Production method of small-specification high-alloy annealed silver bright bar

Abstract

The invention belongs to the technical field of metal material processing and heat treatment, and relates to a production method of a small-specification high-alloy annealed silver bright bar. A process route of a converter, an LF furnace, an RH furnace, continuous casting, cogging, steel billet grinding and flaw detection, steel billet anti-decarburization coating, wire rolling, spheroidizing annealing, cold drawing, straightening, slitting, polishing and rust-proof packaging is adopted. According to the method, the high-quality annealed silver bright round steel with the diameter being 14-19 mm, the hardness being smaller than or equal to 207 HBW, the straightness being smaller than or equal to 1 mm / m, the dimensional tolerance reaching the h8 level and the surface smoothness Ra being smaller than or equal to 3.2 microns is successfully produced by optimizing component design and innovating the technological process and particularly introducing key steps such as a steel billet anti-decarburization coating, combined drawing and controlled straightening, precise polishing and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing and heat treatment technology, and relates to a method for producing small-sized high-alloy annealed bright silver bars. Background Technology

[0002] High-alloy silver bright bar is a high-end steel with high dimensional accuracy, high surface finish and excellent mechanical properties. It is widely used in the manufacture of key components with extremely high requirements for fatigue strength, wear resistance and reliability, such as actuators and engine parts of aerospace vehicles, high-strength fasteners and drive shafts in the automotive industry, and precision instruments in the defense industry.

[0003] Traditional production processes for small-diameter high-alloy bright silver bars typically follow a route of "bar rolling → annealing → drawing / turning → polishing". This route has the following significant drawbacks: 1) Low yield, especially since turning and polishing processes generate a large amount of metal shavings, resulting in low material utilization; 2) Low production efficiency, numerous processes, and long production cycles; 3) High production costs, high energy consumption, and expensive processing fees; 4) For high-alloy steel, traditional processes struggle to precisely control its microstructure and properties, particularly in preventing surface decarburization and ensuring uniform hardness and straightness, often failing to meet the requirements of high-end applications.

[0004] Therefore, developing a new method that has a high yield, high production efficiency, controllable cost, and can stably produce high-precision, high-performance, small-size high-alloy silver bright bars has significant industrial application value and economic significance. Summary of the Invention

[0005] To achieve the above objectives, this invention provides a method for producing small-diameter high-alloy annealed bright silver bars. This method, through optimized composition design and innovative process flow, particularly by introducing key steps such as anti-decarburization coating on steel billets, combined drawing and controlled straightening, and precision grinding, successfully produces high-quality annealed bright silver round bars with diameters of 14-19 mm, hardness ≤207HBW, straightness ≤1 mm / m, dimensional tolerances reaching h8 grade, and surface finish Ra ≤3.2 μm. This product can be directly blanked for tempering or forging, and used to manufacture critical components with stringent requirements for impact resistance and ultra-high strength.

[0006] The technical solution adopted in this invention is a method for producing small-diameter high-alloy annealed bright silver bars, the key process steps of which include:

[0007] S1: In the smelting stage, the steel tapped from the converter has C≥0.06% and P≤0.010%, and adopts the LF+RH furnace refining process. The LF furnace refining process involves argon blowing throughout, slag formation and deoxidation, and the white slag holding time is ≥30min. The process control is Als=0.035~0.055%. The RH vacuum degassing treatment is carried out at a vacuum degree below 0.5tor, and the vacuum holding time is not less than 20min. The molten steel exiting the station has H≤1.5ppm and O≤10ppm.

[0008] S2: Continuous casting stage, full-process protective casting, tundish superheat ≤25℃ in the continuous casting furnace, ≤35℃ in the open casting furnace, billet size is 350×430mm;

[0009] S3: Heating stage, the billet heating time is 360-500 min, the heating section temperature is 1180-1220℃, and the soaking section temperature is 1200-1240℃;

[0010] S4: In the billet rolling stage, the 1150 bar and wire rod two-roll reciprocating mill adopts a large reduction for rolling. The reduction in the first and second passes is controlled at 90mm and 85mm respectively; the rolling temperature is ≥1100℃; the billet is 180×180mm, and the billets are stacked and put into the slow cooling rack for slow cooling.

[0011] S5: Steel billet grinding and flaw detection stage, shot blasting removes surface iron oxide scale from steel billet and performs magnetic particle flaw detection;

[0012] S6: The steel billet is sprayed with a special anti-decarburization layer before entering the wire rod heating furnace;

[0013] S7: Wire rolling stage, preheating temperature ≤ 750℃, furnace exit temperature 1000-1040℃, furnace time 100-200 minutes, final rolling and sizing temperature 850-890℃, wire drawing temperature 820-850℃, delayed cooling is adopted.

[0014] S8: During the spheroidizing annealing stage of wire rod, the temperature is maintained at 760±10℃ for 7.5 hours, then cooled to 650±5℃ for 4 hours, and then cooled to 500℃ in the furnace. The wire rod is then air-cooled, pickled, and phosphated.

[0015] S9: During the cold drawing, straightening, and slitting stages, the combined drawing dimension is reduced by 20%, and the two-roll straightening q≤1.0mm / m;

[0016] S10: Polishing stage, diameter reduced by 0.1mm, diameter tolerance h8, surface finish Ra≤3.2μm.

[0017] S11: Rust-proof packaging.

[0018] Furthermore, during the S7 wire rolling stage, the cooling rate is ≤0.8℃ / s.

[0019] Furthermore, the S11 rust-proof packaging specifically involves: spraying oil-based rust-proof oil onto the surface of the round steel, bundling it with rubber-coated binding wire, then wrapping it with waterproof plastic film, sealing it with transparent tape, then putting it in a woven bag, and finally packing it into a wooden box for protection.

[0020] Furthermore, the chemical composition of the steel by mass percentage is as follows: C: 0.39%–0.41%, Si: 0.22%–0.34%, Mn: 0.72%–0.80%, P≤0.015%, S≤0.005%, Cr: 0.80%–0.88%, Ni: 1.75%–1.82%, Al: 0.020%–0.040%, N: 0.004%–0.008%, Cu≤0.20%, Mo: 0.23%–0.25%, Ti≤0.008%, B≤0.0008%, Sn+As+Pb+Sb+Bi≤0.035%, H≤0.0002%, O≤0.0015%, with the remainder being Fe and essential impurities.

[0021] Furthermore, the hardness of the bright silver round steel is ≤207HBW, and the straightness is ≤1mm / m.

[0022] This invention ensures the high performance, high precision, and high surface quality of the final product mainly from the following aspects:

[0023] 1. Precision and balance in chemical composition design:

[0024] The chemical composition system designed in this invention is a medium-carbon chromium-nickel-molybdenum alloy structural steel, and its composition design reflects a balance of high strength, high toughness, high hardenability and excellent processability.

[0025] C: 0.39%~0.41%: Carbon is the core element that ensures the strength and hardness of steel. Controlling it within a narrow high-carbon range ensures that the product can achieve a hardness requirement of ≤207HBW after annealing, and provides a sufficient carbon content basis for subsequent quenching and tempering to obtain high strength.

[0026] Si: 0.22%–0.34%, Mn: 0.72%–0.80%: Silicon and manganese mainly play a role in solid solution strengthening, improving strength. Manganese can also improve the hardenability of steel and reduce the harmful effects of sulfur.

[0027] Cr: 0.80%–0.88%, Ni: 1.75%–1.82%, Mo: 0.23%–0.25%: Chromium, nickel, and molybdenum are key alloying elements for improving the hardenability, strength, toughness, and tempering resistance of steel. Chromium and molybdenum can form carbides, improving wear resistance; nickel can significantly improve the toughness of steel, especially low-temperature toughness. A combination of these three elements in this ratio achieves the optimal balance of strength and toughness.

[0028] Al: 0.020%~0.040%, N: 0.004%~0.008%: Aluminum acts as a deoxidizer and combines with nitrogen to form fine AlN particles, which can effectively pin the austenite grain boundaries, inhibit the growth of austenite grains during heating, and play a role in refining the grains, thereby improving the strength and toughness of the steel at the same time.

[0029] B≤0.0008%: Boron is an extremely effective element for improving hardenability. The addition of trace amounts of boron can significantly improve the hardenability of steel and ensure the core properties of steel with large cross-sections.

[0030] Extremely low levels of impurity elements such as P, S, gaseous H, O, and residual elements like Sn and As: Extremely low P and S content reduces grain boundary segregation and brittleness, improving the steel's purity, which is crucial for improving toughness, fatigue performance, and reducing hot-working cracks. Extremely low H and O gas content prevents defects such as white spots and porosity. Strict control of residual element content avoids the adverse effects of these elements' segregation at grain boundaries, leading to hot brittleness and ensuring the material's hot-working performance and reliability. This ultra-high purity control is a prerequisite for meeting the requirements of high-end applications such as aerospace.

[0031] 2. Clean steelmaking process and high-quality billet control throughout the entire process:

[0032] LF+RH dual refining and vacuum degassing: Deep deoxidation and desulfurization are achieved by creating white slag in the LF furnace, and deep dehydrogenation and denitrification are achieved by vacuum treatment in the RH furnace. The H and O content of the molten steel leaving the station is controlled at extremely low levels (H≤1.5ppm, O≤10ppm), which ensures the high purity of the molten steel from the source, reduces the number and size of non-metallic inclusions, and lays the foundation for fatigue resistance.

[0033] Full-process protective casting and low superheat control: Full-process protective casting is adopted to prevent secondary oxidation; controlling the low superheat of the tundish (≤25℃) is conducive to the formation of fine equiaxed crystals, reducing central shrinkage and segregation, and obtaining high-quality continuous casting billets with uniform composition and excellent internal quality.

[0034] 3. Controlled rolling and cooling, and microstructure refinement:

[0035] Large reduction rolling during billet opening: The first and second passes of large reduction rolling with a reduction of 90mm and 85mm respectively are used in the billet opening stage, which can fully break up the coarse dendritic structure in the cast state, refine the grains, and improve the internal density.

[0036] Controlled rolling and cooling in wire rod rolling: The furnace exit temperature is controlled at a low level of 1000-1040℃, the final rolling temperature is 850-890℃, and the wire drawing temperature is 820-850℃. Delayed cooling of ≤0.8℃ / s is adopted to obtain a fine-grained ferrite-pearlite structure and avoid excessive rolling stress, thus preparing the microstructure for subsequent spheroidizing annealing.

[0037] 4. Innovative anti-decarburization technology and surface quality control:

[0038] Special anti-decarburization coating for steel billets: This is one of the core innovations of this invention. Applying an anti-decarburization coating to the steel billets before they enter the wire rod heating furnace effectively prevents direct contact between the high-temperature furnace gases and the billet surface, greatly reducing surface decarburization during the heating process. This not only ensures the carbon content and hardness of the product surface, but more importantly, it significantly reduces the depth of the decarburized layer that needs to be removed in the subsequent grinding process, significantly improving yield and production efficiency while reducing costs.

[0039] Full re-grinding and non-destructive testing of steel billets: Shot blasting, flaw detection, and full re-grinding are performed on the steel billets, removing 2mm from each side. This ensures that the surface of the billets used for rolling wire rod is free of any defects, which is the foundation for obtaining a high-quality wire rod surface. Ultrasonic testing is required to reach GB / T 4162B grade, guaranteeing the high quality of the billet's internal structure.

[0040] 5. Precise spheroidizing annealing process:

[0041] A two-stage isothermal spheroidizing annealing process was employed, involving holding at 760±10℃ for 7.5 hours and then at 650±5℃ for 4 hours under gas protection. The high-temperature holding allowed for the complete dissolution and diffusion of carbides, while the low-temperature isothermal process ensured the uniform precipitation of carbides in a spherical form. This process resulted in a carbide spheroidization rate exceeding 95%, yielding a uniform spherical pearlite microstructure with a hardness ≤207 HBW. This structure exhibited excellent cold workability and machinability, and also provided superior microstructure preparation for subsequent heat treatment.

[0042] 6. High-precision cold working and surface treatment:

[0043] Combined drawing and straightening: Utilizing a 20% reduction in diameter during cold drawing not only precisely controls dimensions but also introduces work hardening to enhance strength. Combined with straightening at q≤1.0mm / m, this ensures the product's straightness meets the requirements of high-end applications.

[0044] Precision polishing: The polishing amount is precisely controlled to ensure that the product dimensional tolerance reaches h8 level and the surface roughness Ra≤3.2μm, achieving a "silver-bright" surface that can be used directly by the user.

[0045] Long-lasting rust-proof packaging: Multi-layer composite rust-proof packaging is used, namely sprayed rust-proof oil + waterproof film + woven bag + wooden box, to ensure that the product will not rust within a one-year storage period, meeting the needs of high-end customers for inventory and long-distance transportation.

[0046] The beneficial effects of this invention are:

[0047] (1) This invention solves the problems of low yield, low production efficiency, high cost and unstable quality in traditional bar production lines by using precise chemical composition design, ultra-high purity smelting, innovative anti-decarburization technology, precise spheroidizing annealing heat treatment technology and drawing-straightening-grinding cold working process.

[0048] (2) Annealed bright silver round steel with a diameter of 14-19mm produced by the method of this invention has a hardness ≤207HBW, a flatness ≤1mm / m, and meets the h8 requirement. It fully meets the stringent requirements of high-performance and high-reliability materials in aerospace, automotive, and defense industries, and has significant economic benefits and market competitiveness. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a metallographic image (500X) of the spheroidized structure of the silver bright bar produced by the method of Embodiment 1 of the present invention;

[0051] Figure 2 This is a physical image of the final bright silver bar product produced by the method in Embodiment 1 of the present invention. Detailed Implementation

[0052] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0053] This invention provides a production method for small-sized high-alloy annealed bright silver bars, using the following process route: converter + LF furnace + RH furnace + continuous casting + billet opening + billet grinding and flaw detection + billet anti-decarburization coating + wire rod rolling + spheroidizing annealing + cold drawing + straightening + slitting + polishing + rust prevention packaging.

[0054] The production process includes the following key steps:

[0055] 1) Smelting: The steel tapped from the converter has C≥0.06% and P≤0.010%. The LF+RH furnace refining process is adopted. The LF furnace refining process involves argon blowing throughout, slag formation and deoxidation, and white slag holding time ≥30min. The process control Als=0.035~0.055%. The RH vacuum degassing treatment is carried out at a vacuum degree below 0.5tor, and the vacuum holding time is not less than 20min. The H of the molten steel exiting the station is ≤1.5ppm and O≤10ppm.

[0056] 2) Continuous casting: Full-process protective casting is adopted, the superheat of the tundish in the continuous casting furnace is ≤25℃, the temperature of the open casting furnace is ≤35℃, and the billet size is 350×430mm;

[0057] 3) Heating: The billet heating time is 360-500 min, the heating section temperature is 1180-1220℃, and the soaking section temperature is 1200-1240℃;

[0058] 4) Billet rolling: The 1150 bar and wire rod two-roll reciprocating mill adopts large reduction for rolling. The reduction of the first and second passes is controlled at 90mm and 85mm respectively; the initial rolling temperature is ≥1100℃; the billet is 180×180mm, and the billets are stacked and put into the slow cooling rack for slow cooling.

[0059] 5) Steel billet grinding and flaw detection: The steel billet is shot blasted to remove surface iron oxide scale, then subjected to magnetic particle testing. Surface defects are first removed by grinding, with 2mm removed from each side of the entire billet surface. The surface Ra of the steel billet is ≤2mm. It passes ultrasonic testing according to GB / T 4162 Class B.

[0060] 6) Spraying an anti-decarburization layer on the surface of the billet: Before the billet enters the wire rod heating furnace, a special anti-decarburization layer is sprayed on it to prevent high-temperature decarburization, reduce the grinding depth of the subsequent grinding process, and improve the yield and production efficiency.

[0061] 7) Wire rod rolling: Preheating zone temperature ≤ 750℃, furnace exit temperature 1000-1040℃, furnace time 100-200 minutes. Wire rod dimensions are controlled to C-grade precision. Final rolling sizing temperature 850-890℃, wire drawing temperature 820-850℃, delayed cooling is adopted, cooling rate ≤ 0.8℃ / s, hot coiling, slow cooling to release rolling stress.

[0062] 8) Wire rod spheroidizing annealing: Gas protection, hold at 760±10℃ for 7.5 hours, cool to 650±5℃ and hold for 4 hours, then cool to 500℃ in the furnace, and air cool after removal from the furnace. Hardness ≤207HBW. Pickling and phosphating.

[0063] 9) Cold drawing, straightening, and slitting: Combined drawing reduces the diameter by 20% to prevent dimensional rebound after straightening. Two-roll straightening q≤1.0mm / m.

[0064] 10) Polishing: Diameter reduced by 0.1mm, diameter tolerance h8, surface finish Ra≤3.2μm.

[0065] 11) Rust-proof packaging: The round steel surface is sprayed with oil-based rust-preventive oil and bundled with rubber-coated binding wire. Then, it is wrapped with waterproof plastic film to prevent oil leakage and sealed with transparent tape. Next, it is placed in woven bags. Finally, it is packed into a wooden crate for protection. This ensures the material will not rust within one year of production.

[0066] The chemical composition of the steel by mass percentage is as follows: C: 0.39%–0.41%, Si: 0.22%–0.34%, Mn: 0.72%–0.80%, P≤0.015%, S≤0.005%, Cr: 0.80%–0.88%, Ni: 1.75%–1.82%, Al: 0.020%–0.040%, N: 0.004%–0.008%, Cu≤0.20%, Mo: 0.23%–0.25%, Ti≤0.008%, B≤0.0008%, Sn+As+Pb+Sb+Bi≤0.035%, H≤0.0002%, O≤0.0015%, with the remainder being Fe and essential impurities.

[0067] The following examples provide further details.

[0068] Example 1:

[0069] This embodiment relates to the production of annealed bright silver round steel with a diameter of 16mm.

[0070] The chemical composition of the steel by mass percentage is: C: 0.40, Si: 0.28, Mn: 0.76, P: 0.012, S: 0.004, Cr: 0.84, Ni: 1.78, Al: 0.030, N: 0.006, Cu: 0.15, Mo: 0.24, Ti: 0.005, B: 0.0006, [H]: 0.00018, [O]: 0.0013, Sn+As+Pb+Sb+Bi=0.028.

[0071] The key process parameters are as follows:

[0072] RH vacuum holding time: 22 min, [H] = 1.4 ppm, [O] = 9 ppm at the station.

[0073] Heating time for billet: 380 min, soaking zone temperature: 1210℃.

[0074] Wire rolling: furnace exit temperature 1020℃, wire drawing temperature 835℃, cooling rate 0.7℃ / s.

[0075] Spheroidizing annealing: Hold at 760℃ for 7.5h, then at 650℃ for 4h, with a furnace hardness of 205HBW.

[0076] Cold drawing diameter reduction: 20%.

[0077] Dimensions after polishing: Φ15.9±0.02mm(h8), surface roughness Ra=2.8μm.

[0078] The spheroidized structure 500X metallographic image of the bright silver bar produced according to the above method is shown below. Figure 1As shown in the image, the final product of the silver-bright bar stock is as follows: Figure 2 As shown.

[0079] Final product performance: Hardness 205HBW, flatness 0.8mm / m.

[0080] Example 2:

[0081] This embodiment relates to the production of annealed bright silver round steel with a diameter of 19mm.

[0082] The chemical composition of the steel by mass percentage is: C: 0.41, Si: 0.32, Mn: 0.78, P: 0.010, S: 0.003, Cr: 0.87, Ni: 1.80, Al: 0.035, N: 0.007, Cu: 0.12, Mo: 0.245, Ti: 0.007, B: 0.0007, [H]: 0.00017, [O]: 0.0012, Sn+As+Pb+Sb+Bi=0.025.

[0083] Key process parameters:

[0084] RH vacuum holding time: 25 min, [H] = 1.2 ppm, [O] = 8 ppm at the station.

[0085] Heating time for billet: 450 min, soaking zone temperature: 1220℃.

[0086] Wire rolling: furnace exit temperature 1035℃, wire drawing temperature 845℃, cooling rate 0.6℃ / s.

[0087] Spheroidizing annealing: Hold at 765℃ for 7.5 hours, then at 655℃ for 4 hours, with a furnace hardness of 200 HBW.

[0088] Cold drawing diameter reduction: 20%.

[0089] Dimensions after polishing: Φ18.9±0.023mm(h8), surface roughness Ra=3.0μm.

[0090] Final product performance: Hardness 200HBW, flatness 0.7mm / m.

[0091] Example 3:

[0092] This embodiment relates to the production of annealed bright silver round steel with a diameter of 14mm.

[0093] The chemical composition of the steel by mass percentage is: C: 0.39, Si: 0.25, Mn: 0.73, P: 0.014, S: 0.005, Cr: 0.81, Ni: 1.76, Al: 0.025, N: 0.005, Cu: 0.18, Mo: 0.235, Ti: 0.006, B: 0.0005, [H]: 0.00019, [O]: 0.0014, Sn+As+Pb+Sb+Bi=0.030.

[0094] Key process parameters:

[0095] RH vacuum holding time: 20 min, [H] = 1.5 ppm, [O] = 10 ppm at the outlet.

[0096] Heating time for billet: 400 min, soaking zone temperature: 1205℃.

[0097] Wire rolling: Exit temperature 1010℃, wire drawing temperature 825℃, cooling rate 0.75℃ / s.

[0098] Spheroidizing annealing: Hold at 755℃ for 7.5 hours, then at 645℃ for 4 hours, resulting in a furnace hardness of 207 HBW.

[0099] Cold drawing diameter reduction: 20%.

[0100] Dimensions after polishing: Φ13.9±0.018mm(h8), surface roughness Ra=2.5μm.

[0101] Final product performance: Hardness 207HBW, flatness 0.9mm / m.

[0102] The results of the above embodiments show that the method provided by the present invention can stably produce high-quality, small-size high-alloy annealed bright silver bars that fully meet the technical requirements.

[0103] In summary, the technical solution of this invention produces annealed bright silver round steel with a diameter of 14-19mm, a hardness ≤207HBW, a straightness ≤1mm / m, and dimensions meeting the h8 requirement. This solves the problems of low yield, low production efficiency, and high cost associated with traditional bar production lines that involve rolling small bars, annealing, and then drawing or turning.

[0104] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

[0105] To facilitate understanding by those skilled in the art of the improvements of this invention over the prior art, some of the accompanying drawings and descriptions have been simplified, and for clarity, some other elements have been omitted from this application. Those skilled in the art should realize that these omitted elements may also constitute the content of this invention.

Claims

1. A method for producing small-diameter high-alloy annealed bright silver bars, characterized in that, Key process steps include: S1: In the smelting stage, the steel tapped from the converter has C≥0.06% and P≤0.010%, and adopts the LF+RH furnace refining process. The LF furnace refining process involves argon blowing throughout, slag formation and deoxidation, and the white slag holding time is ≥30min. The process control is Als=0.035~0.055%. The RH vacuum degassing treatment is carried out at a vacuum degree below 0.5tor, and the vacuum holding time is not less than 20min. The molten steel exiting the station has H≤1.5ppm and O≤10ppm. S2: Continuous casting stage, full-process protective casting, tundish superheat ≤25℃ in the continuous casting furnace, ≤35℃ in the open casting furnace, billet size is 350×430mm; S3: Heating stage, the billet heating time is 360-500 min, the heating section temperature is 1180-1220℃, and the soaking section temperature is 1200-1240℃; S4: In the billet rolling stage, the 1150 bar and wire rod two-roll reciprocating mill adopts a large reduction for rolling. The reduction in the first and second passes is controlled at 90mm and 85mm respectively; the rolling temperature is ≥1100℃; the billet is 180×180mm, and the billets are stacked and put into the slow cooling rack for slow cooling. S5: Steel billet grinding and flaw detection stage, shot blasting removes surface iron oxide scale from steel billet and performs magnetic particle flaw detection; S6: The steel billet is sprayed with a special anti-decarburization layer before entering the wire rod heating furnace; S7: Wire rolling stage, preheating temperature ≤ 750℃, furnace exit temperature 1000-1040℃, furnace time 100-200 minutes, final rolling and sizing temperature 850-890℃, wire drawing temperature 820-850℃, delayed cooling is adopted. S8: During the spheroidizing annealing stage of wire rod, the temperature is maintained at 760±10℃ for 7.5 hours, then cooled to 650±5℃ for 4 hours, and then cooled to 500℃ in the furnace. The wire rod is then air-cooled, pickled, and phosphated. S9: During the cold drawing, straightening, and slitting stages, the combined drawing dimension is reduced by 20%, and the two-roll straightening q≤1.0mm / m; S10: Polishing stage, diameter reduced by 0.1mm, diameter tolerance h8, surface finish Ra≤3.2μm; S11: Rust-proof packaging.

2. The method for producing small-diameter high-alloy annealed bright silver bars as described in claim 1, characterized in that, During the S7 wire rolling stage, the cooling rate is ≤0.8℃ / s.

3. The method for producing small-diameter high-alloy annealed bright silver bars as described in claim 2, characterized in that, The S11 rust-proof packaging is specifically as follows: the round steel surface is sprayed with oil-based rust-proof oil, bundled with rubber-coated binding wire, then wrapped with waterproof plastic film, then sealed with transparent tape, then put into a woven bag, and finally placed in a wooden box for protection.

4. The method for producing small-diameter high-alloy annealed bright silver bars as described in claim 3, characterized in that, The chemical composition of the steel by mass percentage is as follows: C: 0.39%–0.41%, Si: 0.22%–0.34%, Mn: 0.72%–0.80%, P≤0.015%, S≤0.005%, Cr: 0.80%–0.88%, Ni: 1.75%–1.82%, Al: 0.020%–0.040%, N: 0.004%–0.008%, Cu≤0.20%, Mo: 0.23%–0.25%, Ti≤0.008%, B≤0.0008%, Sn+As+Pb+Sb+Bi≤0.035%, H≤0.0002%, O≤0.0015%, with the remainder being Fe and essential impurities.

5. The method for producing small-diameter high-alloy annealed bright silver bars as described in claim 4, characterized in that, The hardness of the bright silver round steel is ≤207HBW, and the straightness is ≤1mm / m.

Images