CN113502434A

CN113502434A - Aviation 30CrMnSiNi2A high-strength steel and production method thereof

Info

Publication number: CN113502434A
Application number: CN202110610847.1A
Authority: CN
Inventors: 马恒春; 姚忠; 张振民; 杨勇; 冶廷全; 尚大军; 鲁延明; 芦晓雪; 江海滨
Original assignee: XINING SPECIAL STEEL CO Ltd; Qinghai Xigang Special Steel Technology Development Co ltd
Current assignee: XINING SPECIAL STEEL CO Ltd; Qinghai Xigang Special Steel Technology Development Co ltd
Priority date: 2021-06-01
Filing date: 2021-06-01
Publication date: 2021-10-15
Anticipated expiration: 2041-06-01
Also published as: CN113502434B

Abstract

The invention provides aviation 30CrMnSiNi2A high-strength steel and a production method thereof; the aviation 30CrMnSiNi2A high-strength steel comprises the following chemical components in percentage by weight: c: 0.27 to 0.34, Si: 0.90-1.20, Mn: 1.00-1.30, Cr: 0.90-1.20, Ni: 1.40-1.80, Al: 0.015 to 0.03, Mo: 0.02 to 0.03, V: 0.02 to 0.03, Ti: 0.015 to 0.025, W: 0.15-0.2, P is less than or equal to 0.012, S is less than or equal to 0.01, and the balance is Fe. According to the aviation 30CrMnSiNi2A high-strength steel and the production method, the smelting process of electric furnace die casting, external refining and electroslag remelting which is adopted all the time abroad is completely replaced by electric furnace continuous casting, external refining and electroslag remelting, so that the material structure performance and the fatigue performance are obviously improved. The method can be used for batch, systematic and energy-saving production, and energy and cost are saved obviously.

Description

Aviation 30CrMnSiNi2A high-strength steel and production method thereof

Technical Field

The invention belongs to the technical field of metal materials; in particular to aviation 30CrMnSiNi2A high-strength steel and a production method thereof.

Background

With the rapid development of the aerospace industry technology in China, the requirements on the impact resistance, the fatigue resistance, the toughness and the plasticity of the steel for the aircraft landing gear in the aerospace field are strict. At present, the landing gear of airliners and partial military aircraft which are universally used internationally and in China are made of high-strength steel 30CrMnSiNi2A, and with the rapid development of the aviation industry and the national defense industry in China, the demand of high-strength steel 30CrMnSiNi2A steel is greatly increased. The batch and stable production puts higher requirements on the production process technology of the steel.

For 30CrMnSiNi2A steel for landing gear, because the steel has characteristics and is easy to have transverse crack and longitudinal crack defects in the production process, the smelting process of electric furnace die casting, external refining and electroslag remelting is always adopted abroad; the process can not be used for batch, systematic and energy-saving production, and wastes energy and cost greatly, so that the process for producing the high-strength steel 30CrMnSiNi2A by adopting the smelting process of electric furnace continuous casting, external refining and electroslag remelting becomes a key link and development trend breaking through in the material technology.

In order to solve the problems that the existing material is easy to have transverse crack and longitudinal crack defects in the production process, the mass, systematic and energy-saving production cannot be carried out, and the waste of energy and cost is large, the 30CrMnSiNi2A high-strength steel continuous casting electrode blank electroslag remelting steel for aviation and the production method thereof need to be designed, developed and developed, so that the product performance is stable, the fatigue performance is good, the quality of an object reaches the international advanced level, the international and domestic die casting electrode blank production process mode of the steel is broken through, and the competitiveness of the product in the domestic market is greatly improved.

Disclosure of Invention

The invention aims to provide aviation 30CrMnSiNi2A high-strength steel and a production method thereof.

The invention is realized by the following technical scheme:

the invention relates to aviation 30CrMnSiNi2A high-strength steel which comprises the following chemical components in percentage by weight: c: 0.27 to 0.34, Si: 0.90-1.20, Mn: 1.00-1.30, Cr: 0.90-1.20, Ni: 1.40-1.80, Al: 0.015 to 0.03, Mo: 0.02 to 0.03, V: 0.02 to 0.03, Ti: 0.015 to 0.025, W: 0.15 to 0.2 percent of the total weight of the alloy, less than or equal to 0.012 percent of P, less than or equal to 0.01 percent of S and the balance of Fe.

The invention also relates to a production method of the aviation 30CrMnSiNi2A high-strength steel, which comprises ten steps of primary smelting in a Consteel electric furnace, LF refining, VD vacuum degassing, weak argon operation, continuous casting and pouring, pit-entering heat preservation and stress relief annealing of a continuous casting billet, electroslag remelting and stress relief annealing of an electroslag ingot, heating and cogging of the electroslag ingot, process billet heating, continuous rolling and heat preservation and annealing. The method specifically comprises the following steps:

(1) initial smelting of Consteel electric furnace

The steelmaking raw material consists of blast furnace molten iron and returned scrap steel containing low phosphorus, smelting and slagging are carried out at 1510-1540 ℃ after full melting in the initial smelting stage, and P removal reaction at lower temperature is utilized to facilitate generation of P in the forward and reverse reaction directions₂O₅P can be effectively removed when the steel enters the slag, so that the influence of phosphorus embrittlement on the quality of the steel in the later period is avoided, and the sensitivity of subsequent cracks of the steel is reduced; the temperature in the furnace after the full melting is more than 1560 ℃, an oxygen supply system is controlled to carry out effective C, O reaction in the furnace, the temperature in the furnace is increased, and the decarburization and the desulfurization reaction are carried out simultaneously; wherein, the electric furnace slag charge mainly comprises lime and dolomite, and is added in batches; the dosage of each batch of feeding is as follows: 500-800 Kg of lime, 200-400 Kg of dolomite and 50-80 Kg of total slag charge per ton;

when the electric furnace finishes smelting and tapping, an eccentric bottom tapping mode is adopted, in order to prevent the electric furnace from slagging, the steel retaining quantity in the furnace is required to be more than or equal to 40 tons, the tapping time is more than or equal to 120s, the steel tapping quantity is 60 +/-5 tons, and the tapping temperature is more than or equal to 1620 ℃; the proportion and the dosage of the ladle slag charge during tapping are as follows: 600 plus or minus 50Kg of lime, 100 plus or minus 10Kg of composite deoxidizer and 200Kg of pre-melted slag, wherein the addition amount of pre-deoxidized Al is 1.5Kg/t of pure aluminum, and the total slag amount is as follows: 1000Kg to 1200 Kg;

the addition amount of the tapping alloy is calculated according to the tapping amount and the requirement of internal control components, wherein the added alloy elements are low-carbon ferrochrome, ferromanganese, ferrosilicon, nickel plates and pure aluminum plus steel core aluminum, the components of the electric furnace tapping endpoint are controlled to be more than or equal to 0.06 percent and P is less than or equal to 0.012 percent, and the content of the residual harmful elements meets the requirement of internal control.

(2) LF refining

The temperature of the molten steel entering an LF refining station is more than or equal to 1500 ℃, and the time from the end of tapping to the entering of the refining station is controlled within 15 minutes; heating for more than or equal to 10 minutes by power supply, and then, sampling and analyzing chemical components, and properly adding required alloy elements in batches according to the chemical components to adjust the components; argon control in the refining process: the flow rate is 100 to 400 NL/min. According to the slag condition of the LF station, 0-100Kg of lime and 0-50 Kg of fluorite can be properly added according to the content of phosphorus and sulfur in steel, the slag condition and the like, and slag can not be added except the process specification. Slag system target component: CaO: 50% -58%, SiO 2: 10% -15%, MgO: 3% -6%, Al2O 3: 18 to 25 percent.

Controlling aluminum in the refining process: when the alloy enters an LF refining station, the Al content is required to be 0.020-0.030%; if the content of aluminum is low at the LF station, a wire feeder can be used for feeding aluminum wires to adjust the aluminum component according to the internal control requirement or the content of the Al is not between 0.020 and 0.030 percent, the Al is fed once according to the target of 0.030 percent in the early stage of LF refining, and the aim of complete deoxidation is fulfilled. After VD, if the Al content in the steel is serious (more than or equal to 50 percent), Al is adjusted to 0.020-0.030 percent by adopting a wire feeding mode;

the refining is finished by requiring that the chemical components of the molten steel reach the following internal control ranges: c: 0.29 to 0.31%, Si: 1.00-1.10%, Mn: 1.10-1.20%, Cr: 1.00-1.10%, Ni: 1.50-1.65%, Al: 0.015 to 0.030%, Mo: 0.02-0.03%.

(3) VD vacuum degassing

And after the refining of the LF furnace is finished, carrying out vacuum VD (vacuum degassing) operation on the molten steel, and carrying out degassing operation when the temperature of the molten steel is required to be 1630-1650 ℃. The medium before VD degassing meets the conditions: the water pressure is more than or equal to 0.5MPa, the water temperature is less than or equal to 30 ℃, the steam pressure is more than or equal to 0.8MPa, and the steam temperature is more than or equal to 180 ℃. And controlling the flow of argon in the VD process: the coarse vacuum (200 torr) period is controlled according to 50-100NL/min, the extreme vacuum period is controlled according to 150-200NL/min, and proper adjustment can be made according to air permeability to ensure that the slag surface is 200-300 mm. Controlling the pressure 2-3 min before the air break according to 50-150NL/min, adjusting to the weak argon standard, enabling the slag surface to creep, and not exposing molten steel.

(4) Weak argon operation

After all the element components of the molten steel meet the internal control requirement, weak argon operation is carried out according to the process so as to further homogenize the components of the molten steel and remove impurities, harmful gases, impurities and the like. In the weak argon process, the main blowing flow rate of argon is required to be 50-150NL/min, the auxiliary blowing flow rate is required to be 30-50NL/min, the slag surface creeps, and molten steel is not exposed. The weak argon time is required to be more than or equal to 20min on the premise of meeting the casting temperature of the ladle molten steel.

(5) Continuous casting

After the weak argon is finished, the temperature of the molten steel reaches 1560-1580 ℃ by a first ladle; and when the continuous casting ladle reaches 1545-1565 ℃, hanging the continuous casting ladle into a continuous casting machine for continuous casting, so as to obtain a semi-finished casting blank with lower gas content and endogenous inclusions meeting the standard requirement of high-quality steel.

(6) Continuous casting blank pit-entering heat preservation and stress relief annealing

Cutting the length of the continuous casting billet according to the billet lifting requirement; pit cooling requirements of a 250 x 280mm continuous casting billet: and (3) timely putting the cut continuous casting billets into a pit for slow cooling after cutting, ensuring that the temperature of the continuous casting billets entering the pit is more than or equal to 700 ℃, and the slow cooling time of the casting billets is more than 36 hours, and executing according to the existing hot delivery annealing management regulations (trial). The stress relief annealing process curve is shown in fig. 2.

(7) Electroslag remelting process and electroslag ingot stress relief annealing

The prior 250mm multiplied by 280mm continuous casting billet is adopted to carry out electroslag remelting to produce a phi 470mm ingot. The slag system proportion of the electroslag furnace is as follows: the electroslag remelting slag system adopts quaternary slag (CaF)₂：60％、Al₂O₃: 30%, CaO: 8%, MgO: 2%). Controlling the electroslag remelting process: the electroslag remelting process adopts the smelting production of a common electroslag furnace, and the dosage of the deoxidizer is determined according to the components of an electrode blank and the requirements of a finished product, and the deoxidizer is added uniformly in batches in the required process; controlling the constant melting speed in the smelting process, wherein the melting speed is controlled to be 6.0kg +/-0.5 kg/min, and the cooling water temperature is as follows: 40-55 ℃. The stress relief annealing process is shown in fig. 3.

(8) Heating cogging of electroslag ingot

The process parameters are controlled as follows: the temperature of the electroslag ingot is required to be less than or equal to 500 ℃ when the electroslag ingot is fed into the furnace, the temperature is equalized for 1-2 hours after the electroslag ingot is fed into the furnace, the temperature is increased, the air quantity is reduced in the preheating stage of 500-800 ℃, and the temperature equalizing time of the ingot with the diameter of 470mm is controlled according to 1-1.5 hours. When heating, the high temperature is strictly forbidden, the curve identification temperature is the actual steel ingot temperature, and the deviation between the steel temperature and the furnace temperature is 20-80 ℃. The start rolling temperature of the electroslag ingot is as follows: 1100-1150 deg.c and finishing temperature not lower than 950 deg.c. Controlling the blank to be 240mm multiplied by 240mm in length 5300-5900 mm in the process of rolling and opening the phi 470mm electroslag ingot, wherein the size deviation is +/-5 mm, and the length deviation is +/-30 mm; and (4) after cogging, putting the square billet into a pit in time, slowly cooling and preserving heat for more than or equal to 48 hours.

(9) Process blank heating, continuous rolling and heat preservation

The heating process of the process blank is controlled in such a way that the temperature of the preheating section is less than or equal to 850 ℃, the temperature of the heating section is 1100-; the total heating time of the continuous casting billet is more than or equal to 4 hours, and the high-temperature diffusion time is more than or equal to 2.0 hours;

and (3) water descaling control in the rolling process: carrying out two times of water spraying descaling to reduce the surface temperature of a square billet with the diameter of 240mm to 240mm by 50-80 ℃, forming a water descaling pressure with the non-uniform temperature gradient distribution of the cross section of the square billet of 20-25Mpa, the dephosphorization effect is not less than 95%, the initial rolling temperature is 1030-1120 ℃, the final rolling temperature is not less than 850 ℃, collecting steel by a fast bed and then placing the steel in a cooling bed, then timely placing the steel in a heat preservation pit for heat preservation, wherein the temperature of the steel in the pit is not less than 400 ℃, the heat preservation time is not less than 24 hours, and the temperature of the steel out of the pit is not more than 150 ℃;

(10) annealing

Annealing the continuously rolled steel by using a continuous annealing furnace to prepare the high-quality 30CrMnSiNi2A high-strength steel for aviation, and putting the steel into the annealing furnace for heat treatment within 8 hours after heat preservation, wherein the annealing temperature is as follows: 720 +/-10 ℃, roll speed: 4.0m/h, and adopts a 14-zone staged continuous annealing furnace for temperature control annealing, wherein the annealing temperature range is 600-720 ℃.

The design principle of the method comprises the following three aspects:

firstly, the method comprises the following steps: the method adopts low-P and Mo, V, Ti and Al composite microalloying design that slagging is carried out at 1510 ℃ and 1550 ℃ in the melting period, the P removing reaction is utilized to be beneficial to carrying out effective P removing at a favorable time in the positive reaction direction at a lower temperature, and metal Mn is adopted to replace low-carbon ferromanganese in the smelting process to further inhibit the increase of P in molten steel in the LF refining process. Reasonably controlling the addition of Mo, V, Ti, Al and other elements to raise the coarsening temperature of the steel crystal grains, effectively delaying and inhibiting the growth trend of the steel crystal grains by adding a small amount of Mo, V, Ti and Al (the addition of Mo and V is more appropriate when being 0.02-0.03 percent, the addition of Ti is more appropriate when being 0.015-0.025 percent and the addition of Al is more appropriate), enabling the steel to have ultrafine crystal grains and preventing the quality defects of transverse cracks and longitudinal cracks of steel ingots.

Secondly, the method comprises the following steps: designing the technologies of electroslag remelting high-strength steel clean smelting and the like. Optimizing an electrode blank: stress relief annealing heat treatment control of the electrode blank (the continuous casting electrode blank is put into an annealing furnace to be heated to 740-760 ℃ for stress relief annealing), and shot blasting treatment of the surface of the electrode blank; reasonably selecting a filling ratio: the reasonable electroslag remelting filling ratio is controlled to be 0.20-0.60, and a continuous casting electrode blank is reasonably selected and matched by our company according to the current equipment level, so that the filling ratio is kept in the reasonable control range of 0.23-0.52, and the electroslag remelting quality and the production efficiency are ensured; thirdly, electroslag remelting slag system development and special deoxidizer addition control: the method combines high-purity remelting and purifying slag independently developed by our company with original 'ternary slag' and 'quaternary slag', and finally determines slag system selection and slag amount control under the actual inspection condition of inclusions in steel subjected to electroslag remelting under different slag amounts; meanwhile, the adding amount of special deoxidizer is controlled in the electroslag remelting process so as to ensure the surface quality of the electroslag ingot.

Thirdly, the method comprises the following steps: an oxygen content control technology for electroslag remelting high-strength steel. In order to effectively control the oxygen content in the electroslag ingot, a deoxidizer is used for carrying out final deoxidation on the consumable electrode, treating the surface of the consumable electrode, strictly controlling the content of unstable oxides in slag and reducing the oxygen content in the atmosphere in the electroslag remelting process.

Firstly, continuous casting electrode blanks are adopted to replace die casting forged electrode blanks, and meanwhile, surface shot blasting treatment is carried out on the electrode blanks to remove surface iron oxide scales. Compared with a die casting electrode blank, the casting mode of the continuous casting electrode blank has the advantages that the equipment adopted in the production process is more advanced, the contact with the atmosphere is less, and the gas argon protection effect is good, so that the oxygen content of the original electrode blank is lower;

the oxygen in the atmosphere in the electroslag remelting process refers to the oxygen in the atmosphere above a slag pool, and is always regarded as an important source of the oxygen in the electroslag remelting process.

The practice of experimental production and small-batch formal test production shows that the effect of electroslag remelting under the protection of inert gas is remarkable, the oxygen content of steel can reach below 19PPm, and the average oxygen content can be reduced by about 30% compared with that of the steel smelted by the common process.

The invention has the following advantages:

firstly, the aviation 30CrMnSiNi2A high-strength steel and the production method thereof design the physical proportion of molybdenum, vanadium, titanium and aluminum, can effectively delay and inhibit the growth trend of steel grains, enable the steel to have ultrafine grains, and prevent the quality defects of transverse cracks and longitudinal cracks of steel ingots. The specific parameters are Mo: 0.02 to 0.03, V: 0.02 to 0.03, Ti: 0.015 to 0.025, Al: 0.015 to 0.03.

Secondly, the 30CrMnSiNi2A high-strength steel for aviation and the production method thereof adopt a new independently developed technology of smelting high-purity remelting and purifying slag, combine with the existing external refining and vacuum degassing technology, and actively control the content of harmful elements in the steel, so that the content of the harmful elements in the 30CrMnSiNi2A steel is greatly reduced, steel cracks caused by cold brittleness are avoided, and the P content can reach the level of 0.012 percent and is far lower than the standard specification.

Thirdly, the 30CrMnSiNi2A high-strength steel for aviation and the production method thereof adopt an electroslag remelting high-strength steel inclusion control technology to improve the quality continuity and compactness of a steel substrate. The method for secondary purification and refining of the consumable electrode blank utilizes resistance heat generated when current passes through slag as a heat source. The inclusion control level is remarkably improved by researching the optimization treatment of electrode blanks, the design of an electric power system, the selection of a reasonable filling ratio, the development of an electroslag remelting slag system, the control of the addition amount of a special deoxidizer and the like, so that the surface quality of an electroslag ingot is ensured.

In order to effectively control the oxygen content in the electroslag ingot, the aviation 30CrMnSiNi2A high-strength steel uses a deoxidizer to carry out final deoxidation on the consumable electrode, treats the surface of the consumable electrode, strictly controls the content of unstable oxides in slag, and reduces the oxygen content in the atmosphere in the electroslag remelting process. Effectively avoiding the situation that the material strength, toughness, compactness and the like of the steel are greatly reduced due to the over-high oxygen content. Practice shows that the inert gas protection electroslag remelting effect is remarkable, the oxygen content of steel can reach below 25PPm and is 9.8PPm at the lowest, and the oxygen content can be reduced by about 30% compared with the average oxygen content value of smelting by a common process.

According to the aviation 30CrMnSiNi2A high-strength steel and the production method thereof, the effects of two-fire cogging steel, intermediate billet water descaling and 14-zone staged continuous annealing process are obvious, the surface quality of steel is improved, the rejection rate is reduced, and the effective cost is increased little.

According to the 30CrMnSiNi2A high-strength steel for aviation and the production method thereof, the smelting process of electric furnace die casting, external refining and electroslag remelting which is adopted all the time abroad is completely replaced by external refining, electric furnace continuous casting and electroslag remelting, so that the material structure performance and fatigue performance are obviously improved. The method can be used for batch, systematic and energy-saving production, and energy and cost are saved obviously.

Drawings

FIG. 1 is a structural view of a microstructure of 30CrMnSiNi2A high-strength steel for aviation according to the present invention;

FIG. 2 is a graph of a stress relief annealing process of a continuous casting slab in the process step of the present invention;

FIG. 3 is a graph of an electroslag remelting electroslag ingot stress relief annealing process in the process step of the present invention;

fig. 4 is a diagram of an annealing process involved in the comparative example.

Detailed Description

The present invention will be described in detail with reference to specific examples. It should be noted that the following examples are only illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

Example 1

The embodiment relates to aviation 30CrMnSiNi2A high-strength steel and a production method thereof, and the production method comprises ten steps of primary smelting in a Consteel electric furnace, LF refining, VD vacuum degassing, weak argon operation, continuous casting and pouring, continuous casting billet pit entry heat preservation and stress relief annealing, electroslag remelting and stress relief annealing of an electroslag ingot, electroslag ingot heating cogging, process billet heating, continuous rolling and heat preservation and annealing, and specifically comprises the following steps:

(1) initial smelting of Consteel electric furnace

(2) LF refining

The temperature of the molten steel entering an LF refining station is more than or equal to 1500 ℃, and the time from the end of tapping to the entering of the refining station is controlled within 15 minutes; heating for more than or equal to 10 minutes by power supply, and then, sampling and analyzing chemical components, and properly adding required alloy elements in batches according to the chemical components to adjust the components; argon control in the refining process:the flow rate is 100 to 400 NL/min. According to the slag condition of the LF station, 0-100Kg of lime and 0-50 Kg of fluorite can be properly added according to the content of phosphorus and sulfur in steel, the slag condition and the like, and slag can not be added except the process specification. Slag system target component: CaO: 50% -58% of SiO₂：10％-15％，MgO：3％-6％，Al₂O₃：18％-25％。

(3) VD vacuum degassing

And after the refining of the LF furnace is finished, carrying out vacuum VD (vacuum degassing) operation on the molten steel, and carrying out degassing operation when the temperature of the molten steel is required to be 1630-1650 ℃. The medium before VD degassing meets the conditions: the water pressure is more than or equal to 0.5MPa, the water temperature is less than or equal to 30 ℃, the steam pressure is more than or equal to 0.8MPa, and the steam temperature is more than or equal to 180 ℃. And controlling the flow of argon in the VD process: the coarse vacuum (>200 torr) period is controlled according to 50-100NL/min, the extreme vacuum period is controlled according to 150-200NL/min, and proper adjustment can be made according to air permeability to ensure that the slag surface is 200-300 mm. Controlling the pressure 2-3 min before the air break according to 50-150NL/min, adjusting to the weak argon standard, enabling the slag surface to creep, and not exposing molten steel.

(4) Weak argon operation

(5) Continuous casting

After the weak argon is finished, the temperature of the molten steel reaches 1560-1580 ℃ by a first ladle; and when the continuous casting ladle reaches 1545-1565 ℃, hanging the continuous casting ladle into a continuous casting machine for continuous casting, so as to obtain a semi-finished casting blank with lower gas content and endogenous inclusions meeting the standard requirement of high-quality steel, and the obtained semi-finished casting blank is shown in table 1.

TABLE 1

(6) Stress relief annealing of continuous casting billet

(7) Electroslag remelting process and electroslag ingot stress relief annealing

The prior 250mm multiplied by 280mm continuous casting billet is adopted to carry out electroslag remelting to produce a phi 470mm ingot. The slag system proportion of the electroslag furnace is as follows: the electroslag remelting slag system adopts quaternary slag (CaF260 percent and Al)₂O₃30%, CaO 8%, MgO 2%). Controlling the electroslag remelting process: the electroslag remelting process adopts a protective atmosphere electroslag furnace for smelting production, the dosage of a deoxidizing agent is determined according to the components of an electrode blank and the requirements of a finished product, and the deoxidizing agent is uniformly added in batches in the required process; controlling the constant melting speed in the smelting process, wherein the melting speed is controlled to be 6.0kg +/-0.5 kg/min, and the cooling water temperature is as follows: 40-55 ℃; the stress relief annealing process is shown in fig. 3.

(8) Heating cogging of electroslag ingot

(9) Process blank heating, continuous rolling and heat preservation

(10) annealing

Annealing the continuously rolled steel by using a continuous annealing furnace to prepare the high-quality 30CrMnSiNi2A high-strength steel for aviation, and putting the steel into the annealing furnace for heat treatment within 8 hours after heat preservation, wherein the annealing temperature is as follows: 720 +/-10 ℃, roll speed: 4.0m/h, and the layout of the continuous annealing furnace is 14-zone step-by-step continuous annealing, the annealing temperature range is 600-.

The temperature distribution of the 14-zone staged temperature-controlled annealing process in the step (7) is shown in table 2 below.

TABLE 2

The 30CrMnSiNi2A high-strength steel continuous casting electrode blank electroslag remelting steel for aviation prepared according to the steps comprises the following chemical components in percentage by weight: c: 0.29 to 0.31%, Si: 1.00-1.10%, Mn: 1.10-1.20%, Cr: 1.00-1.10%, Ni: 1.50-1.65%, Mo: 0.02-0.03%, V: 0.02 to 0.03%, Ti: 0.015 to 0.025%, Al: 0.015-0.030%, and the balance Fe.

Comparative example 1

Comparative example 1 relates to a production process of 30CrMnSiNi2A steel, which comprises the steps of carrying out primary EAF electric furnace + LF refining + VD vacuum degassing → casting 1225Kg, 610Kg electrode blank → electrode blank stacking and cooling → surface shot blasting treatment of secondary electrode blank → secondary electroslag remelting phi 470mm electroslag ingot → pit cooling, annealing → surface inspection and cleaning → steel rolling 750 unit starting process of 220mm × 220mm square blank (for small bar lines, length 5.3 m-5.9 m) → sub furnace head and tail management, head and tail and sampling hole cutting clean → pit cooling, inspection and cleaning → large bar lines, small bar lines rolling production material pit cooling and annealing. The main process flow and the production process are shown in the following table 3:

TABLE 3

Example 2

The aviation 30CrMnSiNi2A high-strength steel prepared in the embodiment 1 and the production method thereof are used for preparing 2-furnace aviation 30CrMnSiNi2A high-strength steel, wherein the furnace numbers are L19310117 and L19310118 respectively. The furnace 2 prepared by adopting the production method of the 30CrMnSiNi2A steel of the comparative example 1 is used for comparing 30CrMnSiNi2A steel, and the furnace numbers are L17X16286 and L17X16284 respectively. And (3) carrying out object inspection comparison on the 2-furnace 30CrMnSiNi2A steel prepared by the new method and the 2-furnace 30CrMnSiNi2A steel prepared by the old method, wherein the specific comparison items comprise: oxygen content, non-metallic inclusions, austenite grain level of rolling material, mechanical properties and microstructure.

(1) Gas content detection

The gas content testing method comprises the following steps: respectively taking 30CrMnSiNi2A steel products smelted in normal smelting furnaces with different furnace numbers, and detecting the oxygen content in the steel products.

Specific detection data are shown in table 4: the gas content in the 30CrMnSiNi2A molten steel is as follows:

TABLE 4

The average oxygen content of the 30CrMnSiNi2A high-strength steel continuous casting electrode blank electroslag remelting steel rolled material for aviation prepared in the embodiment 1 is 14.5ppm, the average oxygen content in the comparative example 1 is 21.5ppm, oxide inclusions in the steel are reduced after the oxygen content is reduced, the service life of the aircraft landing gear is greatly prolonged, and the technical advantage is obvious.

(2) Non-metallic inclusion detection

The non-metallic inclusion test method comprises the following steps: respectively taking 30CrMnSiNi2A steel products smelted in normal smelting furnaces with different furnace numbers, and detecting nonmetallic inclusions on the steel products.

Specific detection data are shown in table 5: and (3) detecting data of nonmetallic inclusions in 30CrMnSiNi2A high-strength steel for aviation.

TABLE 5

The cleanliness of the aviation 30CrMnSiNi2A high-strength steel continuous casting electrode blank electroslag remelting steel rolled material prepared in the embodiment 1 is higher than that of the rolled material of the comparative example 1, and is mainly reflected on B-type inclusions. The non-metallic inclusion control can well improve the cleanliness of the steel so as to improve the continuity of the steel matrix and reduce the cracking risk of the steel.

(3) Detection of actual grain grade of rolled stock

The actual grain size test method comprises the following steps: the actual grain size of 30CrMnSiNi2A steel materials smelted in normal smelting furnaces with different furnace numbers is detected and shown in Table 6: and (3) detecting actual grain size detection data of the 30CrMnSiNi2A high-strength steel for aviation.

TABLE 6

The detection shows that the actual grain size of the aeronautical 30CrMnSiNi2A high-strength steel rolled material obtained by the method is about 7.5 grade finer, and is shown in figure 1. Compared with the actual grain size of the aviation 30CrMnSiNi2A high-strength steel rolled material prepared by the method in the comparison ratio 1, the actual grain size is 1-1.5 grade higher, the higher the grain size grade is, the finer the grains are, the stronger the bonding force between grain boundaries is, and the strength plasticity of steel is further improved.

(4) Mechanical property detection

The mechanical property of the 30CrMnSiNi2A steel is tested, and the detection shows that the mechanical property of the aviation 30CrMnSiNi2A high-strength steel is better improved. Elongation after fracture a: 13.5-14%, face shrinkage Z: 53-55%, impact energy AKU: 106-110J, tensile strength Rm of 1733-1742 MPa, and specific detection data are shown in Table 7: the mechanical property of 30CrMnSiNi2A high-strength steel for aviation.

TABLE 7

According to the 30CrMnSiNi2A high-strength steel continuous casting electrode blank electroslag remelting steel for aviation and the production method thereof, the smelting process of electric furnace die casting, external refining and electroslag remelting which is adopted all the time abroad is completely replaced by electric furnace continuous casting, external refining and electroslag remelting, so that the improvement effects of the purity, the gas content, the grain size and the mechanical property of the material are obvious. The method can be used for batch, systematic and energy-saving production, and energy and cost are saved obviously.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims

1. The 30CrMnSiNi2A high-strength steel for aviation is characterized by comprising the following chemical components in percentage by weight:

C：0.27％～0.34％，

Si：0.90％～1.20％，

Mn：1.00％～1.30％，

Cr：0.90％～1.20％，

Ni：1.40％～1.80％，

Al：0.015％～0.03％，

Mo：0.02％～0.03％，

V：0.02％～0.03％，

Ti：0.015％～0.025％，

W：0.15％～0.2％，

P≤0.012％，

S≤0.01％，

the balance being Fe.

2. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 1, characterized by comprising the following steps: initial smelting in a Consteel electric furnace, LF refining, VD vacuum degassing, weak argon operation, continuous casting and pouring, pit-entering heat preservation and stress relief annealing of a continuous casting billet, electroslag remelting and electroslag ingot stress relief annealing processes, heating and cogging of an electroslag ingot, heating of a process blank, continuous rolling, heat preservation and annealing.

3. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters and specific steps of the initial smelting of the Consteel electric furnace are as follows:

the steelmaking raw material consists of blast furnace molten iron and returned scrap steel containing low phosphorus, smelting and slagging are carried out at 1510-1540 ℃ after full melting in the initial smelting stage, and P removal reaction at lower temperature is utilized to facilitate generation of P in the forward and reverse reaction directions₂O₅P can be effectively removed when the steel enters the slag, so that the influence of phosphorus embrittlement on the quality of the steel in the later period is avoided, and the sensitivity of subsequent cracks of the steel is reduced; the temperature in the furnace after the full melting is more than 1560 ℃, an oxygen supply system is controlled to carry out effective C, O reaction in the furnace, the temperature in the furnace is increased, and the decarburization and the desulfurization reaction are carried out simultaneously; wherein the electric furnace slag is lime or dolomiteAdding stone as main material in batches; the dosage of each batch of feeding is as follows: 500-800 Kg of lime, 200-400 Kg of dolomite and 50-80 Kg of total slag charge per ton;

4. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters and specific steps of LF refining are as follows:

the temperature of the molten steel entering the LF refining station is more than or equal to 1500 ℃, and the time from tapping to entering the refining station is within 15 minutes; heating for more than or equal to 10 minutes by power supply and at more than or equal to 1560 ℃, and adding the required alloy elements in batches for component adjustment;

argon gas in LF refining: the flow rate is 100-400 NL/min;

adding 0-100Kg of lime and 0-50 Kg of fluorite according to the contents of phosphorus and sulfur in steel and slag conditions, and blending slag;

slag system target component: CaO: 50% -58% of SiO₂：10％～15％，MgO：3％～6％，Al₂O₃：18％～25％；

Controlling aluminum in the refining process: when the alloy enters an LF refining station, the content of Al is 0.030-0.040%;

after refining is finished, the molten steel comprises the following chemical components: c: 0.29 to 0.31%, Si: 1.00-1.10%, Mn: 1.10-1.20%, Cr: 1.00-1.10%, Ni: 1.50-1.65%, Al: 0.015 to 0.030%, Mo: 0.02-0.03%, V: 0.02% -0.03%, Ti: 0.015% -0.025%, W: 0.15 to 0.2 percent of the total weight of the alloy, less than or equal to 0.012 percent of P and less than or equal to 0.01 percent of S.

5. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the VD vacuum degassing control parameters and the specific steps are as follows:

degassing the molten steel at 1630-1650 ℃;

the medium before VD degassing meets the conditions: the water pressure is more than or equal to 0.5MPa, the water temperature is less than or equal to 30 ℃, the steam pressure is more than or equal to 0.8MPa, and the steam temperature is more than or equal to 180 ℃;

argon flow in VD process: rough vacuum >200 torr, flow rate 50-100 NL/min; the flow rate is 150 plus 200NL/min during the extreme vacuum period, and the slag breaking surface is 200-300 mm according to the air permeability adjustment; and adjusting the flow rate to 50-150NL/min 2-3 min before the air break to the weak argon standard.

6. The method for producing the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of the weak argon operation and the specific steps are as follows:

after various element components of the molten steel meet the internal control requirement, performing weak argon operation, homogenizing the components of the molten steel, and removing impurities, harmful gases and impurities;

in the weak argon process, the main blowing flow of argon is 50-150NL/min, the auxiliary blowing flow is 30-50NL/min, the slag surface is required to creep, and molten steel is not exposed; the weak argon time is more than or equal to 20min on the premise of meeting the continuous casting pouring temperature of the ladle molten steel.

7. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of the continuous casting and pouring and the specific steps are as follows:

after the weak argon is finished, the temperature of the molten steel reaches 1560-1580 ℃ by a first ladle; and when the continuous casting ladle reaches 1545-1565 ℃, hoisting the continuous casting ladle into a continuous casting machine for continuous casting, thus obtaining a semi-finished continuous casting billet with lower gas content and endogenous inclusions meeting the standard requirement of high-quality steel.

8. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of continuous casting slab pit-entering heat preservation and stress relief annealing and the specific steps are as follows:

cutting the length of the continuous casting billet according to the billet lifting requirement; pit cooling requirements of a 250 x 280mm continuous casting billet: and (3) timely entering a pit for slow cooling, wherein the temperature of the casting blank entering the pit is more than or equal to 700 ℃, and the slow cooling time of the casting blank is more than 36 hours.

9. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of the electroslag remelting process and the electroslag ingot stress relief annealing and the specific steps are as follows:

adopting a continuous casting billet with the thickness of 250mm multiplied by 280mm to carry out electroslag remelting to produce a phi 470mm ingot;

the electroslag remelting slag system adopts quaternary slag with the following mass percentage content: CaF₂60％、Al₂O₃30％、CaO 8％、MgO 2％；

The electroslag remelting process adopts the smelting production of a common electroslag furnace, the dosage of the deoxidizer is determined according to the components of an electrode blank and the requirements of a finished product, and the deoxidizer is added uniformly in batches; melting speed of 6.0kg +/-0.5 kg/min, cooling water temperature: 40-55 ℃.

10. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of electroslag ingot heating cogging and the specific steps are as follows:

the process heating parameters are controlled as follows: when the electroslag ingot is fed into the furnace, the furnace temperature is required to be less than or equal to 500 ℃, the temperature is equalized for 1-2 hours after the electroslag ingot is fed into the furnace, then the temperature is increased, the air quantity is reduced in the preheating stage at 500-800 ℃, and the temperature equalizing time of the ingot with the diameter of 470mm is controlled according to 1-1.5 hours; strictly prohibiting high temperature burning during heating, wherein the curve identification temperature is the actual steel ingot temperature, and the deviation between the steel temperature and the furnace temperature is 20-80 ℃; the start rolling temperature of the electroslag ingot is as follows: 1100-1150 deg.c and finishing temperature not lower than 950 deg.c; controlling the blank to be 240mm multiplied by 240mm in length 5300-5900 mm in the process of rolling and opening the phi 470mm electroslag ingot, wherein the size deviation is +/-5 mm, and the length deviation is +/-30 mm; and (4) after cogging, putting the square billet into a pit in time, slowly cooling and preserving heat for more than or equal to 48 hours.

11. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters of the process blank heating, the continuous rolling and the heat preservation comprise the following steps:

the heating process of the process blank is controlled to be that the temperature of the preheating section is less than or equal to 850 ℃, the temperature of the heating section is 1100-; the total heating time of the continuous casting billet is more than or equal to 4 hours, and the high-temperature diffusion time is more than or equal to 2.0 hours;

and (3) water descaling control in the rolling process: and (3) carrying out two times of water spraying descaling to reduce the surface temperature of a square billet with the diameter of 240mm to 240mm by 50-80 ℃, forming a water descaling pressure with the non-uniform temperature gradient distribution of the cross section of the square billet of 20-25Mpa, the dephosphorization effect is more than or equal to 95%, the initial rolling temperature is 1030-1120 ℃, the final rolling temperature is more than or equal to 850 ℃, collecting steel by a fast bed and then placing the steel on a cooling bed, then timely placing the steel into a heat preservation pit for heat preservation, wherein the temperature of the steel in the pit is more than or equal to 400 ℃, the heat preservation time is more than or equal to 24 hours, and the temperature of the steel out of the pit is less than or equal to 150 ℃.

12. The production method of the aviation 30CrMnSiNi2A high-strength steel as claimed in claim 2, wherein the control parameters and specific steps of annealing are as follows:

after heat preservation, the steel is put into an annealing furnace for heat treatment within 8 hours, and the annealing temperature is as follows: 720 +/-10 ℃, roll speed: 4.0m/h, and adopting a 14-zone staged continuous annealing furnace for temperature control annealing, wherein the annealing temperature range is 600-720 ℃.