CN113215488A - Heat-treatment-free NM360 wear-resistant steel plate and manufacturing method thereof - Google Patents
Heat-treatment-free NM360 wear-resistant steel plate and manufacturing method thereof Download PDFInfo
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- 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
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Abstract
The invention provides a heat treatment-free NM360 wear-resistant steel plate and a manufacturing method thereof, and the heat treatment-free NM360 wear-resistant steel plate comprises the following components: 0.15 to 0.25 percent of C; si1.0-2.5%; 1.5 to 2.5 percent of Mn1; p is less than or equal to 0.012 percent; s is less than or equal to 0.005 percent; nb0.010-0.060%; 0.010 to 0.060 percent of Ti0.010 percent of TiAl; v0.010-0.050%; als0.020-0.060%; b0.0010-0.0030%; h is less than or equal to 0.00015 percent; n is less than or equal to 0.0030 percent; o is less than or equal to 0.0030 percent; the balance of Fe and inevitable impurities. The manufacturing method of direct three-section cooling after rolling is adopted, the yield strength of the product is more than or equal to 800MPa, the tensile strength is more than or equal to 1200MPa, the cold bending performance is 180 degrees, D is 4a qualified, the process flow is short, the production cost is low, the product has high strength and hardness, the wear resistance is high, and the cold bending forming performance is good.
Description
Technical Field
The invention relates to the technical field of wear-resistant steel production processes, in particular to a heat-treatment-free NM360 wear-resistant steel plate and a manufacturing method thereof.
Background
With the comprehensive implementation of policies such as low carbon emission, energy conservation and emission reduction, environmental protection, over-treatment and the like advocated by the state, the light weight, heavy load and long service life of the material become inevitable trends in the development of the commercial vehicle industry, so that higher requirements are put forward on the comprehensive performance of the material, and the material not only has high strength, high hardness and high toughness, but also has high wear resistance and cost economy. As one of the most direct and effective methods for weight reduction, demand for ultra-high strength steel, particularly wear resistant steel, is increasing.
There are three main types of wear-resistant steel materials for industrial use: compared with high manganese steel and wear-resistant cast iron (steel), the low alloy wear-resistant steel not only has high strength and toughness, high hardness and high wear resistance, but also has relatively low production cost and wider application field, and is applied to the mechanical fields of engineering, mining, construction, cement, electric power, metallurgy and the like. The low alloy wear-resistant steel can be classified into martensite wear-resistant steel, bainite wear-resistant steel, martensite-ferrite wear-resistant steel, martensite-bainite wear-resistant steel, and austenite-bainite wear-resistant steel according to the microstructure. Compared with austenite, bainite and ferrite structures, the martensite structure has high strength, high hardness, high wear resistance, relatively simple control of the production process and the most extensive industrial application at present.
On one hand, the martensite wear-resistant steel is often added with noble alloy elements such as Cr, Mo, Ni, rare earth and the like in the design of chemical components, and the alloy components are complex in design and higher in cost; on the other hand, the main production technology mainly comprises two processes of hot rolling, quenching, tempering heat treatment and hot rolling and offline tempering heat treatment, the strength and the wear resistance of the material are mainly determined by heat treatment procedures, the production process is long in flow, high in energy consumption and high in cost, the structure after heat treatment is hard and brittle phase martensite, the internal stress is large, the yield ratio is high, the cold bending forming performance is limited, and only 90 degrees and the D-6 a (D-bending pressure head diameter, a-sample thickness) are qualified.
A patent with publication number CN 105861939A, published in 2016, 8, 17, discloses a method for producing NM360 steel, wherein Mo, Cr, Nb and Ti microalloying component design is adopted, and an NM 360-grade wear-resistant steel is obtained by controlling a relaxation ultra-fast cooling process after rolling, but the production lines are a medium plate production line and a non-hot continuous rolling plate and strip rolling production line, and the thickness specification of the product is more than or equal to 8mm, and the product is not suitable for a thin specification product which is less than or equal to 6 mm.
The method for producing the thin-specification high-Ti wear-resistant steel NM360 by online quenching with the publication number CN 107099731A disclosed in 8/29/2017 and the method for producing the thin-specification high-Ti wear-resistant steel NM400 by online quenching with the publication number CN 106987760A disclosed in 28/2017/7 adopt Cr, Mo, Nb, Ti and B microalloyed components for design, have high alloy content and high cost, and the production line is a thin slab continuous casting and rolling short flow, and the production process flows are different and not the traditional hot continuous rolling strip flow.
Disclosure of Invention
The invention aims to provide a heat-treatment-free NM360 wear-resistant steel plate which is high in strength and hardness and good in cold-bending forming performance.
The invention also aims to provide a method for manufacturing the NM 360-grade wear-resistant steel plate without heat treatment, which realizes industrial production of the NM 360-grade wear-resistant steel plate by a heat treatment-free TMCP process on a conventional hot continuous rolling production line and has the characteristics of short process flow and low production cost.
The specific technical scheme of the invention is as follows:
a heat treatment-free NM360 wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.15 to 0.25 percent; si: 1.0-2.5%; mn: 1.5 to 2.5 percent; p: less than or equal to 0.012 percent; s: less than or equal to 0.005 percent; nb: 0.010-0.060%; ti: 0.010-0.060%; v: 0.010-0.050%; and Als: 0.020-0.060%; b: 0.0010-0.0030%; h: less than or equal to 0.00015 percent; n: less than or equal to 0.0030 percent; o: less than or equal to 0.0030 percent; the balance of Fe and inevitable impurities.
The microstructure of the heat-treatment-free NM360 wear-resistant steel plate is martensite and ferrite, wherein the volume fraction of the martensite is 75-85%, the volume fraction of the ferrite is 15-25%, and the average grain size of the ferrite is 3-8 μm;
the thickness of the heat-treatment-free NM360 wear-resistant steel plate is 3.0-6.0 mm;
the yield strength of the heat-treatment-free NM360 wear-resistant steel plate is not less than 800MPa, the tensile strength is not less than 1200MPa, and the elongation A50Not less than 15%, cold bending performance of 180 deg, qualified D-4 a, surface Brinell hardness not less than 360HBW, impact energy A at-20 deg.ckVNot less than 20J (sample size: 2.5X 10X 55mm), the product performance meets the technical requirement of NM360 in GB/T24186-2009, and the cold-bending forming is good.
The invention provides a method for manufacturing a heat-treatment-free NM360 wear-resistant steel plate, which comprises rolling.
The rolling is specifically as follows: the initial rolling temperature of rough rolling is 1100-1150 ℃, the initial rolling temperature of finish rolling is 950-1050 ℃, and the final rolling temperature of finish rolling is 850-900 ℃; and the finish rolling adopts a small-convexity rolling mode, and the convexity C40 is 40 +/-10 mu m.
Further, 2-frame rough rolling and 7-frame finish rolling hot continuous rolling units are adopted for rolling, the accumulated reduction rate of rough rolling is more than or equal to 80%, and the accumulated reduction rate of finish rolling is more than or equal to 80%;
and performing a full-pass descaling process by rough rolling, performing high-pressure water descaling at the inlet of the finishing mill group, and opening secondary descaling among the F1-F3 racks.
And (3) directly cooling after rolling, wherein the cooling means that: after finishing rolling, rapidly cooling at a cooling speed of more than or equal to 100 ℃/s, then cooling in air for 3-8s, cooling to 700-;
and air-cooling to room temperature after coiling, and finally flattening and transversely cutting to obtain a finished product, wherein the flattening rolling force is 4000-.
Heating is carried out before rolling, wherein the heating refers to that the casting blank is hot-charged into a heating furnace, the heating temperature is 1200-1250 ℃, and the heat preservation time is 2-2.5 h;
preferably, the charging temperature of the casting blank is controlled to be more than or equal to 450 ℃.
Further, the invention also comprises converter smelting, LF furnace refining, RH vacuum circulation degassing refining and continuous casting, and specifically comprises the following steps: carrying out converter smelting, LF furnace refining and RH vacuum circulation degassing refining according to the chemical components of the formula; the continuous casting adopts full-protection pouring, dynamic soft reduction or electromagnetic stirring is used, a casting blank is taken out of a continuous casting machine, is cut and directly hot-charged and enters a heating furnace, and the temperature of the casting blank entering the furnace is controlled to be more than or equal to 450 ℃.
The chemical composition design of the invention adopts a micro-alloying design idea of high Si, high Mn, Nb, V, Ti and B.
0.15-0.25% of C, which is used as a basic element in steel and plays a very important role in improving the strength and the hardness of the steel, wherein the volume fraction and the hardness of martensite are directly influenced by the content of C, the volume fraction and the hardness of martensite cannot be ensured by too low content of C, and further the strength and the wear resistance of the material cannot be ensured, in order to obtain higher strength and hardness, the content of C must be ensured to be more than 0.15%, but the content of C is not too high, otherwise, ferrite with a certain proportion is difficult to form in the rolling and cooling process, and the ductility and the toughness of the material are influenced;
si: 1.0-2.5 percent of Si, wherein Si is one of important elements in the invention, Si is an element for enlarging an austenite region, the formation of a ferrite structure in an air cooling stage can be promoted, and a cooling process window for forming a soft-phase ferrite structure in the air cooling stage is enlarged, but on the one hand, if the content of Si is too high, the surface iron scale is too much, the red rust phenomenon is serious, and the surface quality is not favorably controlled; on the other hand, the brittleness of the material is increased, which is not favorable for improving the impact performance.
Mn: 1.5-2.5 percent of Mn is used as a reinforcing element of the steel, the hardenability of the steel can be obviously improved, the strength of the steel is improved, the Mn content is controlled to be more than 1.5 percent in order to ensure the strength of the steel, but the Mn content is used as a stable austenite area element, and the air cooling section cannot form a certain amount of soft-phase ferrite structures due to the excessively high Mn content, so that the steel and the impact toughness are not facilitated. Meanwhile, too high Mn content increases the risk of billet segregation.
P, S, O as impurity elements, the impurity elements can adversely affect the plasticity, forming, welding and other properties of steel, the lower the content, the better, the production cost factor is considered, and the P: less than or equal to 0.012 percent, S: less than or equal to 0.005 percent, O: less than or equal to 0.0030 percent;
n: less than or equal to 0.0030 percent, and in the steel containing B, N and B can generate BN, thereby reducing the effective B content and reducing the influence of B on the hardenability of the material.
H: less than or equal to 0.00015 percent, and the hydrogen brittleness sensitivity of the steel can be increased when the content of H in the molten steel is too high, and particularly for ultrahigh-strength steel, delayed cracking caused by hydrogen can be generated, and the use performances of the steel, such as the plasticity and the toughness, are unfavorable.
Nb: 0.010-0.060%, mainly improving the strength, impact property and cold-bending formability of the steel by refining crystal grains.
Ti: 0.010-0.060%, on one hand, Ti and Nb are matched to refine austenite grains and refine martensite and ferrite tissues which are finally transformed, thereby improving the strength of the steel; and secondly, the welding performance of the material is improved, and TiN formed by combining Ti and N has an obvious inhibiting effect on austenite grain coarsening in the welding process.
V: 0.010-0.050%, on one hand, V is used as a strong carbide forming element, and V (C, N) formed by V and C, N is dispersed in a steel matrix to mainly play a role in precipitation strengthening, so that the strength of the steel is improved; on the other hand, V can pin grain boundaries in the heating process, prevent austenite grains from growing and play a role in refining the grains.
And Als: 0.020-0.060 percent, wherein Als mainly plays a role in deoxidizing in the steel, but the Als cannot be too high, and the Als can react with N in the steel to precipitate coarse AlN particles, so that the grain refining effect is not facilitated.
B: 0.0010-0.0030 percent, B is an important element of the invention, and B is added to increase the hardenability of steel on one hand, and on the other hand, B is an element for stabilizing an austenite region, so that the consistency of transformation from austenite to ferrite and martensite in the rolling and cooling process can be improved, the influence of the surface temperature fluctuation of a steel plate on the phase transformation consistency is reduced, and the mechanical property stability is further improved. Meanwhile, the ferroboron has low cost and economical efficiency. When the content of B is 0.0008%, hardenability can be obviously improved, but the content of B is not too high, B is taken as a stable austenite region element, austenite is strongly delayed to ferrite, a certain proportion of ferrite is difficult to form even by prolonging the air cooling time, or bainite transformation occurs by reducing the temperature of an air cooling section to increase the supercooling degree and further drive the austenite to ferrite transformation, so that the cooling process window is narrowed. Therefore, the B content is preferably controlled to 0.0010 to 0.0030%.
The casting blank is directly hot-charged into a heating furnace, the charging temperature of the casting blank is controlled to be more than or equal to 450 ℃, and the main purpose is to avoid cracks on the surface of the casting blank. In the design of the hot rolling process, the material strengthening approach mainly comprises fine grain strengthening and phase change strengthening, the target microstructure is martensite and ferrite (the martensite is the main), the hard phase martensite is used for improving the strength, hardness and wear resistance of the material, and the soft phase ferrite is used for improving the plasticity and toughness and cold bending forming performance of the material. The heating temperature is controlled at 1200-1250 ℃, and the method is mainly based on the solid solution effect of Nb and Ti second phase particles, improves the precipitation strengthening effect of Nb and Ti second phase, controls the thickness of iron scale, and improves the surface quality of the strip steelConsidering that the heating temperature is too low, the Nb and Ti second phase particles cannot be fully dissolved in the solution, so that the size of the undissolved second phase particles is larger, and the effects of pinning austenite grain boundary, refining austenite grain size and precipitation strengthening are not favorable; when the heating temperature is too high, Si reacts with FeO to generate fayalite Fe2SiO4The iron scale is difficult to remove, and the surface quality of the strip steel is influenced; the rough rolling is carried out with a full-pass descaling process, the inlet of a finishing mill set is subjected to high-pressure water descaling, secondary descaling between F1-F3 racks is opened, the generation amount of the iron scale with higher Si content is more, the thickness of the iron scale is reduced to the maximum extent, the surface quality of the material is improved, the final rolling temperature is controlled at 850-900 ℃, and on the premise of ensuring the rolling stability, the original grain size of the austenite is favorably refined at a lower final rolling temperature, and the fine grain strengthening effect is improved. The finish rolling adopts small-convexity rolling, and the main purpose is to control the thickness precision of the plate in the width direction, reduce the inconsistency of the transformation from austenite to ferrite caused by the thickness fluctuation in the width direction of the plate in the subsequent cooling process and influence the plate shape and the mechanical property uniformity of the steel plate; after rolling, a sectional cooling mode is adopted, a small amount of soft-phase ferrite exists in the material structure, the martensite self-tempering effect is controlled by adopting a reasonable coiling temperature, the final target microstructure is 75-85% of martensite and 15-25% of ferrite, the hard-phase martensite is used for improving the strength, hardness and wear resistance of the material, and the soft-phase ferrite is used for improving the plasticity and toughness and cold-bending forming performance of the material. The first section cooling speed after the final rolling is controlled to be more than 100 ℃/s, so that the material can rapidly enter a ferrite phase change area, ferrite grains formed by full refining and transformation are fully refined, and the cold bending performance and the impact performance of the material can be improved; the second stage air cooling time is controlled to be 3-8s, and the air cooling finishing temperature is controlled to be 700-750 ℃, so as to obtain a certain proportion of ferrite structure and be beneficial to ensuring the plate shape. The air cooling time is too long, the proportion of ferrite is large, and the size of ferrite grains is large, so that the improvement of the strength and the hardness of the material is not facilitated; end temperature of air cooling>750 ℃, the air cooling finishing temperature is in the high temperature section of the ferrite phase transformation area, the supercooling degree is small, the phase transformation driving force is low, and the small proportion of the ferrite structure and the large growth of the ferrite grain size are causedThe speed is high, and the ferrite grain size is large; the air cooling finishing temperature is too low, particularly lower than 670 ℃, although a certain proportion of ferrite can be obtained, the proportion of ferrite is relatively more, which is not beneficial to ensuring the strength and the hardness of the material; the cooling speed of the third section is controlled to be more than 50-100 ℃/s, the purpose is to enable the untransformed austenite structure to be rapidly transformed into a fine martensite structure, and a bainite structure with a certain proportion can be formed when the cooling speed is too low; the coiling temperature is controlled at 200-300 ℃, the aim is to control the self-tempering effect of the martensite, the coiling temperature is too high, the self-tempering degree of the martensite formed by transformation is large, and the strength of the material is reduced due to the decomposition of the martensite; the coiling temperature is too low, on one hand, the coiling temperature fluctuation range in the width direction and the length direction of the plate is large, and the coiling uniformity, the mechanical property stability and the plate shape of the material are difficult to guarantee, and on the other hand, the yield strength of the material is low, the yield ratio is low, the plastic deformation is easy to occur, and the service safety of the high-strength wear-resistant structural member is not facilitated. In order to improve the shape of the material plate and improve the qualification rate of the open plate shape, a flattening process is added after hot rolling, the flattening rolling force is 4000-6000kN, and the flattening rolling force is too small and too large, so that the shape is not beneficial to improving.
The invention realizes the industrial production of the NM 360-grade wear-resistant steel plate on the conventional hot continuous rolling production line by a heat-treatment-free TMCP process, and realizes the production of the NM 360-grade wear-resistant steel plate with good cold-bending forming performance on the conventional hot continuous rolling strip production line by reasonable alloy component design and matched heat-treatment-free TMCP process technology. The microstructure of the produced steel plate is martensite and ferrite, wherein the volume fraction of the martensite is 75-85%, the volume fraction of the ferrite is 15-25%, the average grain size of the ferrite is 3-8 μm, the yield strength is not less than 800MPa, the tensile strength is not less than 1200MPa, and the elongation A is50Not less than 15%, cold bending performance of 180 deg, qualified D-4 a, surface Brinell hardness not less than 360HBW, impact energy A at-20 deg.ckvNot less than 20J (sample size: 2.5X 10X 55mm), and the product performance meets the technical requirement of NM360 in GB/T24186-2009. The NM 360-grade wear-resistant steel plate produced by the invention has the characteristics of short process flow, low production cost, high product strength and hardness, good cold-bending forming performance and the like.
Drawings
FIG. 1 a typical metallographic structure corresponding to the steel sheet of example 1;
FIG. 2 a typical metallographic structure corresponding to the steel sheet of example 2;
FIG. 3 is a typical metallographic structure corresponding to the steel sheet of example 3;
FIG. 4 shows a typical metallographic structure corresponding to the steel sheet of example 4;
FIG. 5 is a typical metallographic structure corresponding to a steel plate of comparative example 1;
fig. 6 shows a typical metallographic structure corresponding to the steel sheet of comparative example 2.
Detailed Description
The technical scheme of the present invention will be described below by way of specific examples and comparative examples.
A heat treatment-free NM360 wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.15 to 0.25 percent; si: 1.0-2.5%; mn: 1.5 to 2.5 percent; p: less than or equal to 0.012 percent; s: less than or equal to 0.005 percent; nb: 0.010-0.060%; ti: 0.010-0.060%; v: 0.010-0.050%; and Als: 0.020-0.060%; b: 0.0010-0.0030%; h: less than or equal to 0.00015 percent; n: less than or equal to 0.0030 percent; o: less than or equal to 0.0030 percent; the balance of Fe and inevitable impurities.
Examples 1 to 4, comparative examples 1 to 2
A heat-treatment-free NM360 wear-resistant steel sheet has chemical compositions shown in Table 1, and the balance not shown in Table 1 is Fe and inevitable impurities.
TABLE 1 actual chemical composition (mass percent, wt%) of each example and comparative example
| Numbering | C | Si | Mn | P | S | Nb | Ti | V | Als | B | H | O | N |
| Example 1 | 0.15 | 1.23 | 1.75 | 0.010 | 0.004 | 0.056 | 0.021 | 0.012 | 0.039 | 0.0011 | 0.00012 | 0.0019 | 0.0024 |
| Example 2 | 0.16 | 1.63 | 1.68 | 0.008 | 0.005 | 0.015 | 0.058 | 0.025 | 0.053 | 0.0013 | 0.00014 | 0.0016 | 0.0019 |
| Example 3 | 0.17 | 1.85 | 1.72 | 0.007 | 0.006 | 0.035 | 0.031 | 0.033 | 0.045 | 0.0016 | 0.00013 | 0.0010 | 0.0027 |
| Example 4 | 0.22 | 2.31 | 2.23 | 0.009 | 0.005 | 0.026 | 0.035 | 0.050 | 0.030 | 0.0021 | 0.00012 | 0.0018 | 0.0022 |
| Comparative example 1 | 0.17 | 1.60 | 1.80 | 0.010 | 0.005 | 0.034 | 0.036 | 0.038 | 0.041 | 0.0015 | 0.00013 | 0.0011 | 0.0028 |
| Comparative example 2 | 0.12 | 1.20 | 1.25 | 0.011 | 0.003 | 0.036 | 0.029 | 0.032 | 0.038 | 0.0008 | 0.00013 | 0.0011 | 0.0028 |
The manufacturing method of the heat-treatment-free NM360 wear-resistant steel plate in the above embodiments 1 to 4 comprises the following steps: carrying out converter smelting, LF furnace refining, RH vacuum circulation degassing refining, continuous casting, heating, rolling, cooling, coiling, flattening and flattening processes.
1) Smelting, refining and continuous casting, wherein the smelting and the refining are carried out in a converter according to the chemical components in the requirement 1, the continuous casting adopts full-protection pouring, dynamic soft reduction or electromagnetic stirring is put into the converter, the casting blank is taken out of a continuous casting machine, cut and directly hot-charged into a heating furnace, and the temperature of the casting blank in the furnace is controlled to be more than or equal to 450 ℃.
2) Heating and rolling, wherein the heating temperature of the casting blank is 1200-1250 ℃, and the heat preservation time is 2-2.5 h; the rolling is carried out by adopting a 2-frame rough rolling hot continuous rolling unit and a 7-frame finish rolling hot continuous rolling unit, wherein the rough rolling start rolling temperature is 1100-1150 ℃, the finish rolling start rolling temperature is 950-1050 ℃, the rough rolling is carried out by a full-pass descaling process, the inlet of the finish rolling unit is subjected to high-pressure water descaling, the secondary descaling among the F1-F3 frames is opened, and the finish rolling temperature is 850-900 ℃; and the finish rolling adopts a small-convexity rolling mode, and the convexity C40 is 40 +/-10 mu m.
3) And (3) cooling: after the final rolling, the steel plate is rapidly cooled at a cooling speed of more than or equal to 100 ℃/s, then is cooled in air for 3-8s and is cooled to 750 ℃ in 700-.
The specific process parameters for the production of each example and comparative example are shown in table 2.
TABLE 2 Main Rolling Process parameters of examples and comparative examples
The microstructure composition phase ratio and the grain size of the steel sheets produced in examples 1 to 4 and comparative examples 1 to 2 are shown in Table 3. The mechanical properties of examples 1 to 4, comparative examples 1 to 2, and NM360 produced by thermal refining treatment, comparative examples 3 to 4, are shown in table 4, and the abrasion loss in the abrasion resistance test is shown in table 5. It can be seen that the strength, elongation, hardness and wear resistance of the embodiment of the invention all reach the level of the traditional NM360 material object, and the cold bending performance is better.
TABLE 3 proportion and size of phase composition of microstructure of each of examples and comparative examples
| Numbering | Martensite volume fraction (%) | Ferrite volume fraction (%) | Ferrite average grain size (μm) |
| Example 1 | 79.83 | 20.17 | 5.73 |
| Example 2 | 81.18 | 18.82 | 6.01 |
| Example 3 | 82.44 | 17.56 | 6.68 |
| Example 4 | 83.19 | 16.81 | 5.96 |
| Comparative example 1 | 57.59 | 42.41 | 7.43 |
| Comparative example 2 | 52.56 | 47.44 | 8.92 |
TABLE 4 mechanical Properties of Steel sheets for examples and comparative examples
Note: comparative examples 3 and 4 are conventional NM360 steel sheets produced by the quenching and tempering heat treatment, and the production processes of chemical composition, rolling and heat treatment are as follows.
Comparative example 3:
NM360 steel plate composition: c: 0.19 percent; si: 0.33 percent; mn: 1.55 percent; p: 0.008 percent; s: 0.003%; cr: 0.17 percent; b: 0.0010%; ti: 0.020%; and Als: 0.030%.
NM360 steel plate manufacturing method: the molten steel is smelted in a converter or an electric furnace and refined outside the furnace, and is cast into a plate blank. The heating temperature of the plate blank is 1200 ℃, the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, and the plate blank is air-cooled to the room temperature after rolling. Rolling the steel plate, and performing heat treatment, including quenching and tempering, wherein the quenching process is performed at the quenching temperature of 950 ℃ and the heat preservation time of 30 mmin; the tempering process comprises the following steps: tempering temperature is 250 ℃, heat preservation is carried out for 30min, and the thickness specification of the finished product is 5.0 mm.
Comparative example 4:
NM360 steel plate composition: c: 0.18 percent; si: 0.35 percent; mn: 1.58 percent; p: 0.010%; s: 0.002%; cr: 0.20 percent; b: 0.0012%; ti: 0.025 percent; and Als: 0.030%.
NM360 steel plate manufacturing method: the molten steel is smelted in a converter or an electric furnace and refined outside the furnace, and is cast into a plate blank. The heating temperature of the plate blank is 1200 ℃, the initial rolling temperature is 1100 ℃, the final rolling temperature is 940 ℃, and the plate blank is air-cooled to the room temperature after rolling. Rolling the steel plate, and performing heat treatment, including quenching and tempering, wherein the quenching process is at the quenching temperature of 950 ℃ and the heat preservation time of 30 min; the tempering process comprises the following steps: the tempering temperature is 235 ℃, the temperature is kept for 30min, and the thickness specification of the finished product is 4.0 mm.
TABLE 5 weight loss on abrasion data for each example and comparative example
| Numbering | Loss on abrasion Δ m (g) |
| Example 1 | 1.5532 |
| Example 2 | 1.5516 |
| Example 3 | 1.5435 |
| Example 4 | 1.5422 |
| Comparative example 1 | 2.0721 |
| Comparative example 2 | 2.0674 |
| COMPARATIVE EXAMPLE 3(NM360) | 1.5700 |
| COMPARATIVE EXAMPLE 4(NM360) | 1.5646 |
Note: the abrasive wear test was performed in an MLS-225 type wet rubber wheel testing machine, and the sample size of the abrasive wear test was: 57mm (length) × 25.5mm (width) × 2.5mm (thickness), wherein the 57mm × 25.5mm face is the wear face, the wear surface is polished. The test parameters were as follows: the hardness of the rubber wheel is 60HS, the rotating speed of the rubber wheel is 240r/min, the grinding material is a solution formed by mixing quartz sand and water according to the proportion of 1:1, the particle size of the quartz sand is 20-40 meshes, and the load is 170N. Firstly, pre-grinding the wear surface of a sample by 1000r, recording the weight m1 of the pre-ground sample, then carrying out accurate grinding for 40min, recording the weight m2 of the accurately ground sample, carrying out ultrasonic cleaning on the pre-ground sample and the accurately ground sample, and measuring the weight by an electronic balance (the precision is 0.1 mg). The abrasion weight loss delta m (m1-m2) is used as a main parameter for evaluating the abrasion resistance of the material, and the smaller the abrasion weight loss is, the better the abrasion resistance of the material is. And (3) respectively selecting 3 pieces of each test material under the same test condition to carry out an abrasive wear test, and taking the average value of the wear weight loss of the 3 samples as the final wear weight loss.
Claims (10)
1. The heat treatment-free NM360 wear-resistant steel plate is characterized in that the heat treatment-free NM360 wear-resistant steel plate comprises the following chemical components in percentage by weight: 0.15 to 0.25 percent; si: 1.0-2.5%; mn: 1.5 to 2.5 percent; p: less than or equal to 0.012 percent; s: less than or equal to 0.005 percent; nb: 0.010-0.060%; ti: 0.010-0.060%; v: 0.010-0.050%; and Als: 0.020-0.060%; b: 0.0010-0.0030%; h: less than or equal to 0.00015 percent; n: less than or equal to 0.0030 percent; o: less than or equal to 0.0030 percent; the balance of Fe and inevitable impurities.
2. The heat-treatment-free NM360 wear resistant steel plate of claim 1, wherein the microstructure of the heat-treatment-free NM360 wear resistant steel plate is martensite + ferrite, wherein the volume fraction of martensite is 75-85%, the volume fraction of ferrite is 15-25%, and the average grain size of ferrite is 3-8 μm.
3. The heat-treatment-free NM360 wear-resistant steel plate of claim 1 or 2, wherein the heat-treatment-free NM360 wear-resistant steel plate has a tensile strength of 1200MPa or more and an elongation A50Not less than 15%, cold bending performance of 180 deg, qualified D-4 a, surface Brinell hardness not less than 360HBW, impact energy A at-20 deg.ckV≥20J。
4. The method for manufacturing the heat-treatment-free NM360 wear resistant steel plate as recited in any one of claims 1-3, wherein the method comprises heating, wherein the heating is performed by hot charging a casting blank into a heating furnace at 1200-1250 ℃ for 2-2.5 h.
5. The manufacturing method according to claim 4, wherein the heating is performed by controlling a charging temperature of the cast slab to be not less than 450 ℃.
6. The manufacturing method according to claim 4 or 5, characterized in that it comprises rolling, in particular: the initial rolling temperature of rough rolling is 1100-1150 ℃, the initial rolling temperature of finish rolling is 950-1050 ℃, and the final rolling temperature of finish rolling is 850-900 ℃; and the finish rolling adopts a small-convexity rolling mode, and the convexity C40 is 40 +/-10 mu m.
7. The production method according to claim 6, wherein the rolling rough rolling cumulative reduction is 80% or more, and the finishing rolling cumulative reduction is 80% or more.
8. A method of manufacture according to claim 6 or 7, characterized in that the rough rolling is performed with a full-pass descaling process, the finishing train inlet is subjected to high-pressure water descaling, and the secondary descaling between the F1-F3 stands is opened.
9. The manufacturing method according to any one of claims 4 to 7, characterized in that it comprises cooling, said cooling being: after the final rolling, the steel plate is rapidly cooled at a cooling speed of more than or equal to 100 ℃/s, then is cooled to 750 ℃ in air cooling for 3-8s, and is cooled to 300 ℃ in air cooling for 200-100 ℃/s to be coiled.
10. The method according to any one of claims 4 to 7, wherein the method comprises temper rolling with a temper rolling force of 4000 and 6000 kN.
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