Production method of 800 MPa grade anchor rod

Abstract

The invention discloses a production method of an 800MPa-grade anchor rod. The technological process comprises the steps of blast furnace molten iron, molten iron pretreatment, converter top and bottom combined blowing smelting, LF external refining, VD vacuum degassing, small square billet continuous casting, slow cooling and rolling. Steel billet heating, high-pressure water descaling, rough rolling, intermediate rolling, finish rolling, stepping cooling bed processing, shearing, checking, bundling, slow cooling and finished product warehousing are conducted; the method is characterized in that a combined blown converter is adopted for smelting, and a double-slag process is adopted; during tapping, a slag stopping ball or a slag stopping plug is used for stopping slag; refining and submerged arc operation are carried out in the whole argon blowing state; the cleanliness of the steel is improved through refining; and the molten steel is subjected to throwing casting by a small square billet casting machine. The invention aims to provide the production method of the 800MPa-grade anchor rod, so as to provide the novel anchor rod steel which is high in performance, low in cost and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical fields of steelmaking and metal materials in metallurgical industrial production, and particularly relates to a production method of 800 MPa grade anchor bolts. Background Art

[0002] Anchor bolt steel is a kind of support material widely used in underground projects such as mines and tunnels. In the field of underground engineering, such as mining, tunnel excavation, and slope reinforcement operations, ensuring the stability and safety of the engineering structure is of crucial importance. As a commonly used support component, anchor bolts play an indispensable role in these projects. Anchor bolt steel, as the key raw material for manufacturing anchor bolts, its performance directly affects the support effect of the anchor bolts and the overall safety of the project.

[0003] With the continuous expansion of the scale of underground engineering and the increasing complexity, the performance requirements for anchor bolt steel are also getting higher and higher. Traditional anchor bolt steel has certain limitations in terms of strength, toughness, corrosion resistance, etc. For example, in some deep mines, the ground stress is relatively large, and ordinary strength anchor bolt steel is prone to deformation or even fracture, unable to effectively maintain the stability of the roadway; in a humid or corrosive medium environment, the corrosion resistance of anchor bolt steel is insufficient, resulting in premature failure of the anchor bolts, increasing the maintenance cost and safety risk of the project.

[0004] In addition, the existing production processes of anchor bolt steel also need to be improved in some aspects. Some production processes are difficult to precisely control the chemical composition and microstructure of the steel, thus affecting the consistency and stability of the steel performance.

[0005] In order to meet the continuously developing needs of underground engineering, the development of new high-performance, low-cost and environmentally friendly anchor bolt steel and the optimization of the production process have become the research hotspots and development trends in this field. Summary of the Invention

[0006] The purpose of the present invention is to provide a production method of 800 MPa grade anchor bolts to provide a new type of high-performance, low-cost and environmentally friendly anchor bolt steel.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions:

[0008] Production method of an 800MPa - grade bolt, process flow: blast furnace hot metal - hot metal pretreatment - combined blowing converter smelting - LF furnace external refining - VD vacuum degassing - small billet continuous casting - slow cooling - rolling; reheating of steel billet - high - pressure water descaling - rough rolling - medium rolling - finish rolling - walking beam cooling bed - shearing - inspection - bundling - slow cooling - finished product warehousing; characterized in that: smelted by a combined blowing converter, adopting the double - slag process; using a slag - blocking ball or a slag - blocking plug to block slag during tapping; refining under the condition of full - process argon blowing, with submerged - arc operation; refining to improve the cleanliness of the steel; the molten steel is cast by a small billet caster; among them:

[0009] Combined blowing converter smelting: During converter smelting, quicklime, dolomite, and fluorite are added according to actual conditions, and alloys are added during tapping. The final slag basicity is controlled at 3.0 ± 0.1.

[0010] LF furnace refining: LF furnace refining adds auxiliary materials to make slag according to the changes in molten steel composition and temperature, adds alloys for fine - tuning and temperature - raising operations; adds quicklime, fluorite, and calcium carbide, and the alloy is fine - tuned for ferromanganese according to the in - position refining composition; carbon content, phosphorus content, and tapping temperature of the molten steel at the converter end: tapping carbon content ≤ 0.15%, tapping phosphorus content ≤ 0.015%, tapping temperature 1625 - 1665°C.

[0011] In continuous casting production, the superheat degree is 20 - 30°C, and the casting speed is 2.0 - 2.2 m / min.

[0012] Rolling: The starting rolling temperature of the steel billet is 940 - 980°C, the temperature entering the finish rolling is 900 - 920°C, and the spinning temperature is 920 - 940°C.

[0013] Furthermore, the slab specification is 150×150 mm.

[0014] Furthermore, the in - position refining temperature is 1550 - 1660°C.

[0015] Furthermore, the off - position refining temperature is 1570 - 1580°C.

[0016] Furthermore, the soft blowing time is 10 - 12 min respectively.

[0017] Furthermore, in continuous casting production, the superheat degree is 22 - 27°C, and the casting speed is 2.1 m / min.

[0018] Furthermore, it also includes tempering treatment: tempering at 300°C for 2 hours.

[0019] Furthermore, the requirements for the chemical composition of the anchor rod in mass percentage are as follows: C 0.25 - 0.27 wt%, Si 0.75 - 0.85 wt%, Mn 1.80 - 2.00 wt%, P ≤ 0.015 wt%, S ≤ 0.020 wt%, Al 0.008 - 0.02 wt%, V 0.08 - 0.12 wt%, Ce 0.002 - 0.006 wt%, Cr 0.45 - 0.65%, and the rest is Fe and impurities.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0021] The finished products rolled by the method of the present invention have relatively high tensile strength and yield strength, and good elongation, meeting the usage requirements of users. Specific embodiments

[0022] 4 furnaces of MG800 were industrially trial-produced, and the specific process parameters are controlled as follows:

[0023] 1) Converter production: During converter smelting, quicklime, dolomite, and fluorite are added according to actual conditions, and alloys are added during the tapping process. The basicity of the final slag is controlled at 3.0.

[0024] 2) LF furnace refining: In LF furnace refining, auxiliary materials are added to make slag according to the changes in the composition and temperature of the molten steel, and alloys are added for fine adjustment and temperature increase operations. Quicklime, fluorite, and calcium carbide are added, and the alloy is fine-tuned with ferromanganese according to the in-position composition of the refining.

[0025] The carbon content, phosphorus content, and tapping temperature of the molten steel at the end of the converter are shown in Table 1.

[0026] Table 1 Composition and temperature of the molten steel tapped from the converter for MG800 steel

[0027]

[0028]

[0029] 2) LF furnace production

[0030] Table 2 Temperature control of the refining LF furnace for MG800 steel

[0031] Test furnace number Refining in-position temperature, °C Refining out-of-position temperature, °C Refining treatment time, min 1# 1558 1578 35 2# 1556 1579 37 3# 1548 1572 35 4# 1554 1577 36

[0032] In addition, the soft blowing times of these 4 furnaces of steel are 10 min, 11 min, 10 min, and 12 min respectively.

[0033] 3) Continuous casting production

[0034] During continuous casting production, the superheat degrees are 22 °C, 27 °C, 23 °C, and 25 °C respectively, the drawing speed is 2.1 m / min, and the composition control of the molten steel is shown in Table 3.

[0035] Table 3 Chemical Composition of Finished Product of MG800 Bolt Steel

[0036]

[0037]

[0038] 4) Steel Rolling Production

[0039] In order to produce high-strength bolt steel of 800 MPa grade, the wire rod plant rolled the above 4 furnaces of steel. The measured values of the billet starting rolling temperatures of the 4 furnaces of steel were 950 °C, 970 °C, 955 °C, and 970 °C respectively, the temperatures entering the finishing mill were 900 °C, 910 °C, 910 °C, and 900 °C respectively, and the laying head temperatures were 930 °C, 934 °C, 930 °C, and 932 °C respectively.

[0040] 5) Mechanical Property Inspection

[0041] The inspection results of the mechanical properties of the wire rod are shown in Table 4.

[0042] Table 4 Inspection Results of Mechanical Properties after Tempering at 300 °C for 2 Hours

[0043]

[0044] It can be seen from the mechanical property indexes that the finished product after rolling has relatively high tensile strength and yield strength, and good elongation, meeting the user's requirements for use.

[0045] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method of an 800MPa grade bolt, process flow: blast furnace hot metal - hot metal pretreatment - combined blowing top and bottom converter smelting - LF furnace external refining - VD vacuum degassing - small billet continuous casting - slow cooling - rolling; reheating of steel billet - high-pressure water descaling - rough rolling - intermediate rolling - finish rolling - walking beam cooling bed - shearing - inspection - bundling - slow cooling - finished product warehousing; characterized in that: Smelted by combined blowing converter, adopting double slag process; slag is blocked by slag ball or slag stopper during tapping; refined under the condition of full-process argon blowing, with submerged arc operation; refining improves the cleanliness of steel; the molten steel is cast by a small billet caster; where: Smelting by combined blowing converter: During converter smelting, quicklime, dolomite, and fluorite are added according to actual conditions, alloys are added during tapping, and the basicity of the final slag is controlled at 3.0±0.

1. LF furnace refining: LF furnace refining adds auxiliary materials for slag making according to the changes in the composition and temperature of the molten steel, adds alloys for fine adjustment and temperature increase operations; quicklime, fluorite, and calcium carbide are added, and the alloy is fine-tuned with ferromanganese according to the in-position composition of refining; The carbon content, phosphorus content, and tapping temperature of the molten steel at the end of the converter: tapping carbon content ≤ 0.15%, tapping phosphorus content ≤ 0.015%, tapping temperature 1625 - 1665°C. In continuous casting production, the superheat degree is 20 - 30°C, and the drawing speed is 2.0 - 2.2 m / min. Rolling: The starting rolling temperature of the billet is 940 - 980°C, the entry temperature into the finishing mill is 900 - 920°C, and the spinning temperature is 920 - 940°C.

2. The production method of the 800 MPa grade anchor rod according to claim 1, characterized in that: Billet specification: 150×150 mm.

3. The production method of the 800 MPa grade anchor rod according to claim 1, characterized in that: In-position refining temperature: 1550 - 1660°C.

4. The production method of the 800 MPa class anchor rod according to claim 1, characterized in that: Off-position refining temperature: 1570 - 1580°C.

5. The production method of the 800 MPa class anchor rod according to claim 1, characterized in that: The soft blowing time is 10 - 12 min respectively.

6. The production method of the 800MPa-level anchor rod according to claim 1, characterized in that: In continuous casting production, the superheat degree is 22 - 27°C, and the drawing speed is 2.1 m / min.

7. The production method of the 800MPa-class anchor rod according to claim 1, characterized in that: It also includes tempering treatment: tempering at 300°C for 2 hours.

8. The production method of the 800MPa-level anchor rod according to claim 1, characterized in that: The quality percentage chemical composition requirements of this anchor bolt are: C 0.25 - 0.27 wt%, Si 0.75 - 0.85 wt%, Mn 1.80 - 2.00 wt%, P ≤ 0.015 wt%, S ≤ 0.020 wt%, Al 0.008 - 0.02 wt%, V 0.08 - 0.12 wt%, Ce 0.002 - 0.006 wt%, Cr 0.45 - 0.65%, and the rest is Fe and impurities.

Images