CN114410937A - Method for preventing cutting delay cracks of large-thickness low-alloy martensitic steel - Google Patents
Method for preventing cutting delay cracks of large-thickness low-alloy martensitic steel Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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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
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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
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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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
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
Abstract
The invention discloses a method for preventing cutting delay cracks of large-thickness low-alloy martensitic steel. Belongs to the field of steel plate surface quality control, and the low-alloy high-strength martensitic steel comprises the following chemical components: C. mn, Si, Ti, Ni, Cr, Mo, Nb, Al, B, S and P, and the balance of Fe and impurities; the preparation method comprises the following steps: preparing low-alloy martensitic steel by molten iron desulfurization, converter, LF + RH, continuous casting, heating by a heating furnace, TMCP, ACC, quenching and tempering; the reasonable content proportion of Ti, Nb, Mo, Al and B elements is adopted, and the hardenability and the inclusion size of the large-thickness steel plate are controlled; in addition, the formation and the expansion of delayed cracks are avoided by adopting a secondary quenching and low-temperature tempering heat treatment process; the steel plate is cut by flame, the steel plate is preheated before being cut by flame, and the fireproof heat-preservation cotton is covered or moved into a heat-preservation pit for slow cooling after wind shielding cutting, so that stress-induced delayed cracks generated after cutting are effectively avoided.
Description
Technical Field
The invention belongs to the field of steel plate surface quality control, relates to a method for preventing cutting delay cracks of large-thickness low-alloy martensitic steel, and particularly relates to a method for preventing cutting delay cracks of large-thickness low-alloy high-strength martensitic steel.
Background
In the prior art, low-alloy high-strength martensitic steel is widely used due to low alloy element content, high strength and high toughness; the later cutting process of the steel plate can adopt cutting methods such as laser cutting, plasma cutting, flame cutting and the like, wherein the laser cutting and the plasma cutting have requirements on the thickness of the cut steel plate, so that certain limitation exists; the flame cutting is widely applied due to low cost, easy operation, high cutting efficiency and large thickness range of the cuttable steel plate; flame cutting is often adopted for the large-thickness high-strength martensitic steel plate, but delayed cracks are easily formed on the hot cut surface after flame cutting. Before the delayed crack is generated, no obvious sign exists, and after the delayed crack is expanded, sudden brittle fracture can be initiated, so that catastrophic results are caused.
The delayed cracks of the fire section are caused by that the cutting surface of the steel plate is influenced by cutting thermal cycle, and the structure phase change occurs, if segregation zones and inclusions with large-size sharp corners exist in the structure, hydrogen atoms are easy to capture, so that hydrogen embrittlement is caused, and the delayed cracks are formed; therefore, how to solve the above problems becomes a matter that needs to be considered by the next staff.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the problem that delayed cracks are generated on a cutting surface after low-alloy martensitic steel is subjected to flame cutting, the invention researches the production process and the flame cutting process of the low-alloy martensitic steel; starting from the regulation and control of steel plate components, on the premise of ensuring the hardenability of the martensite steel plate, the quantity and size of carbonitrides are reduced by optimizing the types and contents of micro-alloying elements; meanwhile, the continuous casting cooling rate and the casting blank soaking temperature are adjusted and controlled, so that the purposes of controlling the size of the inclusions and reducing segregation are achieved; the heat treatment of the steel adopts a secondary quenching and tempering process, wherein the primary quenching temperature is higher than the secondary quenching temperature, and the heat preservation time is longer than the secondary quenching, so that the aim of uniformly distributing alloy elements is fulfilled, and simultaneously, nucleation points are provided for secondary quenching austenite grains; the secondary quenching process is adopted, so that alloy elements can be uniformly distributed, the grain refinement can be ensured, and finally, the tempering process is adopted to make the structure more uniform so as to eliminate the structure stress; in the process of cutting the steel plate, preheating is carried out, wind shielding cutting is carried out by using a flame gun, and slow cooling is carried out at last, so that the thermal stress generated by nonuniform cutting temperature in the cutting process is eliminated, and the problem that delayed cracks are easily generated after the low-alloy martensite steel plate is subjected to flame cutting is solved.
The technical scheme is as follows: the invention relates to a method for preventing the cutting delay cracks of a large-thickness low-alloy martensitic steel; wherein the low-alloy martensitic steel comprises the following chemical components in percentage by weight: 0.15-0.30% of C, 0.50-1.50% of Mn, 0.20-0.60% of Si, less than or equal to 0.25% of Ti, less than or equal to 0.7% of Ni, less than or equal to 1.0% of Cr, less than or equal to 0.5% of Mo, less than or equal to 0.060% of Nb, 0.03-0.075% of Al, 0.001-0.003% of B, less than or equal to 0.005% of S, less than or equal to 0.010% of P, and the balance of Fe and impurities;
the preparation steps of the low-alloy high-strength martensitic steel are as follows: the low-alloy high-strength martensitic steel is finally prepared by molten iron desulphurization, converter, LF + RH, continuous casting, heating by a heating furnace, TMCP, ACC, quenching and tempering.
Further, the content of N element contained in the low-alloy martensitic steel is not more than 45 ppm.
Further, the ratio of the element content of Ti to the element content of N is in the range of 3.4-4.0.
Further, in the continuous casting process, the continuous casting cooling rate is 4-10 ℃/s.
Furthermore, in the heating process of the heating furnace, the soaking temperature is 1200-1240 ℃, and the soaking time is more than or equal to 1.4 h.
Further, in the quenching process, the quenching process is secondary quenching, and the specific steps are as follows:
(1) and primary quenching: heating at 910-;
(2) and secondary quenching: heating at 850-.
Further, in the tempering preparation process, the tempering temperature is 200-.
Further, the low-alloy martensitic steel needs to be subjected to flame cutting after being quenched and tempered at low temperature;
wherein, preheating is needed before flame cutting, and the preheating temperature is 100-200 ℃;
the preheating mode comprises preheating in a heat treatment furnace, preheating by a combustion gun and preheating by an electronic heating pad;
in addition, in the flame cutting process, the starting speed is 150-;
the low-alloy high-strength martensitic steel plate needs to be cooled after flame cutting, and the cooling process is to cover the fireproof heat-preservation cotton or move the low-alloy high-strength martensitic steel plate into a heat-preservation pit for slow cooling.
Furthermore, the size of the carbonitride in the obtained low-alloy martensitic steel is less than 4 μm, and the size of the crystal grains of the steel plate is less than 10 μm.
Has the advantages that: compared with the prior art, the invention is used for the production process of the low-alloy martensitic steel and the flame cutting process of the steel plate; the method has the advantages that the types and the contents of microalloying elements contained in the steel plate are adjusted, the continuous casting cooling rate and the heating temperature of a casting blank in the production process of the steel plate are regulated and controlled, and the process optimization is carried out on the heat treatment process of the steel plate, so that the size of inclusions in the steel plate can be effectively controlled, the segregation phenomenon generated by the enrichment of the alloying elements in the steel plate is improved, and the performance of the steel plate is optimized; in addition, the flame cutting process of the steel plate is optimized; the invention controls delayed crack inducing factors such as inclusions and segregation zones, achieves the effect of controlling the micro-crack expansion by refining grains, and has the effect of dual control of delayed crack generation.
Drawings
FIG. 1 is a flow chart of the preparation of the present invention;
FIG. 2 is a graph showing the grain size of the steel sheet according to the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples.
The invention relates to a method for preventing the cutting delay cracks of a large-thickness low-alloy martensitic steel; specifically, firstly, chemical composition adjustment is carried out; namely, the contents of Ti, Nb, Mo, Al and B elements in production raw materials are adjusted, and specifically, the low-alloy high-strength martensitic steel comprises the following chemical components in percentage by weight: 0.15-0.30% of C, 0.50-1.50% of Mn, 0.20-0.60% of Si, less than or equal to 0.25% of Ti, less than or equal to 0.7% of Ni, less than or equal to 1.0% of Cr, less than or equal to 0.5% of Mo, less than or equal to 0.060% of Nb, 0.03-0.075% of Al, 0.001-0.003% of B, less than or equal to 0.005% of S, less than or equal to 0.010% of P, and the balance of Fe and impurities; thereby ensuring that the hardenability of the steel plate with large thickness is increased, simultaneously ensuring that all elements fully play a role, and avoiding adverse effects on the performance of steel products caused by improper addition of all elements;
the preparation steps are as follows: the low-alloy high-strength martensitic steel is finally prepared by molten iron desulphurization, converter, LF + RH, continuous casting, heating by a heating furnace, TMCP, ACC, quenching and tempering.
Further, controlling the content of N element: the content of N element in the low-alloy martensitic steel is less than or equal to 45ppm, and the aim is to reduce the content of N element in the steel plate as much as possible, effectively control the precipitation of BN, ensure the quenching effect of B element, prevent large-size (Ti, Nb) N inclusions from being generated and avoid inducing delayed cracks.
Further, the ratio of the element content of Ti to the element content of N ranges from 3.4 to 4.0; can fully fix the N by Ti element and prevent the generation of large-size TiN inclusion.
Further, controlling the continuous casting cooling rate; in the continuous casting process, the continuous casting cooling rate is 4-10 ℃/s; the method aims to control the condensation rate of molten steel in the continuous casting process of the steel plate, so that the condensation rate is in the range of 4-10 ℃/s, and the size of the (Ti, Nb) N-type inclusions can be effectively controlled.
Further, controlling the heating temperature of the casting blank (heating process of a heating furnace); the soaking temperature of the casting blank is within the range of 1200 ℃ and 1240 ℃, the soaking time is more than or equal to 1.4h (h is the thickness of the casting blank and cm), the diffusivity of alloy elements can be increased, and the segregation zone generated by the enrichment of the alloy elements can be effectively reduced.
Further, optimizing the heat treatment process of the steel plate; the final heat treatment of the steel plate adopts a secondary quenching and tempering treatment process, and the steps are as follows:
(1) and primary quenching: heating at 910-;
(2) and secondary quenching: heating at 850-.
Further, the method comprises the following steps of; and (3) tempering at the tempering temperature of 200-300 ℃ for 40-60min, and discharging the steel plate out of the furnace for natural cooling after the heat preservation is finished.
Further, the steel plate cutting process is optimally designed; carrying out flame cutting on the low-alloy high-strength martensitic steel plate after quenching and low-temperature tempering treatment; wherein, preheating is carried out before flame cutting, the steel plate is preheated to 100-200 ℃, and a combustion gun is used for wind-shielding cutting; the low-alloy high-strength martensite steel plate is cut in a wind-sheltered manner in the flame cutting process, the starting speed is 150-; after cutting, covering refractory heat-insulating cotton or moving the refractory heat-insulating cotton into a heat-insulating pit to slowly cool the refractory heat-insulating cotton; the cooling process after the low-alloy high-strength martensitic steel plate is cut by flame is to cover refractory heat-insulating cotton or move the low-alloy high-strength martensitic steel plate into a heat-insulating pit for slow cooling;
in addition; the preheating mode comprises preheating in a heat treatment furnace, preheating by a combustion gun and preheating by an electronic heating pad.
Furthermore, the size of the carbonitride in the obtained low-alloy martensitic steel is less than 4 μm, and the size of the crystal grains of the steel plate is less than 10 μm.
In the present invention, 1, for a martensitic steel sheet having a large thickness, the cooling rate of the center of the steel sheet after quenching is low, and therefore, the alloy element B is added to the steel to increase the hardenability of the steel sheet, but the B element is easily combined with the N element present in the steel to form stable BN precipitates, resulting in a decrease in the content of free B element in austenite and a decrease in hardenability; 2. the binding force of Ti element and N element is much higher than that of B element, so that a proper amount of Ti element can be added into steel to be combined with N to form TiN precipitate, the N element is fixed, the B element is dissociated, and the hardenability is increased (Table 1-component 1); meanwhile, the nano TiN plays a role in refining grains; however, since Ti element and N element have strong binding force, when Ti element is added into steel in large amount, it is inevitable to form micron-sized TiN inclusion or long-sized TiC inclusion with regular shape and sharp corner, and it is easy to capture H atom and induceDelayed cracking due to hydrogen evolution; 3. nb element can be combined with N element to form NbN precipitate, fix N element and free B element, but the combination force is weaker than Ti element, so that the addition amount of Ti element can be selectively reduced, and a small amount of Nb element is added into the steel to achieve the effect of fixing N element (Table 1-component 2); alternatively, it is possible to choose not to add Ti, only to add Nb element to the steel above the conventional content to fix the N element (table 1-component 3); the number of regularly shaped micron-sized carbonitrides can be effectively reduced; 4. the combined addition of Mo and Nb can increase the effectiveness of B element, so that Mo element with higher than conventional content and appropriate amount of Nb element can be selectively added into steel to fix N element, so that B element is in free state and plays the role of B element (Table 1-component 4); 5. al also has a certain N fixation function, but Al is firstly combined with O in steel to generate Al2O3(ii) a Therefore, the addition amount of the Al element can be increased to 0.05-0.070%, the Al element left after deoxidation is used for fixing the N element, and the quenching effect of the B element is increased (table 1-component 5);
TABLE 1
6. In order to avoid the formation of micron-sized (Ti, Nb) N inclusion induced delayed cracks by the combination of Ti, Nb and N in the steel, the content of N element is controlled to be less than or equal to 45 ppm; when the Ti element is added independently, in order to ensure that the Ti element is fully fixed with N, the ratio of the Ti content to the N content is more than or equal to 3.4 of the stoichiometric ratio of Ti to N in TiN, and in order to prevent the generation of micron-sized Ti (N, C) inclusions caused by excessive addition of the Ti element, the ratio of the Ti content to the N content needs to be controlled to be less than or equal to 4.0, and hydrogen is easy to capture at the sharp corners of the micron-sized Ti (N, C) inclusions, so that the Ti element is one of the main reasons for inducing delayed cracks; in order to control the size of the inclusion, the cooling rate is 4-10 ℃/s in the continuous casting process so as to prevent the inclusion from growing at an excessively slow cooling rate; 7. the segregation zone has high stress concentration, so that delayed crack initiation is easily caused at the segregation zone, when a casting blank is heated in a heating furnace, the soaking temperature of the casting blank is controlled within the range of 1200 ℃ and 1240 ℃, and the soaking time is more than or equal to 1.4h (h is the thickness of the casting blank and cm), so that alloy elements are uniformly distributed after being fully diffused, and segregation is reduced; in order to make the crystal grains of the steel plate finer and the martensite structure more uniform, the steel plate adopts a heat treatment process of secondary quenching and tempering; wherein the primary quenching mainly makes alloy elements fully dissolved in solid and uniformly distributed to provide nucleation sites for the growth of secondary quenching grains, so that the primary quenching temperature (910-; the second quenching can form uniform and fine grains; namely, the secondary quenching heat treatment process can ensure that alloy elements are fully dissolved in solution and can also ensure that finer grains are obtained; 8. preheating the cut steel plate before cutting the steel plate so as to ensure that the steel plate is heated uniformly during flame cutting and avoid the cutting heat of the steel plate from generating residual thermal stress; in the cutting process, wind is avoided for cutting, and the cutter starting speed and the cutting speed are accurately controlled, so that the cutting defect caused by too high or too low cutting speed is prevented; covering refractory heat-insulating cotton after cutting or moving the cut refractory heat-insulating cotton into a heat-insulating pit for slow cooling.
Example 1:
the chemical components of the embodiment are as follows: 0.22% of C, 0.75% of Mn, 0.40% of Si, 0.22% of Ni, 0.50% of Cr, 0.15% of Mo, 0.008% of Ti, 0.017% of Nb, 0.032% of Al, 0.0012% of B, 0.004% of S, 0.008% of P, and the balance of Fe and impurities.
The production and heat treatment process comprises the following steps:
molten steel is subjected to molten iron desulphurization, converter, LF + RH and continuous casting, and the cooling speed is controlled to be 4-10 ℃/s in the continuous casting process.
Continuously casting into a casting blank with the thickness of 320mm, and heating the casting blank in a heating furnace at the soaking temperature of 1235 ℃ for 47 min. Taking out of the heating furnace, and rolling into steel with the thickness of 70mm by TMCP.
Carrying out secondary quenching and tempering heat treatment processes on the steel. The method comprises the following steps:
primary quenching: heating at 940 deg.C, maintaining for 45min, and cooling with water;
secondary quenching: heating to 880 ℃, preserving heat for 35min, and cooling by water;
tempering treatment: heating at 290 deg.C, maintaining for 55min, and air cooling.
And (3) steel plate cutting process:
heating the steel plate in a heat treatment furnace to 170 ℃, discharging the steel plate out of the furnace, cutting the steel plate by using a combustion gun at a cutter starting speed of 150mm/min and a cutting speed of 350mm/min, and moving the steel plate into a heat preservation pit after cutting to eliminate stress generated by cutting.
The cut steel sheet did not develop delayed cracking after leaving for 45 days.
Example 2:
the chemical components of the embodiment are as follows: 0.18% of C, 1.21% of Mn, 0.50% of Si, 0.15% of Ni, 0.62% of Cr, 0.019% of Ti, 0.032% of Al, 0.0015% of B, 0.004% of S, 0.009% of P and the balance of Fe and impurities.
The production and heat treatment process comprises the following steps:
molten steel is subjected to molten iron desulphurization, converter, LF + RH and continuous casting, and the cooling speed is controlled to be 4-10 ℃/s in the continuous casting process.
Continuously casting into a casting blank with the thickness of 260mm, and heating the casting blank in a heating furnace at the soaking temperature of 1230 ℃ for 40 min. Taking out of the heating furnace, and rolling into steel with the thickness of 50mm by TMCP.
The steel is subjected to secondary quenching and tempering heat treatment. The method comprises the following steps:
primary quenching: heating to 930 deg.C, maintaining for 42min, and cooling with water;
secondary quenching: heating at 870 deg.C, keeping the temperature for 28min, and cooling with water;
tempering treatment: heating at 260 deg.C, keeping the temperature for 50min, and air cooling.
And (3) steel plate cutting process:
and (3) heating the steel plate in a heat treatment furnace to 150 ℃, discharging, cutting by using a combustion gun at a cutter starting speed of 170mm/min and a cutting speed of 370mm/min, and moving the steel plate into a heat preservation pit after cutting to eliminate stress generated by cutting.
The cut steel sheet did not develop delayed cracking after leaving for 45 days.
Example 3:
the chemical components of the embodiment are as follows: 0.25% of C, 0.98% of Mn, 0.30% of Si, 0.12% of Ni, 0.53% of Cr, 0.046% of Nb, 0.032% of Al, 0.0017% of B, 0.0043% of S, 0.009% of P, and the balance of Fe and impurities.
The production and heat treatment process comprises the following steps:
molten steel is subjected to molten iron desulphurization, converter, LF + RH and continuous casting, and the cooling speed is controlled to be 4-10 ℃/s in the continuous casting process.
Continuously casting into a casting blank with the thickness of 260mm, and heating the casting blank in a heating furnace, wherein the soaking temperature is 1220 ℃, and the soaking time is 40 min. Taking out of the heating furnace, and rolling into steel with the thickness of 50mm by TMCP.
The steel is subjected to secondary quenching and tempering heat treatment. The method comprises the following steps:
primary quenching: heating at 927 deg.C, maintaining the temperature for 40min, and cooling with water;
secondary quenching: heating to 875 ℃, preserving heat for 30min, and cooling by water;
tempering treatment: heating to 255 deg.C, keeping the temperature for 45min, and air cooling.
And (3) steel plate cutting process:
and (3) heating the steel plate to 145 ℃ in a heat treatment furnace, discharging the steel plate out of the furnace, cutting the steel plate by using a combustion gun, starting the cutter at a speed of 160mm/min and cutting at a speed of 360mm/min, and moving the steel plate into a heat preservation pit after cutting to eliminate stress generated by cutting.
The cut steel sheet did not develop delayed cracking after leaving for 45 days.
Example 4:
the chemical components of the embodiment are as follows: 0.23% of C, 1.01% of Mn, 0.56% of Si, 0.32% of Ni, 0.55% of Cr, 0.35% of Mo, 0.68% of Al, 0.0019% of B, 0.004% of S, 0.008% of P and the balance of Fe and impurities.
The production and heat treatment process comprises the following steps:
molten steel is subjected to molten iron desulphurization, converter, LF + RH and continuous casting, and the cooling speed is controlled to be 4-10 ℃/s in the continuous casting process.
Continuously casting into a casting blank with the thickness of 150mm, and heating the casting blank in a heating furnace, wherein the soaking temperature is 1210 ℃, and the soaking time is 22 min. Taking out of the heating furnace and rolling into steel with the thickness of 40mm by TMCP.
The steel is subjected to secondary quenching and tempering heat treatment. The method comprises the following steps:
primary quenching: heating to 910 deg.C, and maintaining for 35 min; water cooling;
secondary quenching: heating to 860 deg.C, and maintaining for 25 min; water cooling;
tempering treatment: heating at 240 deg.C, keeping the temperature for 45min, and air cooling.
And (3) steel plate cutting process:
preheating the steel plate to 110 ℃ by using a combustion gun, then cutting by using the combustion gun, wherein the cutter starting speed is 210mm/min, the cutting speed is 540mm/min, and after the cutting is finished, covering refractory heat-insulating cotton and slowly cooling to the room temperature to eliminate the stress generated by cutting.
The cut steel sheet did not develop delayed cracking after leaving for 45 days.
Example 5:
the chemical components of the embodiment are as follows: 0.27% C, 0.83% Mn, 0.50% Si, 0.53% Ni, 0.43% Cr, 0.49% Mo, 0.030% Nb, 0.045% Al, 0.002% B, 0.003% S, 0.008% P, and the balance Fe and impurities.
The production and heat treatment process comprises the following steps:
molten steel is subjected to molten iron desulphurization, converter, LF + RH and continuous casting, and the cooling speed is controlled to be 4-10 ℃/s in the continuous casting process.
Continuously casting into a casting blank with the thickness of 260mm, and heating the casting blank in a heating furnace, wherein the soaking temperature is 1220 ℃, and the soaking time is 37 min. Taking out of the heating furnace, and rolling into steel with the thickness of 50mm by TMCP.
The steel is subjected to secondary quenching and tempering heat treatment. The method comprises the following steps:
primary quenching: heating to 920 deg.C, and keeping the temperature for 40 min; water cooling;
secondary quenching: heating to 870 deg.C, and keeping the temperature for 28 min; water cooling;
tempering treatment: heating at 255 deg.C, maintaining for 55min, and air cooling.
And (3) steel plate cutting process:
heating the steel plate to 140 ℃ by using an electronic heating pad, discharging from the furnace, cutting by using a combustion gun at a cutter starting speed of 180mm/min and a cutting speed of 365mm/min, covering refractory heat-insulating cotton after cutting, and slowly cooling to room temperature to eliminate stress generated by cutting.
The cut steel sheet did not develop delayed cracking after leaving for 45 days.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (9)
1. A method for preventing the cutting delay crack of the large-thickness low-alloy martensitic steel is characterized in that,
the low-alloy martensitic steel comprises the following chemical components in percentage by weight: 0.15-0.30% of C, 0.50-1.50% of Mn, 0.20-0.60% of Si, less than or equal to 0.25% of Ti, less than or equal to 0.7% of Ni, less than or equal to 1.0% of Cr, less than or equal to 0.5% of Mo, less than or equal to 0.060% of Nb, 0.03-0.075% of Al, 0.001-0.003% of B, less than or equal to 0.005% of S, less than or equal to 0.010% of P, and the balance of Fe and impurities;
the preparation steps of the low-alloy high-strength martensitic steel are as follows: the low-alloy high-strength martensitic steel is finally prepared by molten iron desulphurization, converter, LF + RH, continuous casting, heating by a heating furnace, TMCP, ACC, quenching and tempering.
2. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1, wherein,
the low-alloy martensitic steel contains N element in an amount of 45ppm or less.
3. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
the ratio of the element content of Ti to the element content of N is 3.4-4.0.
4. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
and in the continuous casting process, the continuous casting cooling rate is 4-10 ℃/s.
5. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
in the heating process of the heating furnace, the soaking temperature is 1200-1240 ℃, and the soaking time is more than or equal to 1.4 h.
6. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
in the quenching process, the quenching process is secondary quenching, and the method comprises the following specific steps:
(1) and primary quenching: heating at 910-;
(2) and secondary quenching: heating at 850-.
7. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
in the tempering preparation process, the tempering temperature is 200-300 ℃, the heat preservation time is 40-60min, and after the heat preservation is finished, the steel plate is taken out of the furnace and is naturally cooled.
8. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
the low-alloy martensitic steel is subjected to quenching and low-temperature tempering treatment and then needs to be subjected to flame cutting;
wherein, preheating is needed before flame cutting, and the preheating temperature is 100-200 ℃;
the preheating mode comprises preheating in a heat treatment furnace, preheating by a combustion gun and preheating by an electronic heating pad;
in addition, in the flame cutting process, the starting speed is 150-;
the low-alloy high-strength martensitic steel plate needs to be cooled after flame cutting, and the cooling process is to cover the fireproof heat-preservation cotton or move the low-alloy high-strength martensitic steel plate into a heat-preservation pit for slow cooling.
9. The method for preventing the cutting delay cracks of the large-thickness low-alloy martensitic steel as claimed in claim 1,
the size of the carbonitride in the obtained low-alloy martensitic steel is less than 4 mu m, and the size of the steel plate crystal grain is less than 10 mu m.
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| CN109280850A (en) * | 2018-10-29 | 2019-01-29 | 南京钢铁股份有限公司 | A kind of big thickness toughness low alloy wear resistant steel plate of 80mm and its manufacturing method |
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| CN111996441A (en) * | 2020-07-10 | 2020-11-27 | 江阴兴澄特种钢铁有限公司 | TiC enhanced martensite wear-resistant steel plate with high toughness and good bending performance and manufacturing method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106756489A (en) * | 2016-12-14 | 2017-05-31 | 武汉钢铁股份有限公司 | 450 grades of anti-crack high-strength abrasion-proof steels of Brinell hardness and its manufacture method |
| CN109280850A (en) * | 2018-10-29 | 2019-01-29 | 南京钢铁股份有限公司 | A kind of big thickness toughness low alloy wear resistant steel plate of 80mm and its manufacturing method |
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