CN112281064A - Low-alloy high-strength steel plate forging for high-strength structure and forging method - Google Patents
Low-alloy high-strength steel plate forging for high-strength structure and forging method 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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Abstract
The invention discloses a low-alloy high-strength steel plate forging for a high-strength structure and a forging method, wherein the forging comprises the following formula components in percentage by weight: 0.12 to 0.21 percent of C, 0.20 to 0.35 percent of Si, 0.45 to 0.70 percent of Mn, 0.85 to 1.20 percent of Cr, 1.20 to 1.50 percent of Ni, 0.45 to 0.60 percent of Mo0.001 to 0.005 percent of B, less than or equal to 0.06 percent of Nb, 0.01 to 0.10 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S and the balance of Fe. Meanwhile, the carbon equivalent is reduced by 0.18%, and the welding performance is greatly improved. In addition, the adopted completely deoxidized killed steel ensures the purity of the raw material steel and reduces the contents of impurity elements and harmful gases.
Description
Technical Field
The invention relates to the technical field of high-strength steel, in particular to a low-alloy high-strength steel plate forging for a high-strength structure and a forging method.
Background
At present, low-alloy high-strength steel plates (such as Q690) are commonly used in quenched and tempered steel plates for high-strength structures, and are mainly used for structural assembly weldments, connecting parts, bearing seats and other parts, and are convenient to weld and repair. However, at present, such materials are mainly supplied for hot rolled steel plates in China, the area is large (the thickness is 8-100mm, the width is 1600-.
Disclosure of Invention
The invention provides a low-alloy high-strength steel plate forging for a high-strength structure and a forging method.
In order to achieve the purpose, the invention provides the following technical scheme:
a low-alloy high-strength steel plate forging for a high-strength structure comprises the following formula components in percentage by weight:
0.12 to 0.21 percent of C, 0.20 to 0.35 percent of Si, 0.45 to 0.70 percent of Mn, 0.85 to 1.20 percent of Cr0.20 percent of Ni, 1.20 to 1.50 percent of Ni, 0.45 to 0.60 percent of Mo0.001 to 0.005 percent of B, less than or equal to 0.06 percent of Nb, 0.01 to 0.10 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S and the balance of Fe;
the carbon equivalent is CE, and CE is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15 ≦ 0.68%, wherein the element not related to the formula component is regarded as 0.
The carbon content increases, the yield point and tensile strength of the steel increase, but the plasticity and impact properties decrease, and when the carbon content exceeds 0.23%, the weldability of the steel deteriorates, and therefore, low alloy structural steels for welding generally have a carbon content of not more than 0.20%. Meanwhile, the high carbon content can reduce the atmospheric corrosion resistance, and the high-carbon steel in an open-air stock yard is easy to rust. In addition, carbon can increase the cold brittleness and age sensitivity of the steel.
Silicon is used as a reducing agent and a deoxidizing agent in the steel making process, so the killed steel contains 0.15 to 0.30 percent of silicon. If the silicon content in the steel exceeds 0.50 to 0.60%, the alloying elements are not included. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel.
The manganese is used as a good deoxidizer and desulfurizer in the steel-making process, and the manganese content in the steel is 0.30-0.50%. When more than 0.70 percent of manganese steel is added into carbon steel, compared with the steel with the common amount of steel, the manganese steel has enough toughness, higher strength and hardness, and the hardenability of the steel is improved, and the hot workability of the steel is improved. Meanwhile, the manganese content is increased, the corrosion resistance of the steel is weakened, and the welding performance is reduced.
In general, phosphorus is a harmful element in steel, increases cold brittleness of steel, deteriorates welding properties, reduces plasticity, and deteriorates cold bending properties. Therefore, it is generally required that the phosphorus content in the steel is less than 0.045%, and the demand for high-quality steel is lower.
Sulfur is also a harmful element in general, and causes hot brittleness of steel, reduces ductility and toughness of steel, and causes cracks in forging and rolling. Sulfur is also detrimental to welding performance and reduces corrosion resistance. Therefore, a sulfur content of less than 0.035% is generally required, and a higher quality steel is less required.
Chromium can significantly improve strength, hardness and wear resistance, but at the same time reduces plasticity and toughness in structural and tool steels. Chromium can improve the oxidation resistance and corrosion resistance of steel, so that chromium is an important alloy element of stainless steel and heat-resistant steel. However, chromium significantly increases the brittle transition temperature of steel and promotes temper brittleness of steel.
The nickel can improve the strength of steel, maintain good plasticity and toughness, improve the processability and weldability of steel, greatly improve the hardenability of steel, and the chromium-nickel-molybdenum steel matched with chromium and molybdenum can obtain comprehensive mechanical properties with good matching of strength and toughness after heat treatment. The nickel has higher corrosion resistance to acid and alkali and has antirust and heat-resisting capabilities at high temperature. However, since nickel is a scarce resource, other alloy elements should be used as far as possible to replace nickel-chromium steel.
Molybdenum can refine the crystal grains of the steel, improve hardenability and heat strength, and maintain sufficient strength and creep resistance at high temperature. The addition of molybdenum to the structural steel improves the mechanical properties and also suppresses brittleness of the alloy steel due to tempering. The red color can be improved in the tool steel. The main adverse effect of molybdenum is its tendency to graphitize low alloy molybdenum steels.
The addition of niobium in an amount of 0.001% to 0.1% is sufficient to modify the mechanical properties of the steel. For example: when 0.1 percent of alloying element by weight is added, the yield strength of the steel can be improved by niobium to 118MPa, the yield strength of the steel can be improved by vanadium to 71.5MPa, the yield strength of the steel can be improved by molybdenum to 40MPa, the yield strength of the steel can be improved by manganese to 17.6MPa, and the yield strength of the steel can be improved by titanium to zero. In fact, the yield strength of the steel can be improved by more than 30% by only adding 0.03-0.05% of niobium into the steel.
The boron has extremely strong capability of improving the hardenability of steel, and the effect of 0.001-0.003% of boron is respectively equivalent to 0.6% of manganese, 0.7% of chromium, 0.5% of molybdenum and 1.5% of nickel, namely the capability of improving the hardenability of boron is hundreds of times or even thousands of times of that of the alloy elements, so that a large amount of precious alloy elements can be saved by adding a very small amount of boron.
Titanium can refine grains, improve the hardenability of steel and improve the yield strength.
The formulation components of conventional low-alloy high-strength steel sheet Q690 for high-strength structures are shown in table 1, and the mechanical properties thereof are shown in table 2.
Table 1: q690 formula ingredients
The carbon equivalent CE, CE ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15 of the steel is less than or equal to 0.83 percent.
Table 2: q690 mechanical properties
The inventor analyzes to obtain: the contents of Mn, Si, Cr, Ni, Mo and other elements in the formula components of Q690 are high, for example, Mn has the adverse effect of increasing the coarsening and the temper brittleness, and Cr can reduce the plasticity, the toughness and the like of steel. The high content of the above elements will degrade the weldability and heat treatment properties of the steel. Based on the above influence factors, the inventor makes the contents of each element in the formula more concrete, reduces the contents of Mn, Si, Cr, Ni and Mo, and avoids the adverse effect caused by the excessive contents of the elements. Meanwhile, the carbon equivalent is reduced to 0.68% from 0.83%, the carbon equivalent is reduced by 0.18%, and the welding performance is greatly improved. In addition, the external refining and vacuum treatment technology is added in the preparation process, the purity of steel is ensured, the contents of impurity elements and harmful gases are reduced, and the completely deoxidized killed steel is adopted, so that the internal structure is compact, the components are uniform, the sulfur content is low, the performance is stable, and the quality is good.
Preferably, the formula comprises the following components in percentage by weight:
0.57% of C, 0.95% of Si, 0.55% of Mn0.95% of Cr0.95%, 1.35% of Ni0.52%, 0.003% of B, 0.04% of Nb0.06%, 0.015% of P, 0.008% of S and the balance of Fe.
In addition, the invention also provides a forging method of the low-alloy high-strength steel plate forging for the high-strength structure, which comprises the following steps:
s1, smelting:
according to the formula components of the forging, the formula raw materials are put into a smelting furnace for smelting to obtain molten steel, the molten steel is poured into a mold and solidified to form a steel ingot, and the steel ingot is killed steel;
s2, cutting off the bottom and a riser of the steel ingot, and blanking to obtain a steel billet;
s3, loading the steel billet into a furnace, performing primary heat preservation, heating to the initial forging temperature, performing secondary heat preservation, and forging to obtain a forging blank;
s4, heat treatment: and (4) sequentially carrying out normalizing, primary tempering, quenching and secondary tempering on the forging blank to obtain the forging.
Preferably, in step S2, calculating according to drawing size, forging ratio, loss and other factors, determining blanking size, blanking according to a forging blanking specification, cutting off 7-10% of the bottom of the steel ingot, and cutting off 52-30% of the riser, so as to ensure that there are no defects that affect forging quality, such as shrinkage cavity, porosity, crack, severe segregation and the like.
Preferably, in the step S3, the steel slab is loaded into a furnace with a furnace temperature not exceeding 850 ℃, and is primarily heat preserved, and is heated to the initial forging temperature of 1200 and 1240 ℃ at a heating rate not exceeding 100 ℃/h, and is secondarily heat preserved, and is forged, wherein the final forging temperature is not lower than 800 ℃.
Preferably, the primary heat preservation time is not less than 2h, and the secondary heat preservation time is set as t, wherein t is not less than (1-1.2) multiplied by Dmin/mm, and D represents the effective thickness of the billet.
Preferably, in step S3, the heated billet is forged to a shape required by a drawing through the processes of upsetting, drawing, punching and the like, the forging ratio is required to be not less than 4, and increasing the forging ratio is beneficial to improving the microstructure and mechanical properties of the billet, but the forging ratio is too large and is not beneficial. The inventor prefers the forging ratio to be more than or equal to 4 according to experience, can improve the microstructure and the mechanical property of the steel billet to the maximum extent, and ensures the best quality of the forged piece.
Preferably, in the step S4, the normalizing temperature is 900-950 ℃, the tapping air cooling is performed to the room temperature, the primary tempering temperature is 500-650 ℃, the tapping air cooling is performed to the room temperature, so as to obtain the finer grain size, the quenching heating temperature is 890 +/-10 ℃, the quenching liquid is cooled, the quenching cooling medium adopts PAG water-soluble special quenching medium, the concentration of the quenching medium is 6-10%, the temperature of the quenching medium is 30-40 ℃, the secondary tempering temperature is 640 +/-10 ℃, and the tapping air cooling is performed to the room temperature.
Preferably, the quenching heating heat preservation time is calculated according to the effective thickness of the forged piece being 0.5h/inch (less than 1h is calculated according to 1 h), and the secondary tempering heat preservation time is 1.5-2 times of the quenching heating heat preservation time.
Preferably, the microstructure of the forging is tempered sorbite, and the austenite grain size of the forging is greater than 5 grades, so that the mechanical property of the forging is better guaranteed.
The invention has the beneficial effects that:
the contents of all elements in the components of the formula are more specified, the contents of Mn, Si, Cr, Ni and Mo are reduced, and the adverse effect caused by overhigh contents of the elements is avoided. Meanwhile, the carbon equivalent is reduced by 0.18%, and the welding performance is greatly improved. In addition, the adopted completely deoxidized killed steel ensures the purity of the raw material steel and reduces the contents of impurity elements and harmful gases.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
a low-alloy high-strength steel plate forging for a high-strength structure comprises the following formula components in percentage by weight:
0.12% of C, 0.20% of Si, 0.45% of Mn0.85% of Cr0.85%, 1.20% of Ni0.45%, 0.001% of B, 0.02% of Nb0.01%, 0.010% of P, 0.005% of S and the balance of Fe.
The forging method of the low-alloy high-strength steel plate forging for the high-strength structure comprises the following steps:
s1, smelting:
according to the formula components of the forging, the formula raw materials are put into a smelting furnace for smelting to obtain molten steel, the molten steel is poured into a mold and solidified to form a steel ingot, and the steel ingot belongs to killed steel.
And S2, calculating according to drawing size, forging ratio, loss and other factors, determining blanking size, blanking according to a forging blanking specification, cutting off 7% of the bottom of the steel ingot and 52% of a riser so as to ensure that defects of shrinkage cavity, looseness, cracks, serious segregation and the like which affect the forging quality do not exist, and obtaining the steel billet.
S3, placing the steel billet into a furnace with the furnace temperature not more than 850 ℃, preserving heat for the first time, raising the temperature to 1200 ℃ of the initial forging temperature at the temperature rise speed not more than 100 ℃/h, preserving heat for the second time, forging the heated steel billet into the shape required by the drawing through the processes of upsetting, drawing out, punching and the like, wherein the forging ratio is not less than 4, and the finish forging temperature is not less than 800 ℃, thus obtaining the forging blank.
The primary heat preservation time is not less than 2h, and the secondary heat preservation time is set as t, the t is more than or equal to (1-1.2) multiplied by D min/mm, wherein D represents the effective thickness of the steel billet. In this embodiment, the effective thickness of the steel billet is 80mm, and the secondary heat preservation time is not less than 80 min.
S4, heat treatment: and (3) sequentially carrying out normalizing, primary tempering, quenching and secondary tempering on the forging blank to obtain the forging, wherein the microstructure of the forging is tempered sorbite, and the austenite grain size of the forging is more than 5 grades.
Specifically, the normalizing temperature is 900 ℃, the tapping temperature is 900 ℃, the primary tempering temperature is 500 ℃, the tapping temperature is air-cooled to room temperature, so as to obtain finer grain size, the quenching heating temperature is 880 ℃, the quenching liquid is cooled, the quenching cooling medium adopts PAG water-soluble special quenching medium, the concentration of the quenching medium is 6%, the temperature of the quenching medium is 30 ℃, the secondary tempering temperature is 630 ℃, and the tapping temperature is air-cooled to room temperature. The quenching heating heat preservation time is calculated according to the effective thickness of the forge piece of 0.5h/inch (less than 1h is calculated according to 1 h), and the secondary tempering heat preservation time is 1.5 times of the quenching heating heat preservation time.
The mechanical properties of the casting prepared in this example were as follows:
the tensile strength is more than or equal to 1050MPa, the yield strength is more than or equal to 980MPa, the elongation after fracture is more than or equal to 12%, the reduction of area is more than or equal to 45%, and the impact absorption energy is more than or equal to 48J. Compared with the prior art, the tensile strength is improved by more than or equal to 7.71 percent, the yield strength is improved by more than or equal to 9.52 percent, the elongation after fracture is improved by 28.57 percent, and the impact absorption energy is improved by 14.89 percent.
The forged steel piece prepared in the embodiment is subjected to ultrasonic flaw detection by referring to JB/T5000.15 general technical conditions for the nondestructive flaw detection of the forged steel piece, and the acceptance standard is that the quality grade is not lower than grade II. The magnetic powder or the infiltration method is adopted, and no defect visible to naked eyes exists. Compared with the prior art, the invention increases the requirements of ultrasonic II level and no defect of magnetic powder/penetration in the aspect of nondestructive detection, and improves the internal and surface quality of the forging.
Example two:
a low-alloy high-strength steel plate forging for a high-strength structure comprises the following formula components in percentage by weight:
0.57% of C, 0.95% of Si, 0.55% of Mn0.95% of Cr0.95%, 1.35% of Ni0.52%, 0.003% of B, 0.04% of Nb0.06%, 0.015% of P, 0.008% of S and the balance of Fe.
The forging method of the low-alloy high-strength steel plate forging for the high-strength structure comprises the following steps:
s1, smelting:
according to the formula components of the forging, the formula raw materials are put into a smelting furnace for smelting to obtain molten steel, and the molten steel is poured into a mold and solidified to form a steel ingot, wherein the steel ingot belongs to killed steel.
And S2, calculating according to drawing size, forging ratio, loss and other factors, determining blanking size, blanking according to forging blanking specifications, cutting off 8% of the bottom of the steel ingot and 40% of a riser to ensure that defects of shrinkage cavity, looseness, cracks, serious segregation and the like which affect forging quality do not exist, and obtaining the steel billet.
S3, placing the steel billet into a furnace with the furnace temperature not more than 850 ℃, preserving heat for the first time, raising the temperature to the initial forging temperature 1220 ℃ at the temperature rise speed not more than 100 ℃/h, preserving heat for the second time, forging the heated steel billet into the shape required by the drawing through the processes of upsetting, drawing out, punching and the like, wherein the forging ratio is not less than 4, and the finish forging temperature is not less than 800 ℃, thus obtaining the forging blank.
In this embodiment, the effective thickness of the steel billet is 100mm, and the secondary heat preservation time is not less than 110 min.
S4, heat treatment: and (3) sequentially carrying out normalizing, primary tempering, quenching and secondary tempering on the forging blank to obtain the forging, wherein the microstructure of the forging is tempered sorbite, and the austenite grain size of the forging is more than 5 grades.
Specifically, the normalizing temperature is 930 ℃, the tapping air cooling is carried out to the room temperature, the primary tempering temperature is 600 ℃, the tapping air cooling is carried out to the room temperature, so as to obtain the finer grain size, the quenching heating temperature is 890 ℃, the quenching liquid is cooled, the quenching cooling medium adopts PAG water-soluble special quenching medium, the concentration of the quenching medium is 8%, the temperature of the quenching medium is 35 ℃, the secondary tempering temperature is 640 ℃, and the tapping air cooling is carried out to the room temperature. The quenching heating heat preservation time is calculated according to the effective thickness of the forge piece of 0.5h/inch (less than 1h is calculated according to 1 h), and the secondary tempering heat preservation time is 1.8 times of the quenching heating heat preservation time.
The forged steel piece prepared in the embodiment is subjected to ultrasonic flaw detection by referring to JB/T5000.15 general technical conditions for the nondestructive flaw detection of the forged steel piece, and the acceptance standard is that the quality grade is not lower than grade II. The magnetic powder or the infiltration method is adopted, and no defect visible to naked eyes exists.
Example three:
a low-alloy high-strength steel plate forging for a high-strength structure comprises the following formula components in percentage by weight:
0.21% of C, 0.35% of Si, 0.70% of Mn0, 1.20% of Cr1, 1.50% of Ni1, 0.60% of Mo0.005% of B, 0.06% of Nb0, 0.10% of Ti0.020% of P, 0.010% of S and the balance of Fe.
The forging method of the low-alloy high-strength steel plate forging for the high-strength structure comprises the following steps:
s1, smelting:
according to the formula components of the forging, the formula raw materials are put into a smelting furnace for smelting to obtain molten steel, and the molten steel is poured into a mold and solidified to form a steel ingot, wherein the steel ingot belongs to killed steel.
And S2, calculating according to drawing size, forging ratio, loss and other factors, determining blanking size, blanking according to forging blanking specifications, cutting off 10% of the bottom of the steel ingot and 30% of a riser to ensure that defects of shrinkage cavity, looseness, cracks, serious segregation and the like which affect forging quality do not exist, and obtaining the steel billet.
S3, placing the steel billet into a furnace with the furnace temperature not more than 850 ℃, preserving heat for the first time, raising the temperature to 1240 ℃ at the initial forging temperature at the temperature not more than 100 ℃/h, preserving heat for the second time, forging the heated steel billet into the shape required by the drawing through the processes of upsetting, drawing out, punching and the like, wherein the forging ratio is not less than 4, and the finish forging temperature is not less than 800 ℃, thus obtaining the forging blank.
In this embodiment, the effective thickness of the steel billet is 110mm, and the secondary heat preservation time is not less than 132 min.
S4, heat treatment: and (3) sequentially carrying out normalizing, primary tempering, quenching and secondary tempering on the forging blank to obtain the forging, wherein the microstructure of the forging is tempered sorbite, and the austenite grain size of the forging is more than 5 grades.
Specifically, the normalizing temperature is 950 ℃, the tapping temperature is air-cooled to room temperature, the primary tempering temperature is 650 ℃, the tapping temperature is air-cooled to room temperature, so as to obtain finer grain size, the quenching heating temperature is 900 ℃, the quenching liquid is cooled, the quenching cooling medium is PAG water-soluble special quenching medium, the concentration of the quenching medium is 10%, the temperature of the quenching medium is 40 ℃, the secondary tempering temperature is 650 ℃, and the tapping temperature is air-cooled to room temperature. The quenching heating heat preservation time is calculated according to the effective thickness of the forge piece of 0.5h/inch (less than 1h is calculated according to 1 h), and the secondary tempering heat preservation time is 2 times of the quenching heating heat preservation time.
The forged steel piece prepared in the embodiment is subjected to ultrasonic flaw detection by referring to JB/T5000.15 general technical conditions for the nondestructive flaw detection of the forged steel piece, and the acceptance standard is that the quality grade is not lower than grade II. The magnetic powder or the infiltration method is adopted, and no defect visible to naked eyes exists.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (10)
1. The low-alloy high-strength steel plate forging for the high-strength structure is characterized by comprising the following formula components in percentage by weight:
0.12 to 0.21 percent of C, 0.20 to 0.35 percent of Si, 0.45 to 0.70 percent of Mn, 0.85 to 1.20 percent of Cr0.20 percent of Ni, 1.20 to 1.50 percent of Ni, 0.45 to 0.60 percent of Mo0.001 to 0.005 percent of B, less than or equal to 0.06 percent of Nb, 0.01 to 0.10 percent of Ti, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S and the balance of Fe;
the carbon equivalent is CE, and CE is C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15 is less than or equal to 0.68 percent.
2. The low alloy high strength steel plate forging for the high strength structure of claim 1, comprising the following formula components by weight percent:
0.57% of C, 0.95% of Si, 0.55% of Mn0.95% of Cr0.95%, 1.35% of Ni0.52%, 0.003% of B, 0.04% of Nb0.06%, 0.015% of P, 0.008% of S and the balance of Fe.
3. A method of forging a low alloy high strength steel plate forging for high strength structures as claimed in any one of claims 1 to 2, comprising the steps of:
s1, smelting:
according to the formula components of the forging, the formula raw materials are put into a smelting furnace for smelting to obtain molten steel, the molten steel is poured into a mold and solidified to form a steel ingot, and the steel ingot is killed steel;
s2, cutting off the bottom and a riser of the steel ingot, and blanking to obtain a steel billet;
s3, loading the steel billet into a furnace, performing primary heat preservation, heating to the initial forging temperature, performing secondary heat preservation, and forging to obtain a forging blank;
s4, heat treatment: and (4) sequentially carrying out normalizing, primary tempering, quenching and secondary tempering on the forging blank to obtain the forging.
4. The forging method as recited in claim 3, wherein in the step S2, a bottom of the steel ingot is cut off by 7-10%, and a riser is cut off by 52-30%.
5. The forging method as recited in claim 3, wherein the step S3 is performed by charging the slab into a furnace having a furnace temperature of not more than 850 ℃, performing primary heat-preservation at a temperature-raising rate of not more than 100 ℃/h to a forging start temperature of 1200 ℃ and 1240 ℃, performing secondary heat-preservation, and performing forging at a forging finish temperature of not less than 800 ℃.
6. The forging method as recited in claim 5, wherein the primary soaking time is not less than 2 hours, and the secondary soaking time is set to t, which is not less than (1-1.2). times.dmin/mm, wherein D represents an effective thickness of the steel slab.
7. The forging method as recited in claim 6, wherein in step S3, the forging ratio is not less than 4.
8. The forging method as recited in claim 3, wherein in the step S4, the normalizing temperature is 900-950 ℃, the primary tempering temperature is 500-650 ℃, the primary tempering temperature is 890 +/-10 ℃, the quenching liquid is cooled, the concentration of the quenching medium is 6-10%, the temperature of the quenching medium is 30-40 ℃, the secondary tempering temperature is 640 +/-10 ℃, and the secondary tempering temperature is 640 +/-10 ℃, the secondary tempering temperature is taken out and the air is cooled to the room temperature.
9. The forging method as recited in claim 8, wherein the quenching heating holding time is calculated according to the effective thickness of the forging piece of 0.5h/inch, and the secondary tempering holding time is 1.5-2 times of the quenching heating holding time.
10. The forging method of claim 9, wherein the microstructure of the forging is tempered sorbite, and the austenite grain size of the forging is greater than 5 grade.
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