An Optimal Controlled Rolling Method Using Ultra-rapid Cooling to Control Austenite Structure

Abstract

At present, the ultra-rapid cooling technology is mainly applied to cooling steel after two-stage controlled rolling. The invention discloses an optimized controlled rolling method using ultra-rapid cooling to control the austenite structure, which belongs to the technical field of metallurgy. This method rolls the steel completely in the austenite recrystallization zone of the billet, and at the same time precisely controls the rolling temperature and pass reduction rate. Immediately after rolling, the rolled steel is cooled to the phase transformation point by an ultra-fast cooling system, and then According to the needs, different cooling paths are used to control the phase transformation of steel. The invention adopts ultra-rapid cooling to effectively suppress the coarsening of fine recrystallized austenite structure, and retains the effect of dynamic recrystallization and sub-dynamic recrystallization on the refinement of austenite structure in the high-temperature rolling process. The product manufactured by the present invention has comparable mechanical properties to the steel produced by the two-stage controlled rolling process, and at the same time reduces the waiting temperature and low temperature and high pressure in the rolling process, and reduces the rolling time by 2 to 4 minutes compared with the two-stage controlled rolling process. .

Description

technical field

[0001] The invention belongs to the technical field of iron and steel materials, and in particular relates to an optimally controlled rolling method for controlling austenite structure by ultra-rapid cooling. Background technique

[0002] Controlled rolling and controlled cooling technology (Thermomechanical Control Process, TMCP) is one of the greatest achievements in the steel industry in the 20th century. Since the 1950s, TMCP technology has played a pivotal role in improving the comprehensive performance of hot-rolled products. The core features of the traditional TMCP technology are: ① "Low temperature and large reduction" and "addition of microalloying elements" to obtain hardened austenite to the greatest extent; ② Accelerated cooling after rolling (Accelerated Cooling, ACC), controlled hardening of austenite phase transition, refine the structure.

[0003] Japan's JFE Company developed the accelerated cooling process before other steel companies, and...

Examples

Embodiment 1

[0024] The chemical composition of bainitic steel for rolling is as follows: C: 0.04-0.06%, Si: 0.30-0.50%, Mn: 1.40-1.80%, P: ≤0.01%, S: ≤0.005%, Al: ≤0.03%, Ni: 0.20~0.40%, Cr: 0.40~0.60%, Cu: 0.30~0.50%, Ti: 0.02~0.03%, Nb: 0.03~0.05%, Mo: 0.15~0.18%, the balance is Fe And unavoidable impurities, the specific data are shown in Table 1.

[0025] After testing, the RLT of the bainite steel with the above composition is 990-1020°C; reheat the billet to 1200-1250°C and keep it warm for 1-2h, and carry out controlled rolling and controlled cooling on a 450mm two-roll hot rolling mill; The rolling temperature is 1150±10°C, the final rolling temperature is 1050±10°C, ultra-rapid cooling is adopted immediately after rolling, the cooling rate is 75±5°C / s, the steel plate is cooled to 400°C, and then air-cooled to room temperature, the typical steel plate Austenitic structure such as figure 1 As shown, the typical tissue characteristics at room temperature are as follows figure 2...

Embodiment 2

[0045] The chemical composition (mass fraction) of ferritic steel for rolling is: C: 0.05-0.07%, Si: 0.25-0.35%, Mn: 1.20-1.50%, P: ≤0.008%, S: ≤0.005%, Al : ≤0.06%, Ti: 0.09-0.12%, V: 0.05-0.07%, and the balance is Fe and unavoidable impurities. The specific data are shown in Table 6.

[0046] After testing, the RLT of the ferritic steel with the above composition is 960-1010°C; reheat the billet to 1200-1250°C and keep it warm for 1-2 hours, and carry out controlled rolling and controlled cooling on a 450mm two-roll hot rolling mill; The rolling temperature is 1155±5°C, and the final rolling temperature is 1030±5°C. Immediately after rolling, the steel plate is cooled to 700°C by ultra-rapid cooling at a cooling rate of 55±5°C / s, and then air-cooled to room temperature. body structure such as image 3As shown, the TEM morphology is as follows Figure 4 shown.

[0047] The controlled rolling process is shown in 7, and the mechanical properties are shown in Table 8.

[004...

technical field

[0001] The invention belongs to the technical field of iron and steel materials, and in particular relates to an optimally controlled rolling method for controlling austenite structure by ultra-rapid cooling. Background technique

[0002] Controlled rolling and controlled cooling technology (Thermomechanical Control Process, TMCP) is one of the greatest achievements in the steel industry in the 20th century. Since the 1950s, TMCP technology has played a pivotal role in improving the comprehensive performance of hot-rolled products. The core features of the traditional TMCP technology are: ① "Low temperature and large reduction" and "addition of microalloying elements" to obtain hardened austenite to the greatest extent; ② Accelerated cooling after rolling (Accelerated Cooling, ACC), controlled hardening of austenite phase transition, refine the structure.

[0003] Japan's JFE Company developed the accelerated cooling process before other steel companies, and...

Examples

Embodiment 1

[0024] The chemical composition of bainitic steel for rolling is as follows: C: 0.04-0.06%, Si: 0.30-0.50%, Mn: 1.40-1.80%, P: ≤0.01%, S: ≤0.005%, Al: ≤0.03%, Ni: 0.20~0.40%, Cr: 0.40~0.60%, Cu: 0.30~0.50%, Ti: 0.02~0.03%, Nb: 0.03~0.05%, Mo: 0.15~0.18%, the balance is Fe And unavoidable impurities, the specific data are shown in Table 1.

[0025] After testing, the RLT of the bainite steel with the above composition is 990-1020°C; reheat the billet to 1200-1250°C and keep it warm for 1-2h, and carry out controlled rolling and controlled cooling on a 450mm two-roll hot rolling mill; The rolling temperature is 1150±10°C, the final rolling temperature is 1050±10°C, ultra-rapid cooling is adopted immediately after rolling, the cooling rate is 75±5°C / s, the steel plate is cooled to 400°C, and then air-cooled to room temperature, the typical steel plate Austenitic structure such as figure 1 As shown, the typical tissue characteristics at room temperature are as follows figure 2...

Embodiment 2

[0045] The chemical composition (mass fraction) of ferritic steel for rolling is: C: 0.05-0.07%, Si: 0.25-0.35%, Mn: 1.20-1.50%, P: ≤0.008%, S: ≤0.005%, Al : ≤0.06%, Ti: 0.09-0.12%, V: 0.05-0.07%, and the balance is Fe and unavoidable impurities. The specific data are shown in Table 6.

[0046] After testing, the RLT of the ferritic steel with the above composition is 960-1010°C; reheat the billet to 1200-1250°C and keep it warm for 1-2 hours, and carry out controlled rolling and controlled cooling on a 450mm two-roll hot rolling mill; The rolling temperature is 1155±5°C, and the final rolling temperature is 1030±5°C. Immediately after rolling, the steel plate is cooled to 700°C by ultra-rapid cooling at a cooling rate of 55±5°C / s, and then air-cooled to room temperature. body structure such as image 3As shown, the TEM morphology is as follows Figure 4 shown.

[0047] The controlled rolling process is shown in 7, and the mechanical properties are shown in Table 8.

[004...

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