CN116511444A - Preparation method for preparing DC53 flat steel in efficient and energy-saving mode - Google Patents

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method for preparing DC53 flat steel in a high-efficiency and energy-saving manner. The invention provides a preparation method for preparing DC53 flat steel in an efficient and energy-saving way, which comprises the following steps: smelting raw materials according to the element proportion of DC53 steel to obtain a melt; mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel; continuously casting the molten steel to obtain a continuous casting blank; and sequentially carrying out primary rolling and annealing treatment on the continuous casting billet to obtain the DC53 steel. The preparation method provided by the invention has the advantages of simple process, energy consumption saving, production cost reduction and improvement of the yield of the DC53 steel.

Description

Preparation method for preparing DC53 flat steel in efficient and energy-saving mode

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method for preparing DC53 flat steel in a high-efficiency and energy-saving manner.

Background

The die is extremely important and indispensable basic technological equipment in industrial production, and is widely applied to the fields of machinery, military industry, aerospace, automobiles, energy sources and the like. The performance of the mold material directly determines the service life of the mold, thereby affecting the cost and efficiency of industrial production. DC53 (Cr 8Mo2 SiV) is a novel medium-low alloy cold work die steel, and is commonly used for preparing dies for forming in a cold state such as a cold heading die, a cold stamping die, a cold drawing die, and the like. The content of alloy elements of the DC53 steel is lower than that of the high-carbon high-alloy cold-working die steel, and meanwhile, the DC53 steel has the characteristics of high hardness, high toughness, high wear resistance and the like, and the high-temperature tempering hardness and toughness are improved. The existing production process flow of DC53 flat steel still adopts die casting and multiple-firing forging/rolling processes. The traditional process has long manufacturing process, high cost, yield lower than 80 percent and unstable product quality.

Disclosure of Invention

In view of the above, the invention provides a preparation method for preparing DC53 flat steel with high efficiency and energy conservation, and the preparation method provided by the invention has simple and convenient process, and reduces the production energy consumption and thus the production cost; the yield of the DC53 steel manufactured by the preparation method provided by the invention is more than 90%.

In order to solve the technical problems, the invention provides a preparation method for preparing DC53 flat steel in a high-efficiency and energy-saving way, which comprises the following steps:

smelting raw materials according to the element proportion of DC53 steel to obtain a melt;

mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel;

continuously casting the molten steel to obtain a continuous casting blank;

and sequentially carrying out primary rolling and annealing treatment on the continuous casting billet to obtain the DC53 steel.

Preferably, the continuous casting drawing speed is 0.60-1.00 m/min.

Preferably, the continuous casting crystallizer in continuous casting is non-sinusoidal vibration, the frequency of the non-sinusoidal vibration is 80-180 times/min, and the amplitude of the non-sinusoidal vibration is 3.0-6.0 mm.

Preferably, the secondary cooling in the continuous casting process adopts weak cooling, and the specific water quantity of the weak cooling is 0.10-0.18L/kg.

Preferably, the primary rolling includes rough rolling and finish rolling performed sequentially.

Preferably, the initial rolling temperature of the primary rolling is 1050-1150 ℃, the final rolling temperature of the rough rolling is higher than 950 ℃, and the final rolling temperature of the finish rolling is higher than 880 ℃.

Preferably, the number of the first-pass rolling is 10-20, and the single-pass deformation is 10-15%.

Preferably, the means for transferring the continuous casting slab to a hot rolling device comprises hot feeding or slow cooling.

Preferably, the temperature of the annealing treatment is 860-880 ℃, and the heat preservation time of the annealing treatment is 4-8 h.

Preferably, the DC53 steel comprises the following element components in percentage by mass: 0.95 to 1.03wt.% of C, 0.80 to 1.20wt.% of Si, 0.20 to 0.50wt.% of Mn, 7.80 to 8.30wt.% of Cr, 2.00 to 2.80wt.% of Mo, 0.25 to 0.40wt.% of V, and the balance of Fe and unavoidable impurities.

The invention provides a preparation method for preparing DC53 flat steel in a high-efficiency and energy-saving way, which comprises the following steps: smelting raw materials according to the element proportion of DC53 steel to obtain a melt; mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel; continuously casting the molten steel to obtain a continuous casting blank; and sequentially carrying out primary rolling and annealing treatment on the continuous casting billet to obtain the DC53 steel. The continuous casting blank for preparing the DC53 steel by adopting the continuous casting mode has good macrostructure, loose center is lower than 1.0 level, and center segregation is lower than 2.0 level; primary carbides at the edge of the continuous casting blank are tiny and dispersed, and primary carbide aggregation exists in the core. The center segregation condition of the DC53 steel macrostructure is improved after being treated by a primary hot rolling process, the center porosity is lower than 0.5 level, and the center segregation is lower than 0.5 level; the primary carbide of the core is uniformly distributed, and the quality of DC53 steel is improved. The preparation method provided by the invention has the advantages of simple process, energy consumption saving, production cost reduction and improvement of the yield of the DC53 steel.

Detailed Description

The invention provides a preparation method for preparing DC53 flat steel in a high-efficiency and energy-saving way, which comprises the following steps:

smelting raw materials according to the element proportion of DC53 steel to obtain a melt;

mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel;

continuously casting the molten steel to obtain a continuous casting blank;

and sequentially carrying out primary rolling and annealing treatment on the continuous casting billet to obtain the DC53 steel.

In the present invention, all the raw materials are conventionally commercially available products unless otherwise specified.

According to the invention, raw materials are smelted according to the element proportion of DC53 steel to obtain a melt. In the invention, the DC53 steel preferably comprises the following element components in percentage by mass: 0.95 to 1.03wt.% of C, 0.80 to 1.20wt.% of Si, 0.20 to 0.50wt.% of Mn, 7.80 to 8.30wt.% of Cr, 2.00 to 2.80wt.% of Mo, 0.25 to 0.40wt.% of V, the balance of Fe and unavoidable impurities, more preferably 0.96 to 1.00wt.% of C, 0.92 to 1.00wt.% of Si, 0.39 to 0.45wt.% of Mn, 7.90 to 8.10wt.% of Cr, 2.17 to 2.50wt.% of Mo, 0.31 to 0.35wt.% of V, and the balance of Fe and unavoidable impurities.

The invention has no special requirement on the mixing, and can be carried out in a conventional mode in the field.

In the present invention, the smelting furnace is preferably an arc furnace or a line-frequency induction smelting furnace, and more preferably an arc furnace. The invention has no special requirement on the smelting temperature, and the raw materials can be completely melted. In the present invention, the raw material is preferably pig iron or scrap, more preferably scrap.

The invention preferably performs oxygen blowing fluxing in the smelting process, and the oxygen blowing fluxing mode preferably comprises furnace door oxygen lances and furnace wall multifunctional oxygen lances.

The invention preferably also comprises foaming slag, oxygen blowing decarburization and low-temperature dephosphorization in the smelting process. The invention has no special requirements on the foam-making slag, oxygen-blowing decarburization and low-temperature dephosphorization, and can be realized by adopting a conventional mode in the field.

After the molten liquid is obtained, the molten liquid and the alloy are mixed and sequentially subjected to alloying, LF refining and VD degassing treatment to obtain molten steel. In the present invention, the alloy is preferably one or more of ferromolybdenum, ferrovanadium and high carbon ferrochrome, more preferably ferrovanadium and high carbon ferrochrome. The present invention preferably mixes the alloy and the melt during transfer of the melt to the ladle (tapping). In the present invention, the alloying process preferably further includes: and (3) deoxidizing the alloying system. In the invention, aluminum is preferably added into the molten steel in the tapping process for deoxidization; the aluminum is preferably an aluminum block. The invention has no special requirement on the addition amount of the aluminum, and the aluminum can be added according to the conventional mode in the field. In the present invention, lime is preferably added to the melt at the end of tapping, and the amount of lime added is preferably 400 to 600kg, more preferably 450 to 500kg. The invention preferably maintains argon blowing into the melt during tapping. The invention can ensure the uniformity of components and stable temperature in the melt system by blowing argon. In the invention, 30-40 tons of steel is preferably left in the smelting furnace after tapping so as to ensure that the oxidizing slag does not enter the ladle.

In the present invention, the LF refining process preferably includes deoxygenation; the deoxidation preferably comprises precipitation deoxidation and/or diffusion deoxidation. The invention preferably adopts a submerged arc mode for deoxidation. The invention preferably feeds aluminum wires in the earlier stage of LF refining, and also preferably adds refining slag formers into the ladle. In the LF refining process, argon is preferably blown into the bottom of the ladle. In the invention, the flow of argon blowing is higher in the early carburetion and alloy adjustment process, the temperature is uniform in the middle and later stages, the component is uniform, the temperature is reduced in the process, the flow of argon is controlled to be higher again before the steel ladle is discharged, the uniformity of temperature and component is ensured, and the floating removal of gas and inclusion is promoted. In the invention, the time of the white slag in the LF refining process is preferably not less than 30min, more preferably 35-40 min.

In the present invention, the VD degassing treatment is preferably VD vacuum degassing. The vacuum degree and argon flow rate of the VD vacuum degassing are preferably dynamically controlled to avoid slag overflow. The invention has no special requirements on the vacuum degree and the argon flow, and can be realized by adopting a conventional mode in the field. In the invention, when the ultimate vacuum degree of the VD vacuum degassing is less than 67Pa, the flow rate of argon is preferably increased, and the degassing effect is ensured. In the present invention, the holding time of the VD vacuum degassing at the ultimate vacuum is preferably not less than 20 minutes, more preferably 25 to 30 minutes. In the present invention, the soft argon blowing time after vacuum is preferably not less than 20 minutes. The invention preferably detects the components of the liquid in the steel ladle after soft argon blowing, and carries out subsequent continuous casting after the components of the liquid in the steel ladle are qualified.

After molten steel is obtained, the invention carries out continuous casting on the molten steel to obtain a continuous casting blank. In the present invention, the shape of the continuous casting slab is preferably a rectangular parallelepiped. In the present invention, the dimensions of the cross section of the rectangular parallelepiped are preferably 100mm to 180mm×300mm to 750mm, more preferably 150mm to 170mm×400mm to 530mm.

In the present invention, the drawing speed of the continuous casting is preferably 0.60 to 1.0m/min, more preferably 0.75 to 0.90m/min.

In the invention, the continuous casting crystallizer in continuous casting is non-sinusoidal vibration, and the frequency of the non-sinusoidal vibration is preferably 80-180 times/min, more preferably 120-140 times/min. In the present invention, the amplitude of the non-sinusoidal vibration is preferably 3.0 to 6.0mm, more preferably 4.0 to 5.0mm. The invention preferably utilizes an automatic liquid level control device to detect the vortex liquid level, and ensures that the fluctuation of the liquid level of the crystallizer is not more than +/-3 mm. The invention preferably carries out electromagnetic stirring in a crystallizer.

In the invention, the secondary cooling in the continuous casting process adopts weak cooling, and the specific water quantity of the weak cooling is preferably 0.10-0.18L/kg, more preferably 0.12-0.14L/kg. In the invention, the weak cooling is adopted for the secondary cooling, so that the stress generated in the cooling process can be reduced, and the cracking is avoided. The invention preferably performs electromagnetic stirring in a secondary cooling zone, and the electromagnetic stirring is preferably roller type electromagnetic stirring. In the invention, the secondary cooling zone roller type electromagnetic stirring mode is preferably forward and backward rotation, the forward rotation time in the forward and backward rotation process is preferably 15s, and the reverse rotation time is preferably 5s. The invention controls the withdrawal and straightening temperature of continuous casting by controlling the secondary cooling intensity and the withdrawal speed, and simultaneously ensures the internal quality and the surface quality of the casting blank.

In the invention, molten steel enters a continuous casting tundish through a sealed water gap, and the molten steel surface is sealed by a tundish covering agent; molten steel flows into a continuous casting crystallizer through a submerged nozzle, the liquid surface of the crystallizer is covered with special casting powder, and the molten steel is quickly solidified in the water-cooling crystallizer to form a blank shell. In the invention, the whole continuous casting process is protected and poured, the tundish adopts an integral water gap, and the ladle adopts a long water gap sealing ring and argon blowing protection.

In the invention, the continuous casting device is preferably a two-machine two-strand vertical-bending continuous casting machine with an arc radius of 6.5 m.

After a continuous casting blank is obtained, the continuous casting blank is subjected to primary rolling and annealing treatment in sequence, and the DC53 steel is obtained. The means of transferring the continuous casting slab to a hot rolling device according to the invention preferably comprises hot or slow cooling, more preferably hot. In the invention, the heat preservation temperature of the heat transfer is preferably 1170-1190 ℃, more preferably 1185 ℃; the heat-retaining time of the heat transfer is preferably 1.8 to 2.2 hours, more preferably 2 hours. The invention preferably employs a step-wise heating furnace, preferably 30000mm in effective length, to provide the hot air temperature, and preferably a single row of steps.

In the invention, annealing is preferably further included after the slow cooling, and the annealing temperature is preferably 860-880 ℃, more preferably 865-870 ℃; the holding time of the annealing is preferably 4 to 8 hours, more preferably 5 to 7 hours.

In the present invention, the primary rolling preferably includes rough rolling and finish rolling which are sequentially performed. In the invention, the initial rolling temperature of the primary rolling is preferably 1050-1150 ℃, more preferably 1050-1100 ℃; the crude finishing temperature is preferably above 950 ℃, more preferably 960-980 ℃; the finish rolling temperature of the finish rolling is preferably higher than 880 ℃, more preferably 900 to 910 ℃. In the present invention, the number of passes of the first pass rolling is preferably 10 to 20, more preferably 12 to 14. In the present invention, the single pass deformation amount is preferably 10 to 15%, more preferably 12 to 15%.

In the invention, the rolling mill for primary rolling is preferably a 950 vertical flat roll reversible rolling mill, the power of a main motor of the rolling mill is 4000kW, the diameter of a group of flat rolls is 920-980 mm, the length of the roll body is 900mm, the maximum rolling pressure is 15000kN, the rolling speed is 10-20 mm/s, and the diameter of a group of vertical rolls is phi 850mm.

In the invention, the primary rolling process preferably further comprises high-pressure water dephosphorization, wherein the pressure of the high-pressure water dephosphorization is preferably 30-35 MPa, more preferably 32-34 MPa.

In the present invention, the annealing treatment temperature is preferably 860 to 880 ℃, more preferably 865 to 875 ℃; the heat-retaining time of the annealing treatment is preferably 4 to 8 hours, more preferably 4 to 6 hours.

In the present invention, the annealing treatment preferably further comprises: cooling the annealed product, wherein the temperature after cooling is preferably below 650 ℃, more preferably 550-600 ℃; the cooling is preferably furnace-wise cooling.

The invention preferably carries out finishing line treatment on the cooled DC53 steel, and specifically comprises a feeding machine, leveling, online flaw detection, surface inspection, automatic sawing, mark spraying, weighing and collecting and warehousing.

In the present invention, the thickness of the DC53 steel is preferably 10 to 50mm, more preferably 15 to 45mm.

The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.

Example 1

The DC53 steel comprises the following element components in percentage by mass: 0.96wt.% of c, 0.92wt.% of si, 0.39wt.% of mn, 8.10wt.% of cr, 2.17wt.% of mo, 0.31wt.% of v, the balance being Fe and unavoidable impurities;

the preparation method for preparing the DC53 flat steel with high efficiency and energy conservation comprises the following steps:

step 1, preparing raw materials and preparing corresponding alloys according to the chemical components of the DC53 steel;

step 2, adding raw materials into an arc furnace with nominal capacity of 90 tons through a horizontal feeding system, adding alloy for alloying when the electric furnace is used for tapping, and refining molten steel through an LF furnace and carrying out VD vacuum degassing treatment; the electric arc furnace adopts an oxygen lance of a furnace door and a multifunctional oxygen lance of a furnace wall to blow oxygen to promote smelting, foam slag is produced in the whole process, oxygen is blown to decarbonize, the temperature is lower than Wen Tuolin, steel is tapped from the electric arc furnace to leave 30 tons of steel, oxidizing slag cannot enter a ladle, alloying is added in the tapping process, aluminum blocks are added for deoxidization, and 450kg of lime is added in the final tapping stage; after tapping, adding molten ferromolybdenum, ferrovanadium and high-carbon ferrochromium alloy materials into a ladle, and blowing argon in the whole process to ensure uniform components and stable temperature; the addition amount of the earlier-stage alloy of the DC53 steel is large, the steel ladle is rapidly powered on, slagging and determining the original components after entering a station, the earlier-stage aluminum wire feeding is carried out, and refining slag is added; the flow of argon blown from the bottom of the ladle is higher in the early carburetion and alloy adjustment process, the temperature is uniform in the middle and later stages, the component is reduced in the process of uniform composition, the flow of argon is controlled to be higher again before the ladle is out of the station, the uniformity of temperature and components is ensured, and the floating removal of gas and inclusion is promoted; the whole process adopts aluminum powder, carbon powder and calcium carbide to carry out diffusion deoxidation, submerged arc operation is carried out, and the white slag time is 35min; when the VD is carried out in vacuum degassing, the vacuum degree and the argon flow are dynamically controlled, so that slag overflow is avoided; when the vacuum degree is not more than 67Pa, the argon flow is increased, and the degassing effect is ensured; the ultimate vacuum time is 25min, and the soft argon blowing time after vacuum is 25min, so that the floating of the inclusions is promoted; after the detected components are qualified, entering a continuous casting process, wherein the tapping temperature of molten steel is 1480 ℃;

step 3, continuously casting the molten steel by using a two-machine two-strand vertical-bending continuous casting machine with the model of the continuous casting machine being the arc radius of 6.5m to obtain a cuboid continuous casting billet; baking the continuous casting tundish (baking time is 5h, and the tundish temperature reaches 1450+/-10 ℃); argon sealing is adopted for the ladle long nozzle, and a covering agent is added in continuous casting; covering the liquid level of the crystallizer with special covering slag; the section size of the casting blank is 150mm multiplied by 530mm, and the continuous casting drawing speed is 0.75m/min; the eddy current is adopted to detect the liquid level, the liquid level control is automatic, and the fluctuation of the liquid level of the crystallizer is not more than +/-3 mm; the continuous casting crystallizer (combined copper plate crystallizer) is non-sinusoidal vibration, the frequency is 140 times/min, and the amplitude is 4.0mm; roll-type electromagnetic stirring in the secondary cooling zone (current is 350A, frequency is 7 Hz); the whole continuous casting process is protected and poured, the tundish adopts an integral water gap, and the ladle adopts a long water gap sealing ring and argon blowing protection; the secondary cooling of continuous casting adopts weak cooling, and the specific water quantity is 0.12L/kg; the two-cooling-section roller type electromagnetic stirring mode is positive and negative rotation, the positive rotation time is 15s, the reverse rotation time is 5s, and the positive rotation and the reverse rotation are circularly carried out;

step 4, hot-feeding the cuboid continuous casting billet of the DC53 steel to a rolling mill heating furnace, wherein the heating temperature is 1185 ℃, and soaking is carried out for 2 hours;

step 5, performing primary rolling (rough rolling and finish rolling) on the cuboid continuous casting blank of the DC53 steel, wherein the initial rolling temperature is 1050 ℃, the final rolling temperature of rough rolling is 960 ℃, the final rolling temperature of finish rolling is 910 ℃, the dephosphorization pressure of high-pressure water is 32.0MPa, and the single-pass deformation is 1.5%; rolling the cuboid continuous casting blank into DC53 steel with the thickness of 18mm through 12 times;

step 6, annealing the DC53 steel subjected to primary rolling; the annealing process temperature is 870+/-5 ℃, after the heat preservation is carried out for 4 hours, the annealing process temperature is cooled to 650 ℃ along with the furnace and is discharged from the furnace; the rolling DC53 steel is annealed and then is treated by a special finishing line, and a feeding machine, leveling, online flaw detection, surface inspection, automatic sawing, mark spraying, weighing and collecting and warehousing are carried out.

The center porosity grade and center segregation grade of DC53 continuous casting billets and DC53 steel are detected according to GB/T226-2015 steel macrostructure and defect acid etching test method. The results were as follows: the center loosening grade of the DC53 flat steel continuous casting blank is 1.0 grade, and the center segregation grade is 2.0 grade; the core had primary carbide clusters. The center porosity grade of the DC53 steel macrostructure is 0.5 grade, and the center segregation grade is 0.5 grade; the primary carbides of the core are uniformly distributed. The DC53 steel obtained by the preparation method provided by the invention has good quality.

Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.

Claims (10)

1. A preparation method for preparing DC53 flat steel with high efficiency and energy saving comprises the following steps:

smelting raw materials according to the element proportion of DC53 steel to obtain a melt;

mixing the molten liquid and the alloy, and sequentially carrying out alloying, LF refining and VD degassing treatment to obtain molten steel;

continuously casting the molten steel to obtain a continuous casting blank;

and sequentially carrying out primary rolling and annealing treatment on the continuous casting billet to obtain the DC53 steel.

2. The method according to claim 1, wherein the continuous casting drawing speed is 0.60 to 1.00m/min.

3. The production method according to claim 1 or 2, wherein the continuous casting mold in continuous casting is non-sinusoidal vibration, the frequency of the non-sinusoidal vibration is 80 to 180 times/min, and the amplitude of the non-sinusoidal vibration is 3.0 to 6.0mm.

4. The method according to claim 3, wherein the secondary cooling in the continuous casting process is weak cooling, and the specific water content of the weak cooling is 0.10-0.18L/kg.

5. The method according to claim 1, wherein the first hot rolling includes rough rolling and finish rolling performed sequentially.

6. The method according to claim 5, wherein the initial rolling temperature of the primary rolling is 1050 to 1150 ℃, the final rolling temperature of the rough rolling is higher than 950 ℃, and the final rolling temperature of the finish rolling is higher than 880 ℃.

7. The method according to claim 1,5 or 6, wherein the number of passes of the one-pass rolling is 10 to 20, and the single-pass deformation is 10 to 15%.

8. The method of claim 1, wherein transferring the continuous casting to a hot rolling apparatus comprises hot or slow cooling.

9. The method according to claim 1, wherein the annealing treatment is carried out at 860 to 880 ℃ for 4 to 8 hours.

10. The preparation method according to claim 1, wherein the DC53 steel comprises the following elemental components in percentage by mass: 0.95 to 1.03wt.% of C, 0.80 to 1.20wt.% of Si, 0.20 to 0.50wt.% of Mn, 7.80 to 8.30wt.% of Cr, 2.00 to 2.80wt.% of Mo, 0.25 to 0.40wt.% of V, and the balance of Fe and unavoidable impurities.