A hot-rolled steel strip for high-strength, corrosion-resistant hollow anchor rod welded pipe and preparation method thereof

Abstract

The invention discloses a hot-rolled steel strip for a high-strength, corrosion-resistant hollow anchor rod welded pipe and a preparation method thereof. The hot-rolled steel strip comprises the following elements by weight: C 0.18-0.23%, Si 0.15-0.30%, Mn 0.90-1.10%, P≤0.020%, S≤0.007%, Nb 0.02-0.04%, Cr 0.70-0.90%, Cu 0.20-0.50%, Ti 0.01-0.03%, Sb 0.04-0.08%, and the rest is Fe and unavoidable impurities. The present invention controls the content of Si and Mn elements while ensuring the strength of the material and reducing the carbon equivalent, adds a certain amount of Ti element to form precipitates during welding to inhibit the coarsening of the heat affected zone structure to improve the welding performance, controls the content of Nb element to exert the fine grain strengthening effect to further ensure the strength, and controls the content of Cu, Cr and Sb elements to ensure that the corrosion resistance of the anchor steel matches the strength and toughness, thereby improving the corrosion resistance of the material in the wet environment of tunnels and rock and soil.

Description

Technical Field

[0001] The invention relates to the technical field of hot-rolled plates and strips, and in particular to a high-strength corrosion-resistant hollow anchor rod welded pipe, a hot-rolled steel strip and a preparation method thereof. Background Art

[0002] Anchor rods are commonly used in coal mines and engineering enterprises. They are mainly used in deep tunnel support for coal, iron ore and other large-scale construction geotechnical engineering reinforcement such as high-speed railways, highways, dams, etc. With the promotion and development of technology, its application has become more and more extensive, and the demand has increased. The working principle of anchor rods is to overcome the disadvantage that the tensile capacity of rock and soil is far lower than its compressive capacity through the longitudinal tension of the anchor rod body. On the surface, it limits the separation of rock and soil from the original body. On a macroscopic level, it increases the cohesion of rock and soil. It is a rod system structure for rock and soil reinforcement.

[0003] The anchor steel product grades in the existing technology are relatively single, almost all of which are MG335. After in-depth research by technical personnel, it was found that the strength of the current MG335 anchor steel products could not meet the demand. Researchers proposed the use of high-strength anchor steel products to replace MG335 products, and then MG500, SMG600MPa and other grades of products appeared, but these products are almost all produced by rolling rods and wires or drawing seamless steel pipes, with high costs, low yields, precision control, poor surface quality, and no corrosion resistance. During use, due to long-term contact with humid air, the exposed surface of the anchor steel will gradually rust, reducing the strength of the material and shortening its service life.

[0004] Therefore, developing a high-strength, corrosion-resistant anchor steel has become a technical problem that needs to be solved urgently by those skilled in the art.

[0005] Based on this, the existing technology still needs to be improved. Summary of the invention

[0006] The main purpose of the present invention is to provide a high-strength, corrosion-resistant hot-rolled steel strip for hollow anchor rod welded pipe and a preparation method thereof, so as to solve the technical problems existing in the production of anchor rods by rolling rods or drawing seamless steel pipes in the prior art.

[0007] On the one hand, according to some embodiments of the present invention, a hot-rolled steel strip for a high-strength, corrosion-resistant hollow anchor welded pipe is provided, wherein the weight percentage of the elements is as follows: C 0.18-0.23%, Si 0.15-0.30%, Mn 0.90-1.10%, P≤0.020%, S≤0.007%, Nb 0.02-0.04%, Cr 0.70-0.90%, Cu 0.20-0.50%, Ti 0.01-0.03%, Sb 0.04-0.08%, and the rest is Fe and unavoidable impurities.

[0008] Furthermore, the metallographic structure is ferrite+pearlite+granular bainite, and the average grain size is 11 to 13 levels.

[0009] Furthermore, the yield strength Rel≥600MPa, the tensile strength Rm≥700MPa, and the elongation≥20%.

[0010] On the other hand, an embodiment of the present invention further discloses a method for preparing the above-mentioned hot-rolled steel strip, which comprises the following steps in sequence: molten iron desulfurization, converter, LF refining, CC (continuous casting), hot rolling, laminar cooling, and coiling.

[0011] Furthermore, the slab is smelted and continuously casted according to the components, S≤0.008% when entering the converter, the converter tapping temperature is 1640℃-1660℃, calcium treatment is adopted after LF refining, the LF outlet temperature is 1580±5℃, and continuous casting adopts constant speed casting.

[0012] Furthermore, in the hot rolling process, the steel billet soaking temperature is 1210°C to 1250°C, and the final rolling temperature is 840°C to 880°C.

[0013] Furthermore, in the coiling process, the coiling temperature is 560°C to 620°C.

[0014] Furthermore, in the laminar cooling process, a front-stage cooling method is adopted.

[0015] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0016] The high-strength, corrosion-resistant hollow anchor rod welded pipe, hot-rolled steel strip and preparation method provided by the present invention control the contents of Si and Mn elements to ensure material strength while reducing the carbon equivalent, add a certain amount of Ti element to form precipitates during welding to inhibit the coarsening of the heat-affected zone structure to improve welding performance, control the content of Nb element to exert the fine grain strengthening effect to further ensure strength, and control the contents of Cu, Cr and Sb elements to ensure that the corrosion resistance and toughness of the anchor rod steel match, thereby improving the corrosion resistance of the material in wet environments of tunnels and rock and soil.

[0017] The present invention cooperates with corresponding steelmaking, continuous casting and hot rolling production processes to ensure fine and uniform material structure, thereby obtaining a high-strength, corrosion-resistant hot-rolled steel strip for hollow anchor rod welded pipe, with a yield strength Rel≥600MPa, a tensile strength Rm≥700MPa, and an elongation≥20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A flow chart of a method for preparing a hot-rolled steel strip for a high-strength, corrosion-resistant hollow anchor rod welded pipe disclosed in some embodiments of the present invention is shown. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0021] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0022] Some embodiments of the present invention disclose a high-strength, corrosion-resistant, hot-rolled steel strip for hollow anchor welded pipe and a preparation method thereof, which increases the category of high-performance hot-rolled steel strip for hollow anchor welded pipe, solves the problem of insufficient development of corrosion-resistant anchor steel varieties proposed in the background technology, and provides new anchor steel material options. The high-strength, corrosion-resistant, hot-rolled steel strip for hollow anchor welded pipe, the high-strength, corrosion-resistant, hot-rolled steel strip for hollow anchor welded pipe has the following weight percentage composition: C 0.18-0.23%, Si 0.15-0.30%, Mn 0.90-1.10%, P ≤ 0.020%, S ≤ 0.007%, Nb 0.02-0.04%, Cr 0.70-0.90%, Cu 0.20-0.50%, Ti 0.01-0.03%, Sb 0.04-0.08%, and the rest is Fe and unavoidable impurities. The metallographic structure is ferrite + pearlite + granular bainite, the average grain size is 11-13, the yield strength Rel ≥ 600MPa, the tensile strength Rm ≥ 700MPa, and the elongation ≥ 20%.

[0023] like Figure 1As shown, the preparation method of the hot-rolled steel strip comprises the following steps: hot metal desulfurization → converter → LF refining → CC (continuous casting) → hot rolling → laminar cooling → coiling. Smelt and continuously cast into slabs according to the composition, S≤0.008% in the furnace, converter tapping temperature 1640℃-1660℃, calcium treatment after LF refining, LF outlet temperature 1580±5℃, and constant speed casting. In the hot rolling process, the billet soaking temperature is 1210℃~1250℃, the final rolling temperature is 840℃~880℃, the coiling temperature is 560℃~620℃, and the front-end cooling method is adopted.

[0024] The hot-rolled steel strip for high-strength, corrosion-resistant hollow anchor welded pipe disclosed in some embodiments of the present invention has the following element weight percentage composition: C 0.18-0.23%, Si 0.15-0.30%, Mn 0.90-1.10%, P≤0.020%, S≤0.007%, Nb 0.02-0.04%, Cr 0.70-0.90%, Cu 0.20-0.50%, Ti 0.01-0.03%, Sb 0.04-0.08%, and the rest is Fe and unavoidable impurities.

[0025] Among them, carbon directly affects the strength, plasticity, toughness and welding performance of steel. An increase of 0.1% of C can increase the yield strength by about 28MPa and the tensile strength by 70MPa. However, too high a C content will greatly reduce the plasticity, toughness and welding performance of the material. The C content of the present invention is controlled at 0.18-0.23%.

[0026] Silicon can improve the strength of steel, and its effect is second only to phosphorus. However, silicon easily forms banded structures in steel, and silicon has a strong affinity with oxygen, which easily generates low-melting silicates during welding, reducing the welding performance of steel. The Si content of the present invention is controlled at 0.15-0.30%.

[0027] Manganese and iron form a solid solution, which can improve the hardness and strength of ferrite and austenite in steel. It is also a good deoxidizer and desulfurizer. A certain amount of manganese can eliminate or weaken the brittleness caused by sulfur. However, when the manganese content is too high, cracks in the casting are likely to occur during the continuous casting process, and it may cause component segregation in the core of the steel plate and reduce the welding performance of the steel. The Mn content of the present invention is controlled at 0.90-1.10%.

[0028] Phosphorus and sulfur are harmful elements that have an adverse effect on the structure and properties of steel plates. The lower their content, the better. A high phosphorus content will significantly reduce the plasticity and low-temperature toughness of steel, and sulfur will form sulfide inclusions that deteriorate the properties of steel. In the present invention, phosphorus is ≤ 0.020% and sulfur is ≤ 0.007%.

[0029] Niobium is a carbide-forming element. NbC can pin austenite grain boundaries to prevent grain growth. At the same time, NbC can form a second phase reinforcement, which is beneficial to improving the strength, plasticity and toughness of steel. However, too high niobium content increases production costs and reduces strengthening effects. The Nb content of the present invention is controlled at 0.02-0.04%.

[0030] Titanium is a strong carbide and nitride forming element. The precipitates formed with C and N can effectively refine austenite grains and inhibit the coarsening of the coarse grain zone during welding. However, if the titanium content is too high, coarse carbonitrides are easily formed, which reduces the impact, fatigue and forming properties of the material. The Ti content of the present invention is controlled at 0.01-0.03%.

[0031] Chromium has a significant effect on improving the corrosion resistance of steel, and its content is generally greater than 0.2%. At the same time, chromium can improve the strength of steel, increase the hardenability of steel and have a secondary hardening effect, but too high a content will reduce the plastic toughness of steel and reduce the welding performance. The Cr content of the present invention is controlled at 0.70-0.90%; Copper can improve the corrosion resistance of steel and is conducive to forming a dense, well-adhesive amorphous oxide protective layer on the surface of steel, but excessive copper is prone to segregation at the grain boundary, causing the slab to crack and brittle fracture. The Cu content of the present invention is controlled at 0.20-0.50%; Antimony can improve the corrosion resistance of materials in a humid and easily corrosive environment, so that Sb2O5 is formed on the metal surface in the corrosive medium, and the corrosive medium is inhibited from further corroding the substrate, but too high an antimony element reduces the strength and plastic toughness of steel and increases the cost. The Sb content of the present invention is controlled at 0.04-0.08%.

[0032] Example 1

[0033] The weight percentage composition of the hot-rolled steel strip for the high-strength, corrosion-resistant hollow anchor welded pipe in this embodiment is C0.20%, Si 0.25%, Mn 1.03%, P≤0.020%, S≤0.007%, Nb 0.025%, Cr 0.88%, Cu0.30%, Ti 0.027%, Sb 0.007%, and the rest is Fe and unavoidable impurities.

[0034] The production method of hot-rolled steel strip for high-strength corrosion-resistant hollow anchor welded pipe in this embodiment includes molten iron desulfurization → converter → LF refining → CC → hot rolling → laminar cooling → coiling, and the key process steps are as follows: converter entry S≤0.008%, converter tapping temperature 1650°C, LF exit temperature 1580°C, continuous casting adopts constant speed casting, target pulling speed 0.9m / min, billet soaking temperature 1225°C, final rolling temperature 860°C, coiling temperature 580°C, front-stage cooling method is adopted, the average grain size of the material is 12.0 grade, yield strength Rel 611MPa, tensile strength Rm 722MPa, and elongation 23.0%.

[0035] Example 2

[0036] The weight percentage composition of the hot-rolled steel strip for the high-strength, corrosion-resistant hollow anchor welded pipe in this embodiment is C0.20%, Si 0.24%, Mn 0.98%, P≤0.020%, S≤0.007%, Nb 0.035%, Cr 0.81%, Cu0.35%, Ti 0.025%, Sb 0.006%, and the rest is Fe and unavoidable impurities.

[0037] The production method of hot-rolled steel strip for high-strength, corrosion-resistant hollow anchor welded pipe in this embodiment includes molten iron desulfurization → converter → LF refining → CC → hot rolling → laminar cooling → coiling, and the key process steps are as follows: converter entry S≤0.008%, converter tapping temperature 1645°C, LF exit temperature 1580°C, continuous casting adopts constant speed casting, target pulling speed 1.0m / min, billet soaking temperature 1220°C, final rolling temperature 850°C, coiling temperature 590°C, front-stage cooling method is adopted, the average grain size of the material is 12.5 grade, yield strength Rel 620MPa, tensile strength Rm 712MPa, and elongation 22.5%.

[0038] Example 3

[0039] The weight percentage composition of the hot-rolled steel strip for the high-strength, corrosion-resistant hollow anchor welded pipe in this embodiment is C0.23%, Si 0.17%, Mn 0.96%, P≤0.020%, S≤0.007%, Nb 0.025%, Cr 0.80%, Cu0.35%, Ti 0.022%, Sb 0.007%, and the rest is Fe and unavoidable impurities.

[0040] The production method of hot-rolled steel strip for high-strength, corrosion-resistant hollow anchor welded pipe in this embodiment includes molten iron desulfurization → converter → LF refining → CC → hot rolling → laminar cooling → coiling, and the key process steps are as follows: converter entry S≤0.008%, converter tapping temperature 1650°C, LF exit temperature 1580°C, continuous casting adopts constant speed casting, target pulling speed 0.9m / min, billet soaking temperature 1230°C, final rolling temperature 865°C, coiling temperature 600°C, front-stage cooling method is adopted, the average grain size of the material is 12.0 grade, yield strength Rel 607MPa, tensile strength Rm 713MPa, and elongation 23.0%.

[0041] It should be particularly pointed out that the various components or steps in the above-mentioned embodiments can be cross-linked, replaced, added, or deleted with each other. Therefore, the combinations formed by these reasonable arrangements and combinations should also fall within the scope of protection of the present invention, and the scope of protection of the present invention should not be limited to the embodiments.

[0042] The above are exemplary embodiments disclosed in the present invention. The order disclosed in the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. However, it should be noted that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope (including claims) disclosed in the embodiments of the present invention is limited to these examples. Various changes and modifications may be made without departing from the scope defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0043] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A hot-rolled steel strip for high-strength, corrosion-resistant hollow anchor welded pipe, characterized in that: The weight percentage composition of the elements is: C 0.18-0.23%, Si 0.15-0.30%, Mn 0.90-1.10%, P≤0.020%, S≤0.007%, Nb 0.02-0.04%, Cr 0.70-0.90%, Cu 0.20-0.50%, Ti 0.01-0.03%, Sb 0.04-0.08%, and the rest is Fe and unavoidable impurities; The metallographic structure is ferrite + pearlite + granular bainite, with an average grain size of 11~13; Yield strength Rel≥600MPa, tensile strength Rm≥700MPa, elongation≥20%.

2. The method for preparing a hot-rolled steel strip according to claim 1, characterized in that: The process includes the following steps in sequence: molten iron desulfurization, converter, LF refining, continuous casting, hot rolling, laminar cooling and coiling.

3. The preparation method according to claim 2, characterized in that: It is smelted and continuously cast into slabs according to its components. When entering the converter, S is ≤0.008%. The converter tapping temperature is 1640℃-1660℃. Calcium treatment is adopted after LF refining. The LF outlet temperature is 1580±5℃. Constant speed casting is adopted for continuous casting. The target pulling speed is 0.9m / min~1.0m / min.

4. The preparation method according to claim 2, characterized in that: During the hot rolling process, the billet soaking temperature is 1210℃~1250℃, and the final rolling temperature is 840℃~880℃.

5. The preparation method according to claim 2, characterized in that: In the coiling process, the coiling temperature is 560℃~620℃.

6. The preparation method according to claim 2, characterized in that: In the laminar cooling process, the front cooling method is adopted.

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