CN108950422B

CN108950422B - Abrasion-resistant steel plate for 550HB hardness slurry dredging pipe and production method thereof

Info

Publication number: CN108950422B
Application number: CN201710383393.2A
Authority: CN
Inventors: 宋凤明; 温东辉; 王巍; 张华伟; 张国民; 祁捷; 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: CN108950422A

Abstract

The wear-resistant corrosion-resistant steel for dredging slurry with the hardness of 550HB and the production method thereof comprise the following components in percentage by weight: c: 0.30-0.34%, Si is less than or equal to 0.01%, Mn: 1.5-1.8%, 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 impurity elements. The wear-resistant steel of the invention has corrosion resistance and wear resistance, is mainly used for manufacturing dredging pipelines in the fields of sea reclamation, channel dredging and the like, and has the wear resistance 3 times that of the prior common pipe, thereby greatly improving the dredging efficiency and reducing the operation cost.

Description

Abrasion-resistant steel plate for 550HB hardness slurry dredging pipe 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 hardness of 550HB 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.

For example, "HB 500 grade wear-resistant steel plate and preparation method thereof disclosed in Chinese patent publication No. CN 102517509A" and "a martensite series wear-resistant steel and preparation method thereof disclosed in Chinese patent publication No. CN 103397275A". On the one hand, the alloy cost is higher, and simultaneously, Cu and Ni are common corrosion-resistant elements in atmospheric corrosion resistant steel, so that the formation of a protective rust layer on the surface of the steel is promoted, the abrasion weight loss is increased in the abrasion process, and the abrasion failure of the material is accelerated. The patent relates to the field of steel grade hardness of more than 500HBW, good abrasion resistance and mainly used for engineering machinery, mining equipment and the like. However, the component design of the related steel grade does not consider corrosion inhibition, so the wear resistance is poor, and the use requirement cannot be met under the working condition of corrosion and wear.

Japanese patent Nos. JP2007231321A and JP2008169443A describe methods for improving wear resistance by carbide-precipitated particles of Ti and W, which contain noble alloying elements such as Cu, Ni, Cr, Mo, etc. in combination. A large amount of carbide particles in the matrix play a role of a cathode under the working condition of corrosive wear, 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 (compare patent 2) discloses "a corrosion-resistant and wear-resistant steel and a preparation method thereof", which relates to a steel grade added with 0.4-0.9% of C and 14-16% of Mn, wherein the contents of Mo and Cr are both 5-10%, and in addition, the steel grade also contains a certain amount of rare elements such as Pr, Nd, Gd and the like, the hardness can reach above 52HRC, but the addition of a large amount of precious alloy increases the manufacturing cost.

Chinese patent publication No. CN102776445A (comparison patent 1) discloses 'a lower bainite wear-resistant steel pipe for slurry transportation and a manufacturing method thereof', and Chinese patent publication No. CN103436790A (comparison patent 3) discloses 'a wear-resistant steel for a pulp transportation welded pipe pipeline and a manufacturing method thereof', wherein the two patents relate to the conditions that the steel types are bainite or bainite and acicular ferrite tissues, the matrix hardness is not high, the tensile strength is only 600-plus-800 MPa, the steel is mainly applied to the working condition environment with slight wear, such as the transportation of pulp or crude oil with fine particles (dozens of micrometers), and the like, and is not suitable for the field of the transportation of seawater slurry with large particles and high density. The wear-resistant steel pipe disclosed in the Chinese patent publication No. CN102776445A has a high Mn content, and is required to contain certain amounts of Mo, Ca and RE, and is definitely required to be added with N. The wear-resistant steel disclosed by the Chinese patent publication No. CN103436790A has low C content, and is low in strength because a certain amount of V is added.

Disclosure of Invention

The invention aims to provide wear-resistant corrosion-resistant steel for slurry dredging with the hardness of 550HB and a production method thereof, wherein the wear-resistant corrosion-resistant steel has the composition design of both corrosion resistance and wear resistance, is mainly used for manufacturing dredging pipelines in the fields of sea reclamation, channel dredging and the like, and has the wear resistance reaching 3 times of 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 wear-resistant corrosion-resistant steel with the hardness of 550HB for slurry dredging comprises the following components in percentage by weight: c: 0.30-0.34%, Si is less than or equal to 0.01%, Mn: 1.5-1.8%, 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 impurity elements.

The yield strength of the wear-resistant corrosion-resistant steel is more than 1400MPa, the tensile strength is more than 1800MPa, the elongation is more than or equal to 6 percent, the hardness is 550 +/-30 HBW, and the impact power value at the temperature of minus 40 ℃ is more than 20J.

In the composition design of the steel of the invention:

c is the cheapest strengthening element in steel, and proper addition of C is beneficial to obtaining a martensite structure after heat treatment, and can obviously improve the strength and hardness of the steel plate, but more C is unfavorable for welding, toughness and plasticity of the steel plate. The range is limited to 0.30-0.34% 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. Therefore, 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 1.5 and 1.8 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, so the content of N must be controlled below 0.0050 percent.

After the steel grade designed by the components is subjected to heat treatment, a high-strength martensite structure is obtained, the yield strength is more than or equal to 1400MPa, the tensile strength is more than or equal to 1800MPa, the elongation is more than or equal to 8%, and the hardness is 550 +/-30 HB, so that the high-strength 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 abrasion-resistant steel with hardness of 550HB for slurry dredging, 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 casting blank adopts large reduction for rolling in the rough rolling stage, and the pass reduction rate is controlled to be more than 18 percent or more than 40 mm; meanwhile, 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 percent; the finishing temperature is above 840 ℃;

4) coiling

The coiling temperature is controlled at 600-640 ℃;

5) uncoiling, straightening and cutting plate

6) Quenching treatment

The heating temperature is controlled to be 50-80 ℃ above the Ac3 point of the steel, the quenching heating temperature is controlled to be 840-870 ℃, the heat preservation time T1 is calculated from the center of the steel plate to the temperature, T1 is equal to the thickness T x (2.5-3.5) of the steel plate, T1 is measured in unit min, T is measured in unit mm; directly water-quenching the steel plate to room temperature after discharging to form a complete martensite structure; the quenching cooling speed is more than or equal to 20 ℃/s;

7) tempering treatment

Tempering treatment is carried out in the temperature range of 150-; t2 minimum 15 min; a tempered martensite structure is obtained after tempering, and the toughness and the cold bending performance of the steel plate are improved; and finally, finishing the steel plate.

In the method for producing the steel 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 over 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, a casting blank is rolled by adopting large reduction in a rough rolling stage, and the pass reduction rate is controlled to be more than 18% 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 780 ℃, so that a finish rolling temperature of more than 840 ℃ is recommended, thereby ensuring that complete austenite region rolling is realized, further realizing low rolling load and stability of the rolling load, and being beneficial to obtaining high-quality plate shape subsequently. The coiling temperature is controlled between 600 ℃ and 640 ℃, and is unfavorable for the coiling machine when the coiling temperature is too high, and the coiling load is increased when the coiling temperature is lower.

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, the toughness is deteriorated, and the production cost is increased; 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 invention relates to a steel grade Ac3 temperature about 790 ℃, the heating temperature is controlled to be 50-80 ℃ above the Ac3 point (840-870 ℃), 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 beginning of temperature calculation. The steel plate is directly water-quenched to room temperature after being discharged, the martensite critical cooling speed of the steel grade is not high, so that the complete martensite structure can be obtained by requiring the quenching cooling speed to be more than or equal to 20 ℃/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 150-210 ℃, 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 15 min. And finally, finishing (straightening and trimming) the quenched and tempered steel plate, and leaving the factory after the performance is qualified.

The process can realize the production of the high-hardness abrasion-resistant steel plate with the thickness of 8-18 mm. The yield strength of the steel plate is more than 1400MPa, the tensile strength exceeds 1800MPa, the elongation is more than or equal to 6 percent, the hardness is 550 +/-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 high-density seawater slurry conveying environment can reach more than 3 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:

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 property requirements of the steel of the invention are also different from those of the steel of the patent. The steel of the invention requires a yield strength of more than 1400MPa and an elongation of more than or equal to 8 percent. The yield strength range of the alloy is wider than that of the alloy in the patent 1, from 300MPa to 2500MPa, although the alloy can realize high strength, the plasticity is sacrificed, the elongation rate cannot be ensured, and the cold processing application range is limited; in comparison with patent 2, the hardness of the steel can exceed 50HRC by the high content of the strengthening element, but the elongation rate can not be ensured; the strength of the comparison patent 3 is obviously lower and only corresponds to the X70 strength grade of the common pipeline steel.

The invention has the following advantages:

on the basis of the appropriate content of C, Mn, the invention develops the abrasion-resistant corrosion-resistant steel for the slurry conveying pipe with the hardness of 550HBW by adopting a mode of inhibiting corrosion and improving the hardness. The high hardness is realized by C and a small amount of Nb and Ti microalloy elements through a proper off-line heat treatment process; in the aspect of corrosion control, the corrosion resistance of the traditional atmospheric corrosion resistant steel is improved by adding corrosion resistant elements such as Cu, Si, P and the like, but the matrix potential is increased by adding elements such as Cr, Al and the like, and the corrosion in the corrosion process is inhibited by increasing the potential, so that the corrosion resistance of the steel plate is improved. The hardness is improved on the basis of inhibiting corrosion, so that the steel grade has good abrasion resistance in an abrasion and corrosion environment, and particularly the abrasion resistance can reach more than 3 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) plot of the steel of the present invention.

Detailed Description

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 example steels are shown in Table 1, and the process parameters of the example steels are shown in Table 2.

The production process of the embodiment comprises the following steps:

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 steel billet is 1200 ℃, the finishing temperature is 850 ℃, and the steel billet is cooled to 620 ℃ after rolling and coiled; the steel coil is cut into plates after being straightened, and the steel plate is quenched and tempered; the heating temperature exceeds the temperature point of Ac3 of the steel grade by 50-80 ℃, and the tempering temperature is 150-210 ℃. The properties of the abrasion resistant steel sheets of examples are shown in Table 2.

TABLE 1 units wt%

Numbering	C	Si	Mn	P	S	Al	N	Ti	Cr	Nb	B
												A	0.30	0.01	1.60	0.011	0.004	0.21	0.0024	0.015	1.20	0.012	0.0015
B	0.31	0.005	1.51	0.012	0.0045	0.80	0.0031	0.024	0.51	-	0.0017
												C	0.34	0.007	1.73	0.014	0.006	0.98	0.0028	-	0.31	0.026	0.0018
D	0.33	0.004	1.80	0.009	0.003	0.74	0.0033	0.018	1.15	0.021	0.0014
												E	0.32	0.004	1.65	0.009	0.003	0.56	0.0045	0.022	0.85	0.023	0.0012
F	0.34	0.004	1.50	0.009	0.003	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 550HBW, the tensile property also meets the design requirement, and the steel plate has good wear resistance; meanwhile, the addition of Cr and Al effectively improves the self-corrosion potential of the matrix and inhibits the occurrence of corrosion, thereby having excellent wear-resisting property.

In conclusion, the invention develops the steel for the martensite structure slurry dredging pipe with the hardness reaching 550HBW by using simpler and economic components and by adopting the design concept of the abrasion-resistant steel of inhibiting corrosion and improving abrasion resistance. By adopting a proper heat treatment process, the steel grade has higher hardness, and the wear resistance is improved; meanwhile, corrosion resistant elements for promoting the formation of the rust layer are limited to be added, and corrosion resistant elements beneficial to the improvement of the matrix potential are added, so that the corrosion resistant steel has a higher self-corrosion potential than common steel, effectively inhibits the corrosion in the corrosion process, has good wear resistance in the process of conveying seawater slurry with large particles and high density by combining the characteristic of high hardness, and simultaneously has good cold bending processing and welding performance, excellent low-temperature toughness and low cost. These are not available in other known patented steel grades 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 wear-resistant corrosion-resistant steel for dredging slurry with the hardness of 550HB comprises the following components in percentage by weight: c: 0.30-0.34%, Si is less than or equal to 0.01%, Mn: 1.5-1.8%, 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 impurity elements;

the yield strength of the abrasion-resistant steel is more than 1400MPa, the tensile strength exceeds 1800MPa, the elongation is more than or equal to 6 percent, the hardness is 550 +/-30 HBW, and the impact power value at the temperature of minus 40 ℃ exceeds 20J.

2. The method for producing an abrasion resistant steel for slurry dredging having hardness of 550HB according to claim 1, characterized by comprising the steps of:

1) smelting and casting

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

2) slab reheating

3) controlled rolling

4) coiling

The coiling temperature is controlled at 600-640 ℃;

5) uncoiling, straightening and cutting plate

6) Quenching treatment

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 840-870 ℃; 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 carrying out water quenching on the steel plate after the steel plate is taken out of the furnace to room temperature, wherein the quenching cooling speed is more than or equal to 20 ℃/s;

7) tempering treatment

Tempering treatment is carried out in the temperature range of 150-; minimum 15 min; and finally, finishing the steel plate.

3. The method of producing an abrasion resistant steel for slurry dredging having hardness of 550HB as claimed in claim 2, characterized in that said abrasion resistant steel sheet has a thickness of 8-18 mm.

4. The method for producing the abrasion-resistant steel for slurry dredging with hardness of 550HB according to claim 2 or 3, wherein the yield strength of the abrasion-resistant steel is above 1400MPa, the tensile strength exceeds 1800MPa, the elongation is not less than 6%, the hardness is 550 +/-30 HBW, and the impact power value at-40 ℃ is more than 20J.