CN114934239A - Forged non-quenched and tempered steel for hydraulic cylinder rod head and production method thereof - Google Patents
Forged non-quenched and tempered steel for hydraulic cylinder rod head and production method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/35—Blowing from above and through the bath
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- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention discloses forged non-quenched and tempered steel for a hydraulic cylinder rod head and a production method thereof, wherein the forged non-quenched and tempered steel for the rod head consists of the following elements in percentage by mass: 0.34 to 0.37 percent of C, less than or equal to 0.13 percent of Si, 1.05 to 1.25 percent of Mn, 0.15 to 0.25 percent of Cr, less than or equal to 0.10 percent of Cu, less than or equal to 0.10 percent of Ni, less than or equal to 0.0050 percent of Mo, 0.035 to 0.050 percent of V, less than or equal to 0.0050 percent of Nb, less than or equal to 0.0040 percent of As, 0.015 to 0.035 percent of Al, less than or equal to 0.012 percent of P, less than or equal to 0.0050 percent of S, less than or equal to 0.0008 percent of B, less than or equal to 0.0030 percent of Ti, 0.0085 to 0.0110 percent of N, less than or equal to 20ppm of [ O ], [ H ] less than or equal to 2ppm, and the balance of Fe and inevitable impurity elements; wherein (Al + V)/N is controlled to be 4.55-10, and V/Al is controlled to be 1-3.33. The performance of the rod head obtained by forging non-quenched and tempered steel for the hydraulic cylinder rod head with the specification less than or equal to 100mm after forging and controlled cooling after forging is equivalent to that of tempered 45 steel, and the existing medium and small-specification hydraulic cylinder rod head can be completely processed by adopting the non-quenched and tempered steel.
Description
Technical Field
The invention relates to the field of engineering machinery, in particular to forged non-quenched and tempered steel for a hydraulic cylinder head and a manufacturing method thereof.
Background
The hydraulic cylinder has the advantages of simple structure, capability of realizing reciprocating motion, stable work and the like, and the application range of the hydraulic cylinder is determined from birth date. Because of the wide application characteristics, the hydraulic cylinder has various types, but the hydraulic cylinder basically comprises a cylinder barrel, a piston rod, a rod head, a sealing device, a buffer device, an exhaust device and other parts, wherein the rod head and the piston rod are welded into a whole, the other end of the rod head is connected with an action base body through a rod head hole, so that the piston rod drives the base body to realize reciprocating motion under the connection of the rod head, and the rod head becomes a very important connecting piece. The material used by the existing hydraulic cylinder head is mainly 45 steel in GB/T699, the main production process comprises 45 steel medium frequency induction heating, upsetting, die forging, trimming, air cooling and tempering, and the performance requirement of the tempered head at a half radius part meets the following requirements: the tensile strength Rm is more than or equal to 690Mpa, the upper yield strength is more than or equal to 490Mpa, the elongation is more than or equal to 15%, and the U-shaped normal-temperature impact toughness is more than or equal to 49J/cm.
At present, the non-quenched and tempered steel is mainly applied to the field of automobile manufacturing and used for manufacturing various parts on automobiles, such as connecting rods, crankshafts, steering knuckles, control arms and the like. Due to the influence of cost factors, the application of non-quenched and tempered steel in the field of engineering machinery is limited to a certain extent, and in the aspect of manufacturing of hydraulic cylinders, the non-quenched and tempered steel is only applied to piston rod products in a small range in recent years. The existing steel for the hydraulic cylinder rod head is not selected according to the specifications of different hydraulic cylinder rod heads, and is processed by uniformly selecting 45 steel in GB/T699, but the performance of the 45 steel can meet the requirements of the hydraulic cylinder rod head after the 45 steel needs to be quenched and tempered. Compared with the performance of a large-specification hydraulic cylinder rod head, the middle-and-small-specification hydraulic cylinder rod head made of the same material has larger margin in performance. The advent of non-quenched and tempered steel makes it possible to replace quenched and tempered steel, especially of medium and small size. As is well known, non-quenched and tempered steel is relatively green and environmentally friendly because the quenching and tempering process is omitted. Meanwhile, no relevant report of the application of non-quenched and tempered steel is seen in the aspect of the hydraulic cylinder rod head, and in view of the characteristic that the non-quenched and tempered steel is mature in the aspect of the application of medium and small-sized steel, the development of the non-quenched and tempered steel suitable for the medium and small-sized hydraulic cylinder rod head becomes a practical requirement on the premise of cost allowance, particularly, the national increasingly emphasizes on environmental protection, and the development of the non-quenched and tempered steel replacing a quenching and tempering process also becomes a necessary trend of the development of the engineering machinery industry.
Disclosure of Invention
The invention aims to: aiming at the defects in the prior art and the green environmental protection development concept of corresponding countries, an economical and practical forged non-quenched and tempered steel for medium and small-sized hydraulic cylinder heads and a production method thereof are developed on the premise of allowing the cost, so that the existing quenched and tempered 45 steel is replaced.
In the aspect of chemical composition design, in view of the fact that the influence of the silicon element content in the range of 0.15-0.37% on the mechanical property is relatively small, the silicon element content is designed in a lower range, and therefore the adverse effect of the silicon element on the surface decarburization of steel is improved; because nitrogen is added in the component design, the content of titanium is controlled to be in a lower range in order to control the content of titanium nitride inclusions; since the steel grade of the invention is non-quenched and tempered steel for forging, the content of residual elements affecting the mechanical properties of the steel grade, particularly molybdenum, nickel and niobium, is intentionally limited for the purpose of stabilizing the properties after forging. In the aspect of production process, according to the requirement of the sulfur content after desulfurization, the innovative self-made desulfurizer is used for pre-desulfurization; after tapping of the converter is finished, stirring argon for a certain time, and feeding an aluminum wire into molten steel for precipitation and deoxidation; according to the content of acid-soluble aluminum in the molten steel, feeding different amounts of pure calcium wires into the molten steel to fully denature non-metallic inclusions in the steel; selecting a casting blank with a proper section to roll steel with a corresponding specification according to different compression ratios; a certain number of axial flow fans are arranged at the inlet of the cooling bed to forcibly cool the steel, refine crystal grains and improve mechanical properties. The steel grade of the invention can realize mechanical properties after forging and controlled cooling after forging: the lower yield strength is 530-580 Mpa, the tensile strength is 810-860 Mpa, the elongation is 20-24%, the reduction of area is 55-64%, and the normal-temperature U-shaped impact toughness is 55-65J/cm 2; through measurement and calculation, the cost of the steel grade is only increased by about 400-500 yuan/ton on the basis of 45 steel; the mechanical property of the non-quenched and tempered steel after forging is close to that of the tempered 45 steel, and the steel grade can completely replace the quenched and tempered 45 for the forging hydraulic cylinder rod head with the specification of being less than or equal to 100mm in the middle.
The invention is realized by the following technical scheme:
a forged non-quenched and tempered steel for a hydraulic cylinder head comprises the following elements in percentage by mass: 0.34 to 0.37 percent of C, less than or equal to 0.13 percent of Si, 1.05 to 1.25 percent of Mn, 0.15 to 0.25 percent of Cr, less than or equal to 0.10 percent of Cu, less than or equal to 0.10 percent of Ni, less than or equal to 0.0050 percent of Mo, 0.035 to 0.050 percent of V, less than or equal to 0.0050 percent of Nb, less than or equal to 0.0040 percent of As, 0.015 to 0.035 percent of Al, less than or equal to 0.012 percent of P, less than or equal to 0.0050 percent of S, less than or equal to 0.0008 percent of B, less than or equal to 0.0030 percent of Ti, 0.0085 to 0.0110 percent of N, less than or equal to 20ppm of [ O ], [ H ] < 2ppm, and the balance of Fe and inevitable impurity elements; wherein (Al + V)/N is controlled to be 4.55-10, and V/Al is controlled to be 1-3.33.
The invention further adopts the improvement scheme that the forged non-quenched and tempered steel for the hydraulic cylinder rod head comprises the following elements in percentage by mass: 0.34 to 0.36 percent of C, 0.08 to 0.13 percent of Si, 1.20 to 1.25 percent of Mn, 0.15 to 0.20 percent of Cr, less than or equal to 0.08 percent of Cu, less than or equal to 0.04 percent of Ni, less than or equal to 0.0030 percent of Mo, 0.040 to 0.050 percent of V, less than or equal to 0.0040 percent of Nb, less than or equal to 0.0040 percent of As, 0.015 to 0.030 percent of Al, less than or equal to 0.010 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0005 percent of B, less than or equal to 0.0030 percent of Ti, 0.0095 to 0.0110 percent of N, less than or equal to 15ppm of [ O ], less than or equal to 1.5ppm of [ H ], and the balance of Fe and inevitable impurity elements, wherein (Al + V)/N is controlled at 5 to 8.42, and V/Al is controlled at 1.33 to 3.33.
A production method of forged non-quenched and tempered steel for a hydraulic cylinder head comprises the following steps:
1) pre-desulfurization of molten iron: carrying out pre-desulfurization treatment on molten iron by adopting a blowing method, adding nitrogen serving as a carrier into the molten iron for at least 3 times according to the aim that the sulfur content in the desulfurized molten iron is less than or equal to 0.006 percent, spraying a proper amount of desulfurizer (the ratio of CaO + Mg + CaF2 is 7:1.6: 1) into the molten iron through a spray gun, and completely removing desulfurized slag by using a special slag remover after desulfurization reaction is fully performed, so as to prevent resulfurization in the smelting process of a converter;
2) converter smelting (LD): the method is characterized in that self-produced steel scraps and desulfurized molten iron are used as raw materials, wherein the steel scraps are self-produced carbon steel scraps, the ratio of the molten iron to the steel scraps is controlled to be more than 8:2, a top-bottom combined blown converter is adopted for rough smelting, and the main components at the end point of the converter are controlled as follows: 0.12-0.28% of C, less than or equal to 0.015% of S, less than or equal to 0.008% of P, and 1610-1650% of end point temperature, wherein after 20 tons of steel tapping, low common carbon powder, manganese metal, medium carbon ferrochrome, lime and fluorite are sequentially added into molten steel, wherein the content of manganese metal (W (Mn)) is more than or equal to 98% by weight and 10-12 kg/t, the content of medium carbon ferrochrome (W (Cr)) is more than or equal to 55% by weight and 2-4 kg/t, the content of lime is 4-5 kg/t, and the content of fluorite is 1.5-3 kg/t. After 3-5 minutes of treatment in an argon blowing station, feeding an aluminum wire into molten steel for 4-7 m/t according to tapping carbon, and ensuring that 0.26-0.32% of C, less than or equal to 0.08% of Si, 0.90-1.05% of Mn, 0.10-0.15% of Cr and 0.040-0.060% of Al are added into molten steel in an LF furnace;
3) ladle refining (LF): after the molten steel arrives at a station, introducing bottom-blown argon gas, stirring for 2-3 minutes, and deoxidizing the slag surface by using calcium carbide and aluminum particles; in the first step, feeding an aluminum wire to the molten steel on line, and controlling the aluminum content of the molten steel to be 0.040-0.060%; adjusting chemical components in the middle and later refining stages, wherein 0.9 kg/t ferrovanadium (W (V) = 50%) is added into the molten steel in a white slag state, and the white slag time is controlled to be 20-35 min; the main components of the refined final slag meet the following requirements: 50-60% of CaO and 320-30% of Al 2O; after refining of the LF furnace, feeding 0.4-0.6 m pure calcium wires into each ton of steel when Als is less than or equal to 0.035%, and feeding 0.7-1.0 m pure calcium wires into each ton of steel when Als is more than 0.035%; after the silk thread feeding is finished, bottom blowing argon gas is stirred for 2-4 min, and the flow of the bottom blowing argon gas is controlled to be 20-80 NL/min at the stage;
4) vacuum cycle degassing (RH): molten steel is subjected to RH vacuum circulation degassing treatment. Treating the molten steel for 3-5 minutes under the condition that the vacuum degree is not less than 100Pa, then treating the molten steel for 15-20 minutes under the condition of high vacuum degree (the vacuum degree is not more than 50 Pa), wherein argon is used as lifting gas in the whole treatment process, and the flow rate of the lifting gas is 50-80 Nm 3 H is used as the reference value. After the vacuum treatment is finished, soft blowing is carried out for 15-25 min, and the flow of bottom blowing gas during the soft blowing is controlled to be 40-80 NL/min;
5) continuous Casting (CCM): adopting an arc continuous casting machine, carrying out argon protection casting in the whole process, controlling the superheat degree of a first furnace of a tundish at the temperature of more than 35-45 ℃, controlling the superheat degree of a secondary furnace of continuous casting at the temperature of 25-35 ℃, controlling the drawing speed of 200 square at 1.4m/min, controlling the drawing speed of a round billet of 380mm in the middle to be 0.55m/min, and slowly cooling all billets in a pit at the temperature of 500-650 ℃;
6) steel rolling: the steel billet enters the furnace in a cold state, the rolling ratio is more than or equal to 6, the rolling steel specification of the 200 square is less than the middle and the middle of 70mm and the middle of 380mm round billet rolling specification is in the middle of 70mm to the middle of 100 mm. A 200-square heating system: heating for 3 hours at 1000-1120 ℃, rolling at 980-1010 ℃, rolling at 200 square by adopting a flat-vertical staggered 12-frame rolling mill, rolling at 850-880 ℃, controlling the temperature of an upper cooling bed to 700-750 ℃ when rolling steel which is less than 70mm in the middle, and arranging 10 wind pressures of 400pa and 10000m at the inlet of the cooling bed 3 The axial flow type cooling fan is used for cooling steel through the cooling fan, the temperature is controlled to be 12-20 ℃/min, and the steel pit entering temperature is controlled to be 280-350 ℃; in 380mm round billet heating system: heating at 1180-1230 ℃ for 6 hours, and rolling round billets 380mm in the middle of the furnace by using a reciprocating cogging mill and 6 horizontal and vertical staggered continuous rolling mills, wherein the cogging temperature is 1100-1140 ℃, and the finish rolling temperature is 930-980 ℃; when rolling steel which is 90mm in the middle to 100mm in the middle, the temperature of an upper cooling bed is controlled to be 800-880 ℃, and 10 wind pressures of 400pa and 20000m are arranged at the inlet of the cooling bed 3 The axial flow cooling fan is used for cooling steel through the cooling fan, the temperature is controlled to be 6-10 ℃/min, and the steel entering temperature is controlled to be 320-450 ℃.
The reason why the chemical composition of the forged non-heat-treated steel for a head according to the present invention is limited is as follows:
c: the carbon element can obviously improve the strength index, particularly the tensile strength, and the steel grade replaced by the steel grade is quenched and tempered 45 steel, so that the content of the carbon element is determined on the basis of 0.45 percent, but the improvement of the content of the carbon element is not favorable for the toughness index of the product after forging. According to our studies, the impact toughness of carbon element is very significantly affected in non-heat treated steel, and the content of carbon element must be limited. Therefore, the content of C is 0.34-0.37%.
Si: the content range of the silicon element is 0.15-0.37%, the contribution of the silicon element to the mechanical property of the steel is limited, if the silicon element is added, the silicon element is easy to combine with calcium, aluminum and oxygen in the steel to form composite inclusions, and in order to change the composition of the inclusions in the steel, the steel grade controls the silicon in a lower range in the composition design. Comprehensively considering the cost, the Si content is determined to be less than or equal to 0.13 percent.
Mn: as for manganese elements, as long as the content of the manganese elements is not more than 1.40 percent, the effect of the manganese on the banded structure is not obvious, meanwhile, the manganese content is within 1.40 percent, the strength and the toughness can be synchronously increased by increasing the manganese content, and the Mn content is determined to be 1.05-1.25 percent by combining the requirement of the mechanical property of the forged steel grade.
Cr: the chromium element has the characteristics of oxidation resistance, corrosion resistance, wear resistance and the like, but the toughness of the steel grade is deteriorated due to high content of the chromium element, and for the reason, a small amount of chromium element is added in the design of the steel grade, and the content of Cr is determined to be 0.15-0.25% by comprehensive consideration.
V: vanadium is one of the most common microalloying elements in non-quenched and tempered steel, a certain amount of vanadium is added into almost every non-quenched and tempered steel more or less, most of vanadium is dissolved in austenite under a general heating system due to the low solid solution temperature of vanadium, precipitation is performed in the subsequent cooling process to play a role in strengthening, most of vanadium is still dissolved in austenite to play a role in solid solution strengthening, the solid solution strengthening effect is far less remarkable than precipitation strengthening, and in order to control the production cost and simultaneously consider the requirements of toughness and strength, the content of V is determined to be 0.035-0.050%.
Al: aluminum is used in the steel grades of the invention primarily to refine the grains and balance the oxygen content in the steel. When the content of acid-soluble aluminum in the general molten steel is 0.02-0.05%, the balanced oxygen content is 3-7 ppm, and meanwhile, the effect of aluminum, vanadium and nitrogen composite refined grains is considered, and in the component design, the content of Al is designed to be 0.015-0.035%.
N: in the steel, the nitrogen, the added vanadium and the added aluminum are compounded to refine grains, the content of the nitrogen is set by combining the content of the vanadium and the content of the aluminum, and in order to prevent the nitrogen content from being too high and deteriorate the toughness, the content of the N is determined to be 0.0085-0.0110%.
In order to control the production cost and the stability of mechanical property, Ni, Cu, Mo, P, S, Nb, Ti, B, As, [ O ] and [ H ] are all used As residual elements to be controlled, and the content is designed As follows: less than or equal to 0.10 percent of Ni, less than or equal to 0.10 percent of Cu, less than or equal to 0.0050 percent of Mo, less than or equal to 0.012 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.0050 percent of Nb, less than or equal to 0.0030 percent of Ti, less than or equal to 0.0008 percent of B, less than or equal to 0.0040 percent of As, less than or equal to 20ppm of [ O ], and less than or equal to 2ppm of [ H ]. Especially the content of three elements of Mo, Nb and Ti.
The invention has the advantages that:
first, in order to change the inclusion composition of the invented steel grade, the content of silicon element in the forged non-heat treated steel for a hydraulic cylinder head is set within 0.13% according to the content of silicon element in general steel and the characteristics of the steel acting on mechanical properties.
Secondly, the forged non-quenched and tempered steel for the hydraulic cylinder rod head disclosed by the invention innovatively introduces the proportion of vanadium, aluminum and nitrogen composite refined grains in advance under the condition of ensuring that the mechanical property meets the design requirement, and plays the role of vanadium and aluminum on the refined grains to the maximum extent, so that the consumption of refined grain elements is reduced.
Thirdly, the production process of the forging non-quenched and tempered steel for the hydraulic cylinder rod head is characterized in that a proper desulfurizer and a proper proportion are innovatively selected according to the requirement of the sulfur content after desulfurization in the molten iron pre-desulfurization process.
Fourthly, according to the production process of the forged non-quenched and tempered steel for the hydraulic cylinder rod head, pure calcium lines with different amounts are fed into molten steel according to different contents of acid-soluble aluminum in the molten steel to perform modification treatment on inclusions in the steel.
Fifthly, according to the production process for forging the non-quenched and tempered steel for the hydraulic cylinder rod head, a certain number of axial flow fans are arranged at the inlet of a cooling bed to perform forced air cooling on the steel.
Sixthly, according to the forged non-quenched and tempered steel for the hydraulic cylinder head and the production method thereof, on the premise that the rolling ratio is not less than 6, the yield strength is 530-580 Mpa, the tensile strength is 810-860 Mpa, the elongation is 20-24%, the reduction of area is 55-64%, and the normal-temperature U-shaped impact toughness is 55-65J/cm 2 in a hot rolling state of the forged non-quenched and tempered steel for the hydraulic cylinder head produced by the method.
Detailed Description
The following production processes are adopted for preparation in the following steps of 1-3:
1) pre-desulfurization of molten iron: carrying out pre-desulfurization treatment on molten iron by adopting a blowing method, adding nitrogen serving as a carrier into the molten iron for at least 3 times according to the aim that the sulfur content in the desulfurized molten iron is less than or equal to 0.006 percent, spraying a proper amount of desulfurizer (the ratio of CaO + Mg + CaF2 is 7:1.6: 1) into the molten iron through a spray gun, and completely removing desulfurized slag by using a special slag remover after desulfurization reaction is fully performed, so as to prevent resulfurization in the smelting process of a converter;
2) converter smelting (LD): the method is characterized in that self-produced steel scraps and desulfurized molten iron are used as raw materials, wherein the steel scraps are self-produced carbon steel scraps, the ratio of the molten iron to the steel scraps is controlled to be more than 8:2, a top-bottom combined blown converter is adopted for rough smelting, and the main components at the end point of the converter are controlled as follows: 0.12-0.28% of C, less than or equal to 0.015% of S, less than or equal to 0.008% of P, and a final temperature of 1610-1650 ℃, wherein 10-12 kg/t of low common carbon powder, manganese metal, medium carbon ferrochrome, lime and fluorite are sequentially added into molten steel after 20 tons of steel are tapped, wherein the content of manganese metal (W (Mn) is more than or equal to 98%), the content of medium carbon ferrochrome (W (Cr) is more than or equal to 55%) is more than or equal to 2-4 kg/t, the content of lime is 4-5 kg/t, and the content of fluorite is 1.5-3 kg/t. After 3-5 minutes of treatment in an argon blowing station, quickly adding a heat preservation agent to the slag surface, and simultaneously feeding an aluminum wire into molten steel for 4-7 m/t according to tapping carbon to ensure that 0.26-0.32% of C, less than or equal to 0.08% of Si, 0.90-1.05% of Mn, 0.10-0.15% of Cr and 0.040-0.060% of Al are added into molten steel in an LF furnace;
3) ladle refining (LF): after the molten steel arrives at a station, introducing bottom-blown argon gas, stirring for 2-3 minutes, and deoxidizing the slag surface by using calcium carbide and aluminum particles; in the first step, feeding an aluminum wire to the molten steel on line, and controlling the aluminum content of the molten steel to be 0.040-0.060%; adjusting chemical components in the middle and later refining stages, wherein 0.9 kg/t ferrovanadium (W (V) = 50%) is added into the molten steel in a white slag state, and the white slag time is controlled to be 20-35 min; the main components of the refined final slag meet the following requirements: 50-60% of CaO and 320-30% of Al 2O; after refining of the LF furnace, feeding 0.4-0.6 m pure calcium wires into each ton of steel when Als is less than or equal to 0.035%, and feeding 0.7-1.0 m pure calcium wires into each ton of steel when Als is more than 0.035%; after the silk thread feeding is finished, bottom blowing argon gas is stirred for 2-4 min, and the flow of the bottom blowing argon gas is controlled to be 20-80 NL/min at the stage;
4) vacuum cycle degassing (RH): molten steel is subjected to RH vacuum circulation degassing treatment. Treating the molten steel for 3-5 minutes under the condition that the vacuum degree is not less than 100Pa, then treating the molten steel for 15-20 minutes under the condition of high vacuum degree (the vacuum degree is not more than 50 Pa), wherein argon is used as lifting gas in the whole treatment process, and the flow rate of the lifting gas is 50-80 Nm 3 H is used as the reference value. After the vacuum treatment is finished, soft blowing is carried out for 15-25 min, and the flow of bottom blowing gas during the soft blowing is controlled to be 40-80 NL/min;
5) continuous Casting (CCM): adopting an arc continuous casting machine, carrying out argon protection casting in the whole process, controlling the superheat degree of a first furnace of a tundish according to the temperature of more than 35-45 ℃, controlling the superheat degree of a secondary continuous casting furnace according to the temperature of 25-35 ℃, controlling the arc radius R =12m of a 200-square continuous casting machine, controlling the arc radius R =16m of a 380mm round billet continuous casting machine, controlling the drawing speed of the 200-square continuous casting machine to be 1.4m/min, controlling the drawing speed of the 380mm round billet to be 0.55m/min, carrying out electromagnetic stirring on two sections of a crystallizer (current 310A, frequency 6 HZ) and a tail end (current 140A, frequency 10 HZ) in the 200-square continuous casting machine, carrying out electromagnetic stirring on the 380mm round billet in three sections of the crystallizer (current 220A, frequency 3 HZ), secondary cooling (current 190A, frequency 10 HZ) and the tail end (current 410A, frequency 8 HZ), and putting the billet into a pit, and carrying out slow cooling, wherein the temperature of the billet is 500-650 ℃;
6) steel rolling: the steel billet enters the furnace in a cold state, the rolling ratio is more than or equal to 6, the rolling steel specification of the 200 square is less than the middle and the middle of 70mm and the middle of 380mm round billet rolling specification is in the middle of 70mm to the middle of 100 mm. A 200-square heating system: heating for 3 hours at 1000-1120 ℃, rolling at 980-1010 ℃, rolling at 200 square by adopting a flat-vertical staggered 12-frame rolling mill, rolling at 850-880 ℃, controlling the temperature of an upper cooling bed to 700-750 ℃ when rolling steel which is less than 70mm in the middle, and arranging 10 wind pressures of 400pa and 10000m at the inlet of the cooling bed 3 H ofThe axial flow type cooling fan cools the steel through the cooling fan, the temperature is controlled to be 12-20 ℃/min, and the temperature of the steel entering a pit is controlled to be 280-350 ℃; in 380mm round billet heating system: heating at 1180-1230 ℃ for 6 hours, and rolling round billets 380mm in the middle of the furnace by using a reciprocating cogging mill and 6 horizontal and vertical staggered continuous rolling mills, wherein the cogging temperature is 1100-1140 ℃, and the finish rolling temperature is 930-980 ℃; when rolling steel which is 90mm in the middle to 100mm in the middle, the temperature of an upper cooling bed is controlled to be 800-880 ℃, and 10 wind pressures of 400pa and 20000m are arranged at the inlet of the cooling bed 3 The axial flow cooling fan is used for cooling steel through the cooling fan, the temperature is controlled to be 6-10 ℃/min, and the steel entering temperature is controlled to be 320-450 ℃.
7) Forging: heating the non-quenched and tempered steel to 1260 ℃ by using a medium-frequency induction heating furnace, discharging, performing rough forging and die forging, performing air cooling after finish forging, performing air cooling to 580 ℃, and performing air cooling. Chemical compositions (%) of the obtained forged non-heat-treated steel for hydraulic cylinder head are shown in tables 1 and 2.
TABLE 1 main chemical composition (%)% of forged non-heat-treated steel for hydraulic cylinder heads
TABLE 2 main chemical composition (%)% of forged non-heat-treated steel for hydraulic cylinder heads
The mechanical properties of the non-quenched and tempered steels manufactured in examples 1 to 3 were tested according to GB/T228.1 and GB/T229, the mechanical properties at a half radius of the head of the hydraulic cylinder after forging were tested, and the properties of the quenched and tempered 45 steels in the same forging process were compared, and the specific results are shown in tables 3 and 4.
TABLE 3 mechanical properties of forged non-quenched and tempered steel for hydraulic cylinder head
TABLE 4 mechanical properties of the hydraulic cylinder head
Claims (10)
1. The utility model provides a hydraulic cylinder pole head is with forging non quenched and tempered steel which characterized in that: the material consists of the following elements in percentage by mass: 0.34 to 0.37 percent of C, less than or equal to 0.13 percent of Si, 1.05 to 1.25 percent of Mn, 0.15 to 0.25 percent of Cr, less than or equal to 0.10 percent of Cu, less than or equal to 0.10 percent of Ni, less than or equal to 0.0050 percent of Mo, 0.035 to 0.050 percent of V, less than or equal to 0.0050 percent of Nb, less than or equal to 0.0040 percent of As, 0.015 to 0.035 percent of Al, less than or equal to 0.012 percent of P, less than or equal to 0.0050 percent of S, less than or equal to 0.0008 percent of B, less than or equal to 0.0030 percent of Ti, 0.0085 to 0.0110 percent of N, less than or equal to 20ppm of [ O ], [ H ] less than or equal to 2ppm, and the balance of Fe and inevitable impurity elements; wherein (Al + V)/N is controlled to be 4.55-10, and V/Al is controlled to be 1-3.33.
2. The forged non-heat treated steel for a hydraulic cylinder head according to claim 1, wherein: the material consists of the following elements in percentage by mass: 0.34 to 0.36 percent of C, 0.08 to 0.13 percent of Si, 1.20 to 1.25 percent of Mn, 0.15 to 0.20 percent of Cr, less than or equal to 0.08 percent of Cu, less than or equal to 0.04 percent of Ni, less than or equal to 0.0030 percent of Mo, 0.040 to 0.050 percent of V, less than or equal to 0.0040 percent of Nb, less than or equal to 0.0040 percent of As, 0.015 to 0.030 percent of Al, less than or equal to 0.010 percent of P, less than or equal to 0.0030 percent of S, less than or equal to 0.0005 percent of B, less than or equal to 0.0030 percent of Ti, 0.0095 to 0.0110 percent of N, less than or equal to 15ppm of [ O ], less than or equal to 1.5ppm of [ H ], and the balance of Fe and inevitable impurity elements, wherein (Al + V)/N is controlled at 5 to 8.42, and V/Al is controlled at 1.33 to 3.33.
3. A method of producing a forged non heat-treated steel for a hydraulic cylinder head as claimed in claim 1 or claim 2, characterized by comprising the steps of:
1) pre-desulfurization of molten iron: carrying out pre-desulfurization treatment on the molten iron by adopting a blowing method, and carrying out pre-desulfurization treatment on the molten iron according to the desulfurized molten iron
Spraying a desulfurizing agent into the molten iron for at least 3 times by taking nitrogen as a carrier when the sulfur content is less than or equal to 0.006 percent, and completely removing the desulfurized slag by using a slag remover after the desulfurization reaction is fully performed;
2) converter smelting (LD): scrap steel and desulfurized molten iron are taken as raw materials, a top-bottom combined blown converter is adopted for smelting,
the end point temperature is 1610 to 1650 ℃, after 20 tons of steel are tapped, respectively adding low-nitrogen carburant carbon powder, manganese metal, medium-carbon ferrochrome, lime and fluorite into molten steel, processing for 3 to 5 minutes in an argon blowing station, quickly adding a heat preservation agent into a slag surface, and simultaneously feeding an aluminum wire into the molten steel according to the tapped carbon to ensure that the molten steel in an LF furnace contains 0.26 to 0.32 percent of C, less than or equal to 0.08 percent of Si, 0.90 to 1.05 percent of Mn, 0.10 to 0.15 percent of Cr and 0.040 to 0.060 percent of Al;
3) ladle refining (LF): after the molten steel arrives at the station, bottom blowing argon is introduced to stir for 2-3 minutes, and a deoxidizing agent is used
Deoxidizing the slag surface; feeding an aluminum wire into the molten steel according to the aluminum content in the first sample, and adjusting chemical components in the middle and later refining stages, wherein 0.9 kg/t of ferrovanadium is added into the molten steel in a white slag state, the weight content of ferrovanadium is 50%, and the white slag time is controlled to be 20-35 min; the main components of the refined final slag meet the following requirements: 50-60% of CaO and Al 2 O 3 20-30%; after refining of the LF furnace is finished, feeding pure calcium wires into the molten steel according to the content of acid-soluble aluminum in the molten steel, and after the silk feeding is finished, blowing argon at the bottom and stirring for 2-4 min, wherein the flow rate of the argon is controlled at 20-80 NL/min;
4) vacuum cycle degassing (RH): treating the molten steel for 3-5 minutes under the condition that the vacuum degree is more than or equal to 100Pa
Then treating the molten steel for 15-20 minutes under the condition that the vacuum degree is less than or equal to 50Pa, using argon as lifting gas in the whole treatment process, and soft-blowing for 15-25 minutes;
5) continuous Casting (CCM): adopting an arc continuous casting machine, carrying out whole-process argon protection casting, and enabling a tundish to pass through a first furnace
Controlling the heat at 35-45 ℃, controlling the continuous casting furnace superheat degree at 25-35 ℃, controlling the drawing speed of 200 square at 1.4m/min, the drawing speed of a round billet with 380mm in the middle at 0.55m/min, and slowly cooling all the steel billets in a pit at the pit entry temperature of 500-650 ℃;
6) steel rolling: the steel billet enters a furnace in a cold state, the rolling ratio is more than or equal to 6, the specification of the rolled steel in the 200 square is less than or equal to 70mm in half and
the method comprises the following steps that the center of the 380mm round billet rolling specification is 70mm to 100 mm; a 200-square heating system: heating for 3 hours at 1000-1120 ℃, rolling at 980-1010 ℃, rolling at 200 square by adopting a horizontal and vertical staggered 12-frame rolling mill, rolling at 850-880 ℃, controlling the temperature of an upper cooling bed to 700-750 ℃ when rolling steel which is less than 70mm far away, cooling the steel at the inlet of the cooling bed by a cooling fan, controlling the temperature to be 12-20 ℃/min, and controlling the pit entry temperature of the steel to be 280-350 ℃; in 380mm round billet heating system: heating at 1180-1230 ℃ for 6 hours, and rolling round billets 380mm in the middle of the furnace by using a reciprocating cogging mill and 6 horizontal and vertical staggered continuous rolling mills, wherein the cogging temperature is 1100-1140 ℃, and the finish rolling temperature is 930-980 ℃; when 100mm steel is in the middle of 90mm ~ 100mm in the rolling, the temperature of the upper cooling bed is controlled to be 800~880 ℃, the temperature of the steel is cooled by the cooling fan at the entrance of the cooling bed, the temperature is controlled to be 6~10 ℃/min, and the temperature of the steel entering the pit is controlled to be 320~450 ℃.
4. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 1), the desulfurizer is prepared from the following components in percentage by weight: the ratio of CaO + Mg + CaF2 is 7:1.6: 1.
5. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 2), the control requirements of the converter endpoint components are as follows: 0.12-0.28% of C, less than or equal to 0.015% of S and less than or equal to 0.008% of P.
6. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 2), the mass content of Mn in metal manganese is more than or equal to 98%, the mass content of Cr in medium carbon ferrochrome is more than or equal to 55% per ton steel, the mass content of Cr in medium carbon ferrochrome is more than or equal to 2-4 kg/t per ton steel, the mass content of lime steel is 4-5 kg/t per ton steel, and the mass content of fluorite steel is 1.5-3 kg/t; and feeding an aluminum wire 4-7 m/t into the molten steel after the treatment for 3-5 minutes in the argon blowing station.
7. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 3), an aluminum wire is fed into the molten steel in the first step, so that the content of aluminum is controlled to be 0.040-0.060%.
8. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 3), pure calcium lines are fed into the molten steel according to the components of acid-soluble aluminum in the molten steel, 0.4-0.6 m pure calcium lines are fed into each ton of steel when Als is less than or equal to 0.035%, and 0.7-1.0 m pure calcium lines are fed into each ton of steel when Als is more than 0.035%.
9. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: in the step 4), the flow of the lifting gas is controlled to be 50-80 Nm during RH vacuum treatment 3 The flow rate of bottom blowing gas during soft blowing is controlled to be 40-80 NL/min.
10. The production process of the forged non-quenched and tempered steel for a hydraulic cylinder head as claimed in claim 3, wherein: when rolling is less than and 70mm in the middle, 10 wind pressures of 400pa and 10000m of wind volume are arranged at the inlet of the cooling bed 3 An axial flow cooling fan; in the rolling in the 90mm ~ 100mm in the time of 100mm steel, arrange 10 wind pressure 400pa and air volume 20000m in the cold bed entrance 3 An axial flow cooling fan.
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