Method for producing high-rupture-resistance extra-thick super-high-strength ship plate

Abstract

The production method of high crack arrest property super-thick ultra-high strength ship plate belongs to the field of steel material preparation. The chemical composition of the steel is as follows: C=0.05%-0.08%, Si<=0.50%, Mn=0.80%-1.15%, P<=0.010%, S<=0.002%, Al=0.015%-0.05%, Nb=0.01%-0.04%, V=0.05%-0.07%, Ti=0.008%-0.02%, Ni=0.60%-1.20%, Mo=0.20%-0.50%, Cr=0.50%-1.00%, Cu<=0.20%, and the rest is Fe and inevitable impurities. The application breaks through the limitation of the compression ratio of the continuous casting billet rolling thick crack arrest steel, adopts the online DQ+LT process to control the soft and hard phase structure, and produces the super-thick crack arrest steel plate with the maximum thickness of 100mm by using the continuous casting billet. The super-thick crack arrest steel plate integrates the ultra-high strength, high toughness and high crack arrest property, has simple process, low production cost, and provides an effective solution for producing the high crack arrest property super-thick ultra-high strength ship plate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel material preparation, and relates to a production method of high-crack-arrest thick ultra-high-strength ship plate. BACKGROUND

[0002] With the development of economy and the increase of trade volume, container ships gradually develop in the direction of large-scale, and the load of the deck superstructure of the container ship is also getting larger and larger. Some key parts, such as the main deck, the top side plate, the hatch coaming and the like, due to the requirements of high strength, high toughness and high crack arrest performance, the general high-strength ship plate cannot meet the use requirements. Taking a 24000TEU super-large container ship as an example, the thickness of the hatch coaming reaches 95mm, and the steel quantity of the crack arrest steel is more than 1000 tons per ship.

[0003] The Chinese patent CN 101341269 A "High-strength thick steel plate with excellent crack arrest performance" mainly controls the difference of the structure, grain boundary density and texture of the steel plate in the thickness direction, so that the crack propagation direction at different thickness positions is different when the steel plate cracks, thereby increasing the crack propagation resistance to improve the crack arrest performance of the steel plate. However, the essence is that the cooling capacity of the thick plate produced is not enough, and the brittle structure at the 1 / 2 position of the plate affects the crack arrest performance of the steel plate. This method has little effect on the improvement of the crack arrest performance, and the toughness structure at the 1 / 2 position is not fundamentally improved. The Chinese patent CN 102994874 A "High crack arrest toughness steel plate with yield strength of 500Mpa and production method thereof" discloses a method of refining the grain by rapidly cooling to the Ar3 transformation point after rough rolling and then performing finish rolling to prevent crack propagation. However, this method uses low-temperature impact toughness and NDT ductile-brittle transition temperature to measure the crack arrest performance of the steel plate, which is not scientific and rigorous. It can only indicate that the toughness of the steel plate is good, and cannot prove that the crack arrest performance of the steel plate is excellent. Only the ESSO test or double tensile test is the internationally recognized standard test for measuring the crack arrest performance of the steel plate. SUMMARY

[0004] The purpose of the present application is to provide a production method of high-crack-arrest thick ultra-high-strength ship plate, which produces thick crack arrest steel with a maximum thickness of 100mm, and relates to a production method of ultra-high-strength ship plate with yield strengths of 47, 51 and 56kg grades, and particularly requires that the crack arrest toughness Kca at-10℃ is greater than or equal to 8000N / mm 3 / 2 , and has high crack arrest performance.

[0005] The technical scheme of the present application is as follows:

[0006] The application discloses a production method of high-rupture-resistance extra-thick super-high-strength ship plate, and a chemical composition of the steel and a weight percentage of the steel are as follows: C=0.05%-0.08%, Si<=0.50%, Mn=0.80%-1.15%, P<=0.010%, S<=0.002%, Al=0.015%-0.05%, Nb=0.01%-0.04%, V=0.05%-0.07%, Ti=0.008%-0.02%, Ni=0.60%-1.20%, Mo=0.20%-0.50%, Cr=0.50%-1.00%, Cu<=0.20%, and the balance is Fe and inevitable impurities; production process steps include smelting, continuous casting, heating, rolling, cooling, quenching and tempering; the heating is performed at a discharging temperature of 1180-1220 DEG C; the rolling is performed by controlled rolling at a finish rolling temperature of 820-850 DEG C; the cooling is performed by rapid water cooling to room temperature at a cooling speed of greater than or equal to 5 DEG C / s; the quenching is performed by two-phase zone quenching at a quenching temperature of A c1 +(10-30) DEG C, a quenching time of 3.0 min / mm x plate thickness+(15-25) min; the tempering is performed by high-temperature tempering at a tempering temperature of A c1 -(80-100) DEG C, a tempering time of 2.5-3.0 min / mm x plate thickness min; wherein, A c1 is a start temperature of ferrite transformation into austenite in the heating process.

[0007] In a further aspect, the application provides a production method of high-rupture-resistance extra-thick super-high-strength ship plate with a yield strength of 47 kg level, a chemical composition of the steel and a weight percentage of the steel are as follows: C=0.05%-0.07%, Si=0.15%-0.35%, Mn=1.00%-1.15%, P<=0.010%, S<=0.002%, Al=0.015%-0.050%, Nb=0.02%-0.03%, V=0.05%-0.06%, Ti=0.008%-0.02%, Ni=0.60%-0.70%, Mo=0.20%-0.30%, Cr=0.50%-0.60%, and the balance is Fe and inevitable impurity elements; correspondingly preferably, the quenching temperature is 740-760 DEG C, and the tempering temperature is 630-650 DEG C.

[0008] Further, the production method of the high crack arrest property extra-thick ultra-high strength ship plate with yield strength of 51 kg level, the chemical composition of the steel and its weight percentage are as follows: C=0.05%-0.07%, Si=0.15%-0.35%, Mn=0.90%-1.00%, P≤0.010%, S≤0.002%, Al=0.015%-0.050%, Nb=0.02%-0.03%, V=0.055%-0.065%, Ti=0.008%-0.02%, Ni=0.80%-1.00%, Mo=0.30%-0.40%, Cr=0.60%-0.80%, and the balance is Fe and inevitable impurity elements; and correspondingly preferably, the quenching temperature is 750-770 DEG C, and the tempering temperature is 640-660 DEG C.

[0009] Further, the production method of the high crack arrest property extra-thick ultra-high strength ship plate with yield strength of 56 kg level, the chemical composition of the steel and its weight percentage are as follows: C=0.06%-0.08%, Si=0.15%-0.35%, Mn=0.80%-0.90%, P≤0.010%, S≤0.002%, Al=0.015%-0.050%, Nb=0.03%-0.04%, V=0.06%-0.07%, Ti=0.008%-0.02%, Ni=1.00%-1.20%, Mo=0.40%-0.50%, Cr=0.80%-1.00%, Cu=0.10%-0.20%, and the balance is Fe and inevitable impurity elements; and correspondingly preferably, the quenching temperature is 760-780 DEG C, and the tempering temperature is 650-670 DEG C.

[0010] The technical principle of the process of the application is as follows:

[0011] The application is different from the conventional crack arrest steel production process, and the crack arrest property of the steel plate is not improved by refining the grains through the TMCP process, but the phase change organization after rolling is precisely controlled through the DQ+LT process, a two-step heat treatment process is adopted, a fine multi-phase organization is formed, the grains are refined while the organization defects are eliminated, so that the crack arrest property of the extra-thick steel plate is improved. The rolling organization is mainly lath bainite+granular bainite+M / A island, especially in the heart of the extra-thick steel plate, the size and proportion of the granular bainite and M / A island increase, and the toughness and crack arrest property are seriously deteriorated; the first step is to quench in the two-phase region, heated to A c1+ (10~30) ℃, partial reverse transformation of the rolled structure occurs, reverse transformation austenite is formed along the original austenite grain boundaries and between the lath structures, partial austenitization is realized, the un-austenitized matrix structure still maintains a lath structure, and elements such as C, Mn and Ni in the matrix structure are enriched in the reverse transformation austenite, thereby improving the hardenability of the reverse transformation austenite, in the subsequent water cooling process, the reverse transformation austenite is transformed into martensite or bainite, and the un-austenitized structure with depleted C, Mn and Ni content is transformed into critical ferrite. In the second high-temperature tempering, carbides in the martensite / bainite formed in the first quenching and cooling process are precipitated, and residual austenite is decomposed, and finally after air cooling, a multi-phase structure mainly composed of critical ferrite + tempered martensite / bainite + fine residual austenite is obtained, and the soft and hard phase matched structure type makes the steel plate have excellent strength and toughness and crack arrest property.

[0012] The prominent features and significant effects of the present application mainly include:

[0013] (1) The present application produces high crack arrest property super-thick ship plates from continuous casting billets, the maximum thickness can reach 100 mm, while ensuring product quality, the-10 ℃ crack arrest toughness Kca≥8000 N / mm 3 / 2 ;

[0014] (2) The present application breaks through the limitation of compression ratio of traditional TMCP process for rolling thick plates, refines grains through structure regulation technology, improves the core structure performance of thick gauge steel plates, has simple process, reduces alloy and production cost, and has high yield;

[0015] (3) The present application can be realized by using existing equipment and process conditions of the steel plant, without increasing investment and equipment modification, and the process is stable and easy to realize, and can be mass-produced;

[0016] (4) The present application produces a new type of energy-saving, low-carbon and environmentally friendly steel, which can also be widely used in shipbuilding, bridges, pressure vessels, buildings and engineering machinery and other fields, and ensures the crack arrest capability of the steel plate. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Figure 1 is a metallographic structure diagram of the 1 / 4 position in the thickness direction of the steel plate of Example 1 of the present application.

[0018] Figure 2 Figure 2 is a metallographic structure diagram of the 1 / 2 position in the thickness direction of the steel plate of Example 1 of the present application. DETAILED DESCRIPTION

[0019] The present application will be further described below by combining a group of examples and comparative examples with the drawings.

[0020] The chemical composition of the steel in the examples is shown in Table 1, and the balance is Fe and inevitable impurity elements.

[0021] According to the production method of the present application, the steel plates of the above-mentioned embodiments are produced by using a 120t top and bottom combined blowing converter to smelt, carrying out secondary refining and vacuum treatment, pouring into a 350mm section continuous casting billet, then rolling into a 100mm thick steel plate on a 5000mm double rack wide plate production line, and finally obtaining the finished steel plate through the heat treatment process of quenching and tempering. Then the tensile and impact and crack arrest properties of the finished steel plate are detected and the metallographic structure is observed. The key process parameters of the steel plates of the embodiments are shown in Table 2, and the actual performance is shown in Table 3.

[0022] As can be seen from the actual performance results in Table 3, the steel plates of the embodiments of the present application have good comprehensive mechanical properties and crack arrest properties, and the steel plate of Example 1 meets the requirements of the 47kg strength grade.

[0023] As can be seen from the drawings, the multi-phase structure mainly composed of critical ferrite + tempered martensite + fine residual austenite is controlled by the on-line DQ+LT process; the steel plate of Example 2 meets the requirements of the 51kg strength grade; the steel plate of Example 3 meets the requirements of the 56kg strength grade; when the thickness of the steel plate produced by the method of the present application reaches 100mm, the-60℃ impact toughness of the core part is still more than 200J, the elongation is more than 24%, and the steel plate has excellent toughness and plasticity; the crack arrest toughness of the steel plate of the embodiments is tested by using the gradient temperature type double tensile test, and the-10℃ crack arrest toughness Kca value is all more than 8000N / mm 3 / 2 Therefore, the steel plate has high crack arrest performance and can well meet the use requirements of the key parts of the super-large container ship.

[0024] Table 1 Chemical composition of the high crack arrest thick ultra-high strength ship plate in the embodiments

[0025] .

[0026] Table 2 Key process parameters of the steel plates in the embodiments of the present application

[0027] .

[0028] Table 3 Actual performance of the steel plates in the embodiments of the present application

[0029] .

Claims

1. A method for producing extra-thick, ultra-high-strength ship plates with high crack arrest properties, comprising the following production steps: smelting, continuous casting, heating, rolling, cooling, quenching, and tempering, characterized in that: The chemical composition and weight percentage of the steel are as follows: C=0.05%~0.08%, Si≤0.50%, Mn=0.80%~1.15%, P≤0.010%, S≤0.002%, Al=0.015%~0.05%, Nb=0.01%~0.04%, V=0.05%~0.07%, Ti=0.008%~0.02%, Ni=0.60%~1.20%, Mo=0.20%~0.50%, Cr=0.50%~1.00%, Cu≤0.20%, with the balance being Fe and unavoidable impurities. Key processes include: furnace exit temperature of 1180~1220℃; controlled rolling with a final rolling temperature of 820~850℃; rapid water cooling to room temperature at a rate ≥5℃ / s; and two-phase quenching at a quenching temperature of [missing information]. A c1 The quenching temperature is +(10~30)℃, and the quenching time is 3.0 min / mm × plate thickness +(15~25) min; high-temperature tempering is used, and the tempering temperature is... A c1 -(80~100)℃, tempering time is 2.5~3.0min / mm×plate thickness min; where, A c1 This is the starting temperature for the transformation of ferrite to austenite during the heating process; the produced steel plate is 100mm thick, and a multiphase microstructure consisting mainly of critical ferrite, tempered martensite, and fine retained austenite is obtained. The crack arrest toughness Kca at -10℃ is ≥8000N / mm. 3 / 2 .

2. The method for producing high-crack-arresting, extra-thick, ultra-high-strength ship plates according to claim 1, characterized in that, A production method for ultra-thick, high-strength ship plates with high crack arrest properties and a yield strength of 47 kg / m². The chemical composition and weight percentage of the steel are as follows: C=0.05%~0.07%, Si=0.15%~0.35%, Mn=1.00%~1.15%, P≤0.010%, S≤0.002%, Al=0.015%~0.050%, Nb=0.02%~0.03%, V=0.05%~0.06%, Ti=0.008%~0.02%, Ni=0.60%~0.70%, Mo=0.20%~0.30%, Cr=0.50%~0.60%, with the balance being Fe and unavoidable impurity elements. The key processes are a quenching temperature of 740~760℃ and a tempering temperature of 630~650℃.

3. The method for producing high-crack-arresting, extra-thick, high-strength ship plates according to claim 1, characterized in that, A method for producing ultra-thick, high-strength ship plates with high crack arrest properties and a yield strength of 51 kg. The chemical composition and weight percentage of the steel are as follows: C=0.05%~0.07%, Si=0.15%~0.35%, Mn=0.90%~1.00%, P≤0.010%, S≤0.002%, Al=0.015%~0.050%, Nb=0.02%~0.03%, V=0.055%~0.065%, Ti=0.008%~0.02%, Ni=0.80%~1.00%, Mo=0.30%~0.40%, Cr=0.60%~0.80%, with the balance being Fe and unavoidable impurity elements. The key processes are a quenching temperature of 750~770℃ and a tempering temperature of 640~660℃.

4. The method for producing high-crack-arresting, extra-thick, ultra-high-strength ship plates according to claim 1, characterized in that, A method for producing ultra-thick, high-strength ship plates with high crack arrest properties and a yield strength of 56 kg / m². The chemical composition and weight percentage of the steel are as follows: C=0.06%~0.08%, Si=0.15%~0.35%, Mn=0.80%~0.90%, P≤0.010%, S≤0.002%, Al=0.015%~0.050%, Nb=0.03%~0.04%, V=0.06%~0.07%, Ti=0.008%~0.02%, Ni=1.00%~1.20%, Mo=0.40%~0.50%, Cr=0.80%~1.00%, Cu=0.10%~0.20%, with the balance being Fe and unavoidable impurity elements. The key processes are a quenching temperature of 760~780℃ and a tempering temperature of 650~670℃.

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