for Ti45Nb titanium alloy wire, which is as follows: placing the Ti45Nb wire prepared by the rotary forging process in a muffle furnace, heating it to 750-860°C for preheating, keeping it warm for 0.5-1.6h, and then cooling it to room temperature. The method of the present invention controls the preheating temperature, the holding time and the cooling method, so that the microstructure of the heat-treated Ti45Nb titanium alloy wire is uniform, and at the same time, the tensile strength of the Ti45Nb titanium alloy wire is increased to 595MPa, the yield strength is increased to 545MPa, the shear strength is increased to 368MPa, and the elongation is increased to 13.6%, and the mechanical properties of the wire are comprehensively improved, providing technical support for the application of Ti45Nb titanium alloy wire in the production of aviation fasteners. However, since titanium alloy is very easy to burn during muffle furnace annealing, the heat treatment preparation scheme is difficult to implement in industrial production, and the elongation of the wire prepared by this patent is low, and the strength-plasticity matching is poor.

[0006] Ma Fanjiao et al. published a paper on the study of recrystallization behavior of Ti45Nb titanium alloy. The paper systematically studied the effects of different heat treatment temperatures and hot working deformation and other process parameters on the recrystallization behavior of Ti45Nb titanium alloy for new fasteners. The results show that with the increase of heat treatment temperature, the degree of recrystallization gradually increases; with the increase of deformation, the complete recrystallization temperature gradually decreases; for forged specimens, the recrystallization temperature is selected at 850℃; for hot rolled specimens, the recrystallization temperature is selected at 800℃. This paper provides guidance for the production of Ti45Nb wire. The control of heat treatment temperature and deformation will greatly affect the performance of the wire. Therefore, formulating a suitable heat treatment system is of great significance to the mass production of niobium titanium wire, but this paper does not explain the actual industrial application.

[0007] Fan Kailun et al. published a paper on the influence of annealing cooling system on the shear strength of Ti45Nb alloy rivets. The paper studied the influence of different annealing systems on the shear strength of Ti45Nb rivets. The results showed that with the decrease of annealing cooling rate, the shear strength of Ti45Nb rivets increased and could reach 380MPa in air cooling. The paper also explained that the heat treatment system is highly sensitive to the properties of wire, so the key point is to formulate a reasonable wire annealing system. This paper also did not explain the actual industrial application. Summary of the invention

[0008] In view of the above defects, the present invention proposes a method for preparing a high shear strength Nb55Ti wire, comprising the following steps:

[0009] S1 Ingot preparation: Mix Nb: 40-48%; Fe: ≤0.03; O≤0.18; N≤0.03; C≤0.04; H≤0.001 according to mass fraction, and the balance is Ti to form a φ500-600mm Nb55Ti ingot;

[0010] S2 intermediate billet forging: six-fire intermediate billet forging, φ82~92×Lmm, air cooling;

[0011] S3 machining: machining to 80~90×L mm;

[0012] S4 rolling: heating to 650-700℃, keeping warm for 80-90min; rolling to φ9.5-10mm in multiple passes, air cooling, and testing H content;

[0013] S5 gauge round drawing: φ9.5~10mm rolled billet; φ9.0~9.2mm;

[0014] S6 stripping and overhaul: stripping to φ8.5~8.7mm;

[0015] S7 vacuum annealing: heat to 650-700℃, keep warm for 60-80 minutes, and cool in the furnace;

[0016] S8 finished product roller pulling: obtain the finished product;

[0017] S9 finished product polishing: dimensional tolerance is controlled between -0.01 and -0.02;

[0018] S10 detection and rewinding;

[0019] S11 makes the finished product into rivets, shears and punches, and anneals at 800-900℃.

[0020] Preferably, the six-fire intermediate billet upsetting forging in S2 comprises the following steps:

[0021] First fire: preheat at 820-850℃, keep warm for 100-120 minutes, heat up to 1130-1160℃, keep warm for 150-200 minutes; upset and draw twice, draw diagonally and chamfer to 400-410×Lmm; return to the furnace at 980-1040℃; upset and draw once, draw diagonally and chamfer to 400-410×Lmm; chamfer and round to φ430-440×Lmm, water-cool; after forging, grind and pickle completely and re-inspect;

[0022] Second fire: Ensure the surface of the material is clean, perform homogenization heat treatment at 1200-1280℃, and keep warm for 10-15 hours;

[0023] The third fire: preheat at 820-850℃, heat in the furnace for 60-80 minutes, then heat to 900-950℃, heat for 120-150 minutes; two upsetting and three drawing to 450-480×Lmm, one of which is horizontal drawing; return to the furnace at 920-950℃ after chamfering; two upsetting and three drawing to 400-410×Lmm, one of which is horizontal drawing and one is diagonal drawing; rounding to φ430-440×Lmm, water cooling; spot grinding after forging;

[0024] Fourth fire: preheat at 820-850℃, heat in the furnace for 60-80 minutes, then heat to 900-950℃, heat for 120-150 minutes; two upsetting and three drawing to 400-410×Lmm, one of which is horizontal drawing; return to the furnace at 900-920℃ after chamfering; one upsetting and three drawing to 250-280×Lmm, one of which is horizontal drawing; eight-way drawing and rounding to φ220-240×Lmm, air cooling; point grinding after forging;

[0025] Fifth fire: Heat the empty furnace to 880-910℃, keep the furnace warm for 120-150 minutes; draw to 120×L; round the V-shaped anvil to φ110-120×Lmm; re-inspect after complete grinding and pickling after forging;

[0026] Sixth fire: heat the empty furnace to 800-820℃, keep the furnace warm for 90-140 minutes; fine forge to φ82-92×Lmm, air cool, and straighten after forging.

[0027] The present invention prepares an ingot by a vacuum consumable smelting method, and then prepares an intermediate billet with fine and uniform structure by six-fire drawing, and then prepares a small-sized wire by one-fire rolling, cold drawing and two-fire vacuum annealing of the ingot. Finally, the Nb55Ti wire has high precision, uniform structure and consistent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 X-ray test results of the head and tail of the φ240mm intermediate billet (a) head, (b) tail.

[0029] Figure 2 Schematic diagram of the metallographic structure of the head, middle and tail samples of the first billet after six firings. (a) Nb55Ti-head, (b) Nb55Ti-middle, (c) Nb55Ti-tail.

[0030] Figure 3 , 4 This is the φ7.5mm horizontal and vertical 100X crystal phase diagram of Ti45Nb238111.

[0031] Figure 5 , 6 This is the φ6.48mm horizontal and vertical 100X crystal phase diagram of Ti45Nb238111.

[0032] Figure 7 , 8 This is the φ5.6mm horizontal and vertical 100X crystal phase diagram of Ti45Nb238111.

[0033] Fig. 9 , 10 This is the φ4.9mm horizontal and vertical 100X crystal phase diagram of Ti45Nb238111.

[0034] Fig.11 , 12 This is the φ4.5mm horizontal and vertical 100X crystal phase diagram of Ti45Nb238111. DETAILED DESCRIPTION

[0035] Embodiment 1,

[0036] Stability production experiment of φ7.5mm, φ6.48mm, φ5.6mm, φ4.9mm, φ4.5mm high shear strength Nb55Ti wire with batch number Ti45Nb238111:

[0037] S1 Ingot preparation: Mix Nb: 40-48%; Fe: ≤0.03; O≤0.18; N≤0.03; C≤0.04; H≤0.001 according to mass fraction, and the balance is Ti to form a φ500-600mm Nb55Ti ingot;

[0038] S2 intermediate billet forging: six-fire intermediate billet forging, φ82~92×Lmm, air cooling;

[0039] First fire: preheat at 850℃, keep warm for 100 minutes, heat up to 1130℃, keep warm for 150 minutes; upset and draw twice, draw diagonally and chamfer to 400~410×Lmm; return to the furnace at 980℃; upset and draw once, draw diagonally and chamfer to 410×Lmm; chamfer and round to φ430×Lmm, water cooling; after forging, completely grind and pickle and re-inspect;

[0040] Second fire: Ensure the surface of the material is clean, perform homogenization heat treatment at 1280℃, and keep warm for 10 hours;

[0041] Third fire: preheat at 850℃, heat in the furnace for 80 minutes, then heat to 950℃, heat for 150 minutes; two upsetting and three drawing to 480×Lmm, one of which is horizontal drawing; return to the furnace at 950℃ after chamfering; two upsetting and three drawing to 400×Lmm, one of which is horizontal drawing and one is diagonal drawing; rounding to φ430×Lmm, water cooling; spot grinding after forging;

[0042] Fourth fire: preheat at 850℃, heat in the furnace for 60 minutes, then heat to 900℃, heat for 120 minutes; two upsetting and three drawing to 400×Lmm, one of which is horizontal drawing; return to the furnace at 920℃ after chamfering; one upsetting and three drawing to 250×Lmm, one of which is horizontal drawing; eight-way drawing and rounding to φ240×Lmm, air cooling; point grinding after forging;

[0043] After the fourth heat treatment, the head and tail of the intermediate billet φ240mm bar were sampled for X-ray testing. The results are shown in Figure 1 The X-ray photo shows that the distribution of Ti and Nb in the entire cross-sectional field of view is relatively uniform, with no obvious titanium-rich, niobium-rich and niobium-infusible blocks, and the process control of ingot melting and forging is stable.

[0044] Fifth fire: Heat the empty furnace to 880℃, keep the furnace warm for 120 minutes; draw to 120×L; round the V-shaped anvil to φ120×Lmm; polish and pickle after forging and re-inspect;

[0045] Sixth fire: heat the empty furnace to 800℃, keep the furnace warm for 140 minutes; fine forge to φ82×Lmm, air cool, and straighten after forging.

[0046] S3 machining: machining to 90×L mm;

[0047] S4 rolling: heating to 650℃, keeping warm for 80min, then rolling to φ10mm in multiple passes, air cooling, and testing H content;

[0048] S5 gauge round drawing: φ9.5mm rolled billet; to φ9.0mm;

[0049] S6 stripping and overhaul: stripping to φ8.5mm;

[0050] S7 vacuum annealing: heat to 700℃, keep warm for 60 minutes, and cool in the furnace;

[0051] S8 finished product roller pulling: obtain the finished product;

[0052] S9 finished product polishing: dimensional tolerance is controlled within -0.01;

[0053] S10 detection and rewinding;

[0054] S11 makes the finished product into rivets, shears and punches, and anneals at 900℃.

[0055] The head, middle and tail of the rod blank after six firings were sampled for metallographic and hardness analysis. Figure 2 The hardness test results of the forged state (R) of the bar billet are shown in Table 1. The hardness test results of the bar show that the hardness deviation of the head, middle and tail is small, and the performance consistency of the forged bar billet is good. The grain size of the head, middle and tail of the bar billet is uniform and consistent. The forging process has greatly improved the uniformity of the ingot structure, the grains have been refined, and the consistency of the bar billet structure is good, which lays a good organizational foundation for subsequent wire processing.

[0056] Table 1 Bar hardness test results

[0057]

[0058] Embodiment 2,

[0059] Stability production experiment of φ7.5mm, φ6.48mm, φ5.6mm, φ4.9mm, φ4.5mm high shear strength Nb55Ti wire with batch number Ti45Nb238110:

[0060] The steps are the same as those in Example 1, and the process parameters are adaptively adjusted.

[0061] Embodiment 3,

[0062] Stability production experiment of φ7.5mm, φ6.48mm, φ5.6mm, φ4.9mm, φ4.5mm high shear strength Nb55Ti wire with batch number Ti45Nb238104:

[0063] The steps are the same as those in Example 1, and the process parameters are adaptively adjusted.

[0064] The metallographic images of the products of three batches of tests were tested, such as Figure 3-12 The mechanical properties are shown in Table 2. It can be seen from the figure that the products of different specifications have uniform organization in the transverse (cross-section direction of the wire) and longitudinal (length direction of the wire), fine transverse and longitudinal grains, and both are equiaxed organizational structures. Due to cold drawing, the longitudinal direction also has a strip-like structure. The two structures jointly determine the excellent shear force level. The data in the table show that the wires of various specifications maintain a shear strength of 430-465MPa and have high toughness, achieving a good match between strength and toughness.

[0065]

[0066]

[0067] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of this patent.

Claims

1. A method for preparing high shear strength Nb55Ti wire, characterized in that The following steps are involved: S1 Ingot preparation: Mixing by mass fraction Nb: 40-48%; Fe: ≤0.03; O≤0.18; N≤0.03; C≤0.04; H≤0.001, φ500~600mm Nb55Ti ingot with the remainder being Ti; S2 intermediate billet forging: six-fire intermediate billet forging, φ82~92×Lmm, air cooling; S3 machining: machining to 80~90×L mm; S4 rolling: heating to 650-700℃, keeping warm for 80-90min, then rolling to φ9.5-10mm in multiple passes, air cooling, and testing H content; S5 gauge round drawing: φ9.5~10mm rolled billet; φ9.0~9.2mm; S6 stripping and overhaul: stripping to φ8.5~8.7mm; S7 vacuum annealing: heat to 650-700℃, keep warm for 60-80 minutes, and cool in the furnace; S8 finished product roller pulling: obtain the finished product; S9 finished product polishing: dimensional tolerance is controlled between -0.01 and -0.02; S10 detection and rewinding; S11 makes the finished product into rivets, shears and punches, and anneals at 800-900℃.

2. A method for preparing a high shear strength Nb55Ti wire according to claim 1, characterized in that: The six-fire intermediate billet upsetting forging in S2 comprises the following steps: First fire: preheat at 820-850℃, keep warm for 100-120 minutes, heat up to 1130-1160℃, keep warm for 150-200 minutes; upset and draw twice, draw diagonally and chamfer to 400-410×Lmm; return to the furnace at 980-1040℃; upset and draw once, draw diagonally and chamfer to 400-410×Lmm; chamfer and round to φ430-440×Lmm, water-cool; after forging, grind and pickle completely and re-inspect; Second fire: Ensure the surface of the material is clean, perform homogenization heat treatment at 1200-1280℃, and keep warm for 10-15 hours; The third fire: preheat at 820-850℃, heat in the furnace for 60-80 minutes, then heat to 900-950℃, heat for 120-150 minutes; two upsetting and three drawing to 450-480×Lmm, one of which is horizontal drawing; return to the furnace at 920-950℃ after chamfering; two upsetting and three drawing to 400-410×Lmm, one of which is horizontal drawing and one is diagonal drawing; rounding to φ430-440×Lmm, water cooling; spot grinding after forging; Fourth fire: preheat at 820-850℃, heat in the furnace for 60-80 minutes, then heat to 900-950℃, heat for 120-150 minutes; two upsetting and three drawing to 400-410×Lmm, one of which is horizontal drawing; return to the furnace at 900-920℃ after chamfering; one upsetting and three drawing to 250-280×Lmm, one of which is horizontal drawing; eight-way drawing and rounding to φ220-240×Lmm, air cooling; point grinding after forging; Fifth fire: Heat the empty furnace to 880-910℃, keep the furnace warm for 120-150 minutes; draw to 120×L; round the V-shaped anvil to φ110-120×Lmm; re-inspect after complete grinding and pickling after forging; Sixth fire: heat the empty furnace to 800-820℃, keep the furnace warm for 90-140 minutes; fine forge to φ82-92×Lmm, air cool, and straighten after forging.

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