CN113355600B - On-line quenching 800MPa grade extra-thick steel plate for construction machinery and its manufacturing method - Google Patents

Abstract

An extra-thick steel plate for an on-line quenching 800 MPa-grade engineering machine comprises C:0.050-0.080%, si:0.10 to 0.25%, mn:1.30-1.50%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, al:0.020 to 0.040%, nb:0.010-0.020%, ti:0.008-0.015%, ni:0.40-0.50%, cr:0.30-0.40%, mo 0.20-0.30%, cu 0.20-0.30%, B:0.0010-0.0020%, and the balance iron. The steel plate prepared by the invention has stable mechanical property, good internal quality, good strength, toughness and plasticity and low yield ratio, and can effectively meet the requirements of special steel in the engineering machinery industry.

Description

On-line quenching 800MPa grade extra-thick steel plate for construction machinery and its manufacturing method

technical field

The invention belongs to the technical field of metal materials, and in particular relates to a steel for construction machinery with a tensile strength of 800 MPa and a manufacturing method thereof, and in particular to a thickness specification of 0-120 mm, high strength, high toughness and low yield under the condition of an online quenching process. Stronger than extra thick steel plate for construction machinery.

Background technique

The construction machinery industry is an important part of the machinery industry, of which iron and steel materials play an important role in the manufacture of construction machinery. With the development of construction machinery in the direction of high efficiency, high parameters, and large-scale, the requirements of construction machinery component materials in terms of strength, toughness and weldability are more prominent, which promotes the development and production of construction machinery steel. Development in the direction of better comprehensive performance. Traditional construction machinery steel is generally produced by quenching and tempering (off-line reheating quenching + tempering) process, which has problems such as many processes, high energy consumption, and large amount of alloy added. With the development of metallurgical technology and equipment, on-line quenching technology is receiving extensive attention in the steel industry, and on-line quenching equipment has also become the mainstream equipment for controlled cooling in medium and heavy plate production lines. The on-line quenching process is used to produce medium and heavy plates, which can effectively utilize the waste heat after rolling of the steel plate, and organically combine the deformation and heat treatment process; compared with the traditional quenching and tempering process, it can reduce the off-line reheating process, shorten the process flow, and reduce the production cost. With the development of a new generation of on-line quenching technology, the on-line quenching process is gradually being adopted in the production process of steel for construction machinery, and the thickness specifications of the steel plates that can be produced are getting larger and larger.

The patent "An extra-thick Q690 high-strength structural steel plate and its manufacturing method" (application number: CN201410467565), using "0.15-0.18% C, 1.00-1.20% Mn, 1.00-1.20% Cr, 0.54~0.60% Mo, 0.80~1.00% Ni, 0.03~0.05% V, 0.02~0.04% Nb, 0.001-0.002% B" composition design, through recrystallization zone rolling and "DQ+ACC online quenching" process, trial production of 160-180mm thickness specification Q690 ; Among them, the heating temperature is 1190-1230°C, the final rolling temperature is 920-980°C, the cooling temperature is 900-910°C, the final cooling temperature is 150-200°C, the cooling rate is 0.60-0.75°C/s, and the tempering temperature is 600-660°C , the tempering time is 3-3.5mm/min; the impact energy at 1/4, 1/2 and 3/4 of the thickness of steel plates with different thickness specifications ranges from 51-68J at 0°C. This patent uses medium C and adds a large amount of precious alloys, and at the same time adds micro-alloying elements Nb, V, etc., the carbon equivalent is bound to be high, which is unfavorable for the subsequent processing and use process, especially the welding process. The addition of a large amount of precious alloys increases the cost too much. During the rolling process, if a higher temperature rolling strategy is adopted, the rolling process may be in the mixed crystal region, which is unfavorable for the comprehensive mechanical properties of the extra-thick steel plate. In the process of water cooling, the cooling rate is less than 1.0℃/s; with a lower cooling rate, how to obtain the ideal online quenching structure and corresponding mechanical properties, and how to ensure the matching of strength and plastic toughness is worthy of discussion and discussion. The impact energy in the embodiment of the patent is low, and can only meet the requirement of 0°C, which cannot meet the requirement of high-strength steel for high-strength and toughness construction machinery.

The patent "On-line quenching production process method of high-strength and toughness thick steel plate" (application number: CN 200810013604), uses the on-line quenching production process to produce high-strength and toughness thick steel plate with thickness specification of 20-50mm. In terms of composition design, "0.05-0.15% C, 0.15-0.35% Si, 1.40-2.00% Mn, P≤0.010%, S≤0.005%, Nb≤0.06%, V≤0.06%, Ti≤0.04%, Ni≤0.40%, Mo≤0.20%, Cu≤0.40%, Cr≤0.50%, 0.0005-0.0020% B" design. In terms of rolling process control, the heating temperature of the billet is 1100-1250 °C, the final rolling temperature is 860 °C-950 °C, and the two-stage cooling method of aerosol and water curtain is used to realize on-line quenching of the steel plate. The average cooling rate is 25-45 °C/s. Cold temperature 150-300℃ and high temperature tempering at 580-650℃. In the examples, the tensile strength of the steels involved are all below 640MPa, the yield strength is below 565MPa, the impact energy at -20°C is >200J, and the actual performance data is close to that of Q500D. The patent adopts a relatively broad design of C, Mn and some alloying elements. The process design, especially the temperature range of finishing rolling, is too wide. It is in the transition zone of recrystallization and non-recrystallization temperature, and it can control the quality of the steel plate stably, especially the mechanical properties and microstructure. The organization adversely affects the limitations of its design. At the same time, the patent adopts ultra-low P design, which will inevitably increase the smelting cost. The higher cooling rate results in a large temperature gradient in the thickness direction of the steel plate and poor microstructure uniformity. In addition, this patent adopts a complex two-stage cooling method of aerosol and water curtain, but it can only produce steel plates of 50mm and below, with low strength level and impact toughness only reaching -20℃, which cannot meet the requirements of high-strength toughness and extra-thick steel plates.

Patent "On-line quenching process of large thickness and high strength steel plate" (application number: CN201811375040), using "0.13-0.18% C, 0.2-0.4% Si, 1.35-1.6% Mn, P≤0 .02%, S≤0.008%, 0.15-0.4% Ni, 0.2-0.5% Cr, Nb≤0.05%, 0.03-0.06% V, 0.05% 01-0.035%Ti, 0.2-0.35%Mo, 0.001-0.002%B" composition design, blank thickness 300-350mmmm, heating temperature 1170-

1250℃, the final rolling temperature is 840-890℃, the cooling temperature is 810-850℃, the final cooling temperature is less than 200℃, the tempering temperature is 620-660℃, and the holding time is 15-30min. On the basis of medium C component, a large amount of alloying elements Ni, Cr, Mo and micro-alloying elements Nb, V are added. Through online quenching (DQ) + offline tempering (T), it can produce thickness of 60-80mm, yield strength ≥700Mpa, and resistance to The tensile strength is 790-900MPa, the yield ratio is less than or equal to 0.92, the elongation is greater than or equal to 16%, and the impact energy at -20°C is greater than or equal to 100J high-strength steel. In terms of composition design, C is too high and the amount of alloying elements added is large, which increases the cost of the alloy and is not conducive to the mechanical properties, especially the impact toughness. In addition, lower final cooling temperature requirements require higher cooling equipment capacity. Part of the tempered microstructure in the examples is similar to that of the quenched and tempered steel, which is tempered sorbite, rather than the low-carbon lath bainite structure of the in-line quenched steel after tempering. The composition and process design are inconsistent with the results or theories of the examples, and the patent may not have the value of mass promotion.

The patent "A kind of 80-120mm extra-thick high-strength steel plate and its production method using continuous casting slab" (application number: CN103276312A) adopts conventional composition design, that is, "0.15-0.19% C, 1.15-1.35% Mn" On the basis, Ni, Cr, Mo, Nb, B, etc. are added, and the rolling reduction rate of the high temperature recrystallization zone is strictly limited. High-strength steel with Rp0.2>700MPa, Rm>800MPa, A>14%, -20℃ impact energy 70-160J. With normal composition design, too many alloying elements are added, and the alloy cost will increase significantly. The normal off-line quenching and tempering process has many processes, long production cycle and high production cost. In general, from design to process, this patent has no advantages and features.

Document "On-line Quenching Q690D High Strength Steel Plate Microstructure and Properties" (Metallic Materials and Metallurgical Engineering, 2016.06 (004), Zhang Yongwei, etc.), designed with low C-Mn-Cr-Mo composition and produced by "on-line quenching + tempering process" 16-30mm specification Q690D test steel plate and study its microstructure. This document only conducts on-line quenching test research on thin gauge Q690D, which has thin thickness gauge and low toughness index, and puts forward more requirements for the rolling process. For Q690D with conventional thickness, it is less difficult to use in-line quenching technology to produce. In addition, for thin gauge in-line quenching Q690D, the necessity of adding precious alloy Mo also needs to be considered.

The construction machinery industry is developing in the direction of lightweight and large-scale. Therefore, there is an urgent need for a high-strength and high-toughness steel for construction machinery with low cost and simple process, in order to obtain low-alloy high-strength or ultra-high-strength construction machinery steel with excellent comprehensive properties through reasonable and economical composition design and simple process control. .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a steel for construction machinery with a tensile strength of 800 MPa grade and extra-thick specifications under the condition of online quenching, so as to solve the problems in the prior art.

The invention is realized by the following technical scheme: an extra-thick steel plate for on-line quenching of 800MPa grade engineering machinery, which is characterized in that: each component comprises the following mass percentages: C: 0.050-0.080%, Si: 0.10-0.25%, Mn: 1.30-1.50%, P≤0.015%, S≤0.005%, Al: 0.020-0.040%, Nb: 0.010-0.020%, Ti: 0.008-0.015%, Ni: 0.40-0.50%, Cr: 0.30-0.40 %, Mo: 0.20-0.30%, Cu: 0.20-0.30%, B: 0.0010-0.0020%, N≤45ppm, H≤1.5ppm, O≤30ppm, the balance is Fe and inevitable impurities.

The invention also discloses a method for manufacturing an extra-thick steel plate for on-line quenching of 800MPa grade engineering machinery, which is characterized by comprising the following steps: molten steel smelting, LF furnace refining, RH vacuum treatment, thick slab casting, slab heating, steel plate Rolling, DQ+ACC cooling, tempering heat treatment; among them,

(1) The molten steel smelting step, the molten iron enters the converter for smelting through desulfurization and slag removal, and is refined by "LF+RH"; ℃, the end temperature of soft blowing is 1565±5℃, and the temperature of the middle bag is 1538±5℃; during the process, the content of each component is controlled as follows: C: 0.050-0.0.080%, P≤0.015%, S≤0.005%, N≤ 45ppm, H≤1.5ppm, O≤30ppm; deep vacuum treatment time is 15-20min;

(2) Casting steps for thick slabs: keep constant pulling speed during casting, the pulling speed range is 0.45m-0.55m/min, the average superheat is 20-25℃; dynamic light reduction increases the reduction of two-phase region and solid-phase region The reduction rate is 1.10-1.30mm/m, the reduction in the two-phase area is 8-10mm, and the reduction in the solid phase area is 0.5-1.5mm; ensure that the center segregation of the slab is C class ≤ 0.5;

(3) Slab heating step: use a walking beam heating furnace to heat the slab segmentally to a soaking temperature of 1180-1220°C; wherein the temperature of the first heating section is 950-1050°C, and the temperature of the second heating section is 1050-1150°C °C, the temperature of the third heating section is 1150-1200 °C, the temperature of the soaking section of the fourth heating section is 1180-1220 °C, and the slab is in the furnace for 450-550min;

(4) Steel plate rolling steps: the recrystallization zone and the non-recrystallization zone are used for segment rolling; the starting temperature of the rolling stage in the recrystallization zone is ≥1100 °C, the ending temperature is 1000-1050 °C, and the total pressure of the rolling stage in the recrystallization zone is 1000-1050 °C. The reduction is 55-70%, and the single-pass reduction of the last 2-3 passes of the first stage rolling is 35-50mm; The single-pass reduction ratio is ≥15-20%; after the recrystallization zone rolling is completed, the thickness of the intermediate billet to be warmed is 1.7-2.0 times the thickness of the finished steel plate; the starting temperature of the rolling stage in the non-recrystallization zone is 830-850℃, and the end temperature The temperature is 800-820℃, and the single-pass rolling reduction rate in the non-recrystallization zone is ≤12%, and the cumulative reduction rate is ≥40-50%;

(5) DQ+ACC cooling step: During the cooling process, open the DQ slit header and the ACC high-density fast cooling header for cooling, where the water inlet pressure of the DQ slit header is 0.4-0.5MPa, and the water flow density range is 2000-3000L/(m ² . min), the water inlet pressure of the ACC high-density fast cooling header is 0.2-0.3MPa, the water flow density range is 1000-2000L/(m ² .min), the total water volume is ≥15000m ³ /h, and the roller speed is 0.30-0.33m/min; start Cooling temperature 780-800℃, final cooling temperature 200-300℃, cooling rate 10-15℃/s;

(6) Tempering heat treatment step: high temperature tempering process is adopted; among them, the tempering temperature and holding time are "600-650℃" and "80-120min" respectively, and the heating coefficient during the tempering process is 2.4±0.1min/cm .

The advantages of the invention are: (1) On the basis of the existing tooling capacity, simple and reasonable component design and process requirements are adopted to realize the development of large-thickness on-line quenching engineering machinery steel, breaking through the traditional thick specification and extra-thick steel plate that must be "off-line" Reheating quenching + tempering" process production limit, while reducing production processes, improving production efficiency and reducing production costs.

(2) The 800MPa grade extra-thick steel plate involved in the present invention has stable mechanical properties, good internal quality, good strength, toughness and plasticity, low yield-to-strength ratio, flaw detection meets the requirements of the national standard, and meets the needs of special steel in the construction machinery industry. The value of industrial promotion and application.

Description of drawings

Figure 1 shows the microstructure at the 1/4 position of the thickness of the 80mm steel plate;

Figure 2 shows the microstructure at the 1/2 position of the thickness of the 80mm steel plate;

Figure 3 shows the microstructure at the 1/4 position of the thickness of the 120mm steel plate;

Figure 4 shows the microstructure at the 1/2 position of the thickness of the 120mm steel plate.

Detailed ways

Example 1

An on-line quenching 800MPa grade extra-thick steel plate for construction machinery, comprising the following components by mass percentage: C: 0.058%, Si: 0.22%, Mn: 1.32%, P: 0.014%, S: 0.004%, Al: 0.022% , Nb: 0.013%, Ti: 0.015%, Ni: 0.49%, Cr: 0.32%, Mo: 0.23%, Cu: 0.21, B: 0.0015%, N: 42ppm, H: 1.2ppm, O: 23ppm, remainder For Fe and inevitable impurities; welding crack sensitivity index Pcm (%): 0.189%.

Continuous casting billet type: 475mm*2000mm*2800mm; rolled steel plate size: 80mm*2600mm*12750mm.

In the molten steel smelting process, the converter tapping is 1655°C, the LF end is 1642°C, the RH end is 1580°C, the soft blowing end temperature is 1560°C, the middle bag temperature is 1537°C, and the deep vacuum treatment time is 16min.

During the casting process, the pulling speed is 0.48m/min, and the superheat degree is 22℃. The dynamic light reduction increases the reduction of the two-phase area and the solid-phase area, the reduction rate is 1.25mm/m, the reduction of the two-phase area is 9mm, the reduction of the solid-phase area is 1.4mm, and the center segregation of the slab is C class 0.

During the slab heating process, the temperature of the first heating section is 980-1045 °C, the temperature of the second heating section is 1053-1142 °C, the temperature of the third heating section is 1155-1190 °C, and the temperature of the soaking section of the fourth heating section is 1195-1215 °C, Slab in furnace time 470min.

During the steel plate rolling process, the starting temperature of the rolling stage in the recrystallization zone is 1132 °C, the ending temperature range is 1020 °C, and the thickness of the intermediate slab to be warmed is 160 mm; the starting temperature of the rolling stage in the non-recrystallization zone is 848 °C, and the ending temperature is 812 °C. Table 1 shows the reduction ratio of the pass reduction in the rolling process.

During the cooling process, the water inlet pressure of 4 groups of DQ gap headers is 0.48MPa, the water flow density range is 2500-2800L/(m ² .min)), and the 26 groups of ACC high-density fast cooling headers, the water inlet pressure is 0.21MPa, and the water flow density range is 1200-1500L/(m ² .min)), total water volume, 15500m ³ /h, roller speed 33m/s; starting cooling temperature 793℃, final cooling temperature 262℃, average cooling speed 14℃/s.

During the tempering heat treatment process, the tempering temperature was 640°C, the holding time was 80 min, and the heating coefficient during the tempering process was 2.35 min/cm.

The mechanical properties of the 80mm specification produced in Example 1 are shown in Table 2, and the flaw detection results are shown in Table 3.

It can be seen from Figure 1 that after tempering, it is mainly lath bainite (mostly), granular bainite and polygonal ferrite, and the grains are relatively fine and uniform. It can be seen from Figure 2 that after tempering, lath bainite, granular bainite and polygonal ferrite are mainly formed, and the grains are relatively fine and uniform.

This scheme is different from the tempered Soxhlet structure produced by quenching and tempering of medium and high carbon steel. The structure in this scheme is mainly lath bainite, granular bainite and polygonal ferrite, and the grains are relatively fine and uniform. Since the content of low carbon bainite steel is greatly reduced, the adverse effect of carbon on bainite structure and toughness is greatly weakened. The strength of the steel plate no longer depends on the carbon content in traditional quenched and tempered steel, but is ensured by fine grains, dislocations, substructures, and precipitation strengthening and precipitation strengthening of niobium, vanadium, and titanium. The strength and toughness of the steel plate is well matched, and it has good economic benefits and welding performance.

Example 2:

An on-line quenching 800MPa grade extra-thick steel plate for construction machinery, its chemical composition is (weight percentage), C: 0.076%, Si: 0.16%, Mn: 1.48%, P: 0.010%, S: 0.002%, Al: 0.036 %, Nb: 0.018%, Ti: 0.014%, Ni: 0.46%, Cr: 0.37%, Mo: 0.25%, Cu: 0.28%, B: 0.0018%, N: 35ppm, H: 1.0ppm, O: 25ppm, The balance is Fe and inevitable impurities; welding crack sensitivity index Pcm (%): 0.221%.

Continuous casting billet type: 475mm*2000mm*3750mm; rolled steel plate specification: 120mm*2300mm*12900mm, 1 fixed length.

In the molten steel smelting process, the converter tapping is 1648°C, the LF end is 1640°C, the RH end is 1582°C, the soft blowing end temperature is 1559°C, the middle bag temperature is 1535°C, and the deep vacuum treatment time is 19min.

During the casting process, the pulling speed is 0.45m/min, and the superheat degree is 24℃. The dynamic light reduction increases the reduction amount of the two-phase area and the solid phase area, the reduction rate is 1.29mm/m, the reduction amount of the two-phase area is 8mm, the reduction amount of the solid phase area is 1.5mm, and the center segregation of the slab is C class 0.

During the slab heating process, the temperature of the first heating section is 985-1050 °C, the temperature of the second heating section is 1055-1148 °C, the temperature of the third heating section is 1161-1194 °C, and the temperature of the soaking section of the fourth heating section is 1200-1218 °C, Slab in furnace time 495min.

During the steel plate rolling process, the starting temperature of the rolling stage in the recrystallization zone is 1139 °C, the ending temperature range is 1008 °C, and the thickness of the intermediate billet to be warmed is 210 mm; the starting temperature of the rolling stage in the non-recrystallization zone is 841 °C, and the ending temperature is 807 °C. Table 4 shows the reduction ratio of the pass reduction in the rolling process.

During the cooling process, the water inlet pressure of 4 groups of DQ slit headers is 0.49MPa, the water flow density range is 2600-3000L/(m ² .min)), and the 26 groups of ACC high-density fast cooling headers, the water inlet pressure is 0.23MPa, and the water flow density range is 1250-1500L/(m ² .min)), total water volume, 15800m ³ /h, roller speed 0.33m/s; starting cooling temperature 796℃, final cooling temperature 165℃, average cooling rate 11℃/s.

During the tempering heat treatment, the tempering temperature was 610°C, the holding time was 120min, and the heating coefficient during the tempering process was 2.42min/cm.

The mechanical properties of the 120mm specification produced in Example 2 are shown in Table 5, and the flaw detection results are shown in Table 6.

It can be seen from Figure 3 that after tempering, mainly granular bainite, lath bainite and polygonal ferrite are formed. It can be seen from Figure 4 that after tempering, it is mainly granular bainite and polygonal ferrite, and a small part is lath bainite.

To sum up, on the basis of the existing tooling capabilities, the present invention adopts simple and reasonable component design and process requirements to realize the development of large-thickness on-line quenching engineering machinery steel, breaking through the traditional thick-specification extra-thick steel plate that must use "off-line reheating and quenching+". "Tempering" process production limitations, while reducing production processes, improve production efficiency and reduce production costs.

In addition, the 800MPa grade extra-thick steel plate involved in the present invention has stable mechanical properties, good internal quality, good strength, toughness and plasticity, low yield-to-strength ratio, flaw detection meets the requirements of the national standard, meets the needs of special steel in the construction machinery industry, and has excellent Industrial promotion and application value.

Claims (2)

1. On-line quenching 800MPa grade extra-thick steel plate for construction machinery, characterized in that it includes the following components in mass percentage: C: 0.050-0.080%, Si: 0.10-0.25%, Mn: 1.30-1.50%, P≤0.015 %, S≤0.005%, Al: 0.020-0.040%, Nb: 0.010-0.020%, Ti: 0.008-0.015%, Ni: 0.40-0.50%, Cr: 0.30-0.40%, Mo: 0.20-0.30%, Cu : 0.20-0.30%, B: 0.0010-0.0020%, N≤45ppm, H≤1.5ppm, O≤30ppm, the balance is Fe and inevitable impurities; The on-line quenching 800MPa grade extra-thick steel plate for construction machinery is prepared by the following method: including the following steps: molten steel smelting, LF furnace refining, RH vacuum treatment, thick slab casting, slab heating, steel plate rolling, DQ+ACC Cooling, tempering heat treatment; of which, (1) The molten steel smelting step, the molten iron enters the converter for smelting through desulfurization and slag removal, and is refined by "LF+RH"; ℃, the end temperature of soft blowing is 1565±5℃, and the temperature of the middle bag is 1538±5℃; during the process, the content of each component is controlled as follows: C: 0.050-0.0.080%, P≤0.015%, S≤0.005%, N≤ 45ppm, H≤1.5ppm, O≤30ppm; deep vacuum treatment time is 15-20min; (2) Casting steps for thick slabs: keep constant pulling speed during casting, the pulling speed range is 0.45m-0.55m/min, the average superheat is 20-25℃; dynamic light reduction increases the reduction of two-phase region and solid-phase region The reduction rate is 1.10-1.30mm/m, the reduction in the two-phase area is 8-10mm, and the reduction in the solid phase area is 0.5-1.5mm; ensure that the center segregation of the slab is C class ≤ 0.5; (3) Slab heating step: use a walking beam heating furnace to heat the slab segmentally to a soaking temperature of 1180-1220°C; wherein the temperature of the first heating section is 950-1050°C, and the temperature of the second heating section is 1050-1150°C °C, the temperature of the third heating section is 1150-1200 °C, the temperature of the soaking section of the fourth heating section is 1180-1220 °C, and the slab is in the furnace for 450-550min; (4) Steel plate rolling steps: the recrystallization zone and the non-recrystallization zone are used for segment rolling; the starting temperature of the rolling stage in the recrystallization zone is ≥1100 °C, the ending temperature is 1000-1050 °C, and the total pressure of the rolling stage in the recrystallization zone is 1000-1050 °C. The reduction is 55-70%, and the single-pass reduction of the last 2-3 passes of the first stage rolling is 35-50mm; The single-pass reduction ratio is ≥15-20%; after the recrystallization zone rolling is completed, the thickness of the intermediate billet to be warmed is 1.7-2.0 times the thickness of the finished steel plate; the starting temperature of the rolling stage in the non-recrystallization zone is 830-850℃, and the end temperature The temperature is 800-820℃, and the single-pass rolling reduction rate in the non-recrystallization zone is ≤12%, and the cumulative reduction rate is ≥40-50%; (5) DQ+ACC cooling step: During the cooling process, open the DQ slit header and the ACC high-density fast cooling header for cooling, where the water inlet pressure of the DQ slit header is 0.4-0.5MPa, and the water flow density range is 2000-3000L/(m ² · min), the water inlet pressure of the ACC high-density fast cooling header is 0.2-0.3MPa, the water flow density range is 1000-2000L/(m ² ·min), the total water volume is ≥15000m ³ /h, and the roller speed is 0.30-0.33m/min; start Cooling temperature 780-800℃, final cooling temperature 200-300℃, cooling rate 10-15℃/s; (6) Tempering heat treatment step: high temperature tempering process is adopted; among them, the tempering temperature and holding time are "600-650℃" and "80-120min" respectively, and the heating coefficient during the tempering process is 2.4±0.1min/cm ; The thickness of the extra-thick steel plate for on-line quenching of 800MPa grade construction machinery is 80-120mm. 2. the manufacture method of a kind of on-line quenching 800MPa grade construction machinery extra-thick steel plate as claimed in claim 1, it is characterized in that: comprise the steps: molten steel smelting, LF furnace refining, RH vacuum treatment, thick slab casting, plate Billet heating, steel plate rolling, DQ+ACC cooling, tempering heat treatment; among them, (1) The molten steel smelting step, the molten iron enters the converter for smelting through desulfurization and slag removal, and is refined by "LF+RH"; ℃, the end temperature of soft blowing is 1565±5℃, and the temperature of the middle bag is 1538±5℃; during the process, the content of each component is controlled as follows: C: 0.050-0.0.080%, P≤0.015%, S≤0.005%, N≤ 45ppm, H≤1.5ppm, O≤30ppm; deep vacuum treatment time is 15-20min; (2) Casting steps for thick slabs: keep constant pulling speed during casting, the pulling speed range is 0.45m-0.55m/min, the average superheat is 20-25℃; dynamic light reduction increases the reduction of two-phase region and solid-phase region The reduction rate is 1.10-1.30mm/m, the reduction in the two-phase area is 8-10mm, and the reduction in the solid phase area is 0.5-1.5mm; ensure that the center segregation of the slab is C class ≤ 0.5; (3) Slab heating step: use a walking beam heating furnace to heat the slab segmentally to a soaking temperature of 1180-1220°C; wherein the temperature of the first heating section is 950-1050°C, and the temperature of the second heating section is 1050-1150°C °C, the temperature of the third heating section is 1150-1200 °C, the temperature of the soaking section of the fourth heating section is 1180-1220 °C, and the slab is in the furnace for 450-550min; (4) Steel plate rolling steps: the recrystallization zone and the non-recrystallization zone are used for segment rolling; the starting temperature of the rolling stage in the recrystallization zone is ≥1100 °C, the ending temperature is 1000-1050 °C, and the total pressure of the rolling stage in the recrystallization zone is 1000-1050 °C. The reduction is 55-70%, and the single-pass reduction of the last 2-3 passes of the first stage rolling is 35-50mm; The single-pass reduction ratio is ≥15-20%; after the recrystallization zone rolling is completed, the thickness of the intermediate billet to be warmed is 1.7-2.0 times the thickness of the finished steel plate; the starting temperature of the rolling stage in the non-recrystallization zone is 830-850℃, and the end temperature The temperature is 800-820℃, and the single-pass rolling reduction rate in the non-recrystallization zone is ≤12%, and the cumulative reduction rate is ≥40-50%; (5) DQ+ACC cooling step: During the cooling process, open the DQ slit header and the ACC high-density fast cooling header for cooling, where the water inlet pressure of the DQ slit header is 0.4-0.5MPa, and the water flow density range is 2000-3000L/(m ² · min), the water inlet pressure of the ACC high-density fast cooling header is 0.2-0.3MPa, the water flow density range is 1000-2000L/(m ² ·min), the total water volume is ≥15000m ³ /h, and the roller speed is 0.30-0.33m/min; start Cooling temperature 780-800℃, final cooling temperature 200-300℃, cooling rate 10-15℃/s; (6) Tempering heat treatment step: high temperature tempering process is adopted; among them, the tempering temperature and holding time are "600-650℃" and "80-120min" respectively, and the heating coefficient during the tempering process is 2.4±0.1min/cm .

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