CN114606443A - High-hardenability cast steel - Google Patents

High-hardenability cast steel Download PDF

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CN114606443A
CN114606443A CN202210261517.0A CN202210261517A CN114606443A CN 114606443 A CN114606443 A CN 114606443A CN 202210261517 A CN202210261517 A CN 202210261517A CN 114606443 A CN114606443 A CN 114606443A
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cast steel
hardenability
quenching
toughness
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CN114606443B (en
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帅德军
帅德国
胡楚宁
帅莉
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Xiangyang Jinnaite Machinery 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
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • 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
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The high hardenability cast steel comprises the following chemical components in percentage by weight: c: 0.23-0.32%, Si: 0.37-0.65%, Mn: 0.95-1.35%, Cr: 0.75-1.08%Ni: 0.46-0.87%, Mo: 0.25-0.45%, RE: 0.035-0.075%, Al: 0.003-0.008%, B: 0.004-0.008%, N: 0.005-0.01 percent, the balance of Fe and inevitable impurities, and the percentage content of each element satisfies: available nitrogen NeffEffective boron of N-Al/1.93eff＝B‑0.77NeffAvailable nitrogen Neff0.001-0.006% of boron effective Beff0.002-0.006; coefficient of hardenability Qeff＝C×(1+0.53Si)×(1+2.87Mn)×(1+2.34Cr)×(1+0.77Ni)×(1+2.61Mo)×(1.2+5.45RE)×(4753Beff 2+ 5.25); coefficient of hardenability QeffRatio to maximum thickness T of cast steel, Qeffthe/T is more than or equal to 0.55, and the unit of the maximum thickness T is mm.

Description

High-hardenability cast steel
Technical Field
The present invention relates to a high hardenability cast steel having a low austenite critical cooling rate and a high hardenability, and a casting obtained therefrom has a good hardenability even when non-liquid quenching is employed, thereby ensuring excellent strength and toughness of the casting, and being particularly suitable for casting of large castings.
Background
Cast steel is a commonly used engineering structural material, and has strength and toughness superior to cast iron, particularly has obvious advantages over cast iron materials at low temperature, but cast steel has slightly poor casting fluidity, so the cast steel is often used for casting large-wall-thickness castings in engineering.
In the prior art, in order to obtain cast steel with excellent strength and toughness, the cast steel needs to be subjected to heat treatment. The heat treatment of cast steel basically adopts the working procedures of normalizing, quenching and tempering. And since rapid cooling (e.g., up to 3 ℃/s or more) is required after quenching, such cooling rates are typically achieved with the aid of liquid quench media (e.g., oil, water, oil-based, water-based quenches, etc.). This therefore faces two main challenges for large wall thickness cast steel castings: on one hand, due to the wall thickness of the casting, the casting is cracked and scrapped because of the generation of great thermal stress caused by the excessively high cooling speed; on the other hand, the quenching of large castings requires large quenching equipment, the requirements on the quenching equipment are higher, the control difficulty of the quenching process is increased, the quenching of the liquid medium needs to be completed in a short time, the temperature of the quenching medium is rapidly increased due to the large heat exchange in the short time, the quenching medium is easy to boil and splash, and the safe operation of the quenching process is not facilitated.
In view of the above problems, a cast steel has been proposed which has a high hardenability, i.e., can be quenched using a non-liquid medium (e.g., air), and which is excellent in strength and toughness.
Disclosure of Invention
The invention provides a high-hardenability cast steel with excellent strength and toughness, which can obtain a cast steel material meeting performance requirements by quenching in a non-liquid medium (such as air) without quenching in a liquid medium in a heat treatment process after casting.
The technical object of the present invention is achieved by the following means.
The invention provides a cast steel material with high hardenability, which comprises the following chemical components in percentage by weight: c: 0.23-0.32%, Si: 0.37-0.65%, Mn: 0.95-1.35%, Cr: 0.75-1.08%, Ni: 0.46-0.87%, Mo: 0.25-0.45%, RE: 0.035-0.075%, Al: 0.00-0.008%, B: 0.004-0.008%, N: 0.005-0.01%, and the balance of Fe and inevitable impurities; and the percentage content of each element satisfies: available nitrogen NeffN-Al/1.93, boron B availableeff＝B-0.77NeffAvailable nitrogen Neff0.001-0.006% of boron effective Beff0.002-0.006; coefficient of hardenability Qeff＝C×(1+0.53Si)×(1+2.87Mn)×(1+2.34Cr)×(1+0.77Ni)×(1+2.61Mo)×(1.2+5.45RE)×(4753Beff 2+ 5.25); coefficient of hardenability QeffRatio to maximum thickness T (in mm) of cast steel, Qeff/T≥0.55。
The basic principle of the invention is based on the following:
the addition of a small amount of B and the addition of C, Si, Mn, Cr, Ni, Mo and RE elements improve the hardenability of the cast steel and reduce the critical cooling speed of austenite, thereby ensuring that the cast steel can be quenched thoroughly even if the cast steel is quenched by using a non-liquid medium (such as air) and ensuring that the strength and the toughness of the cast steel reach corresponding levels.
Since N is not completely removed in cast steel and its presence is easily combined with B, thus hindering the B action, seriously affecting the improvement of B in hardenability, and N significantly deteriorates the strength and toughness of cast steel, while limiting N to trace levels is not friendly to the cost of the smelting process, and cast steel pieces are generally heavy, and strict control of N at lower levels in steel leads to significant cost increase.
Based on the above knowledge, the inventor of the present invention, from a technical point of view different from "removing N as much as possible", fully utilizes N to exert a positive effect on the premise of maintaining a certain N content, thereby reducing the production cost and ensuring the properties of cast steel. Specifically, a certain amount of Al was added to the cast steel, and Al was combined with N before B to form AlN, and as a result, it was confirmed that a trace amount of AlN was effective for improving both toughness and strength of the cast steel.
AlN also has a strength and toughness improving effect, particularly, in that the strength and toughness of cast steel are more or less reduced to some extent when quenched with a non-liquid medium (e.g., air) as compared with liquid medium quenching, and a slight amount of AlN compensates for the reduction in the strength and toughness, with the result that even cast steel quenched with a non-liquid medium (e.g., air) has excellent strength and toughness as those of cast steel obtained by liquid medium quenching on the basis of containing a slight amount of N, a slight amount of Al, and a slight amount of B.
Therefore, in addition to Al being added to steel, the relation between Al and N is controlled to define NeffIs the available nitrogen remaining after Al and N are combined, and B is also definedeffIs the available boron remaining after B combines with available nitrogen, BeffBoron content for actually improving hardenability.
Further, by limiting NeffTo control the content of N in combination with B, to control the content of BN so as to ensure the achievement of strength and toughness, in combination with BeffTogether with other elements defining the hardenability coefficient Q of the cast steeleffAs a result, it was found that when Q is turned oneffWhen the maximum thickness T of the cast steel satisfies a certain relationship, the steel casting can always have excellent hardenability in non-liquid medium (such as air) quenching, and finally has satisfactory strength and toughness.
By way of non-limiting illustration, the maximum thickness T of the high hardenability cast steel is 30-400 mm; the inventors found that when Q is presenteffWhen the/T satisfies the above relationship, the hardenability effect is particularly sufficient for a steel casting having a thickness of 30 to 400 mm.
In one embodiment, the high hardenability cast steel has a room temperature tensile strength of 800MPa or more, preferably 850MPa or more, a room temperature yield strength of 720MPa or more, preferably 760MPa or more, a room temperature impact toughness of 110J or more, preferably 120J or more, and an-40 ℃ impact toughness of 85J or more, preferably 95J or more.
By way of non-limiting illustration, the high hardenability cast steel of the present invention is excellent in hardenability, and the austenite critical cooling rate is not higher than 0.3 ℃/s, preferably not higher than 0.2 ℃/s, more preferably not higher than 0.1 ℃/s, which is much lower than the cooling rate of liquid quenching, which is generally 3 ℃/s, so that the cast steel of the present invention has excellent hardenability when quenched in a non-liquid medium (such as air) and finally has satisfactory strength and toughness. Based on the characteristics of the cast steel of the invention, although liquid quenching is still feasible (because of the higher cooling rate of liquid quenching), from the cost and operational aspects, the use of quenching in a non-liquid medium (such as air) is the best solution.
As a preferred embodiment, the non-liquid medium quenching is air quenching, including but not limited to a blower, a fan, etc., to increase the flow rate of the air medium and thus to improve the heat exchange efficiency, and is economical when the cooling rate is in the range of 0.05 ℃/s to 0.3 ℃/s and the strength and toughness of the cast steel are satisfactory.
The roles of the individual elements and the significance of the control of the individual parameters are described in more detail below.
C: carbon is an element for improving the strength and hardenability of cast steel, but too high C content causes a decrease in toughness, and therefore, C is controlled to 0.23 to 0.32% in order to obtain the strength and toughness of the present invention.
Si: silicon is an element for improving the strength and hardenability of cast steel, but since an excessively high Si content increases inclusions and drastically lowers toughness, Si is controlled to 0.37 to 0.65% in order to obtain the strength and toughness of the present invention.
Mn: manganese is an element that improves the strength and hardenability of cast steel, but too high Mn content results in a decrease in toughness, and therefore, Mn is controlled to 0.95 to 1.35% in order to obtain the strength and toughness of the present invention.
Cr: chromium is an element that improves the strength and hardenability of cast steel, but too high a Cr content easily forms Cr with carbon23C7And carbides, which serve as starting points for ductile fracture. Therefore, in order to obtain the strength of the present inventionAnd toughness, and Cr is controlled to be 0.75-1.08%.
Ni: nickel can improve the low-temperature toughness, strength and hardenability of cast steel, but once the Ni content is too high, the toughness and strength improvement is no longer significant and the cost is increased, so that Ni is controlled to be 0.46-0.87% in order to obtain the strength and toughness of the invention.
Mo: molybdenum is an element that improves the strength and hardenability of cast steel, but an excessively high Mo content easily forms carbides such as MoC with carbon, and becomes a starting point of ductile fracture. Therefore, in order to obtain the strength and toughness of the present invention, Mo is controlled to be 0.25 to 0.45%.
RE: the rare earth can improve the strength and the toughness of cast steel and remarkably improve the hardenability, and the rare earth has the function of improving the form of inclusions and can effectively improve the low-temperature toughness of the cast steel, but the RE content is too high, so the cost is not economical, and the function is basically not remarkably improved any more, therefore, the RE is controlled to be 0.035-0.075 percent in order to obtain the strength and the toughness of the invention.
Al: in the present invention, aluminum is not added separately, and aluminum is added to the cast steel to deoxidize during the smelting process, so that the present invention finely adjusts the amount of aluminum to be added based on the amount of aluminum for deoxidation, and AlN is produced from the remaining aluminum and N after the deoxidation, and a trace amount of AlN increases the strength and toughness of the cast steel, but if AlN is excessive, the toughness of the cast steel is drastically reduced, and therefore, the present invention controls the Al content to 0.003-0.008%.
N: compared with the traditional technical concept of removing N, the invention does not need to limit N to trace level intentionally, but combines the residual deoxidized aluminum with N on the premise of keeping a certain N content, the trace AlN improves the strength and toughness of the cast steel, fully utilizes N to play a positive role, reduces the production cost, but causes the toughness of the cast steel to be reduced sharply if the AlN content is too high, and controls the N content to be 0.005-0.01 percent.
Neff：NeffI.e. available nitrogen, which characterizes the amount of N remaining after fixation by Al bonds, as can be seen from the contents of Al and N in the invention described aboveeffN-Al/1.93 can always be guaranteed at a level greater than 0That is, N is excessive and Al is not present because excess N can be further bonded by B, and excess Al easily forms oxide inclusions to become a starting point of ductile fracture and cause toughness to be lowered, but N iseffToo high indicates that too much N is bonded to B, and too much BN will drastically reduce the strength and toughness of cast steel, and thus, N of the present inventioneff＝0.001-0.006。
B: boron is an element which strongly improves the strength and hardenability of cast steel, but it is easily bonded to N, so the present invention first bonds N with Al to ensure that a certain amount of B remains after bonding with the remaining N, thereby exerting the effect of improving the strength and hardenability of cast steel, and in order to obtain the above technical effects, the B content of the present invention is limited to 0.004-0.008%.
Beff：BeffNamely available boron, Beff＝B-0.77NeffWhich characterizes B and available nitrogen NeffThe amount of available boron remaining after bonding, i.e. the amount of boron actually exerting the strength-enhancing and hardenability-improving properties, BeffToo high, on the contrary, results in a decrease in strength and toughness, and is not preferable in terms of cost. B of the present invention for obtaining the technical effect of boroneffIs 0.002-0.006%.
Qeff: coefficient of hardenability by synthesis of BeffAnd the content of other elements are obtained to represent the hardenability of the cast steel, and the higher the hardenability coefficient is, the lower the critical cooling speed is, so that the cast steel is more beneficial to obtaining excellent strength and toughness at the lower cooling speed in the quenching process.
QeffT: the quenching effect of the casting is obtained, and Q needs to be controlledeffThe relationship with the maximum thickness of the cast steel, t (mm), is because as the thickness of the cast becomes thicker and thicker, the required critical cooling rate must be as lower as possible, which means that thicker cast steels require a higher hardenability factor. The inventors have found that by defining Qeffhas/T of 0.55 or more, and can achieve good hardenability even in a quenching step using a non-liquid as a quenching medium (such as air) for a thick cast steel, thereby ensuring excellent strength and toughness of the cast steel, and when Q is greater than QeffWhen the/T is less than 0.55, the effect of reducing the quenching cooling speed is brought by the temperature return effect of the steel plate core part, so that the actual cooling speed brought by non-liquid medium quenching cannot be lower than the critical cooling speed, and the quenching cannot be carried out completely.
Another aspect of the present invention is to provide a method for producing the aforementioned cast steel with high hardenability, which employs smelting, casting, and heat treatment, including normalizing, quenching, and tempering, which are sequentially performed. Due to the process design for reducing the cost and simplifying the working procedure, the quenching can be selected to be non-liquid quenching by combining the characteristics of the components of the cast steel, the non-liquid quenching is preferably air quenching, the quenching cooling speed can be 0.1 ℃/s-0.3 ℃/s, and the mechanical property of the cast steel obtained by using the components of the cast steel provided by the invention after quenching and cooling reaches more than 800MPa, the room-temperature yield strength is more than 720MPa, the room-temperature impact toughness is more than 110J, and the-40 ℃ impact toughness can reach more than 85J.
The invention has the beneficial effects that: by adjusting the contents of basic elements C, Si, Mn, Cr, Ni and Mo, a trace amount of B, N, Al is added and N is controlledeff、BeffAnd Qeffthe/T is in a certain range, so that the finally obtained cast steel can obtain excellent strength and toughness under the condition of non-liquid medium quenching (such as air), the room-temperature tensile strength is more than 800MPa, the room-temperature yield strength is more than 720MPa, the room-temperature impact toughness is more than 110J, and the-40 ℃ impact toughness can reach more than 85J.
The cast steel adopting the components of the invention avoids the defect that liquid medium is needed for quenching in the production process, does not need large quenching furnace equipment, does not need to worry about boiling and splashing of liquid quenching liquid in the quenching process, and does not need to worry about the problem of stress cracking caused by overhigh quenching cooling speed, thereby reducing the production cost, simplifying the production process and improving the operation conditions.
Detailed Description
In order to make those skilled in the art fully understand the technical scheme and the beneficial effects of the present invention, the following further description is made in combination with specific test examples.
Molten steel is melted and cast into ingots according to the design components, the specific components are shown in the table 1, Neff、Beff、Qeff、T(mm)、Qeffthe/T is shown in Table 2, all steel ingots are subjected to heat treatment of normalizing, quenching and tempering, the normalizing process is 925 ℃ plus air natural cooling, the quenching process is 915 ℃ plus air quenching to room temperature, the tempering process is 620 ℃ plus air natural cooling, the heat preservation time in the heat treatment process is calculated according to 1.3(min/mm) x T (mm), air quenching adopts an air blower for blowing heat exchange, and the blowing flow is per m2Wind-receiving surface of steel plate 400m3And calculating the/h normal temperature air.
The ingots after heat treatment were tested for tensile strength and room temperature toughness as well as-40 ℃ low temperature toughness, and the results are shown in table 3. The tensile strength is tested according to GB/T228.1-2010, and the room temperature toughness and the low temperature toughness at-40 ℃ are tested according to GB/T229-2020.
Table 1: the components of each cast steel are in mass percentage, and the balance is Fe
Serial number C Si Mn Cr Ni Mo RE Al B N
1 0.31 0.46 1.03 0.88 0.57 0.34 0.038 0.005 0.007 0.007
2 0.25 0.51 1.14 0.96 0.49 0.41 0.057 0.004 0.008 0.006
3 0.26 0.42 1.27 1.04 0.66 0.47 0.062 0.008 0.005 0.007
4 0.32 0.61 1.31 1.07 0.79 0.26 0.044 0.003 0.008 0.007
5 0.29 0.64 1.34 1.02 0.85 0.45 0.071 0.007 0.007 0.009
6 0.23 0.39 0.97 1.06 0.81 0.39 0.074 0.006 0.004 0.005
7 0.27 0.59 1.25 0.79 0.86 0.44 0.069 0.007 0.006 0.008
8 0.32 0.64 1.33 1.05 0.85 0.47 0.072 0.008 0.008 0.01
9 0.23 0.39 0.97 1.06 0.81 0.39 0.074 0.006 0.008 0.005
10 0.32 0.61 1.31 1.07 0.79 0.26 0.044 0.003 0.005 0.007
11 0.27 0.59 1.25 0.79 0.86 0.44 0.069 0.01 0.006 0.008
12 0.25 0.51 1.14 0.96 0.49 0.41 0.057 0.002 0.008 0.006
13 0.26 0.42 1.27 1.04 0.66 0.47 0.062 0.008 0.003 0.007
14 0.29 0.64 1.34 1.02 0.85 0.45 0.071 0.007 0.011 0.009
15 0.32 0.64 1.33 1.05 0.85 0.47 0.072 0.008 0.008 0.012
16 0.32 0.61 1.31 1.07 0.79 0.26 0.044 0.003 0.008 0.009
4 samples with different thicknesses are respectively cast for test numbers 1 and 8 and are respectively named as 1-1, 1-2, 1-3, 1-4, 8-1, 8-2, 8-3 and 8-4, and specific N iseff、Beff、Qeff、T(mm)、QeffThe ingots were cast into rectangular parallelepiped samples of 5T length, 3T width and T thickness, respectively, as shown in Table 2.
Table 2: n of each cast steeleff、Beff、QeffT (mm) and Qeff/T
Figure BDA0003550626450000081
Figure BDA0003550626450000091
Table 3 shows the test results of the strength and toughness of the cast steels described above.
TABLE 3 mechanical Properties of the cast steels
Figure BDA0003550626450000092
Figure BDA0003550626450000101
The above inventive and comparative examples are further illustrated by the following analyses in conjunction with tables 1-3.
Al contents of Nos. 11 and 12 in Table 1 are out of the range of the present invention, B contents of Nos. 13 and 14 are out of the range of the present invention, N content of No. 15 is out of the range of the present invention, Q contents of Nos. 1 to 4 and 8 to 4 in Table 2effB of numbers 9, 10, 13, 14,/T not being within the scope of the inventioneffN numbers 15, 16 not within the scope of the inventioneffNumbers 1 to 4, 8 to 4, and 9 to 16 are comparative examples of the present invention, because they are outside the scope of the present invention.
The comparative examples 1 to 4 adopt the same components as the inventive examples 1 to 3, and the comparative examples 8 to 4 adopt the same components as the inventive examples 8 to 1 to 8 to 3, and the heat treatment processes are the same, only the thickness of the castings is different. Q of the cast steels of comparative examples 1-4 and 8-4 due to their excessive thicknesseffThe steel can not meet the requirement of more than 0.55, the cooling speed actually caused by air-cooled quenching is lower than the critical cooling speed due to the fact that the 'temperature return' phenomenon in the steel plate has a neutralization effect on the quenching cooling speed during air-cooled quenching, and the cast steel can not be fully quenched, so that the tensile strength and yield strength at room temperature, room temperature toughness and-40 ℃ toughness of the cast steel of comparative examples 1-4 can not meet the requirement of the invention, and the strength after air-cooled comparative examples 8-4 is greatly reduced, although the strength is still in the invention range, but the toughness is particularly remarkably deteriorated due to the failure of effective quenching, so that the room temperature toughness and the-40 ℃ toughness can not meet the requirement of the invention.
On the other hand, when comparing the examples 1-1 to 1-3 and 8-1 to 8-3 in the transverse direction, it can be seen that the lower the thickness of the steel casting, the lower the Q value of the steel casting, the same material, under the same air-cooled quenching conditioneffThe larger the/T, the through-hardeningThe better the performance effect, the better the final strength and toughness mechanical properties.
Comparative example 9 is a comparative example of invention example 6, and the content of B was adjusted under the same content of other elements, and although the adjusted content of B was still within the scope of the invention, the adjustment of B resulted in BeffToo high is not in the invention range, which leads to increase of effective boron and reduction of strength and toughness of the cast steel, and finally the obtained cast steel has tensile strength and yield strength at room temperature, room temperature toughness and-40 ℃ toughness which can not meet the requirements of the invention.
Comparative example 10 is a comparative example of invention example 4, and the content of B was adjusted under the same content of other elements, and although the adjusted content of B was still within the scope of the invention, the adjustment of B resulted in B being presenteffIf the content of boron is too low, the effective boron is reduced, the hardenability is greatly reduced, and finally the tensile strength and yield strength at room temperature, room temperature toughness and toughness at-40 ℃ of the cast steel cannot meet the requirements of the invention.
Comparative example 11 is a comparative example of invention example 7, and the Al content was adjusted under the same conditions as the other element contents, although the adjusted Neff、Beff、QeffThough Al is too high, AlN content is too high, AlN slightly contributes to strength and the strength is higher than that of invention example 7, but AlN excessively high becomes a starting point of toughness fracture and causes a sharp decrease in toughness, and the finally obtained cast steel cannot satisfy the requirements of the invention in both room temperature toughness and-40 ℃ toughness.
Comparative example 12 is a comparative example of invention example 2, and the Al content was adjusted under the same conditions as the other element contents, although the adjusted Neff、Beff、Qeffthe/T is still in the invention range, but the Al content is too low, so that the AlN content is insufficient, the strengthening and toughening effects are not obvious enough, and the tensile strength and yield strength at room temperature, room temperature toughness and-40 ℃ toughness of the finally obtained cast steel cannot meet the requirements of the invention.
Comparative example 13 is a comparative example of inventive example 3, and under the same contents of other elements,the content of B is adjusted, and B after adjustmenteffIf the content of boron is too low, the effective boron is reduced, the hardenability is greatly reduced, and finally the tensile strength and yield strength at room temperature, room temperature toughness and toughness at-40 ℃ of the cast steel cannot meet the requirements of the invention.
Comparative example 14 is a comparative example of invention example 5, in which the content of B was adjusted under the condition that the contents of other elements were the same, and B were adjustedeffIf the boron content is too high, the effective boron is increased, the strength and the toughness of the cast steel are reduced, although the strength can meet the requirements of the invention, the toughness is obviously reduced more remarkably, and the room temperature toughness and the-40 ℃ toughness of the finally obtained cast steel can not meet the requirements of the invention.
Comparative example 15 is a comparative example of invention example 8-1, and the N content was adjusted under the same conditions as the contents of the other elements, although B was adjustedeff、QeffThe value of/T is still within the scope of the invention, but its N is so high that NeffAnd the BN is generated too much and the strength and the toughness of the cast steel are reduced, and the finally obtained cast steel cannot meet the requirements of the invention on tensile strength and yield strength at room temperature, room temperature toughness and toughness at-40 ℃.
Comparative example 16 is a comparative example of invention example 4, and the content of N was adjusted under the same content of other elements, and the adjustment of N resulted in N being adjusted to the extent that the content of N was within the range of the inventionffToo high is not in the invention range, so that too much BN is generated, the strength and toughness of the cast steel are reduced, and the finally obtained cast steel cannot meet the requirements of the invention on tensile strength and yield strength at room temperature, room temperature toughness and toughness at-40 ℃.
In conclusion, the invention adjusts the contents of basic elements C, Si, Mn, Cr, Ni and Mo, simultaneously adds a trace B, N, Al and controls Neff、Beff、Qeffthe/T can ensure that the finally obtained cast steel obtains excellent obdurability under the condition of non-liquid medium quenching within a certain range, the room temperature tensile strength is more than 800MPa, more even more than 850MPa, and the room temperature yield strengthMore than 720MPa, even more than 760MPa, the room-temperature impact toughness of the material is more than 110J, even more than 120J, and the-40 ℃ impact toughness of the material can be more than 85J, even more than 95J.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. The high-hardenability cast steel is characterized by comprising the following chemical components in percentage by weight: c: 0.23-0.32%, Si: 0.37-0.65%, Mn: 0.95-1.35%, Cr: 0.75-1.08%, Ni: 0.46-0.87%, Mo: 0.25-0.45%, RE: 0.035-0.075%, Al: 0.003-0.008%, B: 0.004-0.008%, N: 0.005-0.01 percent, the balance of Fe and inevitable impurities, and the percentage content of each element satisfies:
available nitrogen NeffN-Al/1.93, boron B availableeff＝B-0.77NeffAvailable nitrogen Neff0.001-0.006% of boron, Beff0.002-0.006;
coefficient of hardenability Qeff＝C×(1+0.53Si)×(1+2.87Mn)×(1+2.34Cr)×(1+0.77Ni)×(1+2.61Mo)×(1.2+5.45RE)×(4753Beff 2+5.25)；
Coefficient of hardenability QeffRatio to maximum thickness T of cast steel, Qeffat/T is not less than 0.55, mostThe large thickness T is in mm.
2. The cast steel with high hardenability according to claim 1, characterized in that the maximum thickness T of the cast steel with high hardenability is 30-400 mm.
3. The cast steel with high hardenability according to any one of claims 1 to 2, characterized in that the cast steel with high hardenability has a room temperature tensile strength of 800MPa or more, a room temperature yield strength of 720MPa or more, and a room temperature impact toughness of 110J or more.
4. A high hardenability cast steel according to any one of claims 1 to 2, characterized in that it has an impact toughness at-40 ℃ of more than 85J.
5. A high hardenability cast steel according to any one of claims 1-2, characterized in that said high hardenability cast steel has an austenite critical cooling rate not higher than 0.3 ℃/s.
6. The cast steel with high hardenability as claimed in claim 5, wherein said quenching is non-liquid quenching.
7. The cast steel with high hardenability as claimed in claim 6, wherein said non-liquid quenching is air quenching.
8. A method of producing the high hardenability cast steel as claimed in any one of claims 1 to 7, characterized by: smelting, casting and heat treatment are adopted, wherein the heat treatment comprises normalizing, quenching and tempering which are sequentially carried out.
9. The method of claim 8, wherein the quenching is a non-liquid quenching.
10. The method of any one of claims 8-9, wherein the non-liquid quench is an air quench.
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Publication number Priority date Publication date Assignee Title
EP0705908A2 (en) * 1994-09-02 1996-04-10 MANNESMANN Aktiengesellschaft Low alloy C-Mn steel
CN104831189A (en) * 2015-04-16 2015-08-12 河北钢铁股份有限公司 HB600 grade wear-resistant non-quenched and tempered steel plate and making method thereof
CN106676390A (en) * 2017-03-28 2017-05-17 宁波禾顺新材料有限公司 Low-carbon martensite cast steel applied to heavy cross section and heat treatment method of low-carbon martensite cast steel
US20190048445A1 (en) * 2016-03-07 2019-02-14 Nippon Steel & Sumitomo Metal Corporation High-strength flat steel wire excellent in hydrogen induced cracking resistance
CN112522593A (en) * 2019-09-19 2021-03-19 宝山钢铁股份有限公司 Thin 30CrMo hot rolled steel plate/strip and production method thereof
CN113025914A (en) * 2021-03-04 2021-06-25 东北大学 High-performance online quenching high-strength steel pipe and production method thereof

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0705908A2 (en) * 1994-09-02 1996-04-10 MANNESMANN Aktiengesellschaft Low alloy C-Mn steel
CN104831189A (en) * 2015-04-16 2015-08-12 河北钢铁股份有限公司 HB600 grade wear-resistant non-quenched and tempered steel plate and making method thereof
US20190048445A1 (en) * 2016-03-07 2019-02-14 Nippon Steel & Sumitomo Metal Corporation High-strength flat steel wire excellent in hydrogen induced cracking resistance
CN106676390A (en) * 2017-03-28 2017-05-17 宁波禾顺新材料有限公司 Low-carbon martensite cast steel applied to heavy cross section and heat treatment method of low-carbon martensite cast steel
CN112522593A (en) * 2019-09-19 2021-03-19 宝山钢铁股份有限公司 Thin 30CrMo hot rolled steel plate/strip and production method thereof
CN113025914A (en) * 2021-03-04 2021-06-25 东北大学 High-performance online quenching high-strength steel pipe and production method thereof

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