Green low-carbon steel for undercarriage wheel of excavator and preparation method thereof

Abstract

The present application relates to a kind of green low-carbon excavator supporting wheel steel, the alloying component of the supporting wheel steel is as follows by weight percentage: C:0.30~0.37%, Si:0.15~0.30%, Mn:1.20~1.50%, Cr:0.30~0.40%, Cu:0.08~0.15%, Alt:0.020~0.050%, Ti:0.020~0.040%, B:0.0008~0.0030%, P:≤0.015%, S:≤0.010%, Ni:≤0.15%, Mo:≤0.06%, the balance is Fe and inevitable impurities.The method is used "ECOARC ecological electric furnace smelting+LF furnace refining+RH vacuum treatment+continuous casting+continuous rolling unit" to produce and manufacture excavator supporting wheel steel, ensure that the supporting wheel steel has higher hardenability, better mechanical properties, meet the requirements of wear resistance, high toughness and corrosion resistance of supporting wheel steel, while having the characteristics of low-carbon environmental protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of steel metallurgy, and particularly relates to a green low-carbon steel for excavator track roller and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the engineering machinery industry, the production of excavators is increasing year by year and developing towards large-scale. The track roller of the crawler excavator bears the entire weight of the excavator and is responsible for the travel function of the excavator and various impacts and dirt corrosion in work. The main damage form is wear, which is caused by, for example, the contact with the rolling surface of the track link, and is specifically manifested in the reduction of the diameter of the outer flange, the diameter of the rolling surface, the diameter of the double-sided inner flange, the width of the double-sided inner flange, and the width of the outer flange. Therefore, the track roller needs to have high wear resistance, good impact toughness and strong corrosion resistance to ensure the long-term stable operation of the excavator.

[0003] At present, with the continuous improvement of global environmental awareness, the steelmaking industry is also facing the pressure of transformation and upgrading, and needs to better meet the low-carbon environmental protection demand. A commonly used way is resource recycling and reuse, such as recycling and reusing scrap steel and other resources to reduce the mining amount of raw ore and achieve the purpose of low-carbon environmental protection. In addition, using ECOARC ecological electric furnace smelting is also a relatively effective method, which can reduce carbon emissions by 1.855t per ton of steel compared with traditional steelmaking processes, dioxin emissions ≤0.1ng-TEQ / Nm 3 , and power consumption is reduced by more than 100kWh / t.

[0004] Therefore, how to produce a track roller steel that has high comprehensive mechanical properties while also considering green environmental protection is of great economic value and broad market prospects. SUMMARY

[0005] To solve the above technical problems, the present application provides a green low-carbon steel for excavator track roller and a preparation method thereof. The method uses "ECOARC ecological electric furnace smelting + LF furnace refining + RH vacuum treatment + continuous casting + continuous rolling mill unit" to produce and manufacture the excavator track roller steel, which ensures that the track roller steel has high hardenability, good mechanical properties, and meets the requirements of wear resistance, high toughness and corrosion resistance of the track roller steel, and also has the characteristics of low carbon and environmental protection.

[0006] The specific application content is as follows:

[0007] A kind of green low-carbon excavator support wheel steel, alloying component of the support wheel steel is as follows by weight percentage: C: 0.30~0.37%, Si: 0.15~0.30%, Mn: 1.20~1.50%, Cr: 0.30~0.40%, Cu: 0.08~0.15%, Alt: 0.020~0.050%, Ti: 0.020~0.040%, B: 0.0008~0.0030%, P: ≤0.015%, S: ≤0.010%, Ni: ≤0.15%, Mo: ≤0.06%, the balance is Fe and inevitable impurities.

[0008] Another object of the present application is to provide a preparation method of a green low-carbon excavator support wheel steel, the method comprises the steps of electric furnace smelting, LF furnace refining, RH refining, continuous casting and rolling, wherein the electric furnace smelting adopts ECOARC ecological electric arc furnace for smelting: scrap steel is added into preheating shaft furnace for 10 to 12 times, graphite pressure ball is used for C matching, oxygen oxidation, violent boiling, automatic slag flow process is used for blowing, oxidation temperature is 1555~1585℃, tapping temperature is 1610~1630℃, other ladle is temperature compensated according to temperature compensation system. End point steel C≥0.10%, P≤0.015%, the amount of pre-deoxidizer is 2.5~3.0kg / t, the carbonizer, slag and alloy are added into the ladle when the tapping is 20~25t.

[0009] Light and thin scrap steel is used as furnace charge, the size of scrap steel should not be too large, the single weight of scrap steel is ≤1000Kg. Copper, lead, tin and other non-ferrous metals and impurities should not be mixed. Mud, cement, sticky sand and other requirements on the surface of scrap steel iron should not exist, and water is required. Tubular objects, closed vessels, flammable and explosive materials, radioactive and toxic materials and other materials should not be allowed in scrap steel. The first furnace scrap steel is added by a tank, the first tank scrap steel (about 50t, including 25t pig iron and 25t returned steel), after the cover is rotated to open, the scrap steel is loaded into the central position of the electric furnace. After the scrap steel basket is loaded, the cover is rotated to start power supply, when the input power reaches 18000~19000kwh, the temperature of the waste gas in the shaft furnace starts to rise, and the scrap steel is added into the preheating shaft furnace. The volume of the first scrap steel added into the preheating shaft furnace should be half of the volume of the shaft furnace (2~3 baskets of scrap steel). And the scrap steel is pushed into the furnace by a pusher. In continuous production state, the scrap steel is added into the preheating shaft furnace once every 3~5 minutes, and preheating treatment is carried out. The preheated scrap steel is pushed into the smelting area of the furnace by a pusher.

[0010] Preferably, when the molten pool is formed in the furnace, when the distance between the oxygen lance and the upper surface of the molten steel is 1000~1200mm, the oxygen lance is moved to the position of the molten pool, and the oxygen lance is moved to the position of the molten pool. 3The oxygen lance is blown at a speed of 20-30 m / h, and the oxygen flow is gradually increased, and the distance between the oxygen lance and the upper surface of the molten steel is reduced while increasing the oxygen flow, until the oxygen flow reaches 4000-6000 Nm 3 When the oxygen flow is 4000-6000 Nm / h, the distance between the oxygen lance and the upper surface of the molten steel is ≥500 mm. During this process, the temperature difference between the inlet and outlet of the oxygen lance cooling water is checked. When the temperature difference between the inlet and outlet exceeds 5°C, it is checked whether the oxygen lance automatically stops oxygen supply.

[0011] Preferably, after the formation of a molten pool in the furnace, carbon powder is sprayed into the slag in a continuous or intermittent manner to form a foamed slag, and the arc is wrapped with the slag surface. When the temperature is ≥1580°C and P≤0.015%, the process is stopped, and the height of the foamed slag is maintained at 500-1000 mm.

[0012] Preferably, the slag-making process is as follows: after the formation of a molten pool in the furnace, 1000-2000 kg of lime and 300 kg of dolomite or magnesite are first added for slag making. After the sixth car of scrap steel is loaded into the preheating shaft furnace, 800-1000 kg of lime is added. After the last car of scrap steel is loaded into the preheating shaft furnace, 500 kg of lime is added. After the eighth car of scrap steel is loaded into the preheating shaft furnace, the first concentrated slagging is performed, and the second concentrated slagging is performed before temperature sampling at the end of the oxidation period.

[0013] For the first furnace, after the formation of a molten pool in the furnace, 2000 kg of lime and 300 kg of dolomite or magnesite are added into the furnace. After the sixth car of scrap steel is loaded into the preheating shaft furnace, 1000 kg of lime is added for the second time. After the last car of scrap steel is loaded into the furnace, 500 kg of lime is added for the third time. After the eighth car of scrap steel is loaded into the furnace, the first concentrated slagging is performed, and the second concentrated slagging is performed before temperature sampling at the end of the oxidation period. For the third car of scrap steel in the subsequent continuous smelting, 1000 kg of lime and 300 kg of dolomite or magnesite are added into the furnace after the scrap steel is loaded into the preheating shaft furnace. After the sixth car of scrap steel is loaded into the preheating shaft furnace, 800 kg of lime is added for the second time. After the last car of scrap steel is loaded into the furnace, 500 kg of lime is added for the third time. After the eighth car of scrap steel is loaded into the furnace, the first concentrated slagging is performed, and the second concentrated slagging is performed before temperature sampling at the end of the oxidation period.

[0014] Further, the LF refining process is as follows: after argon blowing for 3 minutes, one or more slagging materials such as lime, fluorite and carbide are added to perform slagging operation, aluminum wire is fed, and batched ferrosilicon powder is added to perform diffusion deoxidation, the first batch of ferrosilicon powder is 1-3 kg / t, the second batch is added after closing the furnace door for 10 minutes, and the total amount of the ferrosilicon powder is 2-4 kg / t, and a sample is taken when the slag white temperature meets the requirements. After full analysis, continue to perform diffusion deoxidation, maintain the reducing atmosphere until the ladle is lifted, the white slag retention time is ≥10 minutes; when the diffusion deoxidation effect is good, add ferrosilicon, high manganese, high chromium, ferrotitanium and boron iron alloy according to the control component target to adjust the alloy component of the molten steel to the target value; the argon pressure is controlled at 0.2-0.4 MPa throughout the process, and the slag surface fluctuation is used as the criterion, and the molten steel is not exposed to prevent secondary oxidation caused by the exposure of the molten steel. The Alt content is controlled at 0.020-0.040% when leaving the station, and the temperature is 1640-1675℃.

[0015] Preferably, the titanium content in the molten steel is ≥0.03% before adding the boron iron to ensure the effective boron content in the steel.

[0016] Further, the RH refining process is as follows: the vacuum degree is below 100 Pa and the holding time is ≥20 minutes, the static argon blowing time is ≥25 minutes after re-pressurization, the argon pressure is 0.1-0.3 MPa, the slag surface is slightly moving, and the molten steel is not exposed to prevent secondary oxidation. The temperature of the first ladle is controlled at 1600-1610℃, and the temperature of the last ladle is controlled at 1580-1590℃.

[0017] Further, the continuous casting process is as follows: the first furnace temperature on the tundish platform is 1595-1605℃, the continuous casting temperature is 1575-1585℃, and the tundish temperature is 1530-1540℃; the casting speed is 0.35 m / min-1.30 m / min; the specific water consumption of the secondary cooling water is 0.30 L / kg; the current of the electromagnetic stirring in the mold is 280-320 A, and the frequency is 2 Hz; the current of the electromagnetic stirring at the end is 360-420 A, and the frequency is 7 Hz; the whole process of protection casting is strictly implemented, and the mold powder for protection is a special medium-carbon steel protection powder. The cast blank is hot sent or heat preserved, and the heat preservation time is ≥36 h for the bloom and ≥30 h for the billet.

[0018] Further, the rolling process is as follows: the reheating type walking beam furnace can be used for heating, the heating temperature is 1190-1230℃, the soaking time is 98-130 minutes, the total heating time is 240-280 minutes, and the discharge temperature is 1100-1200℃; the Φ1150 mm BD blooming mill can be used for blooming, and the Φ850 mm finishing mill group can be used for rolling. The blooming temperature is 1100℃-1200℃, the finish rolling temperature is 800-1000℃, the steel after rolling is heat preserved in the pit at a temperature ≥550℃, the out-pit temperature is ≤200℃, and the heat preservation time is ≥48 h.

[0019] The preparation method of the green low-carbon excavator support wheel steel only limits the key parameters in the preparation process, and other conventional steps for preparing the steel material are performed in the manner disclosed in the prior art, and the process requirements can be met.

[0020] The beneficial effects of the present application are:

[0021] ①The method of the present application uses "ECOARC ecological electric furnace smelting + LF furnace refining + RH vacuum treatment + continuous casting + continuous rolling mill set" to produce the excavator support wheel steel, which ensures that the support wheel steel has high hardenability and purity, and meets the requirements of wear resistance, high toughness and corrosion resistance of the support wheel steel.

[0022] ②The method of the present application can effectively reduce production cost, reduce carbon emissions, and the product performance is excellent, which meets the use requirements of users. DETAILED DESCRIPTION

[0023] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way.

[0024] The test methods in the following examples are conventional methods unless otherwise specified; the reagents and materials can be obtained commercially unless otherwise specified.

[0025] Example 1

[0026] The green low-carbon excavator support wheel steel is prepared by using the technical scheme of the present application, and the specific steps are as follows:

[0027] 1. ECOARC ecological electric arc furnace smelting

[0028] The first furnace scrap steel is added from the hopper, and after the cover is rotated open, the scrap steel is loaded into the central position of the electric furnace. The first tank of steel and iron material is 50t (including 25t of pig iron and 25t of returned steel), and the present furnace is the first furnace for production. A total of 12 cars of scrap steel are loaded during the smelting process, each car weighing 9.5t. Add 3.3t of lime, 2.5t of dolomite and 2t of graphite briquettes as slagging materials.

[0029] (1) Start sending electricity after adding 4 cars of steel and iron materials into the shaft furnace, voltage gear 9 (690V); start spraying carbon at a flow rate of 40kg / min with 1# carbon gun, and keep 2#, 3# carbon guns open; keep the oxygen lance open on the furnace wall; and the pusher automatically runs.

[0030] (2) After the 5th car of material is loaded, send electricity for 2 minutes, add 2t of graphite briquettes, and after the graphite briquettes are added, add 2200kg of lime and 1650kg of dolomite. Start the oxygen lance at the furnace door, with a flow rate of 4000Nm 3 / h.

[0031] (3) After the 6th car is loaded, the voltage is adjusted to 8 (720V) at the 5th minute of power supply.

[0032] (4) At the 8th minute of power supply, the oxygen lance flow rate of the furnace door is adjusted to 5500 Nm 3 / h, and the 1# carbon lance flow rate is 60 kg / min.

[0033] (5) At the 10th minute of power supply, the voltage is adjusted to 7 (750V).

[0034] (6) After the 9th car is loaded, at the 14th minute of power supply, the oxygen lance flow rate of the furnace door is adjusted to 6000 Nm 3 / h, the 1# and 2# furnace wall oxygen lances are turned on, and the flow rate is 2500 Nm 3 / h.

[0035] (7) At the 15th minute of power supply, the 2# and 3# carbon lances are turned on, and the flow rate is 55 kg / min.

[0036] (8) After the 11th car is loaded into the shaft furnace, the slag is discharged, and the slagging time is 5-6 minutes. During slagging, the furnace body does not tilt, and the furnace door is opened to automatically flow slag.

[0037] (9) After the 12th car is loaded and the slagging is completed, 1100 kg of lime and 850 kg of dolomite are added; the furnace door oxygen lance and 0# oxygen lance are stopped, the 2# oxygen lance continues to blow oxygen at 2500 Nm 3 / h; the 1#, 2#, and 3# carbon lances are kept on (if necessary, the 3# carbon lance can be continuously turned on according to the actual smelting slag condition in the furnace); the pusher stops moving; the voltage is adjusted to 6 (780V); the temperature is measured and sampled, and the temperature rising period is entered.

[0038] (10) At the 6th minute of the temperature rising period, the temperature is measured, and after the temperature rising period is completed, the 2# furnace wall oxygen lance is stopped.

[0039] (11) The tapping temperature of the electric furnace is 1600-1630℃. Before tapping, argon is connected, and the flow rate is set to 750 Nl / min. When 18 tons of molten steel is tapped, the carbon additive, alloy, and slag (600 kg of active lime) are sequentially added, and the tapping amount is 106 t.

[0040] 2. LF Refining

[0041] After argon blowing for 3 minutes, the temperature was measured and a sample was taken. Slagging material, active lime 400 kg, was added to perform slagging operation. Aluminum wire 140 m was fed to perform precipitation deoxidation. Power was supplied to perform slagging and temperature rising. Silicon-iron powder 80 kg was added in batches to perform diffusion deoxidation. The furnace door was closed for 10 minutes. Silicon carbide 120 kg was added in batches. The temperature of the white slag met the requirements and a sample was taken. After full analysis, diffusion deoxidation was continued. The reducing atmosphere was maintained until the ladle was lifted. The white slag was maintained for no less than 15 minutes. After good deoxidation, silicon-iron, high manganese, high chromium, ferro-titanium, and boron-iron were added to adjust the C, Si, Mn, Cr, Ti, and Al contents to meet the standard requirements. The B content in the steel was adjusted to about 0.0015% by adding boron-iron to ensure the effective B content in the steel. The argon pressure was controlled at 0.2-0.4 MPa throughout the process. The slag surface fluctuated, and the molten steel was not exposed to prevent secondary oxidation.

[0042] 3. RH refining

[0043] The RH temperature was 1670°C. The Alt was adjusted to 0.035% before entering the RH to ensure that the finished product Alt reached the target requirements. The vacuum degree reached below 100 Pa, and the holding time was 18 minutes. After re-pressurizing, the argon blowing time was 22 minutes, and the argon pressure was 0.3 MPa. The slag surface was slightly moving, and the molten steel was not exposed to prevent secondary oxidation. The temperature of the first ladle was controlled at 1605°C.

[0044] 4. Continuous casting

[0045] The first furnace temperature on the ladle platform was 1600°C. The tundish temperature was measured every 10 minutes, which was 1561°C, 1548°C, 1535°C, and 1534°C, respectively. The casting speed was 0.42 m / min. The specific water quantity of the secondary cooling water was 0.30 L / kg. The electromagnetic stirring current of the mold was 320 A, and the frequency was 2 Hz. The electromagnetic stirring current of the end was 420 A, and the frequency was 7 Hz. Strict protection was implemented throughout the process of casting. Special medium-carbon steel protection slag was used for mold protection slag. The cast billet was hot sent or heat preserved, and the heat preservation time was guaranteed to be no less than 36 h for large blooms and no less than 30 h for medium blooms.

[0046] 5. Rolling

[0047] The heating was performed using a regenerative walking beam furnace. The heating temperature was 1210°C. The soaking time was 98 min. The total heating time was 270 min. The out-of-furnace temperature was 1180°C.

[0048] The rolling was performed using a Φ1150 mm BD blooming mill for blooming and a Φ850 mm finishing mill group for rolling. The blooming temperature was 1170°C. The finish rolling temperature was 950°C. The steel was heat preserved after rolling. The pit entry temperature was 650°C. The pit exit temperature was 180°C. The heat preservation time was 52 h.

[0049] Example 2

[0050] The steps for preparing the green low-carbon steel for excavator supporting wheel by adopting the technical scheme of the present application are as follows:

[0051] 1. ECOARC ecological electric arc furnace smelting

[0052] In the continuous production state, scrap steel is added to the preheating shaft furnace every 3-5 minutes, and preheating treatment is performed thereon. 3.5t of lime, 1.5t of dolomite and 1t of graphite briquettes are added as slagging materials.

[0053] (1) Select a full scrap steel smelting power supply model; start spraying carbon at a flow rate of 40kg / min of 1# carbon gun, and keep 2#, 3# carbon guns open; keep the oxygen lance of the furnace wall open; and automatically operate the pusher.

[0054] (2) After the 5th vehicle of materials is loaded, power is supplied for 2 minutes, 2t of graphite briquettes are added, after the graphite briquettes are added, 2000kg of lime and 1000kg of dolomite are added. Start the oxygen lance at the furnace door, and the flow rate is 4000Nm 3 / h.

[0055] (3) After the 6th vehicle of materials is loaded, power is supplied for the 5th minute, and the voltage gear is adjusted to 8 gears (720V).

[0056] (4) After power is supplied for the 8th minute, the flow rate of the oxygen lance at the furnace door is adjusted to 5500Nm 3 / h, and the flow rate of 1# carbon gun is 60kg / min.

[0057] (5) The voltage gear is adjusted to 7 gears (750V) after power is supplied for the 10th minute.

[0058] (6) After the 9th vehicle of materials is loaded, power is supplied for the 14th minute, the flow rate of the oxygen lance at the furnace door is adjusted to 6000Nm 3 / h, 1#, 2# oxygen lances of the furnace wall are opened, and the flow rate is 2500Nm 3 / h.

[0059] (7) 2#, 3# carbon guns are opened after power is supplied for the 15th minute, and the flow rate is 55kg / min.

[0060] (8) After the 11th vehicle of materials is loaded into the shaft furnace, slagging is started, and the slagging time is 5 minutes. When slagging, the furnace body does not tilt, and the furnace door is opened to automatically flow slag.

[0061] (9) After the 12th vehicle of materials is completely loaded and slagging is finished, 1500kg of lime and 500kg of dolomite are added; the oxygen lance at the furnace door and 0# oxygen lance are stopped, 2# oxygen lance continues to blow oxygen at a flow rate of 2500Nm 3 / h; 1#, 2#, 3# carbon guns are kept open (if necessary, 3# carbon gun can be continuously opened according to the actual smelting slag condition in the furnace); the pusher stops moving; the voltage is adjusted to 6 gears (780V); temperature measurement and sampling are performed, and the temperature rising period is entered.

[0062] (10) Temperature rising period 6 minutes, temperature measurement, after the temperature rising period stop 2# furnace wall oxygen lance.

[0063] (11) The temperature of the electric furnace tapping 1600℃. Before tapping, connect argon, flow rate set at 750 Nl / min, 20 tons of tapping, sequentially add carbon additive, alloy, slag material (active lime 600 kg), the tapping amount is 110 t.

[0064] 2, LF refining

[0065] After entering the station, measure the temperature and take samples after blowing argon for 3 minutes, add slag-making material active lime 500 kg for slagging operation, feed aluminum wire 160 m for sedimentation deoxidation, power on for slagging and temperature rising, and add silicon iron powder 85 kg in batches for diffusion deoxidation. Close the door for 11 minutes, add silicon carbide 130 kg in batches, and the temperature after slagging meets the requirements to take a sample. After full analysis, continue diffusion deoxidation, maintain the reducing atmosphere until the ladle is lifted, and the white slag maintains for 18 minutes. After good deoxidation, add silicon, high manganese, high chromium, and ferrotitanium according to the control composition target, determine the C, Si, Mn, Cr, Ti, and Al composition after sampling to meet the standard requirements, and then add boron iron to adjust the B content in the steel to 0.0020% to ensure the effective boron content in the steel. Throughout the process, the argon pressure is controlled at 0.3 MPa, and the slag surface fluctuation is used as the standard to prevent the steel from being exposed to cause secondary oxidation.

[0066] 3, RH refining

[0067] The RH temperature is 1640℃, and the Alt is adjusted to 0.025% before entering the RH to ensure that the finished product Alt reaches the target requirement. The vacuum degree reaches below 100 Pa, and the holding time is 18 minutes. After repressurization, the argon blowing time is 22 minutes, and the argon pressure is 0.3 MPa. The slag surface is slightly moving, and the steel is not exposed to prevent secondary oxidation. The ladle temperature is controlled at 1580℃.

[0068] 4, Continuous casting

[0069] The ladle platform temperature is 1575℃, the tundish temperature is measured every 10 minutes, which is 1532℃, 1538℃, 1538℃, and 1536℃ respectively; the casting speed is 0.44 m / min; the secondary cooling water ratio is 0.30 L / kg; the mold electromagnetic stirring current is 280 A, and the frequency is 2 Hz; the end electromagnetic stirring current is 360 A, and the frequency is 7 Hz. Strictly implement the whole process protection casting, and use special medium carbon steel protection slag for mold protection slag. The billet is kept for 40 hours.

[0070] 5, Rolling

[0071] The heating adopts a regenerative step beam heating furnace, the heating temperature is 1190℃, the soaking time is 110 minutes, and the total heating time is 240 minutes. The out-of-furnace temperature is 1180℃.

[0072] The rolling adopts Φ1150mm BD roughing cogging mill cogging, and Φ850mm finishing rolling mill group rolling. The roughing temperature is 1100℃, the finish rolling temperature is 900℃, the steel is kept after rolling, the pit temperature is 550℃, the pit temperature is 150℃, and the keeping time is 50h.

[0073] Example 3

[0074] The steel for green low-carbon excavator supporting wheel is prepared by adopting the technical scheme of the patent, and the specific steps are as follows:

[0075] 1. ECOARC ecological electric arc furnace smelting

[0076] A total of 12 cars of scrap steel are loaded in the smelting process, each car is 9.5t. Add 4t of lime, 2.5t of dolomite and 2t of graphite briquettes as slagging materials.

[0077] (1) Select the full scrap steel smelting power supply model; 1# carbon gun flow 40kg / min starts to spray carbon, 2#, 3# carbon gun keeps open; the furnace wall oxygen lance keeps open; the pusher automatically runs.

[0078] (2) After the 5th car of material is loaded, send power for 2 minutes, add 2t of graphite briquettes, after the graphite briquettes are added, add 2500kg of lime and 1500kg of dolomite. Start the furnace door oxygen lance, the flow is 4000Nm 3 / h.

[0079] (3) After the 6th car of material is loaded, send power for the 5th minute, and adjust the voltage gear to 8 gears (720V).

[0080] (4) Start sending power for the 8th minute, adjust the furnace door oxygen lance flow to 5500Nm 3 / h, and the 1# carbon gun flow is 60kg / min.

[0081] (5) Adjust the voltage gear to 7 gears (750V) for the 10th minute of power sending.

[0082] (6) After the 9th car of material is loaded, send power for the 14th minute, adjust the furnace door oxygen lance flow to 6000Nm 3 / h, open the 1#, 2# furnace wall oxygen lances, and the flow is 2500Nm 3 / h.

[0083] (7) Open the 2#, 3# carbon lances for the 15th minute of power sending, and the flow is 55kg / min.

[0084] (8) Start slagging after the 11th car of material is loaded into the shaft furnace, and the slagging time is 6 minutes. When slagging, the furnace body does not tilt, and the furnace door is opened to automatically flow slag.

[0085] (9) After the 12th car is fully loaded and the slagging is finished, add lime 1500 kg and dolomite 1000 kg; stop the oxygen lance, 0# oxygen lance, and 2# oxygen lance, and continue to blow oxygen at 2500 Nm 3 / h; stop the pusher; adjust the voltage to 6 gears (780 V); measure the temperature and sample, and enter the heating period.

[0086] (10) The temperature is measured for 6 minutes in the heating period, and the 2# furnace wall oxygen lance is stopped after the heating period is over.

[0087] (11) The tapping temperature of the electric furnace is 1630℃. Before tapping, connect the argon gas with a flow rate of 750 Nl / min, and add the carbon additive, alloy, and slag material (active lime 600 kg) in sequence when 22 tons of molten steel is tapped, and the tapping amount is 112 t.

[0088] 2. LF refining

[0089] After entering the station, measure the temperature and sample after blowing argon for 3 minutes, add slagging material active lime 400 kg for slagging operation, feed aluminum wire 140 m for sedimentation deoxidation, power on for slagging and heating, and add silicon iron powder 80 kg in batches for diffusion deoxidation. Close the furnace door for 10 minutes, add silicon carbide 120 kg in batches, and take a sample after the slag temperature meets the requirements. After full analysis, continue diffusion deoxidation, maintain the reducing atmosphere until the ladle is lifted, and the white slag remains for 25 minutes. After good deoxidation, add silicon iron, high manganese, high chromium, and ferrotitanium according to the control composition target, determine the C, Si, Mn, Cr, Ti, and Al composition after sampling to meet the standard requirements, add boron iron to adjust the B content in the steel to about 0.0028%, and control the argon pressure to 0.4 MPa throughout the process to prevent secondary oxidation caused by exposure of the molten steel.

[0090] 3. RH refining

[0091] The RH temperature is 1650℃, and the Alt is adjusted to 0.040% before entering the RH to ensure that the finished product Alt meets the target requirements. The vacuum degree reaches below 100 Pa, and the holding time is 23 minutes. After repressurization, the argon blowing time is 25 minutes, and the argon pressure is 0.25 MPa to prevent secondary oxidation. The ladle temperature is controlled at 1590℃.

[0092] 4. Continuous casting

[0093] The first furnace temperature of the large package platform is 1585℃, the tundish temperature is measured every 10 minutes, and is respectively 1524℃, 1527℃, 1532℃, 1530℃; the drawing speed is 0.44m / min; the secondary cooling water ratio is 0.30L / kg; the crystallizer electromagnetic stirring current is 300A, and the frequency is 2Hz; the end electromagnetic stirring current is 360A, and the frequency is 7Hz. The whole process protection casting is strictly implemented, the crystallizer protection slag uses special medium carbon steel protection slag. The cast blank is hot sent.

[0094] 5. Rolling

[0095] The heating uses a regenerative walking beam heating furnace to heat, the heating temperature is 1230℃, the soaking time is 130min, and the total heating time is 280min. The furnace discharge temperature is 1200℃.

[0096] The rolling uses a Φ1150mm BD primary rolling cogging mill to cog, and a Φ850mm finishing rolling mill group to roll. The cogging temperature is 1200℃, the finish rolling temperature is 1000℃, the steel is kept after rolling, the pit entering temperature is 600℃, the pit discharging temperature is 120℃, and the keeping time is 50h.

[0097] Product inspection and performance test

[0098] The final products of examples 1-3 are respectively subjected to chemical composition, end quenching property and inclusion inspection, and the inspection results are shown in tables (1)-(3):

[0099] Table (1) Chemical composition (mass percentage) / %

[0100]

[0101] Table (2) End quenching property

[0102]

[0103] Table (3) Inclusion condition

[0104]

[0105] It can be seen that the chemical composition, end quenching property and inclusion of the steel for support wheel produced by the application meet the standard requirements, and the product quality is at the domestic advanced level.

Claims

1. A green low carbon steel for use in ground engaging wheels of excavators, characterized by: The alloy composition of the steel for the supporting wheel comprises, by weight percent, C: 0.30-0.37%, Si: 0.15-0.30%, Mn: 1.20-1.50%, Cr: 0.30-0.40%, Cu: 0.08-0.15%, Alt: 0.020-0.050%, Ti: 0.020-0.040%, B: 0.0008-0.0030%, P: ≤0.015%, S: ≤0.010%, Ni: ≤0.15%, Mo: ≤0.06%, and the balance of Fe and inevitable impurities; The preparation method of the steel for the supporting wheel comprises the steps of electric furnace smelting, LF furnace refining, RH refining, continuous casting and rolling, wherein the electric furnace smelting is performed by using an ECOARC ecological electric arc furnace: scrap steel is added into a preheating shaft furnace in 10 to 12 times, graphite pressure ball is used for C matching, oxygen oxidation, intense boiling, and automatic slag flow process is used for blowing, the oxidation temperature is 1555-1585℃, the tapping temperature is 1610-1630℃, the end point steel C is ≥0.10%, P is ≤0.015%, the pre-deoxidizer dosage is 2.5-3.0 kg / t, and the 20-25t tapping starts to add carbon additive, slag and alloy into the ladle; After the molten pool is formed in the furnace, the oxygen is blown at a speed of 1500Nm3 / h when the distance between the oxygen lance and the upper surface of the molten steel is 1000-1200mm, and the oxygen flow is gradually increased, and at the same time, the distance between the oxygen lance and the upper surface of the molten steel is reduced until the oxygen flow reaches 4000-6000Nm3 / h, and the distance between the oxygen lance and the upper surface of the molten steel is ≥500mm; After the molten pool is formed in the furnace, the carbon powder can be sprayed into the slag in a continuous or intermittent manner to form a foamed slag, and the foamed slag height is kept at 500mm-1000mm when the temperature is ≥1580℃ and P is ≤0.015%; The slag making process is as follows: after the molten pool is formed in the furnace, 1000-2000kg of lime and 300kg of white cloud stone or magnesite are first added for slag making, 800-1000kg of lime is added after the sixth vehicle of scrap steel is loaded into the preheating shaft furnace, and 500kg of lime is added after the last vehicle of scrap steel is loaded into the preheating shaft furnace; after the eighth vehicle of scrap steel is loaded into the preheating shaft furnace, the slag is first concentrated, and the slag is secondly concentrated before the temperature sampling at the end of the oxidation period. The LF refining process is: after blowing argon for 3 minutes, adding one or more slagging materials such as lime, fluorite and calcium carbide to perform slagging operation, feeding aluminum wire, performing sedimentation deoxidation, and adding ferrosilicon powder in batches to perform diffusion deoxidation, the first addition of the ferrosilicon powder is 1-3 kg / t, the second addition is added after closing the furnace door for 10 minutes, the total addition amount of the ferrosilicon powder is 2-4 kg / t, and the white slag retention time is ≥10 min; when the diffusion deoxidation effect is good, adding ferrosilicon, high manganese, high chromium, ferrotitanium and boron iron alloy according to the control component target to adjust the alloy component of the molten steel to the target value; the argon pressure is controlled at 0.2-0.4 MPa throughout the process, the Alt content is controlled at 0.020-0.040% when leaving the station, and the temperature is 1640-1675℃; The LF refining process needs to ensure that the titanium content in the molten steel is ≥0.03% before adding the boron iron; The RH refining process is: the vacuum degree is maintained at below 100 Pa for ≥20 min, the static argon blowing time after re-pressurization is ≥25 min, and the argon pressure is 0.1-0.3 MPa.

2. The steel for use in a shovel bogie wheel according to claim 1, characterized by: The continuous casting process is: the casting speed is 0.35 m / min-1.30 m / min; the specific water quantity of the secondary cooling water is 0.30 L / kg; the electromagnetic stirring current of the crystallizer is 280-320 A, and the frequency is 2 Hz; the electromagnetic stirring current at the end is 360-420 A, and the frequency is 7 Hz; the billet holding time is ≥30 h.

3. The shovel bogie wheel steel according to claim 1, characterized in that: The rolling process is: the heating temperature is 1190-1230℃, the soaking time is 98-130 min, the total heating time is 240-280 min, the discharge temperature is 1100-1200℃; the opening rolling temperature is 1100℃-1200℃, the final rolling temperature is 800-1000℃, the post-rolling steel holding into pit temperature is ≥550℃, the out-of-pit temperature is ≤200℃, and the holding time is ≥48 h.

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