CN113832404A - Boron-containing high-performance gear forging and production method thereof - Google Patents

Boron-containing high-performance gear forging and production method thereof Download PDF

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CN113832404A
CN113832404A CN202111127143.5A CN202111127143A CN113832404A CN 113832404 A CN113832404 A CN 113832404A CN 202111127143 A CN202111127143 A CN 202111127143A CN 113832404 A CN113832404 A CN 113832404A
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boron
furnace
equal
gear forging
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CN113832404B (en
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宫彦华
江波
毛亚男
姚三成
刘学华
高伟
童乐
邹强
万志键
赵海
钟斌
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Maanshan Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/002—Hybrid process, e.g. forging following casting
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • C—CHEMISTRY; METALLURGY
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • 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
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Abstract

The invention provides a boron-containing high-performance gear forging and a production method thereof, and the boron-containing high-performance gear forging comprises the following components: 0.21 to 0.23 percent of C, 0.25 to 0.35 percent of Si, 0.75 to 0.85 percent of Mn, 0.55 to 0.65 percent of Cr0.55, 0.30 to 0.40 percent of Mo, 0.55 to 0.65 percent of Ni0.025 to 0.035 percent of Als0.0006 to 0.0020 percent of B, less than or equal to 0.0020 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of [ O ], lessthan or equal to 40ppm of [ N ], lessthan or equal to 1.5ppm of [ H ], and the balance of Fe and inevitable impurity elements; compared with the prior art, the invention adds a small amount of B, controls the content of Als, N and Ti, improves the content of acid-soluble boron, further improves the hardenability, mechanical property and service performance of the gear forging, and has good hardness and machining performance by matching with a heat treatment process.

Description

Boron-containing high-performance gear forging and production method thereof
Technical Field
The invention belongs to the technical field of medium and large size gear forgings, and particularly relates to a boron-containing high-performance gear forging and a production method thereof, in particular to a gear forging for rail transit with chemical component control requirements and a heat treatment production method.
Background
Along with the development of industries such as automobile, rail transit, wind power and the like, the application range of carburized gear steel is wider and wider, the demand is larger and larger, the carburized gear steel technology is mainly from countries which enter the industrialization stage earlier such as the United states, Japan, Germany and the like, systematization and standardization are realized, the carburized gear steel with more applications comprises Cr-Mn, Cr-Mo, Cr-Ni and Cr-Ni-Mo series steel types, and the key technical requirements comprise:
1) terminal hardenability: the size of the end hardenability bandwidth directly influences the carburizing quenching heat treatment deformation of the gear steel, namely the narrower the hardenability bandwidth is, the smaller the dispersion is, the smaller the deformation of the gear after heat treatment is, the more beneficial to gear processing is, and the higher the quality of the gear is.
2) Cleanliness: cleanliness is critical to gear steel, and especially oxygen content has a great influence on the fatigue properties of the material. The research shows that: oxide inclusions in the gear steel are reduced along with the reduction of the oxygen content, and the service life of the carburized part is prolonged. The study showed that: when the oxygen content is reduced from 25ppm to 11ppm, the contact fatigue strength of the specimen can be increased by 4 times.
3) Grain size: the grain size level affects the deformation of the gear after heat treatment, the stability of end hardenability and the rotary bending fatigue performance. The study indicated that: when the grain size is larger than 5, the brittle fracture resistance of the gear steel is remarkably reduced, and surface spalling is easily caused. The national standard of the gear steel specifies that the grain size grade is not less than 5 grade.
From the demand of a gear manufacturing side, the gear forging has to meet two requirements, namely, the mechanical processing performance is good, and therefore, the gear section has low hardness; and secondly, the gear forging has good tail end hardenability, tensile strength and fatigue performance, so that the gear forging is designed with reasonable chemical components. At present, the gear for rail transit mainly takes 18CrNiMo7-6 as a material, has the comprehensive properties of high wear resistance, pressure resistance, impact resistance, plastic deformation resistance, surface contact fatigue resistance, bending fatigue resistance and the like, but has high alloy content, complex heat treatment process and high production cost.
Patent CN101319294A published in 12.10.2008 develops a fine grain carburized gear steel and a preparation method thereof, and the fine grain carburized gear steel comprises the following components: 0.15 to 0.25 percent of C, less than or equal to 0.35 percent of Si, 0.60 to 0.90 percent of Mn, 0.80 to 1.20 percent of Cr0.80, less than or equal to 0.015 percent of P, less than or equal to 0.010 percent of S, 0.02 to 0.08 percent of Nb0.0005 to 0.0035 percent of B, 0.15 to 0.35 percent of Mo0.02 to 0.06 percent of Al, 0.01 to 0.04 percent of Ti0.01 to 0.015 percent of [ N ], [ O ], [ 0.0015 percent of [ O ], and the balance of Fe and inevitable impurities. According to the invention, the effects of refining crystal grains and improving the thermoplastic property of the gear steel are achieved by adding Nb, B and Ti, compared with carburized gear steel 20CrMoH, the carburized crystal grains are improved, and the bending fatigue strength and the contact fatigue life are correspondingly improved. The product is added with a plurality of alloy components, such as Nb, Ti and the like, and has high content and high cost.
Patent CN101148737A published in 2008, 3, 26, discloses boron-containing steel and a preparation method thereof, wherein the boron-containing steel comprises the following components in percentage by weight: 0.32 to 0.44 percent of C, 0.15 to 0.37 percent of Si, 1.10 to 1.40 percent of Mn1, 0.0005 to 0.0035 percent of B, less than or equal to 0.030 percent of P, less than or equal to 0.030 percent of S, 0.015 to 0.070 percent of Al, and the balance of Fe and inevitable impurities. The hardenability is improved by controlling trace B elements, and the acid-soluble boron plays a main role in improving the hardenability, but the composition design is not reasonable, the content of the acid-soluble boron is influenced, and the improvement of the performance stability of steel is not favorable.
Patent CN101812643A published in 2010, 8 months and 25 days discloses a preparation method of boron-containing gear steel, which comprises the following components: 0.16 to 0.24 percent of C, less than or equal to 0.35 percent of Si, 0.70 to 1.25 percent of Mn0.80 to 1.45 percent of Cr0.80, less than or equal to 0.030 percent of P, less than or equal to 0.030 percent of S, 0.0005 to 0.0030 percent of B, 0.015 to 0.050 percent of Al, 0.020 to 0.080 percent of Ti, less than or equal to 0.00025 percent of H, 0.003 to 0.012 percent of N, less than or equal to 0.0018 percent of T.O, and the balance of Fe and inevitable impurities.
Patent CN106834960A published in 2017, 6 and 13 provides boron-containing high-grade gear steel for automobiles and a production process thereof, wherein the boron-containing high-grade gear steel comprises the following components: 0.15 to 0.20 percent of C, 0.15 to 0.40 percent of Si, 1.00 to 1.30 percent of Mn1.00 to 1.30 percent of Cr1.00 to 1.30 percent of P, less than or equal to 0.030 percent of S, less than or equal to 0.035 percent of B, 0.0005 to 0.0030 percent of B, less than or equal to 0.30 percent of Cu, 0.020 to 0.045 percent of Al, 0.015 to 0.035 percent of Ti, 0.12 to 0.18 percent of Ni, and the balance of Fe and inevitable impurities.
Disclosure of Invention
The invention aims to provide a boron-containing high-performance gear forging and a production method thereof, wherein the content of Als, N and Ti elements is controlled by adding a small amount of B elements, so that the content and distribution of acid-soluble boron are improved, the hardenability, the mechanical property and the service performance of the gear forging are further improved, meanwhile, a reasonable heat treatment process is invented in a matching manner, sufficient nucleation of ferrite is ensured, the metallographic structure of the gear forging is a ferrite plus pearlite structure, and the gear forging has good hardness and machining performance.
The specific technical scheme of the invention is as follows:
a boron-containing high-performance gear forging comprises the following components in percentage by mass:
0.21 to 0.23 percent of C, 0.25 to 0.35 percent of Si, 0.75 to 0.85 percent of Mn, 0.55 to 0.65 percent of Cr0.55, 0.30 to 0.40 percent of Mo0.55 to 0.65 percent of Ni0.025 to 0.035 percent of Als0.0006 to 0.0020 percent of B, less than or equal to 0.0020 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of [ O ], lessthan or equal to 40ppm of [ N ], lessthan or equal to 1.5ppm of [ H ], and the balance of Fe and inevitable impurity elements.
Preferably, the content of B is between 0.0010 and 0.0012 percent.
The metallographic structure of the boron-containing high-performance gear forging is a massive ferrite and pearlite structure, wherein the volume fraction of the ferrite is 55-85%; the grain size grade is 7-9.
The tensile strength of the boron-containing high-performance gear forging is 1050-.
In the invention, the carbon content is strictly required to ensure that the part has enough strength and toughness and simultaneously has excellent carburizing performance and hardenability, so the invention determines the range of C to be 0.21-0.23%.
Boron mainly acts to increase the hardenability of steel, and very small amount of boron added to steel can greatly increase the hardenability of steel, and when the boron content is less than 0.0005%, the effect of increasing the hardenability is very small. Because the solubility of boron in steel is extremely low, when more B element is added, inclusions are easily formed, and meanwhile, boron phase is generated in the steel and precipitated along austenite crystal boundary, so that the phenomenon of hot brittleness is generated. The combination of the hardenability influence results requires that the B element is controlled between 0.0006 and 0.0020 percent. Preferably, in order to ensure that the gear forging has a narrow hardenability strip, the B element is controlled to be 0.0010-0.0012%.
Molybdenum greatly enhances the hardenability of boron. Niobium in the steel has a certain compounding effect with boron in a solid solution state, and a strong inhibiting effect on austenite transformation is generated. Cr has a large effect of increasing the hardenability of steel, Ni has a small effect of increasing the hardenability, but Ni and Cr can be added into the steel simultaneously to remarkably increase the hardenability of the steel. Therefore, the invention requires 0.55 to 0.65% of Cr0.55, 0.30 to 0.40% of Mo and 0.55 to 0.65% of Ni0.
Boron is a strong grain boundary segregation element, and is easy to separate out boron nitride at the grain boundary, thereby seriously influencing the existence and distribution of acid-soluble boron and reducing the effect of B element on the hardenability of the gear. In order to further protect the boron existing in the form of acid-soluble boron, aluminum with stronger bonding force with oxygen and nitrogen than boron is added before adding boron during steel making to form AlN which can fix nitrogen and refine crystal grains of the gear forging, so that the invention requires that [ N ] is less than or equal to 40ppm and Als is 0.025-0.035%.
At present, N is generally not controlled, high-content Ti is added for nitrogen fixation treatment, the Ti is very easy to combine with the N to form TiN, but the TiN is very easy to deteriorate the toughness, the fatigue performance and even the machining performance of steel, and the TiN is very stable, is hardly changed once formed, and is difficult to further play a role in balancing and stabilizing the content of acid-soluble boron; and the Ti further grows into TiN inclusions in the hot working process, so that the toughness and the fatigue property of the gear forging are further reduced, and therefore, the addition of the Ti element is controlled in the invention, and the Ti is required to be less than or equal to 0.0020%.
The invention provides a production method of a boron-containing high-performance gear forging, which comprises the following process flows of: electric furnace → LF furnace refining → RH furnace vacuum degassing → continuous casting → rolling → ingot cutting → upsetting → preforming → shaping → slow cooling → heat treatment.
In the refining process of the LF furnace, in order to protect boron, aluminum with stronger bonding force with oxygen and nitrogen than boron is added before adding boron during steel making to form AlN, so that nitrogen fixation can be achieved, and crystal grains of the gear forging are refined, so that Als0.025-0.035% is controlled.
In the rolling process, a phi 700-600 mm continuous casting blank is changed into an octagonal rolling blank or a round blank, and the forging ratio of the gear forging is more than or equal to 6, and the forging ratio of the rolling blank is more than or equal to 3. The rolling process adopts 10-13 passes of rolling process, and can be used for rolling into octagonal rolling billets or round billets.
In order to ensure that the structure state of the finished gear forging is massive ferrite and pearlite, the heat treatment process comprises the following steps: heating the gear forge piece to 930-950 ℃ along with the furnace, preserving heat for 2.5-4.0 h, air-cooling for 25-35 min, then directly entering an isothermal furnace at 600-650 ℃, preserving heat for at least 15h, and then discharging from the furnace for air-cooling.
Preferably, the heat treatment process is as follows: heating the gear forging along with a furnace to 950 ℃, preserving heat for 2.5h, air-cooling for 30min, then directly entering a 620 ℃ isothermal furnace, preserving heat for 18h, discharging from the furnace and air-cooling.
Aiming at the problems of high alloy content, complex heat treatment process and high production cost of the existing carburized gear forging for the train, the invention adds boron, controls Als, N and Ti elements, and is matched with a reasonable heat treatment process, so that the hardenability, the texture state, the mechanical property, the processability, the fatigue property and the like of the gear forging are improved, and the invention is suitable for carburized gear forgings for different trains.
The gear forging piece provided by the invention mainly utilizes a small amount of B elements to greatly improve the hardenability of the gear steel: the acid-soluble boron reduces the nucleation rate of ferrite but does not affect the growth rate thereof and the formation rate of pearlite and martensite, thereby improving the hardenability of the steel. Based on the principle, in order to ensure the content and distribution of acid-soluble boron in the gear forging, the existence of N element in steel is strictly controlled, and meanwhile, aluminum which has stronger bonding force with oxygen and nitrogen than boron is properly added to generate AlN, so that the generation of BN can be reduced, crystal grains can be refined by using AlN, and the performance of the gear forging is improved. The addition of Ti element is strictly controlled, Ti element is easy to combine with N element to form TiN, so that the toughness, fatigue property and machining property of steel are easy to deteriorate, TiN is very stable, and TiN inclusions are easy to form.
In order to ensure that the gear forging has good processing performance, the metallographic structure of the finished gear forging is required to be a massive ferrite and pearlite structure, and the heat treatment process requirement of generating a balanced structure of the high-alloy boron-containing gear forging is strict, the heat treatment process of the gear forging is set as follows: heating the gear forge piece to 930-950 ℃ along with the furnace, preserving heat for 2.5-4.0 h, air-cooling for 25-35 min, then directly entering an isothermal furnace at 600-650 ℃, preserving heat for 15h or more, and then discharging from the furnace for air-cooling. Wherein the purpose of heating to 930-950 ℃ is to further refine the grain size of the gear forging; the purpose of air cooling for 25-35 min is to ensure that the gear forging has a certain cooling speed at a high temperature stage and relieve the formation of a banded structure; due to the addition of the element B, the ferrite nucleation rate is reduced, and the heat preservation is carried out at 600-650 ℃ for 15 hours or more, so that enough time is provided for ferrite nucleation, the complete transformation of ferrite and pearlite of the structure of the gear forging is ensured, and the structure enables the gear forging to have lower hardness and good processing performance.
Compared with the prior art, a small amount of B element is added into the gear steel, the content of Als, N and Ti elements is controlled, the hardenability, the mechanical property and the service performance of the gear forging are improved, and meanwhile, a reasonable heat treatment process is invented, so that the metallographic structure of the gear forging is a massive ferrite + pearlite structure, the grain size grade is 7-9 grade, the tensile strength is 1050-1300Mpa, the end hardenability J19 is 33-37HRC, the hardness is 175-205HB, and the gear forging has good hardness and machining performance.
Drawings
FIG. 1 is a metallographic structure state diagram of example 1;
FIG. 2 is a metallographic structure state diagram of comparative example 1;
FIG. 3 is a metallographic structure state diagram of comparative example 2;
FIG. 4 is a metallographic structure state diagram of comparative example 3;
FIG. 5 is a diagram showing the morphology of TiN inclusions in comparative example 2;
FIG. 6 is a graph showing the peeling of the rolling contact fatigue test specimen of example 1;
FIG. 7 is a graph showing the peeling of the rolling contact fatigue test piece of comparative example 1.
Detailed Description
The present invention will be described in detail with reference to examples.
According to the invention, a small amount of B element is added into the gear steel, the content of Als, Ti, N and other elements is controlled, the content and distribution of acid-soluble boron are improved, the nucleation rate of ferrite is reduced, the hardenability of the steel is further improved, crystal grains are refined, and the comprehensive performance and the service performance of the gear are improved. The gear forging formed by the gear steel is heated to 930-950 ℃ along with a furnace, is subjected to heat preservation for 2.5-4.0 hours, is subjected to air cooling for 25-35 min, then directly enters an isothermal furnace at 600-650 ℃, is subjected to heat preservation for 15 hours or more, and then is discharged from the furnace for air cooling, so that the gear forging has a better structural state (a fine crystalline grain, a massive ferrite and pearlite structure).
Example 1
A production method of a boron-containing high-performance gear forging comprises the following steps: electric furnace steel making → LF furnace refining, firstly adding aluminum for deoxidation and nitrogen fixation, and finally adding boron into the furnace or ladle, adjusting main chemical elements to approach even to reach target components → RH furnace vacuum treatment → phi 700mm continuous casting blank → phi 380mm octagonal rolling blank (adopting 11-pass rolling process, forging ratio is not less than 3) → ingot cutting → heating → pier thickening → preforming → forming → slow cooling-heat treatment, and the heat treatment is carried out on the gear blank according to the heat treatment process in Table 2.
The chemical compositions of the boron-containing high-performance gear forging of the embodiment 1 are shown in table 1, and the balance of Fe and inevitable impurities which are not shown in table 1. Sampling gear blanks according to GB/T2975 and GB/T228.1, performing tensile property test after heat treatment of small samples, and obtaining results shown in Table 3; performing end hardenability test according to GB/T225, and the result is shown in Table 3, and performing hardness test according to GB/T231, and the result is shown in Table 3; sampling a gear blank, carrying out austenite grain size inspection according to GB/T6394, wherein the result is shown in Table 3, carrying out metallographic structure analysis according to GB/T13299 steel microstructure evaluation method, and the result is shown in FIG. 1; a point contact fatigue test is carried out on a rolling contact fatigue testing machine by referring to YB/T5345-.
Comparative example 1
A production method of a boron-containing high-performance gear forging comprises the following process flows of: electric furnace steelmaking → LF furnace refining (slag mixing, wire feeding, stirring, deoxidation and desulfurization, component mixing) → RH furnace vacuum processing → continuous casting blank → 380mm forged blank (forging ratio ≥ 3) → ingot cutting → heating → pier thickening → preforming → molding → slow cooling → heat treatment, and the heat treatment process is the same as example 1.
Chemical compositions of the boron-containing high-performance gear forging of comparative example 1 are shown in table 1, and the balance not shown in table 1 is Fe and inevitable impurities.
Tensile properties, terminal hardenability, hardness, and contact fatigue properties were measured in the same manner as in example 1, and the results are shown in tables 3, 4, 5, and fig. 2 and 7.
It is clear that the gear forging of example 1 is significantly better than that of comparative example 1, especially in hardenability, mechanical properties and rolling contact fatigue properties.
TABLE 1 chemical compositions of gear forgings of examples and comparative examples
Figure BDA0003275546530000081
TABLE 2 Heat treatment process for gear forgings of examples and comparative examples
Figure BDA0003275546530000082
Figure BDA0003275546530000091
TABLE 3 Properties of examples and comparative examples
Figure BDA0003275546530000092
TABLE 4 Rolling contact fatigue test parameters
Figure BDA0003275546530000093
TABLE 5 Rolling contact fatigue test results
Figure BDA0003275546530000101
Example 2
A production method of a boron-containing high-performance gear forging comprises the following steps: the production procedure of example 2 is essentially the same as in example 1, namely: electric furnace steel making → LF furnace refining, firstly adding aluminum for deoxidation and nitrogen fixation, and finally adding boron into the furnace or ladle, adjusting main chemical elements to approach even to reach target components → RH furnace vacuum treatment → phi 700mm continuous casting → phi 380mm round billet (trial production process adopts 13-pass rolling process, forging ratio is not less than 3) → ingot cutting → heating → pier thickening → pre-forming → slow cooling, and carrying out tooth billet heat treatment according to the heat treatment process in Table 2.
The chemical compositions of the boron-containing high-performance gear forging of the embodiment 2 are shown in table 1, and the balance of Fe and inevitable impurities which are not shown in table 1.
Sampling gear blanks according to GB/T2975 and GB/T228.1, performing tensile property test after heat treatment of small samples, and obtaining results shown in Table 3; performing end hardenability test according to GB/T225, and the result is shown in Table 3, and performing hardness test according to GB/T231, and the result is shown in Table 3; sampling a gear blank, carrying out austenite grain size test according to GB/T6394, wherein the result is shown in Table 3, carrying out metallographic structure analysis according to GB/T13299 Steel microstructure evaluation method, and the result is basically the same as that of example 1; a point contact fatigue test is carried out on a rolling contact fatigue testing machine by referring to YB/T5345-2014 rolling contact fatigue test method, the test parameters are shown in Table 4, and the test results are shown in Table 5.
Comparative example 2
The production process of the boron-containing high-performance gear forging is basically the same as that of the embodiment 1 in the comparative example 2, namely: electric furnace steel making → LF furnace refining, firstly adding aluminum for deoxidation and nitrogen fixation, and finally adding boron into the furnace or ladle, adjusting main chemical elements to approach even to reach target components → RH furnace vacuum treatment → phi 700mm continuous casting → phi 380mm round billet (trial production process adopts 13-pass rolling process, forging ratio is not less than 3) → ingot cutting → heating → pier thickening → pre-forming → slow cooling, and carrying out tooth billet heat treatment according to the heat treatment process in Table 2.
The chemical compositions of the boron-containing high-performance gear forging of comparative example 2 are shown in table 1, and the balance of Fe and inevitable impurities not shown in table 1.
In comparison with example 2, comparative example 2 added a certain amount of Ti element while controlling N element. Tensile properties, terminal hardenability, hardness, texture analysis and contact fatigue property test were carried out in the same manner as in example 2, and the results are shown in tables 3, 4, 5 and 3.
It is clear that the gear forging of example 2 is significantly better than that of comparative example 2, especially in hardenability, mechanical properties and rolling contact fatigue properties. The sample of comparative example 2 was analyzed by a scanning electron microscope to find a large amount of TiN inclusions (fig. 5), which are the main cause of deterioration of the overall performance of the gear forging of comparative example 2.
Example 3
A production method of a boron-containing high-performance gear forging comprises the following steps: the production procedure of example 3 is essentially the same as in example 1, namely: electric furnace steel making → LF furnace refining, firstly adding aluminum for deoxidation and nitrogen fixation, and finally adding boron into the furnace or ladle, adjusting main chemical elements to approach even to reach target components → RH furnace vacuum treatment → phi 700mm continuous casting → phi 380mm round billet (trial production process adopts 13-pass rolling process, forging ratio is not less than 3) → ingot cutting → heating → pier thickening → pre-forming → slow cooling, and carrying out tooth billet heat treatment according to the heat treatment process in Table 2.
The chemical compositions of the boron-containing high-performance gear forging of the embodiment 3 are shown in table 1, and the balance of Fe and inevitable impurities which are not shown in table 1.
Sampling gear blanks according to GB/T2975 and GB/T228.1, performing tensile property test after heat treatment of small samples, and obtaining results shown in Table 3; the end hardenability test was carried out according to GB/T225, the results are shown in Table 3; the hardness test of the gear blank according to GB/T231 shows that the result is shown in Table 3, and the hardness is slightly higher than that of the gear blank in the embodiment 3; sampling a gear blank, and carrying out austenite grain size test according to GB/T6394, wherein the result is shown in Table 3; metallographic analysis was carried out in accordance with GB/T13299 "method for evaluating microstructure of Steel", and the results were substantially the same as in example 1.
Comparative example 3
A production method of a boron-containing high-performance gear forging is completely the same as that of example 3 in the production process of comparative example 3, only the heat treatment process is different, and the gear blank heat treatment is carried out on comparative example 3 according to the heat treatment process in the table 2. Tensile properties, terminal hardenability, hardness, and structure analysis were performed as in example 1, and the results are shown in Table 3, and the metallographic structure results are shown in FIG. 4.
The chemical compositions of the boron-containing high-performance gear forging of comparative example 3 are shown in table 1, and the balance of Fe and inevitable impurities not shown in table 1.
Obviously, the hardenability, the mechanical property and the grain size grade of the gear forging in the comparative example 3 are equivalent to those of the gear forging in the example 3, but the hardness in the comparative example 3 is higher, and the structure is needle-shaped F + P + B, namely, the product produced by adopting the heat treatment process in the comparative example 3 has poor structure state and higher hardness, and has larger influence on the subsequent processing performance of the product. Rolling contact fatigue tests were not performed.
The boron-containing high performance gear forgings for trains and the heat treatment method thereof have been described in detail with reference to the embodiments and the accompanying drawings, which are merely illustrative and not restrictive, and several embodiments can be enumerated within the limited scope, so that changes and modifications without departing from the general concept of the present invention shall fall within the protection scope of the present invention.

Claims (9)

1. The boron-containing high-performance gear forging is characterized by comprising the following components in percentage by mass:
0.21 to 0.23 percent of C, 0.25 to 0.35 percent of Si, 0.75 to 0.85 percent of Mn, 0.55 to 0.65 percent of Cr0.55, 0.30 to 0.40 percent of Mo, 0.55 to 0.65 percent of Ni0.025 to 0.035 percent of Als, 0.0006 to 0.0020 percent of B, less than or equal to 0.0020 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of [ O ], lessthan or equal to 40ppm of [ N ], lessthan or equal to 1.5ppm of [ H ], and the balance of Fe and inevitable impurity elements.
2. The boron-containing high performance gear forging of claim 1, wherein the B content is between 0.0010 and 0.0012%.
3. The boron-containing high-performance gear forging of claim 1, wherein the metallographic structure of the boron-containing high-performance gear forging is a bulk ferrite + pearlite structure, wherein the volume fraction of ferrite is 55-85%; the grain size grade is 7-9.
4. The boron-containing high-performance gear forging as claimed in claim 1, wherein the tensile strength of the boron-containing high-performance gear forging is 1050-.
5. The method for producing the boron-containing high-performance gear forging according to any one of claims 1 to 4, wherein the method comprises the following process flows: electric furnace → LF furnace refining → RH furnace vacuum degassing → continuous casting → rolling → ingot cutting → upsetting → preforming → shaping → slow cooling → heat treatment.
6. The production method according to claim 5, wherein the LF furnace is refined by adding aluminum for deoxidation and nitrogen determination, and finally adding boron into the furnace or the ladle.
7. The production method according to claim 5, wherein the rolling and rolling billet forging ratio is equal to or greater than 3.
8. The production method according to claim 5, wherein the heat treatment process comprises: the heat treatment process comprises the following steps: heating the gear forge piece to 930-950 ℃ along with the furnace, preserving heat for 2.5-4.0 h, air-cooling for 25-35 min, then directly entering an isothermal furnace at 600-650 ℃, preserving heat for at least 15h, and then discharging from the furnace for air-cooling.
9. The production method according to claim 5 or 9, characterized in that the heat treatment process is: heating the gear forging along with a furnace to 950 ℃, preserving heat for 2.5h, air-cooling for 30min, then directly entering a 620 ℃ isothermal furnace, preserving heat for 18h, discharging from the furnace and air-cooling.
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JPH09287644A (en) * 1996-04-23 1997-11-04 Toa Steel Co Ltd High strength low heat treatment deformation gear and manufacture thereof
CN101812643A (en) * 2009-11-30 2010-08-25 莱芜钢铁股份有限公司 Boracic pinion steel and preparation method thereof
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