CN111945067A

CN111945067A - Wear-resistant bar with silicon content of 0.8-1.2% and preparation method thereof

Info

Publication number: CN111945067A
Application number: CN202010777638.1A
Authority: CN
Inventors: 张海霞; 梁建国; 韩蕾蕾; 修冬; 马传庆; 李金浩
Original assignee: Shandong Iron and Steel Co Ltd
Current assignee: Shandong Iron and Steel Co Ltd
Priority date: 2020-08-05
Filing date: 2020-08-05
Publication date: 2020-11-17

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a wear-resistant bar with 0.80-1.2% of silicon content and a preparation method thereof, wherein the wear-resistant bar comprises the following chemical components in percentage by weight: c: 0.30 to 0.34%, Si: 0.80-1.20%, Mn: 1.10-1.25%, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cr: 1.10% -1.25%, Ti: 0.06% -0.08% of Al: 0.020 to 0.040%, and the balance being Fe and inevitable impurities. The preparation method comprises the following steps: 1) smelting in an electric furnace; 2) refining in an LF furnace; 3) vacuum refining in a VD furnace; 4) continuous casting; 5) and (6) rolling. The wear-resistant bar disclosed by the invention has the tensile strength of 1661-1886 MPa, the elongation of 12-13.5%, the reduction of area of 49-58% and the hardness value of 195-235 HBW, and has the advantages of appropriate hardness, high strength and high wear resistance.

Description

Wear-resistant bar with silicon content of 0.8-1.2% and preparation method thereof

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a wear-resistant bar with 0.8-1.2% of silicon content and a preparation method thereof.

Background

A great deal of work is done in research and development of wear-resistant materials in various countries, and the wear-resistant materials are developed into two major types of wear-resistant steel and wear-resistant cast iron at present in several stages from initial single-phase austenitic manganese steel (Mn13) to improved high manganese steel, common white cast iron and nickel hard cast iron to high chromium cast iron, bainite wear-resistant cast iron, wear-resistant cast steel, metal-based surface composite materials and hard alloys, and the wear-resistant steel is used as a key research object of the wear-resistant materials due to the widest application range and the largest consumption. The wear-resistant steel can be divided into four types of low-carbon, medium-high carbon and high-carbon alloy wear-resistant steel according to the difference of carbon content, and can be divided into three types of low-alloy, medium-alloy and high-alloy wear-resistant steel according to the difference of alloy element content. In actual production, high alloy steel is required to be selected for working conditions which require heat resistance and corrosion resistance besides wear resistance, and low and medium alloy steel with relatively low price can be selected for general application.

A series of low alloy steel wear-resistant materials are researched and developed at home and abroad. In order to ensure that the steel has enough toughness, the low-alloy steel is mostly of a medium-low carbon type, and the carbon content is generally between 0.30 and 0.50 percent. Cr, Ni, Mo, Si, Mn, Ti, B, etc. as main alloying elements to improve hardenability of steel or to form carbides to improve wear resistance of steel. The low Mn, Mn-Cr, Cr-Mo, Mn-Cr-Mo, Ni-Cr-Mo, Si-Mn-Cr-Mo and the like are representative alloy systems of the prior low alloy steel wear-resistant material, wherein the Mn-Cr low alloy steel is more in application.

Disclosure of Invention

An object of the present invention is to provide a wear resistant bar having good strength and toughness. The wear-resistant bar has the tensile strength of 1661-1886 MPa, the elongation of 12-13.5%, the reduction of area of 49-58%, the hardness value of 195-235 HBW, and has proper hardness, high strength and high wear resistance. In order to achieve the purpose, the invention adopts the following technical scheme:

a wear-resistant bar with 0.80-1.2% of silicon content comprises the following chemical components in percentage by weight: c: 0.30 to 0.34%, Si: 0.80-1.20%, Mn: 1.10-1.25%, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cr: 1.10% -1.25%, Ti: 0.06% -0.08% of Al: 0.020 to 0.040%, and the balance being Fe and inevitable impurities.

In the invention, the tensile strength of the wear-resistant bar is not less than 1470Mpa, the hardness is not more than 280HBW, and the specification is phi 60-160 mm.

The invention also aims to provide a preparation method of the wear-resistant bar with the silicon content of 0.8-1.2%, which comprises the following steps:

1) smelting in an electric furnace;

2) refining in an LF furnace;

3) vacuum refining in a VD furnace;

4) continuous casting;

5) rolling:

rolling the continuous casting billet, and emptying a multiple length cooling bed before rolling; reducing the temperature of a soaking section of the heating furnace to 1120-1150 ℃, wherein the total heating time is 4.0-5.0 hours, and the allowable temperature difference is less than or equal to 30 ℃; the initial rolling temperature is 1010-1060 ℃, the final rolling temperature is 900-960 ℃, the rolled steel is collected in a heat preservation pit in time, hot steel in the heat preservation pit is paved, a heat preservation cover is covered, and the slow cooling time is not less than 48 hours, so that the wear-resistant bar is obtained.

Preferably, step 1) electric furnace smelting:

the raw materials of the furnace are molten iron and scrap steel, the mass percent of the molten iron is not less than 40%, the whole smelting process of the electric furnace is used for preparing foamed slag, oxygen is blown in a low-oxygen mode in the early stage, the thickness of the foamed slag is more than or equal to 200mm, the molten carbon is more than or equal to 0.30%, the control end point [ C ] is more than or equal to 0.10%, P is less than or equal to 0.015%, and the content of residual elements meets the; the tapping temperature of the molten steel is 1630-1680 ℃, and steel core aluminum is added along with the tapping flow in the electric furnace tapping process for pre-deoxidation.

Preferably, step 2) LF furnace refining:

refining molten steel smelted by an electric furnace in an LF furnace, controlling the alkalinity of the slag to be more than 3.0, producing white slag in the whole process, keeping the white slag for more than or equal to 20 minutes, and refining for more than or equal to 40 minutes; feeding calcium wire according to the steel of 1.0-1.5 m/t, and soft blowing for more than or equal to 2 min.

Preferably, step 3) vacuum refining in a VD furnace:

slagging off the molten steel refined in an LF furnace, vacuum degassing the molten steel, keeping the molten steel for more than or equal to 12 minutes under the vacuum degree of less than 67Pa, blowing soft argon for more than or equal to 15 minutes, adding a covering agent after the vacuum is broken by VD, and determining hydrogen, wherein the target [ H ] is less than or equal to 2.0 PPM.

Preferably, step 4) continuous casting:

the molten steel vacuum-refined by the VD furnace is continuously cast by adopting an integral tundish, is subjected to full-process protective casting, adopts a double-layer tundish covering agent, adopts medium-carbon alloy steel special covering slag, and has the thickness of 45-60 mm, the thickness of a liquid slag layer of 7-12 mm and the liquid level fluctuation of a crystallizer of +/-3 mm; pouring with low superheat degree, controlling the superheat degree of tundish molten steel at 15-30 ℃, adopting an ultra-weak cooling mode for secondary cooling water distribution, electromagnetically stirring the crystallizer and the solidification tail end, adopting three constant operations of constant liquid level, constant temperature and constant drawing speed for pouring, controlling the temperature of a casting blank in a drawing and straightening machine to be more than or equal to 900 ℃, and slowly cooling the casting blank for more than or equal to 24 hours.

Preferably, step 5) rolling:

Specifically, the preparation method of the wear-resistant bar with the silicon content of 0.8-1.2% comprises the following steps:

1) electric furnace smelting:

the raw materials of the molten iron and the scrap steel are fed into the furnace, a fine material policy is adopted to ensure that the percentage of the molten iron is not less than 40 percent, the foamed slag is manufactured in the whole electric furnace smelting process, the low-oxygen mode is used for oxygen blowing in the early stage to fully melt the slag, carbon powder is properly injected, and the thickness of the foamed slag is more than or equal to 200 mm. The molten carbon is more than or equal to 0.30 percent, uniform decarburization is realized, good oxidation boiling is ensured, inclusions and gas in steel are promoted to float upwards, the end point [ C ] is controlled to be more than or equal to 0.10 percent, P is less than or equal to 0.015 percent, and the content of residual elements meets the standard requirement; the tapping temperature of the molten steel is 1630-1680 ℃, steel and slag are left during tapping, slag is strictly forbidden to be discharged, and alloy is added according to the lower component limit during steel ladle alloying; adding steel core aluminum along with the steel tapping flow in the electric furnace steel tapping process for pre-deoxidation;

2) refining in an LF furnace:

and (2) refining the molten steel smelted by the electric furnace in the step 1) in an LF furnace, controlling the alkalinity of the slag to be more than 3.0, and enhancing the refining of desulfurization operation. White slag is produced in the whole process, the white slag holding time is more than or equal to 20 minutes, the refining period is more than or equal to 40 minutes, and refining argon blowing is carried out according to the principle of promoting inclusions to float upwards and reducing secondary oxidation; before LF tapping, fine adjustment of components and temperature is carried out, so that stable performance of steel and temperature requirements of a continuous casting process are guaranteed; feeding calcium wires according to the steel of 1.0-1.5 m/t, and soft blowing for more than or equal to 2 min;

3) vacuum refining in a VD furnace:

slagging off the molten steel refined by the LF furnace in the step 2), carrying out vacuum degassing on the molten steel, keeping the molten steel for more than or equal to 12 minutes under the vacuum degree of less than 67Pa, carrying out soft argon blowing for more than or equal to 15 minutes, and strictly keeping bare molten steel and large argon stirring for cooling during the soft argon blowing; after the VD breaks the empty, adding a covering agent, and determining hydrogen, wherein the target [ H ] is less than or equal to 2.0 PPM;

4) continuous casting:

the molten steel treated in the step 3) is continuously cast by adopting an integral tundish, the whole process is protected and poured, a double-layer tundish covering agent is used, the covering of the slag surface cannot be red, medium-carbon alloy steel special covering slag is adopted, the thickness of the covering slag is 45-60 mm, the thickness of the liquid slag layer is 7-12 mm, the slag surface cannot be red visually by adding the principle of 'sequentially adding, adding less and uniformly adding', and the covering of blue flame on the slag surface is optimal, so that the secondary oxidation of the molten steel is prevented; the fluctuation of the liquid level of the crystallizer is less than or equal to +/-3 mm; pouring with low superheat degree, controlling the superheat degree of the tundish molten steel at 15-30 ℃, adopting an ultra-weak cooling mode for secondary cooling water distribution, and electromagnetically stirring a crystallizer and a solidification tail end to reduce segregation and other tissue defects and improve the quality of a casting blank; the pouring adopts three constant operations of constant liquid level, constant temperature and constant pulling speed, the temperature of the casting blank in the pulling and straightening machine is more than or equal to 900 ℃, and the slow cooling of the casting blank is more than or equal to 24 hours;

5) rolling:

rolling the continuous casting blank in the step 4); the steel is easy to bend, so that the bending experience of the bar produced in the last time is absorbed, and the rolling process is optimized; the production of the steel grade needs to replace a new saw blade; emptying other steel grades of a multiple length cooling bed before rolling; controlling the rolling rhythm and the sawing speed to enable the steel to quickly pass through the multiple length cooling bed, so that the steel is prevented from being accumulated on the multiple length cooling bed; the control parameters during rolling are as follows: reducing the temperature of a soaking section of the heating furnace to 1120-1150 ℃ and the total heating time to 4.0-5.0 hours so as to ensure that the steel billets are uniformly burnt, the allowable temperature difference is less than or equal to 30 ℃, ensuring that the steel billets are uniformly heated and preventing decarburization and furnace sticking; the initial rolling temperature is 1010-1060 ℃, the control on the rolling rhythm is enhanced, and the final rolling temperature is guaranteed to be 900-960 ℃; in the rolling process, the process control is required to be enhanced, the material type condition of each pass is closely noticed, and the defects of scratch, folding, ear and the like cannot occur; the steel grade not only requires that the tensile strength is not less than 1470Mpa, but also requires that the hardness is not more than 280HBW, the steel is collected into a heat preservation pit in time after rolling, hot steel in the heat preservation pit is paved, a heat preservation cover is covered, and the slow cooling time is not less than 48 hours, so that the wear-resistant bar with the specification phi of 60-160 mm and good strength and toughness is obtained.

Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:

1. the technical scheme provided by the invention adopts medium carbon steel as a matrix and adds Si, Mn, Cr, Al and Ti through reasonable component design. The material has better hardenability, obdurability and wear resistance because noble metal elements Mo and Ni are not added and Si, Mn and Cr with relatively low price are added. The Ti element with relatively low price is added to play the roles of grain refinement and precipitation strengthening, so that the steel has better strength, toughness, hardness and wear resistance, lower cost and better economic benefit.

2. The silicon content of the invention is between 0.80 and 1.20 percent, and the bending is easy to occur in the rolling process due to different expansion coefficients of phase change structures, so that the rolling process needs to be optimized, the heating temperature and the finish rolling temperature are reduced in the rolling process, and the cooling speed of a cooling bed is reduced at the same time.

3. The invention has higher contents of Si, Mn and Cr, so the hardness of the bar is higher, and in order to meet the requirement of a user on saw cutting, the hardness is required to be less than or equal to 280HBW, so the high-temperature collection and slow cooling work are required.

4. The wear-resistant bar with 0.8-1.2% of silicon prepared by the invention has the tensile strength of 1661-1886 MPa, the elongation of 12-13.5% and the reduction of area of 49-58%. The steel has high strength and high wear resistance.

Drawings

FIG. 1 shows a macrostructure of a wear-resistant steel continuous casting billet with silicon content of 0.8-1.2% obtained by the method;

FIG. 2 is a metallographic structure diagram (100 x) of a wear-resistant steel bar with a silicon content of 0.8-1.2% obtained by the method;

FIG. 3 is a diagram of the bending condition of the wear-resistant bar before the optimization of the rolling process according to the present invention;

FIG. 4 is a diagram of the condition of the wear-resistant bar material after the rolling process is optimized.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention. The embodiment of the invention adopts the processes of UHP ultrahigh power electric furnace smelting, LF furnace refining, VD vacuum degassing treatment process smelting, continuous casting and casting continuous casting blank and rolling to form the steel.

The preparation method of the wear-resistant bar with the silicon content of 0.8-1.2% comprises the following steps:

1. electric furnace smelting: the raw materials of the molten iron and the scrap steel are fed into the furnace, a concentrate guideline is adopted, the percentage of the molten iron is 79.34-82.06%, the foamed slag is made in the whole electric furnace smelting process, a low-oxygen mode is used for blowing oxygen in the early stage, the slag is fully melted, carbon powder is properly injected, and the thickness of the foamed slag is more than or equal to 200 mm. Melting and carbon cleaning: 0.43-1.27%, uniform decarburization, good oxidation boiling, promotion of inclusions and gas floating in steel, and end point carbon: 0.13-0.19%, end point P: 0.005-0.012%, and the content of residual elements meets the standard requirement. Tapping temperature of the molten steel is 1646-1656 ℃, steel and slag are remained during tapping, slag is strictly forbidden to be discharged, and alloy is added according to lower component limit during ladle alloying; and adding steel core aluminum along with the tapping flow in the electric furnace tapping process for pre-deoxidation.

2. Refining in an LF furnace: and (3) refining the molten steel smelted by the electric furnace in the step (1) in an LF furnace, controlling the alkalinity of the slag to be more than 3.0, and enhancing the refining of desulfurization operation. White slag is produced in the whole process, the white slag retention time is more than or equal to 20 minutes, and the refining period is as follows: and refining and argon blowing are carried out for 40-50 minutes according to the principle of promoting floating of inclusions and reducing secondary oxidation. Before LF tapping, the components and the temperature are finely adjusted, so that the stable performance of the steel and the temperature requirement of the continuous casting process are ensured. Feeding calcium wire according to the steel of 1.4-1.5 m/t, and soft blowing for more than or equal to 2 min.

3. Vacuum refining in a VD furnace: and (3) slagging off the molten steel refined by the LF furnace in the step (2), carrying out vacuum degassing on the molten steel, keeping the molten steel for more than or equal to 12 minutes under the vacuum degree of less than 67Pa, carrying out soft argon blowing for more than or equal to 15 minutes, and strictly keeping bare molten steel and large argon stirring and cooling during the soft argon blowing. After the VD breaks the air, a covering agent is added, and hydrogen is determined, [ H ]: 1.5 PPM.

4. Continuous casting: and 3, continuously casting the molten steel treated in the step 3 by adopting an integral tundish, adopting full-process protective casting, using a double-layer tundish covering agent, wherein the covering of the slag surface cannot be red, adopting medium-carbon alloy steel special covering slag, wherein the thickness of the covering slag is 45-60 mm, the thickness of the liquid slag layer is 7-12 mm, and the slag surface cannot be red by visual observation according to the adding principle of 'sequentially adding, adding less and uniformly adding', and optimally covering the blue flame on the slag surface to prevent the molten steel from being secondarily oxidized. The fluctuation of the liquid level of the crystallizer is less than or equal to +/-3 mm; pouring with low superheat degree is adopted, the superheat degree of the tundish molten steel is controlled to be 18-26 ℃, the secondary cooling water distribution adopts an ultra-weak cooling mode, and the crystallizer and the solidification tail end adopt electromagnetic stirring, so that the segregation and other structure defects are reduced, and the quality of a casting blank is improved. The pouring adopts three constant operations of constant liquid level, constant temperature and constant pulling speed, the temperature of the casting blank in the pulling and straightening machine is more than or equal to 900 ℃, and the slow cooling of the casting blank is more than or equal to 24 hours.

5. Rolling: and (4) rolling the continuous casting billet in the step (4). The steel grade is easy to bend, so that the bending experience of the bar produced in the last time is absorbed, and the rolling process is optimized. The production of the steel grade needs to replace a new saw blade; emptying other steel grades of a multiple length cooling bed before rolling; the rolling rhythm and the sawing speed are controlled, so that the steel can quickly pass through the multiple length cooling bed, and the steel is prevented from being accumulated on the multiple length cooling bed. The control parameters during rolling are as follows: the temperature of a soaking section of the heating furnace is controlled to be 1120-1150 ℃, the total heating time is 4.0-5.0 hours, so that the steel billets are uniformly burnt through, the allowable temperature difference is less than or equal to 30 ℃, the uniform heating of the steel billets is ensured, and decarburization and furnace sticking are prevented. The initial rolling temperature is 1010-1060 ℃, the control on the rolling rhythm is enhanced, and the final rolling temperature is 900-960 ℃. In the rolling process, the process control needs to be strengthened, the material type condition of each pass is closely paid attention, and the defects of scratching, folding, lugs and the like cannot occur. The steel grade not only requires that the tensile strength is not less than 1470Mpa, but also requires that the hardness is not more than 280HBW, the steel is collected into a heat preservation pit in time after rolling, hot steel in the heat preservation pit is paved, a heat preservation cover is covered, and the slow cooling time is not less than 48 hours, so that the wear-resistant bar with the specification phi of 60-160 mm and good strength and toughness is obtained.

Examples 1 to 9

Examples 1 to 9 provide abrasion resistant rods containing 0.8 to 1.2% silicon, the chemical composition of which is shown in table 1.

Table 1 examples 1-9 chemical composition table of wear resistant bars

Require that	C	Si	Mn	P	S	Cr	Ti	Alt
									Example 1	0.32	1.01	1.18	0.013	0.004	1.19	0.062	0.029
Example 2	0.32	1.01	1.17	0.014	0.002	1.19	0.066	0.028
									Example 3	0.34	1.03	1.18	0.016	0.003	1.20	0.072	0.036
Example 4	0.32	1.02	1.19	0.017	0.001	1.20	0.069	0.03
									Example 5	0.31	1.03	1.17	0.018	0.002	1.18	0.061	0.025
Example 6	0.32	1.01	1.18	0.015	0.003	1.19	0.073	0.029
									Example 7	0.33	1.02	1.2	0.016	0.003	1.20	0.066	0.026
Example 8	0.32	1.00	1.17	0.019	0.005	1.17	0.064	0.028
									Example 9	0.32	1.00	1.18	0.017	0.004	1.19	0.070	0.030

The macrostructures of the wear-resistant steel continuous casting blanks prepared in the above examples 1 to 9 and having the silicon content of 0.8 to 1.2% are shown in fig. 1.

The macrostructures of the steel materials of examples 1 to 9 are shown in Table 2. The general porosity is 0.5 grade, the central porosity is 1 grade, the segregation is 0.5 grade, the general and edge point segregation is 0 grade, and the technical requirements of steel macrostructure are well met.

Table 2 examples 1-9 macrostructures (grades) of abrasion resistant bars

The mechanical properties of examples 1-9 are shown in Table 3. Oil cooling at 880 +/-15 ℃ for the first quenching, oil cooling at 850 +/-15 ℃ for the second quenching, tempering at 200 +/-20 ℃, air cooling, and measuring the longitudinal mechanical properties of the bar. The wear-resistant bar with 0.8-1.2% of silicon prepared by the invention has the tensile strength of 1661-1886 MPa, the elongation of 12-13.5% and the reduction of area of 49-58%.

TABLE 3 mechanical Properties of abrasion-resistant bars of examples 1 to 9

The non-metallic inclusions of examples 1 to 9 were evaluated by method A in GB/T10561, and the grade of the non-metallic inclusions is shown in Table 4.

TABLE 4 examples 1-9 non-metallic inclusions (grades) of wear resistant bars

The structure, decarburized layer, grain size and hardness of examples 1 to 9 are shown in Table 5. The material is 1 grade in banded structure, 0 grade in Widmannstatten structure, 0.2-0.4 mm in decarburized layer depth, 8 grade in grain size and 195-235 HBW in hardness value, and meets the requirements of users on sawing and blanking.

TABLE 5 grain size, decarburized layer, texture, hardness of wear resistant bars of examples 1-9

The metallographic structure of the wear-resistant bar prepared in the above examples 1 to 9 and having a silicon content of 0.8 to 1.2% is 100 ×, as shown in fig. 2;

the rolling process prepared in examples 1-9 above optimizes the bending of the wear resistant rods, as shown in fig. 3.

The situation of the wear-resistant bar material after the rolling process prepared in the above examples 1-9 is optimized is shown in fig. 4, and as can be seen from the comparison between fig. 3 and fig. 4, the wear-resistant bar material prepared by the invention has no bending, and each and the whole wear-resistant bar material are in a straight line.

The method can be realized by upper and lower limit values and interval values of intervals of process parameters (such as temperature, time and the like), and embodiments are not listed.

Conventional technical knowledge in the art can be used for the details which are not described in the present invention.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The wear-resistant bar with the silicon content of 0.80-1.2% is characterized by comprising the following chemical components in percentage by weight: c: 0.30 to 0.34%, Si: 0.80-1.20%, Mn: 1.10-1.25%, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cr: 1.10% -1.25%, Ti: 0.06% -0.08% of Al: 0.020 to 0.040%, and the balance being Fe and inevitable impurities.

2. The wear-resistant bar material with the silicon content of 0.80-1.2% as claimed in claim 1, wherein the tensile strength of the wear-resistant bar material is not less than 1470MPa, the hardness of the wear-resistant bar material is not more than 280HBW, and the specification of the wear-resistant bar material is phi 60-160 mm.

3. A method for preparing a wear-resistant bar material according to claim 1 or 2, wherein the wear-resistant bar material contains 0.8-1.2% of silicon, and the method comprises the following steps:

1) smelting in an electric furnace;

2) refining in an LF furnace;

3) vacuum refining in a VD furnace;

4) continuous casting;

5) rolling:

4. The production method according to claim 3, wherein the step 1) is an electric furnace smelting:

5. The preparation method according to claim 3, characterized in that step 2) LF furnace refining:

6. The manufacturing method according to claim 3, wherein the step 3) comprises vacuum refining in a VD furnace:

7. The production method according to claim 3, wherein the step 4) of continuous casting: