CN115747634A - High-quality non-quenched and tempered steel, crankshaft and preparation method - Google Patents
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Abstract
The invention discloses a high-quality non-quenched and tempered steel, a crankshaft and a preparation method thereof, wherein the non-quenched and tempered steel comprises the following components in percentage by mass: c:0.36 to 0.40%, si:0.50 to 0.65%, mn: 1.30-1.60%, S:0.050 to 0.065%, P: less than or equal to 0.025%, cr:0.10 to 0.20%, mo: less than or equal to 0.04%, cu: less than or equal to 0.25%, ni: less than or equal to 0.25%, V:0.08 to 0.13%, al:0.010 to 0.050%, N: 0.012-0.020%, B is less than or equal to 0.0005%, and H is less than or equal to 2.0ppm. In the smelting process, nitrogen is blown without adding nitrides, noble alloy metal Mn is not used, low-carbon ferromanganese is used to realize the content of residual B less than or equal to 5ppm, the production cost can be saved, and the method is suitable for large-scale economical and industrial production.
Description
Technical Field
The invention relates to a process method of quenched and tempered steel, in particular to high-quality non-quenched and tempered steel, a crankshaft and a preparation method.
Background
The non-quenched and tempered steel has the advantages of excellent short flow, zero deformation, energy conservation, low emission, easy cutting, uniform performance, high yield and the like, reduces about 1/4 of processing procedures, improves the utilization rate of materials by 5-10 percent, and comprehensively reduces the energy consumption and the manufacturing cost by more than 25 percent.
Due to the implementation of the national six new regulations, the engine develops towards high explosion pressure, new requirements on the strength of the engine crankshaft are put forward, and non-quenched and tempered steel is developed towards high strength and high performance in order to realize light weight of an automobile. The traditional non-quenched and tempered steel has the tensile strength of 750-850Mpan, which is difficult to meet new requirements, and the non-quenched and tempered steel with higher strength is developed to meet new changes of steel for engine crankshafts. Meanwhile, the traditional crankshaft forging technology is difficult to meet the technical requirements.
The prior patent application CN 113862576AB belongs to the field of special steel production and processing in metallurgy industry, relates to non-quenched and tempered steel, a crankshaft and a production method thereof, and introduces medium-high carbon non-quenched and tempered steel, a crankshaft and a production method thereof. The reasonable design of the components, carbon equivalent and nitrogen content in the non-quenched and tempered steel is mainly adopted, so that the hardenability of the non-quenched and tempered steel can meet the requirement, and the non-quenched and tempered steel can obtain good surface hardness in the subsequent surface induction heating process; and the strip structure in the steel is reduced by controlling the process parameters in the continuous casting process and the controlled rolling and controlled cooling process, particularly controlling the pit entering slow cooling temperature of the rolled round steel. But can only reach the use requirement of medium strength but not the use requirement of high strength, the yield can only reach more than 500Mpa, the tensile can only reach more than 820Mpa, and the higher use requirement can not be met.
Therefore, it is desired to solve the above problems.
Disclosure of Invention
The purpose of the invention is as follows: the first purpose of the invention is to provide high-quality non-quenched and tempered steel, which achieves the synergistic effect of precipitation strengthening, fine grain strengthening and structure strengthening through economic alloy proportion, and improves the strength and toughness of the steel.
The second purpose of the invention is to provide a preparation method of the high-quality non-quenched and tempered steel, which can obtain a fine pearlite structure through a controlled rolling and controlled cooling technology and further improve the strength.
A third object of the present invention is to provide a crankshaft made of high-quality non-heat-treated steel.
The fourth purpose of the invention is to provide the preparation method of the crankshaft, and the preparation method adjusts the structure of the crankshaft forging by controlling the cooling speed of the crankshaft forging in different temperature ranges, so that the strength of the crankshaft forging is improved, and the crankshaft forging meets the technical requirements of high-quality and high-strength automobile engine crankshafts.
The technical scheme is as follows: in order to achieve the purpose, the invention discloses high-quality non-quenched and tempered steel, which comprises the following components in percentage by mass: c:0.36 to 0.40%, si:0.50 to 0.65%, mn: 1.30-1.60%, S:0.050 to 0.065%, P: less than or equal to 0.025 percent, cr:0.10 to 0.20%, mo: less than or equal to 0.04%, cu: less than or equal to 0.25 percent, ni: less than or equal to 0.25%, V:0.08 to 0.13%, al: 0.010-0.050%, N:0.012 to 0.020 percent, less than or equal to 0.0005 percent of B, less than or equal to 2.0ppm of H, and the balance of Fe and other inevitable impurities.
Wherein the non-quenched and tempered steel comprises the following components in percentage by mass: c:0.36 to 0.40 percent; si:0.50 to 0.65 percent; mn:1.35 to 1.55 percent; s:0.050 to 0.065 percent; p: less than or equal to 0.020%; cr:0.10 to 0.20 percent; mo: less than or equal to 0.03 percent; cu: less than or equal to 0.15 percent; ni: less than or equal to 0.15 percent; v:0.08 to 0.13 percent; al: 0.010-0.030%; 0.013 to 0.020 percent of N; b is less than or equal to 0.0005 percent; h is less than or equal to 2.0ppm; the balance of Fe and other inevitable impurities.
Preferably, the structure of the non-quenched and tempered steel is pearlite and ferrite, and the grain size of the metallographic structure of the round steel can reach 7-8 grades.
Furthermore, the tensile strength of the non-quenched and tempered steel is more than or equal to 900MPa, the yield strength is more than or equal to 800MPa, the elongation is more than or equal to 10 percent, and the reduction of area is more than or equal to 35 percent.
The invention relates to a preparation method of high-quality non-quenched and tempered steel, which comprises the following steps:
electric furnace smelting, LF refining, VD refining, continuous casting, heating, rolling, flaw detection, induction heating, forging and cooling,
the slag discharge is strictly controlled in the smelting and tapping process of the electric arc furnace, and the tapping B is less than or equal to 0.0003 percent; adjusting Alt to 0.020-0.030% by tapping aluminum;
the LF refining process carries out point component control on components according to a judgment target value, high-purity graphite carbon materials, ferromanganese, ferrosilicon, ferrochromium and ferrovanadium are respectively used for adjusting C, mn, si, cr and V elements to the lower limit or the target value of a judgment range, N is blown in the refining process, siC is used for deoxidation in the early stage, the white slag time is not less than 30min, the Alt content is more than 0.025%, feS is used for adjusting S to 0.050-0.065% before the refining is finished and vacuum, the components are adjusted to a specified range, and VD vacuum degassing is carried out after the temperature is proper;
in the VD vacuum degassing treatment process, treatment is carried out for more than or equal to 15min under the vacuum degree of less than or equal to 1mbar, sampling analysis is carried out after static stirring is carried out for more than or equal to 10min after vacuum breaking, nitrogen can be added by using a high-silicon-nitride cored wire, al wire is fed according to a target, sulfur can be adjusted by feeding sulfur wire according to an S analysis result, sampling analysis is carried out after the static stirring is carried out for more than or equal to 5min after the sulfur wire is fed, fine adjustment is carried out according to the analysis result, all elements meet the judgment range, and continuous casting pouring can be carried out after the soft argon blowing time meets the process requirements.
Further, full-protection pouring is adopted in the whole continuous casting pouring process, electromagnetic stirring is used in the continuous casting process, the electromagnetic stirring strength of a crystallizer is 150-300A, the electromagnetic stirring strength of the tail end of the crystallizer is 500-700A, and the reduction amount is 8-13 mm through a soft reduction technology.
Preferably, the rolling process comprises heating, start rolling and finish rolling; the rolling heating temperature is 1200-1250 ℃, the initial rolling temperature is 1050-1150 ℃, and the final rolling temperature is 850-930 ℃.
The invention relates to a crankshaft which is prepared from the high-quality non-quenched and tempered steel.
The invention relates to a preparation method of a crankshaft, which comprises the following steps: induction heating, forging and forming, deburring and cooling,
the temperature of induction heating is 1200-1240 ℃;
the forging forming comprises initial forging and final forging, wherein the initial forging temperature is 1190-1230 ℃, and the final forging temperature is 1050-1100 ℃; and placing the blank crankshaft after trimming on a cooling line.
Wherein, in the cooling step, the forging piece is cooled at a cooling rate of 1.0-2.0 ℃/s, cooled to 600-700 ℃, slowly cooled in a heat-preserving cover, controlled to be cooled to 280-350 ℃ in the heat-preserving cover at a cooling rate of less than 0.5 ℃/s, and then cooled to room temperature in water.
Has the beneficial effects that: compared with the prior art, the invention has the following remarkable advantages:
(1) According to the process scheme, nitrogen is blown in the smelting process without adding nitrides, a noble alloy metal Mn is not used, the content of residual B which is less than or equal to 5ppm is realized by using a low-carbon ferromanganese alloy, the production cost can be saved, and the method is suitable for large-scale economical and industrial production.
(2) The invention adopts LF + VD smelting and protective pouring, combines with a new technology of electromagnetic stirring and continuous casting under light pressure, and obtains high-cleanness and high-homogeneity metallurgical quality.
(3) The invention adopts medium carbon microalloy non-quenched and tempered steel bar containing V, N and other elements, and obtains fine and uniform crystal grain structure through controlled rolling and controlled cooling process, the crystal grain size and the pearlite lamellar spacing are fine, reasonable ferrite content is obtained, and the high strength and the high toughness of the hot rolled round steel are improved.
(4) The crankshaft steel produced by the process scheme of the invention does not need quenching and tempering treatment, and the cooling mode and the cooling rate are controlled after forging, so that the ferrite is promoted to nucleate in supercooled austenite crystal, and more fine intragranular ferrite is obtained. In addition, the precipitation of fine intragranular ferrite is beneficial to the segmentation of non-transformed super-cooled austenite, so that transformed pearlite colony is refined, and the problem that the strength of non-quenched and tempered steel is surplus and the toughness is insufficient is further solved. The yield strength of the crankshaft reaches 650-670 Mpa, the tensile strength reaches 960-980 Mpa, the elongation is more than or equal to 12%, the reduction of area is more than or equal to 30%, and the crankshaft can be directly used for turning by a user and has good cutting performance.
Drawings
FIG. 1 (a) to FIG. 1 (d) are schematic diagrams of the metallographic phase of the edge and the core of the round steel in the invention;
fig. 2 (a) to 2 (d) are schematic views of the crank shaft structure according to the present invention.
Detailed Description
The technical solution of the present invention is further explained below.
The invention relates to high-quality non-quenched and tempered steel, which comprises the following components in percentage by mass: c:0.36 to 0.40%, si:0.50 to 0.65%, mn: 1.30-1.60%, S:0.050 to 0.065%, P: less than or equal to 0.025 percent, cr:0.10 to 0.20%, mo: less than or equal to 0.04 percent, cu: less than or equal to 0.25 percent, ni: less than or equal to 0.25%, V:0.08 to 0.13%, al: 0.010-0.050%, N: 0.012-0.020%, B less than or equal to 0.0005%, H less than or equal to 2.0ppm, and the balance of Fe and other inevitable impurities. The invention provides a non-quenched and tempered crankshaft steel for an engine, which is characterized in that the most economical alloy proportion is selected, expensive metal Mn is not added in the smelting process, low-carbon ferromanganese is used to achieve the purpose of controlling B, certain N content is controlled, V and Ti microalloy elements are added, N is combined with V and Ti to form an M (C, N) compound, and a proper amount of Al is added to be combined with N to form an AlN compound. The synergistic effect of precipitation strengthening, fine grain strengthening and structure strengthening is achieved by controlling the precipitation of the compound of M (C, N) with fine dispersion and the AlN compound, and the toughness of the steel is improved. In addition, the strength can be further improved by obtaining a finer pearlite structure through a controlled rolling and controlled cooling technology.
The non-quenched and tempered steel further preferably comprises the following components in percentage by mass: c:0.36 to 0.40 percent; si:0.50 to 0.65 percent; mn:1.35 to 1.55 percent; s:0.050 to 0.065 percent; p: less than or equal to 0.020%; cr:0.10 to 0.20 percent; mo: less than or equal to 0.03 percent; cu: less than or equal to 0.15 percent; ni: less than or equal to 0.15 percent; v:0.08 to 0.13 percent; al: 0.010-0.030%; 0.013 to 0.020 percent of N; b is less than or equal to 0.0005 percent; h is less than or equal to 2.0ppm; the balance of Fe and other inevitable impurities. The invention adopts medium carbon microalloy non-quenched and tempered steel bar containing V, N and other elements, obtains a fine and uniform crystal grain structure through a controlled rolling and controlled cooling process, has fine crystal grain size and pearlite lamella spacing, obtains reasonable ferrite content, improves the high strength of hot-rolled round steel and obtains high toughness and plasticity.
After the quenched and tempered steel crankshaft is subjected to quenching and medium-high temperature tempering treatment, a blank crankshaft matrix structure consists of pearlite and ferrite; the grain size of the crankshaft metallographic structure of the round steel can reach 7-8 grades, the mechanical property is higher, the tensile strength is larger than or equal to 900MPa, the yield strength is larger than or equal to 800MPa, the elongation is larger than or equal to 10%, and the reduction of area is larger than or equal to 35%. Although 42CrMo quenched and tempered steel has good strength and mechanical properties, expensive Mo and Cr alloy elements are required, and the defects of crankshaft quenching deformation, high energy consumption due to quenching and tempering and the like exist, so that the 42CrMo quenched and tempered steel is limited in use.
The preparation method of the high-quality non-quenched and tempered steel comprises the following steps:
electric furnace smelting, LF refining, VD refining, continuous casting, heating, rolling, flaw detection, induction heating, forging and cooling,
the slag discharge is strictly controlled in the smelting and tapping process of the electric arc furnace, and the tapping B is less than or equal to 0.0003 percent; adjusting Alt to 0.020-0.030% by tapping aluminum; according to the process scheme, nitrogen is blown in the smelting process without adding nitrides, a noble alloy metal Mn is not used, the content of residual B which is less than or equal to 5ppm is realized by using a low-carbon ferromanganese alloy, the production cost can be saved, and the process scheme is suitable for large-scale economical and industrial production;
the LF refining process carries out point component control on components according to a judgment target value, high-purity graphite carbon materials, ferromanganese, ferrosilicon, ferrochromium and ferrovanadium are respectively used for adjusting C, mn, si, cr and V elements to the lower limit or the target value of a judgment range, N is blown in the refining process, siC is used for deoxidation in the early stage, the white slag time is not less than 30min, the Alt content is more than 0.025%, feS is used for adjusting S to 0.050-0.065% before the refining is finished and vacuum, the components are adjusted to a specified range, and VD vacuum degassing is carried out after the temperature is proper;
in the VD vacuum degassing treatment process, treatment is carried out for more than or equal to 15min under the condition that the vacuum degree is less than or equal to 1mbar, sampling analysis is carried out after static stirring is carried out for more than or equal to 10min after vacuum breaking, nitrogen can be added by using a high-silicon-nitride cored wire, al wire is fed according to a target, sulfur can be adjusted by feeding a sulfur wire according to an S analysis result, sampling analysis is carried out after the static stirring is carried out for more than or equal to 5min after the sulfur wire is fed, fine adjustment is carried out according to the analysis result, all elements meet the judgment range, and the soft argon blowing time meets the process requirements, and then continuous casting pouring can be carried out; the invention adopts LF + VD smelting and protective pouring, combines with the new technology of electromagnetic stirring and continuous casting under light pressure, and obtains high-cleanness and high-homogeneity metallurgical quality;
the whole continuous casting process adopts full-protection casting, electromagnetic stirring is used in the continuous casting process, the electromagnetic stirring strength of a crystallizer is 150-300A, the electromagnetic stirring at the tail end is 500-700A, and the reduction amount is 8-13 mm by adopting a light reduction technology;
the rolling process comprises heating, initial rolling and final rolling; the rolling heating temperature is 1200-1250 ℃, the initial rolling temperature is 1050-1150 ℃, and the final rolling temperature is 850-930 ℃.
A crankshaft of the present invention is produced from the high-quality non-heat treated steel. The invention relates to a preparation method of a crankshaft, which comprises the following steps: induction heating, forging and forming, deburring and cooling,
the temperature of induction heating is 1200-1240 ℃;
the forging forming comprises initial forging and final forging, wherein the initial forging temperature is 1190-1230 ℃, and the final forging temperature is 1050-1100 ℃; placing the blank crankshaft after trimming on a cooling line; cooling at the cooling rate of 1.0-2.0 ℃/s, cooling to 600-700 ℃, slowly cooling in a heat-insulating cover, controlling the forge piece to be cooled to 280-350 ℃ in the heat-insulating cover at the cooling rate of less than 0.5 ℃/s, and then cooling the forge piece to room temperature in water.
The invention adjusts the structure of the crankshaft forging by controlling the cooling speed of the crankshaft forging in different temperature ranges, thereby improving the strength of the crankshaft forging and meeting the technical requirements of high-quality and high-strength automobile engine crankshafts. The crankshaft steel produced by the method does not need to be subjected to quenching and tempering, and the cooling mode and the cooling rate are controlled after forging, so that ferrite is promoted to nucleate in supercooled austenite crystal, and more fine intragranular ferrite is obtained. In addition, the precipitation of fine intragranular ferrite is beneficial to the segmentation of non-transformed super-cooled austenite, so that transformed pearlite colony is refined, and the problem that the strength of non-quenched and tempered steel is surplus and the toughness is insufficient is further solved. The yield strength of the crankshaft reaches 650-670 Mpa, the tensile strength reaches 960-980 Mpa, the elongation is more than or equal to 12%, the reduction of area is more than or equal to 30%, and the crankshaft can be directly used for turning by a user and has good cutting performance.
Example 1
This example 1 provides a high-quality non-quenched and tempered steel and a crankshaft, wherein the non-quenched and tempered steel comprises the following components by mass percent: c:0.38%, si:0.56%, mn:1.4%, S:0.058%, P:0.013%, cr:0.16%, mo:0.02%, cu:0.05%, ni:0.11%, V:0.11%, al:0.016%, N:0.0155 percent, B0.0004 percent, H0.00013ppm, and the balance of Fe and other inevitable impurities.
The preparation method of the high-quality non-quenched and tempered steel comprises the following steps:
electric furnace smelting, LF refining, VD refining, continuous casting, heating, rolling, flaw detection, induction heating, forging and cooling,
the slag discharge is strictly controlled in the smelting and tapping process of the electric arc furnace, and the tapping B is less than or equal to 0.0003 percent; adjusting Alt to 0.020-0.030% by tapping aluminum; according to the process scheme, nitrogen is blown in the smelting process without adding nitrides, a noble alloy metal Mn is not used, the content of residual B which is less than or equal to 5ppm is realized by using a low-carbon ferromanganese alloy, the production cost can be saved, and the process scheme is suitable for large-scale economical and industrial production;
the LF refining process carries out point component control on components according to a judgment target value, high-purity graphite carbon materials, ferromanganese, ferrosilicon, ferrochromium and ferrovanadium are respectively used for adjusting C, mn, si, cr and V elements to the lower limit or the target value of a judgment range, N is blown in the refining process, siC is used for deoxidation in the early stage, the white slag time is not less than 30min, the Alt content is more than 0.025%, feS is used for adjusting S to 0.050-0.065% before the refining is finished and vacuum, the components are adjusted to a specified range, and VD vacuum degassing is carried out after the temperature is proper;
in the VD vacuum degassing treatment process, treatment is carried out for more than or equal to 15min under the condition that the vacuum degree is less than or equal to 1mbar, sampling analysis is carried out after static stirring is carried out for more than or equal to 10min after vacuum breaking, nitrogen can be added by using a high-silicon-nitride cored wire, al wire is fed according to a target, sulfur can be adjusted by feeding a sulfur wire according to an S analysis result, sampling analysis is carried out after the static stirring is carried out for more than or equal to 5min after the sulfur wire is fed, fine adjustment is carried out according to the analysis result, all elements meet the judgment range, and the soft argon blowing time meets the process requirements, and then continuous casting pouring can be carried out; the invention adopts LF + VD smelting and protective pouring, combines with the new technology of electromagnetic stirring and continuous casting under light pressure, and obtains high-cleanness and high-homogeneity metallurgical quality;
the whole continuous casting process adopts full-protection casting, electromagnetic stirring is used in the continuous casting process, the electromagnetic stirring strength of a crystallizer is 150-300A, the electromagnetic stirring at the tail end is 500-700A, and the reduction amount is 8-13 mm by adopting a light reduction technology;
the rolling process comprises heating, initial rolling and final rolling; the rolling heating temperature is 1200-1250 ℃, the initial rolling temperature is 1050-1150 ℃, and the final rolling temperature is 850-930 ℃.
The invention discloses a crankshaft which is prepared from the high-quality non-quenched and tempered steel, and a preparation method of the crankshaft, which comprises the following steps: induction heating, forging and forming, deburring and cooling,
the temperature of induction heating is 1200-1240 ℃;
the forging forming comprises initial forging and final forging, wherein the initial forging temperature is 1190-1230 ℃, and the final forging temperature is 1050-1100 ℃; placing the blank crankshaft after edge removal on a cooling line; cooling at the cooling rate of 1.0-2.0 ℃/s, cooling to 600-700 ℃, slowly cooling in a heat-insulating cover, controlling the forge piece to be cooled to 280-350 ℃ in the heat-insulating cover at the cooling rate of less than 0.5 ℃/s, and then cooling the forge piece to room temperature in water.
The chemical compositions of non-heat-treated steels and the crankshaft property comparisons of examples 1-3 and comparative examples 1-3 are given in table 1, and the contents not mentioned in the table are the same as those of example 1.
TABLE 1 chemical composition of non-tempered steels (wt%)
| Composition (A) | C | Si | S | P | Mn | Ni | Cr | Mo | V | Cu | Al | B | N | H |
| Example 1 | 0.38 | 0.56 | 0.058 | 0.013 | 1.40 | 0.11 | 0.16 | 0.02 | 0.11 | 0.05 | 0.016 | 0.0004 | 0.0155 | 0.00013 |
| Example 2 | 0.39 | 0.57 | 0.055 | 0.015 | 1.39 | 0.10 | 0.15 | 0.01 | 0.11 | 0.06 | 0.015 | 0.0003 | 0.0158 | 0.00014 |
| Example 3 | 0.37 | 0.55 | 0.053 | 0.012 | 1.41 | 0.12 | 0.14 | 0.01 | 0.12 | 0.04 | 0.017 | 0.0003 | 0.0151 | 0.00012 |
| Comparative example 1 | 0.37 | 0.59 | 0.060 | 0.013 | 1.43 | 0.12 | 0.14 | 0.04 | 0.16 | 0.05 | 0.008 | 0.0008 | 0.0131 | 0.00017 |
| Comparative example 2 | 0.39 | 0.62 | 0.059 | 0.015 | 1.38 | 0.14 | 0.13 | 0.03 | 0.15 | 0.06 | 0.009 | 0.0009 | 0.0139 | 0.00018 |
| Comparative example 3 | 0.40 | 0.64 | 0.063 | 0.012 | 1.45 | 0.15 | 0.12 | 0.04 | 0.16 | 0.04 | 0.010 | 0.0008 | 0.0135 | 0.00016 |
TABLE 2 crankshaft Performance
With reference to fig. 1 (a) to 1 (d), it can be seen that based on the recrystallization behavior and rule of the high-temperature austenite deformation-temperature synergistic effect, the rapid cooling in the high-temperature region above Ar3 after the high-temperature deformation inhibits the growth of recrystallized grains, and the precise controlled cooling in the two-phase region of Ar3 to Ar1 adjusts the ratio of ferrite to pearlite, so as to obtain the uniform and fine F + P structure of the round steel in fig. 1 (a) to 1 (d). According to the invention, through controlling the cooling process of the forged crankshaft blank, the cut-edge workpiece is dispersed on a cooling line from the temperature of Ar3 or above, and is rapidly cooled to the temperature of Ar1 at the cooling speed of 1.0-2.0 ℃/s, and austenite grains can be prevented from growing by rapidly cooling above the temperature of Ar 3. The rapid cooling is carried out at the temperature of Ar 3-Ar 1 to inhibit the precipitation of ferrite and refine the interlayer spacing of pearlite plates, thereby achieving the purpose of improving the strength of the crankshaft forging. Then the crankshaft forging piece cooled to 600-700 ℃ is placed into a heat-insulating cover for slow cooling, the crankshaft forging piece is controlled to be cooled to 280-350 ℃ in the cover at a cooling speed of less than 0.5 ℃/s, and the crankshaft forging piece is cooled to room temperature by water spraying. The structure of the obtained crankshaft forging is pearlite + a small amount of ferrite, the bainite structure basically disappears, and the content of the ferrite in the shaft neck part of the connecting rod is 5-10%, as shown in fig. 2 (a) -2 (d).
Claims (10)
1. A high-quality non-quenched and tempered steel, characterized in that the non-quenched and tempered steel comprises, in mass percent: c:0.36 to 0.40%, si:0.50 to 0.65%, mn: 1.30-1.60%, S:0.050 to 0.065%, P: less than or equal to 0.025 percent, cr:0.10 to 0.20%, mo: less than or equal to 0.04 percent, cu: less than or equal to 0.25 percent, ni: less than or equal to 0.25%, V:0.08 to 0.13%, al: 0.010-0.050%, N:0.012 to 0.020 percent, less than or equal to 0.0005 percent of B, less than or equal to 2.0ppm of H, and the balance of Fe and other inevitable impurities.
2. The high quality non heat treated steel according to claim 1, wherein the non heat treated steel has a composition comprising, in mass percent: c:0.36 to 0.40 percent; si:0.50 to 0.65 percent; mn:1.35 to 1.55 percent; s:0.050 to 0.065 percent; p: less than or equal to 0.020%; cr:0.10 to 0.20 percent; mo: less than or equal to 0.03 percent; cu: less than or equal to 0.15 percent; ni: less than or equal to 0.15 percent; v:0.08 to 0.13 percent; al: 0.010-0.030%; 0.013 to 0.020 percent of N; b is less than or equal to 0.0005 percent; h is less than or equal to 2.0ppm; the balance of Fe and other inevitable impurities.
3. The high-quality non-heat-treated steel according to claim 1 or 2, wherein the structure of the non-heat-treated steel is pearlite and ferrite, and the grain size of the metallographic structure of the round steel can reach 7 to 8 grades.
4. The high-quality non-quenched and tempered steel according to claim 3, wherein the tensile strength of the non-quenched and tempered steel is not less than 900MPa, the yield strength is not less than 800MPa, the elongation is not less than 10%, and the reduction of area is not less than 35%.
5. A method for producing a high quality non heat treated steel according to any one of claims 1 to 4, characterized by comprising the steps of:
electric furnace smelting, LF refining, VD refining, continuous casting, heating, rolling, flaw detection, induction heating, forging and cooling,
slag discharging is strictly controlled in the smelting and tapping process of the electric arc furnace, and the tapping B is less than or equal to 0.0003 percent; adjusting Alt to 0.020-0.030% by tapping aluminum;
point component control is carried out on components according to a determination target value in the LF refining process, high-purity graphite carbon materials, ferromanganese, ferrosilicon, ferrochrome and ferrovanadium are respectively used for adjusting C, mn, si, cr and V elements to the lower limit or the target value of a determination range, N is blown in the refining process, siC is used for deoxidation in the early stage, the white slag time is not less than 30min, the Alt content is more than 0.025 percent, feS is used for adjusting S to 0.050-0.065 percent before the refining is finished and vacuum is carried out, the components are adjusted to a specified range, and VD vacuum degassing is carried out after the temperature is proper;
in the VD vacuum degassing treatment process, treatment is carried out for more than or equal to 15min under the condition that the vacuum degree is less than or equal to 1mbar, sampling analysis is carried out after static stirring is carried out for more than or equal to 10min after vacuum breaking, nitrogen can be added by using a high-silicon-nitride cored wire, al wire is fed according to a target, sulfur can be adjusted by feeding a sulfur wire according to an S analysis result, sampling analysis is carried out after the static stirring is carried out for more than or equal to 5min after the sulfur wire is fed, fine adjustment is carried out according to the analysis result, all elements meet the judgment range, and the soft argon blowing time meets the process requirements, and then continuous casting can be carried out.
6. The method for producing a high-quality non-quenched and tempered steel according to claim 5, wherein the method comprises the steps of: the whole continuous casting process adopts full-protection casting, electromagnetic stirring is used in the continuous casting process, the electromagnetic stirring strength of a crystallizer is 150-300A, the electromagnetic stirring strength of the tail end is 500-700A, and the reduction amount is 8-13 mm by adopting a light reduction technology.
7. The method of producing a high-quality non-quenched and tempered steel according to claim 6, wherein the method comprises the steps of: the rolling process comprises heating, initial rolling and final rolling; the rolling heating temperature is 1200-1250 ℃, the initial rolling temperature is 1050-1150 ℃, and the final rolling temperature is 850-930 ℃.
8. A crankshaft produced from the high-quality non-heat-treated steel according to any one of claims 1 to 4.
9. A method of manufacturing a crankshaft according to claim 8, comprising the steps of: induction heating, forging and forming, deburring and cooling,
the temperature of induction heating is 1200-1240 ℃;
the forging forming comprises initial forging and final forging, wherein the initial forging temperature is 1190-1230 ℃, and the final forging temperature is 1050-1100 ℃; and placing the blank crankshaft after the edge is removed on a cooling line.
10. A method of producing a crankshaft as claimed in claim 9, wherein: in the cooling step, cooling is carried out at a cooling speed of 1.0-2.0 ℃/s, the forging piece is cooled to 600-700 ℃ and enters a heat-preserving cover for slow cooling, the forging piece is controlled to be cooled to 280-350 ℃ in the heat-preserving cover at a cooling speed of less than 0.5 ℃/s, and then the forging piece is cooled to room temperature in water.
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