1. The steel for the wind power fastener is characterized by comprising the following components in percentage by mass:

0.4 to 0.42 percent of C, 0.72 to 0.76 percent of Mn, 1.12 to 1.16 percent of Cr, 0.21 to 0.23 percent of Mo, 0.1 to 0.14 percent of Ni, 0.02 to 0.05 percent of Al, and the balance of Fe and other inevitable impurities.

2. The steel product as claimed in claim 1 where the strip grade in the steel product is no more than 2;

preferably, the austenite grain size in the steel is more than or equal to 7.5 grade;

preferably, the inclusion K3 in the steel is less than or equal to 20.

3. A method of producing a steel product as claimed in claim 1 or claim 2, characterized in that the production method comprises:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the content of aluminum oxide more than or equal to 35 percent is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; the VD vacuum refining is started by adding Ni materials.

4. The method of claim 3, wherein the basicity of the refining slag system in refining is in the range of 8 to 10;

preferably, the mass percentage content of the aluminum oxide of the refining slag system in the refining is more than or equal to 35 percent;

preferably, the inclusion K3 is less than or equal to 20 in the refining.

5. The production method according to claim 3 or 4, wherein a degree of superheat in the continuous casting is 35 ℃ or less;

preferably, the pouring speed in the continuous casting is 1-2 m/min.

6. A method of manufacturing as claimed in any one of claims 3 to 5 wherein the rolling is carried out by preheating, heating and soaking the cold billet in sequence.

7. The method of claim 6, wherein the pre-heating temperature is 850 ℃;

preferably, the preheating time is more than or equal to 100 min.

8. The method of claim 6 or 7, wherein the heating temperature is 1140-1235 ℃;

preferably, the heating time is more than or equal to 80 min;

preferably, the soaking temperature is 1170-1220 ℃;

preferably, the soaking time is more than or equal to 80 min.

9. The method according to any one of claims 3-8, wherein the rolling temperature at the beginning of the rolling is 1080-1120 ℃;

preferably, the finishing temperature of the rolling is 960-.

10. The method of any one of claims 3-9, comprising:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the content of aluminum oxide more than or equal to 35 percent is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; adding a Ni material when the VD vacuum refining is started; the alkalinity of the refining slag system in the refining is 8-10; the aluminum oxide content of the refining slag system in the refining is more than or equal to 35 percent; the inclusion K3 in the refining is less than or equal to 20; the degree of superheat in the continuous casting is less than or equal to 35 ℃; the pouring speed in the continuous casting is 1-2 m/min; preheating, heating and soaking the cold blank in sequence in the rolling process; the preheating temperature is less than or equal to 850 ℃; the preheating time is more than or equal to 100 min; the heating temperature is 1140-1235 ℃; the heating time is more than or equal to 80 min; the soaking temperature is 1170-1220 ℃; the soaking time is more than or equal to 80 min; the rolling starting temperature of the rolling is 1080-1120 ℃; the final rolling temperature of the rolling is 960-.

Background

At present, in recent years, the wind power industry in China, particularly large-scale wind generating sets with large capacity at megawatt level, is rapidly developed, wind power fasteners are main connecting parts of the wind generating sets, and in the wind generating sets, a large number of high-strength bolts are used for connection, and occupy about 22% of parts of the wind generating sets. The pitch bearing and the hub, the pitch bearing and the blades, the hub and the generator main shaft, the main frame and the yaw bearing, the main frame and the generator frame, the main bearing and the main frame, the gear box elastic supporting seat and the main frame, the tower and the yaw brake disc, the tower and the like all adopt high-strength bolts, and all key connecting parts are connected through the high-strength bolts and comprise the connection of electrical components. The quality of the high-strength bolt fastener of the wind turbine generator is greatly influenced by raw materials, and the mechanical property and the grain size are particularly required to be stable.

For example, CN110643881A discloses a steel for large-specification wind power fasteners, which comprises the following elements in percentage by mass: c: 0.38-0.45%, Si: 0.20-0.35%, Mn: 0.60-0.80%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, Cr: 0.95-1.20%, Mo: 0.18-0.30%, Ni: 0.10 to 0.25%, Nb: 0.02-0.08%, Al: 0.020-0.050%, N less than or equal to 0.008%, and the balance of Fe and inevitable impurities; the center of the steel after heat treatment has more than 90% of martensite structure, the surface hardness difference of the center is small, particularly, the low-temperature impact performance is excellent, the steel has better mechanical property, the tensile property meets the requirement of 10.9-level strength, and the processing and using requirements of users on the steel for the large-size wind power fasteners of 48mm-65mm can be met.

For example, CN109402320A discloses a method for preparing a high-purity wind power fastener, which comprises the following steps: (1) smelting in a converter: controlling the mass percentage content of C to be more than or equal to 0.06 percent or the oxygen level of the tapping TSO to be less than or equal to 400ppm at the end point, and controlling the tapping temperature to be more than or equal to 1560 ℃; (2) tapping by a converter: a. bottom stirring; b. discharging slag; (3) and (3) deoxidation alloying: adding a carburant for pre-deoxidation at the early stage of tapping, then sequentially adding an alloy, a deoxidizer and slag charge, and keeping argon blowing in the whole deoxidation alloying process; (4) and (3) LF treatment: controlling the mass percentage of inclusions in the steel: CaO 50-60%, Al₂O₃15-25%, controlling the final slag alkalinity at 3-6, and performing composite diffusion deoxidation by adopting SiC, aluminum particles, calcium silico-aluminum and a deoxidation slagging agent in the power supply smelting process to ensure that the total mass percentage content of TFe and MnO is less than or equal to 1%; (5) RH treatment: controlling the vacuum degree below 2.5 mbar and keeping for 0-5min, keeping the high vacuum for more than or equal to 8min, feeding aluminum wire for 1-2min, performing calcium treatment, and soft-blowing for more than 10 min; (6) and (4) continuous casting.

However, the fastening piece in the prior art still has the problems of substandard mechanical property, short service life and the like.

Disclosure of Invention

In view of the problems in the prior art, the invention aims to provide a steel for a wind power fastener and a preparation method thereof, which improve the grain size, banding, inclusion and the like of the internal structure of a bar material through regulating and controlling the chemical components of the steel, remarkably stabilize the performance and hardness of the bar material after heat treatment and enable the obtained steel to have good structure performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a steel for a wind power fastener, which comprises the following components in percentage by mass:

0.4 to 0.42 percent of C, 0.72 to 0.76 percent of Mn, 1.12 to 1.16 percent of Cr, 0.21 to 0.23 percent of Mo, 0.1 to 0.14 percent of Ni, 0.02 to 0.05 percent of Al, and the balance of Fe and other inevitable impurities.

The steel provided by the invention improves the internal structure of the bar material to contain grain size, banding, impurities and the like through regulating and controlling chemical components, and obviously stabilizes the performance and hardness of the bar material after heat treatment, so that the obtained steel has good structure performance. The Ni element which is used as an impurity in the field is introduced, and the content of Ni is adjusted to control the grain size, the belt shape and the inclusion, so that the obtained steel has good hardness and mechanical property.

In the present invention, C in the steel material for a wind turbine fastening member may be 0.4 to 0.42% by mass, for example, 0.4%, 0.402%, 0.404%, 0.406%, 0.408%, 0.41%, 0.412%, 0.414%, 0.416%, 0.418%, or 0.42%, but is not limited to the above-mentioned values, and other combinations not listed in this range are also applicable.

In the present invention, Mn in the steel for a wind power fastener is 0.72 to 0.76% by mass, and may be, for example, 0.72%, 0.73%, 0.74%, 0.75%, or 0.76%, but is not limited to the above-mentioned values, and other combinations not listed in this range are also applicable.

In the present invention, the steel material for wind turbine fasteners contains Cr in an amount of 1.12 to 1.16% by mass, for example, 1.12%, 1.13%, 1.14%, 1.15%, or 1.16%, but not limited to the above-mentioned values, and other combinations not listed in this range are also applicable.

In the present invention, Mo in the steel for a wind power fastener may be 0.21 to 0.23% by mass, for example, 0.21%, 0.0212%, 0.214%, 0.216%, 0.218%, 0.22%, 0.222%, 0.224%, 0.226%, 0.228%, or 0.23%, but is not limited to the above-mentioned values, and other combinations not listed in this range are also applicable.

In the present invention, Ni in the steel material for wind power fasteners is 0.1 to 0.14% by mass, and may be, for example, 0.1%, 0.11%, 0.12%, 0.13%, or 0.14%, but is not limited to the above-mentioned values, and other combinations not shown in the above-mentioned range are also applicable.

In the present invention, Al in the steel material for a wind power fastener is 0.02 to 0.05% by mass, and may be, for example, 0.02%, 0.03%, 0.04%, or 0.05%, but is not limited to the above-mentioned values, and other combinations not shown in the above-mentioned range are also applicable.

In a preferred embodiment of the present invention, the steel material may have a band grade of not more than 2, for example, 2, 1.5, 1 or 0.5, but is not limited to the above-mentioned values, and other combinations not shown in the above-mentioned range are also applicable.

Preferably, the austenite grain size in the steel is not less than 7.5, such as 7.5, 8, 8.5, 9 or 9.5, but not limited to the values listed, and other combinations not listed within this range are equally suitable.

Preferably, the inclusion K3 in the steel material is 20 or less, for example 20, 18, 16, 14, 12, 10, 8, 6, 4 or 2, etc., but is not limited to the values listed, and other combinations not listed within this range are also applicable.

In a second aspect, the present invention provides a method of producing a steel material according to the first aspect, the method comprising:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the content of aluminum oxide more than or equal to 35 percent is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; the VD vacuum refining is started by adding Ni materials.

According to the preparation method provided by the invention, the Ni material is added in a specific process, so that the austenite grain size can be stabilized in a certain range, and the performance of the steel is improved.

In the present invention, the amount of the refining slag having an alumina content of not less than 35% by mass may be, for example, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, or 43% by mass, but is not limited to the above-mentioned values, and other combinations not listed in the above range are also applicable.

In a preferred embodiment of the present invention, the basicity of the refining slag system in the refining is 8 to 10, and may be, for example, 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8 or 10, but is not limited to the values listed above, and other combinations not listed within this range are also applicable.

Preferably, the alumina content of the refining slag system in the refining is 35% or more, for example, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, etc., but not limited to the values listed, and other combinations not listed within this range are also applicable.

Preferably, the inclusion K3 ≦ 20 in the refining, such as 20, 18, 16, 14, 12, 10, 8, 6, 4, or 2, but not limited to the values recited, and other combinations not listed in this range are equally applicable.

In a preferred embodiment of the present invention, the degree of superheat in the continuous casting is 35 ℃ or less, and may be, for example, 35 ℃, 30 ℃, 25 ℃, 20 ℃, 15 ℃, 10 ℃ or 5 ℃, but is not limited to the values listed, and other combinations not listed within the range are also applicable.

Preferably, the casting speed in the continuous casting is 1 to 2m/min, and may be, for example, 1m/min, 1.1m/min, 1.2m/min, 1.3m/min, 1.4m/min, 1.5m/min, 1.6m/min, 1.7m/min, 1.8m/min, 1.9m/min, or 2m/min, etc., but is not limited to the values listed, and other combinations not listed in this range are also applicable.

As a preferable technical scheme of the invention, the cold billet is sequentially preheated, heated and soaked in the rolling process.

In a preferred embodiment of the present invention, the temperature of the preheating is not more than 850 ℃, and may be, for example, 850 ℃, 800 ℃, 750 ℃, 700 ℃, 650 ℃, 600 ℃, 550 ℃, 500 ℃, 450 ℃, 400 ℃, 350 ℃, or 300 ℃, etc., but is not limited to the values listed, and other combinations not listed in this range are also applicable.

Preferably, the preheating time is 100min or more, for example, 100min, 110min, 120min, 130min, 140min, 150min, 160min, etc., but not limited to the values listed, and other combinations not listed within this range are also applicable.

In a preferred embodiment of the present invention, the heating temperature is 1140-, 1235 deg.C, such as 1140 deg.C, 1150 deg.C, 1160 deg.C, 1170 deg.C, 1180 deg.C, 1190 deg.C, 1200 deg.C, 1210 deg.C, 1220 deg.C, 1230 deg.C or 1235 deg.C, but not limited to the above-mentioned values, and other combinations not listed in the above range are also applicable.

Preferably, the heating time is 80min or more, for example, 80min, 90min, 100min, 110min or 120min, etc., but is not limited to the values listed, and other combinations not listed within this range are also applicable.

Preferably, the soaking temperature is 1170-1220 ℃, for example 1170 ℃, 1180 ℃, 1190 ℃, 1200 ℃, 1210 ℃ or 1220 ℃, but not limited to the enumerated values, in this range other combinations are also applicable.

Preferably, the soaking time is 80min or more, for example, 80min, 90min, 100min, 110min, 120min, 130min or 140min, etc., but is not limited to the values listed, and other combinations not listed in this range are also applicable.

In a preferred embodiment of the present invention, the rolling temperature at the start of rolling is 1080-.

Preferably, the finish rolling temperature of the rolling is 960-.

As a preferred technical solution of the present invention, the preparation method comprises:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the content of aluminum oxide more than or equal to 35 percent is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; adding a Ni material when the VD vacuum refining is started; the alkalinity of the refining slag system in the refining is 8-10; the aluminum oxide content of the refining slag system in the refining is more than or equal to 35 percent; the inclusion K3 in the refining is less than or equal to 20; the degree of superheat in the continuous casting is less than or equal to 35 ℃; the pouring speed in the continuous casting is 1-2 m/min; preheating, heating and soaking the cold blank in sequence in the rolling process; the preheating temperature is less than or equal to 850 ℃; the preheating time is more than or equal to 100 min; the heating temperature is 1140-1235 ℃; the heating time is more than or equal to 80 min; the soaking temperature is 1170-1220 ℃; the soaking time is more than or equal to 80 min; the rolling starting temperature of the rolling is 1080-1120 ℃; the final rolling temperature of the rolling is 960-.

Compared with the prior art, the invention at least has the following beneficial effects:

the steel provided by the invention improves the internal structure of the bar material to contain grain size, banding, impurities and the like through regulating and controlling chemical components, and obviously stabilizes the performance and hardness of the bar material after heat treatment, so that the obtained steel has good structure performance. The grain size, the belt shape and the inclusions are controlled by adjusting the content of Ni, so that the obtained steel has good hardness and mechanical property. The Ni material is added in a specific process, so that the austenite grain size can be stabilized within a certain range of 0.1-0.14%, and the performance of the steel is improved.

Detailed Description

To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows:

example 1

The embodiment provides a steel for a wind power fastener, which comprises the following components in percentage by mass:

0.41% of C, 0.724% of Mn, 1.14% of Cr, 0.22% of Mo, 0.12% of Ni, 0.04% of Al, and the balance of Fe and other inevitable impurities.

The preparation method comprises the following steps:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with 35 percent of aluminum oxide content is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; adding a Ni material when the VD vacuum refining is started; the alkalinity of the refining slag system in the refining is 9; the aluminum oxide content of the refining slag system in the refining is 35 percent; the inclusion K3 in the refining is 20; the degree of superheat in the continuous casting is 35 ℃; the pouring speed in the continuous casting is 1.5 m/min; preheating, heating and soaking the cold blank in sequence in the rolling process; the preheating temperature is 850 ℃; the preheating time is 100 min; the heating temperature is 1200 ℃; the heating time is 80 min; the soaking temperature is 1200 ℃; the soaking time is 80 min; the initial rolling temperature of the rolling is 1100 ℃; the finishing temperature of the rolling is 990 ℃.

The properties of the steel obtained are specified in Table 1.

Example 2

The embodiment provides a steel for a wind power fastener, which comprises the following components in percentage by mass:

0.4% of C, 0.72% of Mn, 1.16% of Cr, 0.23% of Mo, 0.14% of Ni, 0.02% of Al, and the balance of Fe and other inevitable impurities.

The preparation method comprises the following steps:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the alumina content of 38 percent is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; adding a Ni material when the VD vacuum refining is started; the alkalinity of the refining slag system in the refining is 8; the mass percentage content of the aluminum oxide of the refining slag system in the refining is 39 percent; the inclusion K3 in the refining is 10; the degree of superheat in the continuous casting is 30 ℃; the pouring speed in the continuous casting is 1 m/min; preheating, heating and soaking the cold blank in sequence in the rolling process; the preheating temperature is 800 ℃; the preheating time is 200 min; the heating temperature is 1235 ℃; the heating time is 100 min; the soaking temperature is 1170 ℃; the soaking time is 120 min; the initial rolling temperature of the rolling is 1120 ℃; the finishing temperature of the rolling is 960 ℃.

The properties of the steel obtained are specified in Table 1.

Example 3

The embodiment provides a steel for a wind power fastener, which comprises the following components in percentage by mass:

0.42% of C, 0.76% of Mn, 1.12% of Cr, 0.21% of Mo, 0.1% of Ni, 0.05% of Al, and the balance of Fe and other inevitable impurities.

The preparation method comprises the following steps:

carrying out converter steelmaking, deoxidation alloying, refining, continuous casting, heating and rolling on blast furnace molten iron in sequence to obtain the steel;

wherein, refining slag with the content of 40 percent of aluminum oxide is added in the deoxidation alloying; the refining comprises LF refining and VD vacuum refining which are sequentially carried out; adding a Ni material when the VD vacuum refining is started; the alkalinity of the refining slag system in the refining is 10; the aluminum oxide content of the refining slag system in the refining is more than or equal to 37 percent; the inclusion K3 in the refining is 5; the degree of superheat in the continuous casting is 15 ℃; the pouring speed in the continuous casting is 2 m/min; preheating, heating and soaking the cold blank in sequence in the rolling process; the preheating temperature is 500 ℃; the preheating time is 150 min; the heating temperature is 1140 ℃; the heating time is 90 min; the soaking temperature is 1220 ℃; the soaking time is 100 min; the initial rolling temperature of the rolling is 1080 ℃; the finishing temperature of the rolling is 1020 ℃.

The properties of the steel obtained are specified in Table 1.

TABLE 1

	Tensile strength	Yield strength	Elongation percentage	Reduction of area	Work of percussion (-40 ℃ C.)
						Example 1	1081MPa	976MPa	51％	13％	45-48J
Example 2	1123MPa	981MPa	52％	12％	72-76J
						Example 3	1092MPa	963MPa	55％	13％	64-66J

The results of the above embodiments show that the steel provided by the invention improves the internal structure of the bar material including grain size, banding, inclusions and the like through the regulation and control of chemical components, and remarkably stabilizes the performance and hardness of the bar material after heat treatment, so that the obtained steel has good structure performance. The grain size, the belt shape and the inclusions are controlled by adjusting the content of Ni, so that the obtained steel has good hardness and mechanical property. The Ni material is added in a specific process, so that the austenite grain size can be stabilized in a certain range, and the performance of the steel is improved.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.