High-strength multiphase wear-resistant seamless steel pipe and preparation method thereof

Abstract

The invention relates to a high-strength multiphase wear-resistant seamless steel pipe, comprising the following components in mass percentage: C: 0.22%-0.26%; Si: 0.65%-0.80%; Mn: 2.15%-2.40%; Cr: 1.20%-1.30%; Mo: 0.10%-0.15%; V: 0.03%-0.05%; Al: 0.010%-0.020%; the rest is iron and inevitable impurities. A preparation method of the seamless steel pipe is also provided. The invention has simple production process, high process feasibility, direct hot rolling to produce finished products, low alloy addition amount and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of seamless steel pipe manufacturing, and in particular relates to a high-strength multi-phase wear-resistant seamless steel pipe and a preparation method thereof. Background Art

[0002] Wear-resistant seamless steel pipes have the characteristics of high strength, high hardness and high wear resistance. They are widely used in electric power, metallurgy, mining, coal, petroleum, chemical industry, machinery and other industries. They are suitable for the transportation of gas, liquid and solid such as powder, mortar fluid, cement coal slurry, coal powder carbon slag and solid particles. They are important accessories for conveying wear-resistant pipes and concrete pump trucks.

[0003] The current state of the art is that, in the production of high-strength multiphase wear-resistant seamless steel pipes, especially when the tensile strength is ≥1300MPa, the production process is difficult to control and the process is complicated; moreover, most of them add a large amount of alloy elements such as Mo, Nb, Ni, etc., which is costly; in addition, they also need to undergo a tempering heat treatment process, which greatly increases the probability of quenching cracking, and the resulting structure is single and has poor wear resistance.

[0004] Chinese patent number CN104726781 discloses "a wear-resistant seamless steel pipe for transportation and its production method", whose components by mass percentage are: C: 0.28% ~ 0.36%; Si: 0.70% ~ 1.30%; Mn: 2.80% ~ 3.20%; V: 0.05% ~ 0.15%; Nb: 0.02% ~ 0.04%; Cr: 0.40% ~ 0.80%; Mo: 0.14% ~ 0.26%; B: 0.0005% ~ 0.0035%; As: 0 ~ 0.015%; Sn: 0 ~ 0.010%; P: 0 ~ 0.015%; S: 0 ~ 0.010%, and the remainder of Fe, etc. The tensile strength of this invention can reach 1300MPa, but a large amount of V and Nb alloys are added, and after rolling, it undergoes a tempering heat treatment process, which increases the cost and also increases the risk of quenching cracking of the steel pipe.

[0005] Chinese patent number CN105239011 discloses "Manufacturing method of wear-resistant seamless steel pipe for concrete pump truck", with the following mass percentages: C: 0.57% to 0.65%; Si: 0.17% to 0.37%; Mn: 0.70% to 1.00%; P: ≤0.025%; S: ≤0.020%; Cr: 0.20% to 0.80%; Ti: 0.01% to 0.05%; Ni: ≤0.25%; Cu: ≤0.30%; the remainder is Fe. The production method of this invention is simple, and the alloy addition is cost-effective, but it does not specify the strength level, only stating that it meets the use requirements, and cannot consider its specific applicability and wear resistance.

[0006] Chinese patent number CN114058973 discloses "a NM450 grade low carbon low alloy bainitic wear-resistant steel and its preparation method", whose mass percentage is: C: 0.15% ~ 0.25%; Si: 1.50% ~ 2.10%; Mn: 1.90% ~ 2.10%; Mo: 0.22% ~ 0.28%; Cr: 0.85% ~ 1.15%; V: 0.03% ~ 0.04%; P: ≤ 0.008%; S: ≤ 0.005%; N: ≤ 0.005%; the balance is Fe and unavoidable impurities; the strength of the invention can reach 1300MPa, and the amount of alloy elements is low, the production process is simple, but the rolling process control of steel plates and seamless steel pipes is essentially different. Summary of the invention

[0007] The purpose of the present invention is to provide a high-strength multiphase wear-resistant seamless steel pipe and a preparation method thereof. Through chemical composition design and seamless steel pipe rolling process and deformation parameter control, a high-strength multiphase wear-resistant steel pipe with good strength and toughness matching is achieved with a high cost-effectiveness and a convenient production process. Its technical indicators are: tensile strength ≥1300MPa, room temperature longitudinal full-size impact energy ≥25J, and the metallographic structure is a bainite + martensite multiphase structure.

[0008] The present invention solves the technical problem by adopting the following technical solutions:

[0009] The high-strength multiphase wear-resistant seamless steel pipe comprises the following components in percentage by mass:

[0010] C: 0.22% ~ 0.26%; Si: 0.65% ~ 0.80%; Mn: 2.15% ~ 2.40%; Cr: 1.20% ~ 1.30%; Mo: 0.10% ~ 0.15%; V: 0.03% ~ 0.05%; Al: 0.010% ~ 0.020%; the rest is iron and unavoidable impurities.

[0011] Furthermore, the composition also includes the following mass percentages: P≤0.013%; S≤0.004%.

[0012] The method for preparing the high-strength multiphase wear-resistant seamless steel pipe comprises the following steps:

[0013] S1. Steelmaking: electric furnace smelting, refining outside the furnace, vacuum treatment;

[0014] S2. Casting: continuous casting. The cross section of the continuous casting billet is Φ210~270mm;

[0015] S3, rolling: ring furnace heating, perforation, continuous rolling, sizing, cooling;

[0016] in:

[0017] When heating in a ring furnace, the heating temperature of the tube billet is 1230℃~1290℃, and the holding time is 3.5~5.5h;

[0018] During perforation, the inlet temperature is 1160℃~1220℃, and the outlet capillary axial speed is 0.80~1.15m / s.

[0019] Furthermore, the inlet temperature during continuous rolling is 1050℃~1110℃, the axial speed of the outlet rough pipe is 3.75~4.50m / s; the rough pipe diameter reduction rate is 11%~23%, and the rough pipe wall reduction rate is 27%~42%. m -Outer diameter of rough pipe D o ) / capillary outer diameter D m ; capillary wall reduction rate ω = (capillary wall thickness S m -Wall thickness of rough pipe S o ) / capillary wall thickness S m .

[0020] Furthermore, the inlet temperature during sizing is 950℃~1030℃, the axial speed of the finished pipe at the outlet is 1.55~2.50m / s; the rough pipe deformation coefficient is 0.73~0.95. Where: rough pipe deformation coefficient μ = rough pipe cross-sectional area A 1 / Finished pipe cross-sectional area A2.

[0021] Furthermore, during cooling, the finished tube is cooled to 450°C to 465°C at a rate of 1 to 2°C to reach the bainite phase transformation zone, and then air-cooled to room temperature.

[0022] The advantages and positive effects of the present invention are:

[0023] The present invention realizes tensile strength ≥1300MPa, longitudinal full-size impact energy ≥25J at room temperature, good matching of strength and toughness through component control and rolling process, including reasonable use of tube blank heating temperature and time, perforation inlet temperature and rough tube axial speed, continuous rolling inlet temperature and rough tube axial speed, sizing inlet temperature and outlet finished tube axial speed, rough tube diameter reduction rate ε, rough tube wall reduction rate ω, rough tube deformation coefficient μ, cooling rate and temperature control, and obtains metallographic structure of bainite + martensite complex phase wear-resistant structure, which is more wear-resistant than single martensite structure, and the production process is simple, the process can be realized with high degree, the finished product can be directly produced by hot rolling, the alloy addition amount is low, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0025] Figure 1 200 times the bainite + martensite microstructure of Example 1 in Example 2 of the present invention;

[0026] Figure 2 The metallographic structure of bainite + martensite in Example 1 in Example 2 of the present invention is 500 times larger than that in Example 1;

[0027] Figure 3 CCT curve of the steel of Example 1 in Example 2 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0029] Example 1

[0030] The high-strength multiphase wear-resistant seamless steel pipe provided in this embodiment includes the following components in percentage by mass:

[0031] C: 0.22% ~ 0.26%; Si: 0.65% ~ 0.80%; Mn: 2.15% ~ 2.40%; Cr: 1.20% ~ 1.30%; Mo: 0.10% ~ 0.15%; V: 0.03% ~ 0.05%; Al: 0.010% ~ 0.020%; the rest is iron and unavoidable impurities;

[0032] In addition, the following components in mass percentage are included: P≤0.013%; S≤0.004%.

[0033] The method for preparing the high-strength multiphase wear-resistant seamless steel pipe comprises the following steps:

[0034] S1. Steelmaking: electric furnace smelting, refining outside the furnace, vacuum treatment;

[0035] S2. Casting: continuous casting. The cross section of the continuous casting billet is Φ210~270mm;

[0036] S3, rolling: ring furnace heating, perforation, continuous rolling, sizing, cooling;

[0037] in:

[0038] When heating in a ring furnace, the heating temperature of the tube billet is 1230℃~1290℃, and the holding time is 3.5~5.5h;

[0039] During perforation, the inlet temperature is 1160℃~1220℃, and the outlet capillary axial speed is 0.80~1.15m / s;

[0040] During continuous rolling, the inlet temperature is 1050℃~1110℃, the axial speed of the raw tube at the outlet is 3.75~4.50m / s; the diameter reduction rate of the raw tube is 11%~23%, and the wall reduction rate of the raw tube is 27%~42%. m -Outer diameter of rough pipe D o ) / capillary outer diameter D m ; capillary wall reduction rate ω = (capillary wall thickness S m -Wall thickness of rough pipe S o ) / capillary wall thickness S m ;

[0041] The inlet temperature during sizing is 950℃~1030℃, the axial speed of the finished pipe at the outlet is 1.55~2.50m / s; the deformation coefficient of the rough pipe is 0.73~0.95. Among them: the deformation coefficient of the rough pipe μ = the cross-sectional area of ​​the rough pipe A 1 / Finished pipe cross-sectional area A2;

[0042] During cooling, the finished tube is cooled to 450℃~465℃ at a rate of 1~2℃ to reach the bainite phase transformation zone, and then air-cooled to room temperature.

[0043] Example 2

[0044] In this embodiment, steel pipes with the following chemical compositions are prepared by the preparation method in Example 1, as shown in Table 1:

[0045] Table 1: Chemical composition of steel pipes in the examples by weight

[0046]

[0047]

[0048] During preparation, the rolling method is shown in Table 2 and Table 3:

[0049] Table 2: Rolling process control of the steel pipe of the embodiment

[0050]

[0051] Table 3: Rolling deformation parameters of the steel pipe of the embodiment

[0052]

[0053]

[0054] The prepared steel pipe was tested, and the obtained mechanical properties are shown in Table 4:

[0055] Table 4: Mechanical properties and metallographic structure of the steel pipes in the examples

[0056]

[0057] Among them: the metallographic structures of the steel pipes in Examples 1-12 are all bainite + martensite complex phase structures.

[0058] From Table 4, it can be seen that the tensile strength is stable above 1300MPa, and the longitudinal full-size impact energy at room temperature is ≥25J, which has good strength and toughness matching; Figure 1 , 2 , 3. It can be seen that the bainite and martensite multiphase wear-resistant structure is obtained, which is more wear-resistant.

[0059] It should be noted that the rough pipe in this patent refers to the steel pipe after being rolled by the piercer; the rough pipe refers to the steel pipe after being rolled by the continuous rolling mill; the CCT curve is the continuous cooling transformation curve of supercooled austenite, which reflects the transformation law of supercooled austenite under continuous cooling conditions and is the basis for analyzing the organization and performance of the transformation product.

[0060] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a high-strength multiphase wear-resistant seamless steel pipe, characterized in that: The high-strength multiphase wear-resistant seamless steel pipe includes the following components in percentage by mass: C: 0.22% ~ 0.26%; Si: 0.65% ~ 0.80%; Mn: 2.15% ~ 2.40%; Cr: 1.20% ~ 1.30%; Mo: 0.10% ~ 0.15%; V: 0.03% ~ 0.05%; Al: 0.010% ~ 0.020%; the rest is iron and unavoidable impurities; The method comprises the following steps: S1. Steelmaking: electric furnace smelting, refining outside the furnace, vacuum treatment; S2. Casting: continuous casting; wherein: the cross section of the continuous casting billet is Φ210~270mm; S3, rolling: ring furnace heating, perforation, continuous rolling, sizing, cooling; in: When heating in the annular furnace, the heating temperature of the tube billet is 1230℃~1290℃, and the holding time is 3.5~5.5h; During perforation, the inlet temperature is 1160℃~1220℃, and the outlet capillary axial speed is 0.80~1.15m / s; The inlet temperature during continuous rolling is 1050℃~1110℃, the axial speed of the outlet rough pipe is 3.75~4.50m / s; the rough pipe diameter reduction rate is 11%~23%, and the rough pipe wall reduction rate is 27%~42%; where: the rough pipe diameter reduction rate ε=(the rough pipe outer diameter D m -Outer diameter of rough pipe D o ) / capillary outer diameter D m ; capillary wall reduction rate ω = (capillary wall thickness S m -Wall thickness of rough pipe S o ) / capillary wall thickness S m ; The inlet temperature during sizing is 950℃~1030℃, the axial speed of the finished pipe at the outlet is 1.55~2.50m / s; the deformation coefficient of the rough pipe is 0.73~0.95; where: the deformation coefficient of the rough pipe μ = the cross-sectional area of ​​the rough pipe A 1 / Finished pipe cross-sectional area A2; During cooling, the finished tube is cooled to 450℃~465℃ at a rate of 1~2℃ to reach the bainite phase transformation zone, and then air-cooled to room temperature.

2. According to the method for preparing a high-strength multiphase wear-resistant seamless steel pipe according to claim 1, the high-strength multiphase wear-resistant seamless steel pipe further comprises the following components in mass percentage: P≤0.013%; S≤0.004%.

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