CN108930002B

CN108930002B - Abrasion-resistant steel plate for slurry dredging pipe with hardness of 500HB and production method thereof

Info

Publication number: CN108930002B
Application number: CN201710383618.4A
Authority: CN
Inventors: 宋凤明; 温东辉; 胡晓萍; 杨阿娜; 暴文帅; 吴祖国; 华骏山
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2017-05-26
Filing date: 2017-05-26
Publication date: 2020-08-25
Anticipated expiration: 2037-05-26
Also published as: CN108930002A

Abstract

The abrasion-resistant steel plate for the slurry dredging pipe with the hardness of 500HB and the production method thereof comprise the following components in percentage by weight: c: 0.25-0.28%, Si is less than or equal to 0.01%, Mn: 1.3-1.6%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.2-1.0%, Cr: 0.3-1.2%, B: 0.001-0.002%, N is less than or equal to 0.005%; further contains Nb: 0.01-0.03% or Ti: 0.01-0.025%, and satisfies 6.65N < Nb + Ti < 0.045, and the balance is Fe and inevitable impurities. The yield strength of the abrasion-resistant steel plate is more than 1200MPa, the tensile strength exceeds 1500MPa, the elongation is more than or equal to 8 percent, and the impact power value at minus 40 ℃ is more than 20J, wherein the hardness is 500 +/-30 HBW. The composition design of the abrasion-resistant steel plate of the invention gives consideration to the corrosion resistance and the abrasion resistance, and the abrasion-resistant steel plate is mainly used for manufacturing dredging pipelines in the fields of sea reclamation, channel dredging and the like, and the abrasion resistance of the abrasion-resistant steel plate reaches 2.5 times of that of the prior common pipe, thereby greatly improving the dredging efficiency and reducing the operation cost.

Description

Abrasion-resistant steel plate for slurry dredging pipe with hardness of 500HB and production method thereof

Technical Field

The invention relates to the field of low alloy steel manufacturing, in particular to an abrasion-resistant steel plate for a slurry dredging pipe with the hardness of 500HB and a production method thereof.

Background

During operations such as land reclamation, channel dredging, bank maintenance and the like, a large amount of solid particles such as silt, sand and the like are conveyed in a long distance through a dredging pipeline in the form of slurry, a pipe body simultaneously bears electrochemical corrosion of slurry media, abrasion of the solid particles and interaction of the slurry media and the solid particles, particularly, the seawater slurry contains weathered rocks, coral reefs and medium and coarse sand, the pipe body is more seriously abraded, and the service life of a pipeline made of ordinary Q235B and Q345B materials is short under severe working conditions, and even the pipeline is scrapped for less than 1 year.

The wear-resistant steel is made of HB500 grade wear-resistant steel plate disclosed in Chinese patent publication No. CN102517509A and its preparation method, and martensite series wear-resistant steel disclosed in Chinese patent publication No. CN103397275A and its preparation method, and these two patents are C-Mn and added with a large amount of alloy elements such as Cu, Mo, Ni and the like, so that the alloy cost is high. The patent relates to the field of steel grade with hardness of about 500HBW and good wear resistance, and is mainly used in the fields of engineering machinery, mining equipment and the like. However, the component design of the related steel is not considered to inhibit corrosion, particularly Cu and Ni are used as common alloy elements in atmospheric corrosion resistant steel, and the higher addition amount promotes the formation of a surface protective rust layer, increases the material weight loss in the abrasion process, has poor abrasion resistance, and cannot meet the use requirement under the working condition of corrosion and abrasion.

Also, "wear-resistant steel sheet" disclosed in Japanese patent No. JP2007231321A and "wear-resistant steel sheet super in manufacturing and manufacturing method" disclosed in Japanese patent No. JP2008169443A both describe methods for improving wear resistance by carbide-precipitated particles of Ti and W, and the components contain noble alloy elements such as Cu, Ni, Cr, Mo, etc. at the same time. Although the steel type has high hardness and wear resistance, a large amount of carbide particles in a matrix play a role of 'cathode' under the working condition of corrosive wear, so that the electrochemical corrosion is promoted, the corrosion resistance is reduced, the wear resistance of the material is deteriorated, and the requirements of large particle size and high content of slurry abrasion in the slurry dredging environment are difficult to meet.

Chinese patent publication No. CN101886225A (reference patent 2) discloses "a corrosion-resistant and wear-resistant steel and a preparation method thereof", which relates to steel grades with added C up to 0.4-0.9% and Mn up to 14-16%, and Mo and Cr contents of 5-10%, and also contains a certain amount of rare elements such as Pr, Nd, Gd, and the like, belonging to high alloy steel grades, and having high cost; the two patents relate to the steel types which are bainite or bainite and acicular ferrite tissues, have low matrix hardness and tensile strength of only 600-plus-800 MPa, are mainly applied to the working condition environment with slight abrasion, such as ore pulp with fine particles (dozens of mum) or crude oil transportation, and the like, and are not suitable for the field of large-particle and high-density seawater slurry transportation.

Disclosure of Invention

The invention aims to provide an abrasion-resistant steel plate for a slurry dredging pipe with the hardness of 500HB and a production method thereof, wherein the steel has the composition design with both corrosion resistance and abrasion resistance, is mainly used for manufacturing dredging pipelines in the fields of sea reclamation, channel dredging and the like, and has the abrasion resistance which is 2.5 times that of the conventional common pipe, so that the dredging efficiency is greatly improved, and the operation cost is reduced.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the abrasion-resistant steel plate for the slurry dredging pipe with the hardness of 500HB comprises the following components in percentage by weight: c: 0.25-0.28%, Si is less than or equal to 0.01%, Mn: 1.3-1.6%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.2-1.0%, Cr: 0.3-1.2%, B: 0.001-0.002%, N is less than or equal to 0.005%; further contains Nb: 0.01-0.03% or Ti: 0.01-0.025%, and satisfies 6.65N < Nb + Ti < 0.045, and the balance is Fe and inevitable impurities.

The yield strength of the steel plate is more than 1200MPa, the tensile strength exceeds 1500MPa, the elongation is more than or equal to 8 percent, and the impact power value at minus 40 ℃ and minus 30HBW exceeds 20J.

In the composition design of the steel of the invention:

c is the cheapest strengthening element in steel, and a high-hardness martensite structure is obtained after heat treatment, so that the strength of the steel plate can be remarkably improved, but more C is unfavorable for welding, toughness and plasticity of the steel plate. The range is limited to 0.25-0.28% under the condition of meeting the performance requirement;

si is a deoxidizing element, is a solid solution strengthening element and is a common corrosion-resistant element in atmospheric corrosion resistant steel. The atmospheric corrosion resistant steel mainly inhibits the occurrence of corrosion by forming a surface protective rust layer, and achieves the aim of improving the atmospheric corrosion resistance. The weather resistance index I is generally used to define the corrosion resistance of atmospheric corrosion resistant steel, and I is usually required to be more than or equal to 6.0. Wherein:

I＝26.01*Cu+3.88*Ni+1.49*Si+1.2*Cr+17.28*P-7.29*Cu*Ni-9.1*Ni*P-33.39*Cu*Cu。

as can be seen from the composition of the weathering index, the formation of protective rust layers on the steel surface is promoted at higher Si contents, which rapidly detach from the surface in abrasive environments, promoting abrasive failure of the material. Therefore, in the present invention, Si is controlled as a harmful element, and the amount of Si added is minimized to 0.01% or less. Meanwhile, Cu and Ni are not added into the steel grade of the invention.

Mn is a common strengthening element in steel, improves yield strength through solid solution strengthening, reduces elongation, obviously reduces phase transition temperature of the steel, refines microstructure of the steel, is an important strengthening and toughening element, but increases hardenability due to excessive Mn content, thereby causing weldability and toughness of a welding heat affected zone to be deteriorated, so that the content is controlled to be between 1.3 and 1.6 percent.

P is a main corrosion resistant element in the traditional atmospheric corrosion resistant steel, promotes the formation of a surface protective rust layer, effectively improves the atmospheric corrosion resistance of the steel, but the formation of the surface rust layer in the abrasion process accelerates the abrasion weight loss of materials and reduces the abrasion resistance, and meanwhile, the existence of P is easy to generate segregation, reduces the toughness and plasticity of the steel, makes the steel plate become brittle and affects the toughness, so the content of P in the steel is required to be reduced as much as possible, and the content of P in the steel is required to be controlled below 0.015 percent.

S can increase the yield strength of steel, but the presence of S deteriorates the atmospheric corrosion resistance of steel, makes steel sheet brittle, and lowers the low-temperature toughness of steel, and it is required to control the content thereof to 0.005 or less.

Al is usually added into steel as a deoxidizer in the steelmaking process, and trace Al is simultaneously beneficial to refining grains and improving the toughness of steel. On one hand, Al is added as a deoxidizer, and after proper Al is added, the corrosion potential of the steel is improved, so that the generation of corrosion in the abrasion process is inhibited, and the abrasion resistance is improved. However, too high Al content is controlled to 0.2 to 1.0% because it increases ferrite brittleness in steel and decreases toughness of steel.

B has good hardenability, thereby improving the hardness of the steel plate, but the content of B is too high, which is unfavorable for welding, so that the content of B is respectively controlled to be 0.001-0.002%;

cr has a solid solution strengthening effect and is a corrosion-resistant element with the smallest contribution coefficient in the weather resistance index I, and meanwhile, Cr has a remarkable effect on improving the potential of a matrix. The addition of a proper amount of Cr can effectively improve the self-corrosion potential of steel and inhibit the occurrence of corrosion, thereby effectively reducing the promotion effect of corrosion on material failure in the abrasion process and improving the abrasion resistance. However, since Cr is a noble alloy element, its content is limited to 0.3 to 1.2%.

Nb is a strong nitrogen carbide forming element and can be combined with carbon and nitrogen in steel to form intermediate phases such as NbC, Nb (CN), NbN and the like, and formed fine carbide particles can refine the structure and generate precipitation strengthening effect to remarkably improve the strength of a steel plate, but more Nb is not favorable for welding and can be selectively added, and the content is recommended to be not more than 0.03%.

On one hand, the selection of the addition of not more than 0.025 percent of Ti inhibits the growth of austenite grains in the reheating process of the plate blank, and simultaneously inhibits the growth of ferrite grains in the recrystallization controlled rolling process, thereby improving the toughness of the steel. The corrosion rate can be obviously reduced by adding a trace amount of Ti into the Al-containing steel, and the Ti can be preferentially combined with N in the steel and reduce the amount of AlN in the steel.

Al element in steel combines with N to easily form AIN, so that the number of nitrides in steel is significantly increased. When AIN independently exists in steel as a non-metallic inclusion, the continuity of a steel matrix is damaged, and particularly, when the AIN is in a large quantity and is in an aggregation distribution, the damage degree is higher. The steel grade of the invention is added with more Al, and the content of N must be controlled below 0.0050 percent.

The steel grade designed by adopting the components is subjected to heat treatment to obtain a high-strength tempered martensite structure, the yield strength is more than or equal to 1200MPa, the tensile strength is more than or equal to 1500MPa, the elongation is more than or equal to 8%, and the hardness is 500 +/-30 HB, so that the high-strength tempered martensite structure has good wear resistance; meanwhile, the addition of Cr and Al and the limitation on components such as Si, P and the like improve the self-corrosion potential of the matrix, effectively slow down and inhibit the corrosion, and improve the corrosion resistance of the material, so that the steel grade has good corrosion resistance, and is suitable for the field of large-particle and high-density slurry conveying.

The invention relates to a production method of an abrasion-resistant steel plate for a slurry dredging pipe with the hardness of 500HB, which comprises the following steps:

1) smelting and casting

Smelting and casting into a blank according to the components;

2) slab reheating

The heating temperature is more than 1200 ℃, the heat preservation time is more than 2h, and the soaking and heat preservation time is not less than 40 min;

3) controlled rolling

The rolling is divided into two stages of rough rolling and finish rolling, the rough rolling stage adopts large reduction rolling, the pass reduction is controlled to be more than 18 percent or more than 40mm, meanwhile, the thickness ratio of the intermediate billet to the finished product is required to be more than or equal to 3, and the final pass reduction of the finish rolling is controlled to be not less than 16 percent; the finishing temperature is not lower than 860 ℃;

4) coiling

The coiling temperature is controlled between 640 ℃ and 680 ℃;

5) uncoiling, straightening and cutting plate

6) Heat treatment, quenching and tempering

Quenching, wherein the heating temperature is controlled to be 50-80 ℃ above the Ac3 point of the steel grade, and the heating temperature is 860-890 ℃; the heat preservation time T1 is calculated from the center of the steel plate to the temperature, T1 is the thickness T x (2.5-3.5) of the steel plate, T1 is the unit min, T and mm; directly water-quenching the steel plate to room temperature after discharging to form a martensite structure, wherein the cooling speed is required to be more than or equal to 50 ℃/s;

tempering, wherein tempering treatment is carried out in the temperature range of 180-240 ℃, the tempering heat preservation time T2 is counted from the center of the steel plate to the temperature, T2 is the thickness T x (2.5-3.5) of the steel plate, T2 is unit min, T is unit mm; t2 minimum not less than 10 min; the tempered steel plate matrix is a tempered martensite structure, has proper hardness and good low-temperature impact toughness, and simultaneously improves the cold bending performance. And finally, finishing the steel plate.

In the production method of the steel sheet of the present invention:

and (3) heating and preserving the heat of the casting blank before rolling, wherein the heating temperature is over 1200 ℃, the heat preservation time is 2h, and the soaking and heat preservation time is not less than 40 min. In addition, the casting blank can be hot-charged into the furnace after the casting is finished, namely the casting blank is directly conveyed to the heating furnace for heating and heat preservation from the casting area through the roller way after the fact that the surface of the casting blank has no quality problem is confirmed, so that the energy consumption can be reduced; if the casting blank can not be hot-charged, the cast blank must be placed in a heat preservation pit for slow cooling, and the heat preservation pit can be removed for air cooling after the temperature is reduced to below 200 ℃.

The rolling is divided into two stages of rough rolling and finish rolling, in order to obtain fine original austenite grain size, the casting blank adopts large reduction rolling in the rough rolling stage, and the pass reduction rate is controlled to be more than 18 percent or the pass reduction is controlled to be more than 40 mm. In order to obtain fine grain size and good plate shape, the thickness ratio of the intermediate blank to the finished product is required to be more than or equal to 3, and the reduction rate of the last pass of finish rolling is controlled to be not less than 16% so as to ensure that the deformation exceeds the critical deformation, thereby obtaining good plate shape and uniform matrix structure.

The invention relates to off-line heat treatment of steel after rolling, and has no special requirement on the rolling temperature of a casting blank. However, in order to reduce the rolling load, the finishing rolling and coiling temperatures are set to be as high as possible. From the continuous transformation curve shown in fig. 1, the a → γ transformation point of the steel grade is about 815 ℃, so that a finish rolling temperature of 880 ℃ or higher is recommended, thereby ensuring that complete austenite region rolling is realized, further realizing low rolling load and stability of the rolling load, and facilitating subsequent high-quality plate shape obtaining; when the steel plate is thicker, the finishing rolling temperature can be properly reduced, but the temperature is not lower than 860 ℃. The coiling temperature is controlled between 640 ℃ and 680 ℃, and when the coiling temperature is too high, the coiling machine is not favorable, and when the coiling temperature is lower, the coiling load is increased.

And uncoiling and straightening the steel coil cooled to room temperature, then cutting the steel coil into plates, and quenching and tempering the steel plate. The quenching heating temperature directly influences the granularity of the subsequent martensite structure, and further influences the toughness of the steel plate. The austenite grains are easy to coarsen due to the overhigh heating temperature, the martensite structure is coarse after quenching, and the toughness is deteriorated; however, the heating temperature is too low to achieve sufficient austenitization, and a complete martensitic structure cannot be obtained after quenching. The heat preservation time has a similar rule to the quenching performance, crystal grains are easy to be large if the time is too long, energy consumption is increased, cost is improved, austenitizing is insufficient if the time is too short, and the hardness and strength after quenching cannot meet the requirements. The heating temperature is required to be controlled to be 50-80 ℃ (860-890 ℃) above the Ac3 point of the steel grade, and the heat preservation time is 2.5-3.5 times of the thickness of the steel plate from the center of the steel plate to the temperature. Directly water-quenching the steel plate to room temperature after discharging, wherein the cooling speed is required to be more than or equal to 50 ℃/s.

Tempering mainly slows down and eliminates quenching stress and improves toughness and toughness. The higher tempering temperature easily causes the strength and hardness of the steel plate to be reduced too much, so that the design requirements cannot be met, and meanwhile, the cost is increased. The tempering process parameters of the steel sheet should be limited. In the invention, the steel plate is tempered in the temperature range of 180-240 ℃, and the tempering heat preservation time is 2.5-3.5 times of the plate thickness from the center of the steel plate to the beginning of the temperature, but the minimum time is not less than 10 min. And finally, finishing (straightening and trimming) the quenched and tempered steel plate, and leaving the factory after the performance is qualified.

The method can realize the production of the high-hardness abrasion-resistant steel plate with the thickness of 8-20 mm. The yield strength of the steel plate is more than 1200MPa, the tensile strength exceeds 1500MPa, the elongation is more than or equal to 8 percent, the hardness is 500 +/-30 HBW, and the impact power value at the temperature of minus 40 ℃ is more than 20J. The steel plate has good abrasion resistance by combining the corrosion resistance design of the steel grade. The abrasion resistance in the large-particle and high-density seawater slurry conveying environment can reach more than 2.5 times of that of a common Q235B pipe.

Compared with the prior patents, the steel of the invention has obvious differences in components and properties from the comparative patents. In terms of components, compared with patent 1, 0.01-1.0% of Mo, Ca and RE are required to be added, meanwhile, the content of N is required to be 0.01-0.1%, the strength is improved through N, and meanwhile, the upper limit of the content of Mn reaches 5%, which is close to the components of medium manganese steel; the contents of C, Mn and Cr in the comparative patent 2 are respectively as high as 0.4-0.9%, 14-16% and 5-10%, and various rare elements such as Pr, Dy, Gd, Nd and the like are required to be added; the comparison patent 3 adopts a lower C design, V is used for precipitation strengthening, meanwhile, the Al content is maintained at a lower level, the corrosion resistance of the steel grade is improved through Cr and Al, and the Al content is obviously higher than that of the comparison patent 3.

In addition, the mechanical properties of the steels of the invention are also different from those of the comparative steels. The steel of the invention requires a yield strength of more than 1200MPa and an elongation of more than or equal to 8 percent. The yield strength range of the steel in the patent 1 is wider, from 300MPa to 2500MPa, although the steel can realize high strength, the plasticity is sacrificed, the elongation rate cannot be ensured, and the cold machining application range is limited; the steel of the patent 2 can realize the hardness exceeding 50HRC through high content of strengthening elements, but has the problem that the elongation rate can not be ensured; the strength of the steel of the comparative patent 3 is obviously lower and is only equivalent to the X70 strength grade of the common pipeline steel.

The invention has the following advantages:

the invention adopts simple and economic C-Mn component design, and is assisted by a small amount of Nb and Ti microalloy elements, thereby realizing the high hardness of the steel grade; meanwhile, the addition of corrosion resistant elements such as Cr, Al and the like improves the matrix potential, inhibits the occurrence of corrosion in the corrosion process and improves the corrosion resistance of the steel plate. Therefore, the steel grade has good abrasion resistance in an abrasion and corrosion environment, and particularly the abrasion resistance can reach more than 2.5 times of that of a common pipe under the condition of large-particle and high-density seawater slurry conveying.

The steel grade has good low-temperature impact toughness and cold bending processability, meets the pipe-making processing requirement of a subsequent dredging pipeline, and can realize easy pipe making of a high-hardness steel plate on the basis of the existing equipment.

The invention relates to a steel grade with simple production process and low content of noble alloy elements, which reduces the production difficulty and the production cost and is beneficial to the large-scale popularization of the steel grade.

Drawings

FIG. 1 is a CCT curve (calculated) for the steel grade of the present invention.

The specific implementation mode is as follows:

the present invention will be further described with reference to the following examples.

According to the chemical component requirements of the abrasion-resistant steel plate, steel plates with different thickness specifications are prepared. The chemical compositions of the steels of the examples of the invention are shown in Table 1, and the production processes are shown in Table 2.

The production method of the embodiment is as follows:

the method comprises the following steps of iron water deep stripping S (ensuring low S content in steel) → converter top and bottom combined blowing (controlling C content) → external refining → continuous casting (mechanical cleaning) → slab reheating → controlled rolling → controlled cooling → coiling → uncoiling → straightening → cutting plate → heat treatment (quenching + tempering) → finishing → delivery.

Wherein the heating temperature of the billet is 1200 ℃, the finishing temperature is 870 ℃, and the billet is cooled to 660 ℃ after rolling and coiled; and cutting the steel coil after straightening, and quenching and tempering the steel plate. The heating temperature exceeds the temperature point of Ac3 of the steel grade by 50-80 ℃, and the tempering temperature is 180-240 ℃. The properties of the abrasion resistant steel sheets of examples are shown in Table 3.

Table 1 units: wt.%

Numbering	C	Si	Mn	P	S	Al	N	Ti	Cr	Nb	B
												A	0.252	0.01	1.60	0.011	0.004	0.28	0.0044	0.015	1.20	0.012	0.0015
B	0.264	0.006	1.31	0.012	0.0045	0.8	0.0031	0.024	0.51	-	0.0017
												C	0.241	0.008	1.33	0.014	0.005	1.12	0.0038	-	0.31	0.028	0.0018
D	0.280	0.004	1.40	0.007	0.0031	0.64	0.0033	0.018	0.85	0.0021	0.0014
												E	0.242	0.004	1.55	0.013	0.0034	0.56	0.0045	0.022	0.85	0.023	0.0012
F	0.278	0.004	1.45	0.009	0.0037	0.48	0.0038	0.012	0.78	0.015	0.0019

TABLE 2

TABLE 3

As seen from the table above, the hardness of the steel plate related by the invention exceeds 500HBW, the tensile property also meets the design requirement, and the wear resistance is excellent; meanwhile, the addition of elements such as Cr, Al and the like improves the self-corrosion potential of the matrix and inhibits the occurrence of corrosion, thereby having excellent abrasion resistance which is about 2.5 times that of plain carbon steel.

In conclusion, the invention develops the steel for the high-hardness slurry dredging pipe reaching the 500HBW level by using simpler and economic components according to the design concept of corrosion-resistant steel for inhibiting corrosion and improving wear resistance. The steel plate has good wear resistance, inhibits corrosion, has good wear resistance in the process of conveying large-particle and high-density seawater slurry, has good cold bending processing and welding performance, has excellent low-temperature toughness and low cost, and is not possessed by other known patent steels at present.

The abrasion-resistant steel plate can be used for manufacturing slurry dredging pipes, is widely applied to the fields of sea reclamation, channel dredging, inland river dredging, ore pulp conveying and the like, and replaces the conventional Q235 and Q345-level common dredging pipelines, so that the production efficiency is improved, and the operation cost is reduced.

Claims

1. The abrasion-resistant steel plate for the slurry dredging pipe with the hardness of 500HB comprises the following components in percentage by weight: c: 0.25-0.28%, Si is less than or equal to 0.01%, Mn: 1.3-1.6%, P is less than or equal to 0.015%, S is less than or equal to 0.005%, Al: 0.2-1.0%, Cr: 0.3-1.2%, B: 0.001-0.002%, N is less than or equal to 0.005%; further contains Nb: 0.01-0.03% or Ti: 0.01-0.025 percent of one or two of the components, and satisfies that Nb + Ti is more than 6.65N and less than or equal to 0.045, and the balance is Fe and inevitable impurities; the yield strength of the steel plate is more than 1200MPa, the tensile strength exceeds 1500MPa, the elongation is more than or equal to 8 percent, and the impact power value at minus 40 ℃ is more than 20J, wherein the hardness is 500 +/-30 HBW.

2. The method for producing an abrasion-resistant steel plate for a slurry dredging pipe having a hardness of 500HB as set forth in claim 1, comprising the steps of:

1) smelting and casting

Smelting and casting a blank according to the composition of claim 1;

2) slab reheating

3) controlled rolling

The rolling is divided into two stages of rough rolling and finish rolling, the rough rolling stage adopts large reduction rolling, the pass reduction is controlled to be more than 18 percent or more than 40mm, meanwhile, the thickness ratio of the intermediate billet to the finished product is required to be more than or equal to 3, and the final pass reduction of the finish rolling is controlled to be not less than 16 percent;

the finishing temperature is not lower than 860 ℃;

4) coiling

The coiling temperature is controlled between 640 ℃ and 680 ℃;

5) uncoiling, straightening and cutting plate

6) Heat treatment, quenching and tempering

Quenching, wherein the heating temperature is controlled to be 50-80 ℃ above the Ac3 point of the steel grade, and the quenching heating temperature is controlled to be 860-890 ℃; the heat preservation time T1 is calculated from the center of the steel plate to the temperature, T1 is the thickness T x (2.5-3.5) of the steel plate, T1 is the unit min, T and mm; directly water-quenching the steel plate to room temperature after discharging, wherein the cooling speed is required to be more than or equal to 50 ℃/s;

tempering, wherein tempering treatment is carried out in the temperature range of 180-240 ℃, the tempering heat preservation time T2 is counted from the center of the steel plate to the temperature, T2 is the thickness T x (2.5-3.5) of the steel plate, T2 is unit min, T is unit mm; t2 minimum not less than 10 min; and finally, finishing the steel plate.

3. The method for producing an abrasion-resistant steel plate for a slurry dredging pipe having a hardness of 500HB as set forth in claim 2, wherein the abrasion-resistant steel plate has a thickness of 8 to 20 mm.

4. The method for producing an abrasion-resistant steel plate for a slurry dredging pipe having a hardness of 500HB according to claim 2 or 3, wherein the steel plate has a yield strength of 1200MPa or more, a tensile strength of more than 1500MPa, an elongation of 8% or more, a hardness of 500 + -30 HBW and an impact work value of 20J or more at-40 ℃.