Production method of low-cost ultrahigh-strength bainite anchor rod steel

Abstract

The invention discloses a low-cost ultrahigh-strength bainite anchor rod steel production method which is characterized in that a process route of composite microalloying, two-stage controlled rolling and ultra-fast cooling (UFC) is adopted; the low-cost bainite anchor rod steel comprises the following chemical components in percentage by mass: 0.18-0.25% of C, 0.60-1.20% of Si, 1.90-2.50% of Mn, 0.08-0.10% of V, less than or equal to 0.015% of P and S, and the balance of Fe and impurity elements, and the gas content [O] is less than or equal to 0.0030%, the gas content [N] is less than or equal to 0.0080%, and the gas content [H] is less than or equal to 0.0002%. According to the low-cost ultrahigh-strength bainite anchor rod steel production method, through precise component design and process optimization, the use amount of key precious metal such as Mo and Ni is reduced, and a high-performance structure with (ultra) fine grain bainite as the main component is strived to be stably obtained under the industrial condition.

Description

Technical Field

[0001] This invention belongs to the field of mine support materials technology, and in particular relates to a low-cost, ultra-high-strength bainitic anchor steel production method. Background Technology

[0002] Currently, anchor bolt steel generally suffers from the following problems: strength bottleneck: traditional MG500 and MG600 grade anchor bolt steels are difficult to meet the high ground pressure requirements of deep wells, and quenched alloy steels are expensive; martensitic steels have high strength but poor toughness and are prone to brittle fracture, which affects the safety of the support. In addition, air cooling after hot rolling leads to uneven microstructure and pearlite phase transformation, which reduces strength and toughness. Based on this, it is necessary to develop high-strength, high-toughness, and low-cost anchor bolt steels.

[0003] Achieving excellent impact toughness while maintaining strength is the biggest challenge. Simplifying the production process and reducing costs are also key challenges, requiring the avoidance or minimization of offline heat treatment (such as quenching and tempering) and reducing the addition of expensive alloying elements (such as Ni and Mo). Precise control and uniformity of the microstructure are crucial, requiring the stable and consistent acquisition of a fine-grained (ultra-fine) bainite-dominant microstructure (>90%) on an industrial scale. Fine-grained bainite provides both high strength (derived from high dislocation density bainitic ferrite) and good toughness (refined grains, small laths). It effectively suppresses the appearance of abnormal phases such as quenched martensite, proeutectoid ferrite, and Widmanstätten. It ensures the uniformity of microstructure and properties along the length and cross-section of the rod. This invention patent provides a low-cost bainitic anchor steel with a yield strength ≥800MPa, tensile strength ≥900MPa, elongation ≥17%, and impact performance at 20℃ ≥35J, as well as its controlled rolling and controlled cooling production process, to solve the above-mentioned problems. Summary of the Invention

[0004] Existing methods for producing ultra-high-strength anchor steel suffer from significant technical bottlenecks, including difficulty in balancing strength and toughness, complex production processes, long workflows, high energy consumption and costs, over-reliance on expensive alloying elements, and challenges in controlling microstructure uniformity and stability. Against this backdrop, there is an urgent need to develop a new anchor steel production method that can comprehensively address these problems and offer significant technical and economic advantages. The purpose of this invention is to provide a low-cost method for producing ultra-high-strength bainitic anchor steel. By precisely designing the composition and optimizing the process, the method reduces the use of key precious metals such as Mo and Ni, striving to stably obtain a high-performance microstructure dominated by (ultra)fine-grained bainite under industrial conditions. The main process is based as much as possible on continuous rolling combined with precise online cooling control, eliminating or greatly reducing offline quenching processes, thereby reducing energy consumption, shortening the cycle time, and improving efficiency. Simultaneously, it requires precise control of key parameters such as rolling temperature and cooling path (temperature and rate).

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention discloses a low-cost, ultra-high-strength bainitic anchor steel production method, employing a "composite microalloying + two-stage controlled rolling + ultra-fast cooling (UFC)" process route. Specifically: billet → heating (1100-1150℃) → rough rolling 950-1050℃ → finish rolling 880-950℃ → ultra-fast cooling → slow cooling in the bainitic phase transformation zone → collection on a cooling bed → bundling → weighing; In the ultra-fast cooling stage: water mist cooling is activated within 3 seconds after the finish rolling, with a cooling rate ≥60℃ / s to 550-650℃; then air mist cooling is switched, with a controlled cooling rate of 0.5-1℃ / s; the collection temperature is limited to 280-320℃ before being placed in the slow cooling pit;

[0007] The chemical composition of the low-cost bainitic anchor steel by mass percentage is: C 0.18-0.25%, Si 0.60-1.20%, Mn 1.90-2.50%, V 0.08-0.10%, P, S≤0.015%, with the balance being Fe and impurity elements. The required gas content is [O]≤0.0030%, [N]≤0.0080%, and [H]≤0.0002%.

[0008] Furthermore, the cooling rate of the ultra-fast cooling is 60-80℃ / s.

[0009] Furthermore, the chemical composition of the low-cost bainitic anchor steel by mass percentage is as follows: C 0.22%, Si 0.85%, Mn 2.0%, V 0.09%, P 0.014%, S 0.002%, gas content [O] 0.0022%, [N] 0.0056%, [H] 0.00012%, with the balance being Fe and impurity elements.

[0010] Furthermore, the roughing process involves 6 passes, with a final rolling temperature of 1020℃.

[0011] Furthermore, the intermediate rolling process involves 6 passes, with a final rolling temperature of 990℃.

[0012] Furthermore, the finishing rolling process involves six passes with a final rolling temperature of 900℃.

[0013] Furthermore, the water cooling rate is 70℃ / s to 580℃.

[0014] Furthermore, the aerosol is cooled from 0.7℃ / s to 300℃ and collected in a slow-cooling pit.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0016] The purpose of this invention is to provide a low-cost bainitic anchor steel and its controlled rolling and cooling production process. The aim is to significantly improve the strength of the anchor steel while ensuring good toughness and plasticity through optimized chemical composition design and rolling and cooling processes. Its performance meets the following requirements: yield strength ≥ 800 MPa, tensile strength ≥ 900 MPa, elongation ≥ 17%, and impact resistance at 20℃ ≥ 35 J. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 Production process flow chart;

[0019] Figure 2 Microscopic photograph of bainitic structure. Detailed Implementation

[0020] Example 1:

[0021] Taking the production process of Φ22mm anchor bolt steel as an example:

[0022] Billet: Continuously cast into 150mm×150mm square billets with the following composition: C 0.22%, Si 0.85%, Mn 2.0%, V 0.09%, P 0.014%, S 0.002%, gas content [O] 0.0022%, [N] 0.0056%, [H] 0.00012%; the remainder is Fe and impurities.

[0023] Rolling: 6 passes for roughing (final rolling temperature 1020℃), 6 passes for intermediate rolling (final rolling temperature 990℃); 6 passes for finishing rolling (final rolling temperature 900℃); Cooling: water cooling at a rate of 70℃ / s to 580℃, and air mist cooling at a rate of 0.7℃ / s to 300℃, collected in a slow cooling pit. Mechanical properties were tested after cooling to room temperature, as shown in the table below.

[0024] Example Yield strength / MPa Tensile strength / MPa Elongation / % Impact performance at 20℃ Example 1 839 980 18 36 Example 2 857 970 19 39 Example 3 864 1020 19 42 Example 4 853 996 20 38 Example 5 823 976 21 44

[0025] This technical approach of "obtaining ultra-high strength bainitic structure directly through medium and low carbon microalloying + controlled rolling and controlled cooling" aims to achieve ultra-high strength, excellent toughness (especially low temperature toughness), simple and efficient production process, and low overall cost, thus becoming an important alternative to the traditional high-cost and high-energy-consumption quenching and tempering process.

[0026] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low-cost, ultra-high-strength bainitic anchor steel production method, characterized in that, The process route adopted is "composite microalloying + two-stage controlled rolling + ultra-fast cooling (UFC)", specifically: billet → heating to 1100-1150℃ → rough rolling to 950-1050℃ → finish rolling to 880-950℃ → ultra-fast cooling → slow cooling in the bainitic phase transformation zone → collection on the cooling bed → bundling → weighing; ultra-fast cooling stage: water mist cooling is turned on within 3 seconds after the finish rolling, with a cooling rate ≥60℃ / s to 550-650℃; switch to air mist cooling, with a controlled cooling rate of 0.5-1℃ / s; The collection temperature is limited to 280-320℃ before being placed in a slow cooling pit; The chemical composition of the low-cost bainitic anchor steel by mass percentage is: C 0.18-0.25%, Si 0.60-1.20%, Mn 1.90-2.50%, V 0.08-0.10%, P, S≤0.015%, with the balance being Fe and impurity elements. The required gas content is [O]≤0.0030%, [N]≤0.0080%, and [H]≤0.0002%.

2. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The cooling rate of the ultra-fast cooling is 60-80℃ / s.

3. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The chemical composition of the low-cost bainitic anchor steel by mass percentage is as follows: C 0.22%, Si 0.85%, Mn 2.0%, V 0.09%, P 0.014%, S 0.002%, gas content [O] 0.0022%, [N] 0.0056%, [H] 0.00012%, with the balance being Fe and impurity elements.

4. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The roughing process consists of 6 passes, with a final rolling temperature of 1020℃.

5. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The intermediate rolling process involves 6 passes, with a final rolling temperature of 990℃.

6. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The finishing rolling process involves 6 passes, with a final rolling temperature of 900℃.

7. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The ultra-fast cooling: cooling speed from 70℃ / s to 580℃.

8. The method for producing low-cost ultra-high-strength bainitic anchor steel according to claim 1, characterized in that, The slow cooling process involves cooling the gas mist at a rate of 0.7°C / s to 300°C and collecting it in a slow cooling pit.

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