High-toughness easy-to-weld q1100e steel plate and method for manufacturing the same

Abstract

The application discloses a high-toughness and easy-to-weld Q1100E steel plate and a preparation method thereof, and belongs to the technical field of steel metallurgy. The steel plate adopts an optimized component design, a carbon equivalent CEV is less than or equal to 0.57%, and molten iron pretreatment, converter smelting, LF refining, RH refining, continuous casting, controlled rolling and quenching and tempering heat treatment are matched, so that the strength and toughness, low-temperature toughness and weldability are synergistically improved. The application can produce the Q1100E steel plate with a thickness of 8-15 mm, a yield strength greater than or equal to 1100 MPa, a tensile strength of 1200-1500 MPa, an elongation greater than or equal to 9%, and an impact energy at-40 DEG C greater than or equal to 90 J; the steel plate has low welding cold crack sensitivity, good matching of joint strength and toughness, no obvious embrittlement in the weld and the heat-affected zone, and is suitable for high-end load-bearing structural parts such as engineering machinery and mine equipment.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy and materials processing technology, specifically relating to a high-toughness, easy-to-weld Q1100E steel plate and its preparation method, which is particularly suitable for ultra-high strength structural steel for high-end load-bearing structural components such as engineering machinery, mining machinery, and lifting equipment. Background Technology

[0002] As construction machinery, lifting equipment, mining and port machinery develop towards larger size, lighter weight, and higher reliability, the requirements for the strength, toughness, weldability, and formability of structural steel continue to increase. Q1100E is an ultra-high strength construction machinery steel with a yield strength ≥1100MPa. It possesses excellent low-temperature impact toughness at -40℃ and is widely used in key load-bearing components such as truck crane booms, crawler crane plates, pump trucks, and hydraulic supports. It is a core material for high-end equipment manufacturing.

[0003] Compared to traditional Q960 and lower grade steels, 1100MPa grade ultra-high strength steels generally suffer from problems such as high alloy content, high carbon equivalent and cold cracking sensitivity, poor weldability, and easy embrittlement of the heat-affected zone. These issues make them prone to welding defects, difficult to match joint strength and toughness, and challenging to achieve synergistic control, with complex and unstable preparation methods. Therefore, developing Q1100E with excellent strength and toughness, good weldability, and stable processing, along with its preparation method, is of great significance for breaking the foreign monopoly, achieving domestic production, and ensuring the needs of critical equipment.

[0004] Patent CN113308643B discloses a method for producing ultra-high strength Q1100E steel plates with good formability. It can produce Q1100E steel plates with a thickness of 6-12mm with good formability, but it does not have a systematic design for welding performance and cannot guarantee the strength and toughness of the welded joint and the reliability of field use.

[0005] Patent CN 109207858 A discloses a production method for Q1100E thin plates of low alloy ultra-high strength steel. The invention uses a two-fire rolling method and a direct tempering process to obtain Q1100E steel plates. This production method does not use a quenching and tempering process, resulting in poor overall performance stability of the steel plates. Furthermore, the process is complex and the production cycle is long, which is not conducive to industrial mass production.

[0006] Therefore, the present invention provides a Q1100E steel plate with reasonable composition, stable process and excellent welding performance and its production method, so as to solve the defects of the prior art. Summary of the Invention

[0007] To address the problems of poor weldability, cold cracking sensitivity, heat-affected zone embrittlement, poor joint strength-toughness matching, and unstable preparation methods in existing 1100MPa grade ultra-high strength steel, this invention provides a high-toughness, easily weldable Q1100E steel plate and its preparation method. Through composition optimization, precise control of the entire process, tempering heat treatment, and matching welding processes, a balance between strength, toughness, low-temperature toughness, and weldability is achieved.

[0008] This invention is achieved through the following technical solution: A high-toughness, easily weldable Q1100E steel plate has the following chemical composition and mass percentage: C: 0.13-0.18%, Mn: 1.00-1.40%, Si: 0.20-0.50%, Cr: 0.20-0.50%, Mo: 0.40-0.65%, Ti: 0.008-0.020%, Als: 0.025-0.050%, B: 0.0012-0.0025%, Nb: 0.015-0.035%, V: 0.035-0.060%, Ni: 0.30-0.50%, P≤0.015%, S≤0.003%, with the balance being iron and unavoidable impurities. The carbon equivalent (CEV) is controlled to ≤0.57%, calculated using the formula: CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15.

[0009] The present invention also provides a method for preparing the above-mentioned steel plate: This invention also provides a high-toughness, easily weldable Q1100E steel plate and its preparation method, comprising, in sequence: hot metal pretreatment, converter smelting, LF refining, RH refining, continuous casting, rolling, and heat treatment, wherein: (1) Hot metal pretreatment: Desulfurization is carried out using the KR method or injection method, and slag is removed; after treatment, S≤0.010%; (2) Converter smelting: Top and bottom blowing converter for decarburization, desiliconization, and desulfurization, and slag blocking before steel tapping; (3) LF refining: white slag operation, submerged arc heating, and slightly positive pressure reducing atmosphere; (4) RH refining: vacuum pressure holding ≥18min, argon blowing throughout the process; (5) Continuous casting: full-process protective casting, electromagnetic stirring + light pressure; tundish superheat 20±5℃; constant casting speed, liquid level fluctuation ≤±3mm; (6) Rolling: The billet heating temperature is 1220±20℃, the billet thickness is 200-350mm, and the time is 1.0~1.3min / mm; Two-stage controlled rolling: the first stage initial rolling temperature is ≥1000℃, the second stage final rolling temperature is 840±20℃; after rolling, water cooling is applied to 680±20℃;

[0010] (7) Heat treatment: Quenching: 880~920℃, 2.8~3.5min / mm; Tempering: 200~250℃, 2.8~3.5min / mm; slow cooling to room temperature.

[0011] Matching welding process: Steel plate is processed into a Y-shaped 60° bevel; no preheating is required before welding; GMAW multi-layer multi-pass welding; φ1.2mm ER83-G welding wire; current 200-230A, voltage 25V, speed 30-40cm / min; layer temperature ≤180℃; heat input 8-12kJ / cm; no heat treatment is required after welding.

[0012] The advantages of this invention are: the steel plate described herein has a reasonable composition design, low carbon equivalent, and significantly reduced sensitivity to welding cold cracking. It exhibits excellent strength-toughness matching, high impact toughness at -40℃, meeting the requirements of high-end equipment. The welded joint shows no obvious embrittlement or hardening, and its strength and toughness are well matched with the base material. The preparation method described herein has a stable and controllable process flow, suitable for industrial-scale mass production of 8-15mm specifications. Attached Figure Description

[0013] Figure 1 This is a macroscopic photograph of a 15mm thick steel plate cold bending test according to the present invention; Figure 2 This is a macroscopic photograph of the 15mm thick steel plate after welding according to the present invention; Figure 3 The images show the metallographic structure of a typical weld location after welding a 15mm thick steel plate according to the present invention; where A is the base material, B is the heat-affected zone, C is the fusion line, and D is the weld location. Figure 4 This is a macroscopic photograph of the welded joint of the 15mm thick steel plate of the present invention after side bending. Detailed Implementation

[0014] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0015] This application provides a high-toughness, easily weldable Q1100E steel plate, the chemical composition and mass percentage of which are as follows: C: 0.13-0.18%, Mn: 1.00-1.40%, Si: 0.20-0.50%, Cr: 0.20-0.50%, Mo: 0.40-0.65%, Ti: 0.008-0.020%, Als: 0.025-0.050%, B: 0.0012-0.0025%, Nb: 0.015-0.035%, V: 0.035-0.060%, Ni: 0.30-0.50%, P≤0.015%, S≤0.003%, with the balance being iron and unavoidable impurities.

[0016] This application also provides a high-toughness, easily weldable Q1100E steel plate and a method for preparing the same, the method comprising the following steps: Hot metal pretreatment: Desulfurization of molten hot metal is performed using the KR method or injection method, followed by slag removal. The mass fraction of sulfur in the molten hot metal after pretreatment is ≤0.010%. Converter smelting: Top and bottom blowing converters are used for decarburization, desiliconization, and desulfurization of molten iron, and slag blocking is used for steel tapping; LF refining: white slag operation, during heating, maintain submerged arc operation and ensure a slightly positive pressure state and reducing atmosphere inside the furnace; RH refining: vacuum holding time ≥18min, argon gas is blown throughout the production of this steel grade; Continuous casting: Full-process protective casting is implemented, with electromagnetic stirring and light pressure applied to the casting machine. The superheat of the tundish in each continuous casting furnace is 20±5℃. A constant casting speed is maintained, and liquid level fluctuations are controlled within ±3mm. Slab heating: The slab heating temperature is 1220±20℃, the slab thickness is 200-350mm, and the heating time is 1.0~1.3min / mm; Rolling: Two-stage controlled rolling is adopted. The first stage rolling temperature is ≥1000℃, the second stage target final rolling temperature is 840±20℃, and the rolling is water-cooled to 680±20℃. Heat treatment: Quenching temperature is 880~920℃, furnace time is 2.8~3.5min / mm, tempering temperature is 200~550℃, furnace time is 2.8~3.5min / mm, and slow cooling to room temperature.

[0017] The welding process of this scheme is as follows: Cut two sample blanks with dimensions of steel plate thickness * 250mm (width direction) * 1000mm (length direction) from the steel plate, and make a Y-shaped 60° bevel; no preheating is required; GMAW multi-layer multi-pass welding; φ1.2mm ER83-G welding wire; current 200-230A, voltage 25V, speed 30-40cm / min; layer temperature ≤180℃; heat input 8-12kJ / cm; no heat treatment is required after welding.

[0018] The above technical solution will be described below through specific embodiments.

[0019] Example 1: The target steel plate obtained in this example has a thickness of 15 mm. The chemical composition and mass percentage of the steel plate are as follows: C: 0.164%, Si: 0.232%, Mn: 1.13%, P: 0.011%, S: 0.0018%, Als: 0.032%, Cr: 0.23%, B: 0.0013%, Mo: 0.56%, Ni: 0.31%, Nb: 0.023%, Ti: 0.013%, V: 0.043%. In preparing the above target steel plate, after alloying and deoxidation in the converter, it was refined by LF+RH, continuously cast, heated to 1234℃, rough rolling temperature of 1046℃, finishing rolling temperature of 849℃, quenching temperature controlled at 900℃, furnace time of 45 min, tempering temperature controlled at 200℃, furnace time of 45 min, and slow cooling to room temperature. Cut two sample blanks from the steel plate, each measuring 250mm (width) * 1000mm (length). Use a 60° Y-shaped bevel. No preheating is required. Perform multi-layer, multi-pass GMAW welding. Use φ1.2mm ER83-G welding wire. Current: 200-230A; Voltage: 25V; Welding speed: 30-40cm / min; Layer temperature: ≤180℃; Heat input: 8-12kJ / cm; No post-weld heat treatment.

[0020] Example 2: The target steel plate obtained in this example has a thickness of 12mm. The chemical composition and mass percentage of the steel plate are as follows: C: 0.158%, Si: 0.236%, Mn: 1.11%, P: 0.013%, S: 0.0021%, Als: 0.033%, Cr: 0.21%, B: 0.0014%, Mo: 0.55%, Ni: 0.30%, Nb: 0.022%, Ti: 0.014%, V: 0.041%. In preparing the above target steel plate, after alloying and deoxidation in the converter, it was refined by LF+RH, continuously cast, heated to 1229℃, rough rolling temperature of 1055℃, finishing rolling temperature of 856℃, quenching temperature controlled at 890℃, furnace time of 40min, tempering temperature controlled at 220℃, furnace time of 40min, and slow cooling to room temperature. Cut two sample blanks from the steel plate, each measuring 250mm (width) * 1000mm (length). Use a 60° Y-shaped bevel. No preheating is required. Perform multi-layer, multi-pass GMAW welding. Use φ1.2mm ER83-G welding wire. Current: 200-230A; Voltage: 25V; Welding speed: 30-40cm / min; Layer temperature: ≤180℃; Heat input: 8-12kJ / cm; No post-weld heat treatment.

[0021] Table 1 shows the actual performance of the steel plates corresponding to Examples 1 and 2.

[0022] As shown in Table 1, the 12mm and 15mm steel plates prepared in Examples 1-2 exhibit stable and excellent longitudinal impact toughness at -40℃, with an average single impact value exceeding 90J, moderate strength, and good strength and toughness. Cold bending tests were conducted on 15mm thick Q1100E steel plates using test parameters of a bending mandrel diameter D=4a (a being the sample thickness) and a bending angle of 180°, combined with… Figure 1 It can be observed that no defects such as cracks were generated on the surface of the sample after the test, indicating that the base material has good cold working plasticity.

[0023] Table 2 shows the tensile properties of the steel plates after welding in Examples 1 and 2. As can be seen from Table 2, the fracture location of the steel plate after welding in the tensile test is the weld, which meets the requirements of low-strength matching welding performance.

[0024] Table 3 shows the impact performance of the steel plates after welding in Examples 1 and 2.

[0025] As shown in Table 3, the impact energy at -40℃ at typical locations such as the weld center, FL (Fusion Line), and HAZ 2mm (Heat Affected Zone, 2mm from the fusion line) of the steel plate after welding is ≥40J, which fully meets the requirements of Q1100E.

[0026] Macroscopic and microscopic defect detection was performed on the welded joint of the steel plate, combined with... Figure 2 It can be observed that there are no welding defects such as cracks, lack of fusion, or inclusions inside the weld metal, the weld formation is good, and the macroscopic quality of the welded joint is qualified.

[0027] The microstructure of each region of the welded joint was observed and analyzed, and the metallographic structure at each typical location was as follows: Figure 3 As shown: the base metal microstructure is tempered, maintaining the martensitic lath morphology; the heat-affected zone microstructure consists of lath bainite, granular bainite, and a small amount of martensite; the microstructure at the fusion line consists of bainite, ferrite, and carbides, without coarse upper bainite, Widmanstätten structure, continuous network grain boundaries, or coarse twinned martensite and other embrittlement structures; the weld metal microstructure consists of acicular ferrite, proeutectoid ferrite, and a small amount of granular bainite, with a uniform microstructure distribution. These microstructural characteristics indicate that there are no hardened embrittlement phases or grain boundary embrittlement features in any region of the weld joint, demonstrating good weld microstructure compatibility.

[0028] A weld side bending test was conducted on the welded joint, using test parameters of mandrel diameter D=6a (a is the steel plate thickness) and bending angle 180°, combined with... Figure 4 No cracks were found in the weld area after the test. According to the relevant provisions of GB / T2653, the plasticity and crack resistance of the welded joint meet the technical requirements.

[0029] In summary, this invention provides a high-toughness, easily weldable Q1100E steel plate and its preparation method. The steel plate itself possesses excellent low-temperature impact toughness and good strength and toughness. After welding using the given welding process, the steel plate exhibits excellent properties and good weldability.

Claims

1. A high-toughness, easily weldable Q1100E steel plate, characterized in that: The composition includes the following components by mass percentage: C: 0.13-0.18%, Mn: 1.00-1.40%, Si: 0.20-0.50%, Cr: 0.20-0.50%, Mo: 0.40-0.65%, Ti: 0.008-0.020%, Als: 0.025-0.050%, B: 0.0012-0.0025%, Nb: 0.015-0.035%, V: 0.035-0.060%, Ni: 0.30-0.50%, P≤0.015%, S≤0.003%, with the balance being iron and unavoidable impurities, wherein CEV≤0.57, CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15.

2. A method for preparing a high-toughness, easily weldable Q1100E steel plate, characterized in that: The process includes hot metal pretreatment, converter smelting, LF refining, RH refining, continuous casting, rolling, and heat treatment, among which: Hot metal pretreatment includes: desulfurization of hot metal using the KR method or injection method, followed by slag removal. After hot metal pretreatment, the mass percentage of sulfur in the hot metal is ≤0.010%. Converter smelting includes: using a top-and-bottom blown converter for decarburization, desiliconization, and desulfurization of molten iron, and slag blocking before tapping steel; LF refining includes: white slag operation, submerged arc heating, and a slightly positive pressure reducing atmosphere inside the furnace; RH refining includes: vacuum holding time ≥18min, and argon blowing throughout the process; Continuous casting includes: full-process protective casting, electromagnetic stirring + light reduction, tundish superheat 20±5℃, constant casting speed, and liquid level fluctuation ≤±3mm; The rolling process includes: the billet heating temperature is 1220±20℃, the heating time is 1.0~1.3min / mm; two-stage controlled rolling is adopted, the first stage initial rolling temperature is ≥1000℃, the second stage target final rolling temperature is 840±20℃, and the rolling is water-cooled to 680±20℃. The heat treatment includes: quenching at a temperature of 880–920℃ for 2.8–3.5 min / mm; tempering at a temperature of 200–250℃ for 2.8–3.5 min / mm; and slow cooling to room temperature.

3. The method for preparing high-toughness, easily weldable Q1100E steel plate according to claim 2, characterized in that: The steel plate is welded using the following process: it is machined into a Y-shaped groove with a groove angle of 60°; no preheating is required before welding; multi-layer, multi-pass welding is used with gas metal arc welding; the welding material is φ1.2mm ER83-G solid core welding wire; the welding current is 200-230A, the voltage is 25V, the welding speed is 30-40cm / min, the interpass temperature is ≤180℃, the heat input is 8-12kJ / cm, and no heat treatment is performed after welding.

4. The method for preparing high-toughness, easily weldable Q1100E steel plate according to claim 3, characterized in that: The prepared high-toughness, easy-to-weld Q1100E steel plate has a thickness of 8-15mm, a yield strength ≥1100MPa, a tensile strength of 1200~1500MPa, an elongation ≥9%, and an impact energy of ≥90J at -40℃. The impact energy of the steel plate at -40℃ at typical locations after welding is ≥40J.

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