[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

CN114107790A - 980 MPa-grade ultra-low-carbon martensite high-reaming steel and manufacturing method thereof - Google Patents

980 MPa-grade ultra-low-carbon martensite high-reaming steel and manufacturing method thereof Download PDF

Info

Publication number
CN114107790A
CN114107790A CN202010896455.1A CN202010896455A CN114107790A CN 114107790 A CN114107790 A CN 114107790A CN 202010896455 A CN202010896455 A CN 202010896455A CN 114107790 A CN114107790 A CN 114107790A
Authority
CN
China
Prior art keywords
steel
equal
less
content
low carbon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202010896455.1A
Other languages
Chinese (zh)
Other versions
CN114107790B (en
Inventor
王焕荣
杨峰
张晨
柏明卓
杨阿娜
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Baoshan Iron and Steel Co Ltd
Original Assignee
Baoshan Iron and Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Baoshan Iron and Steel Co Ltd filed Critical Baoshan Iron and Steel Co Ltd
Priority to CN202010896455.1A priority Critical patent/CN114107790B/en
Priority to EP21860562.4A priority patent/EP4206350A4/en
Priority to US18/043,217 priority patent/US20230313332A1/en
Priority to JP2023513798A priority patent/JP2023539649A/en
Priority to PCT/CN2021/115431 priority patent/WO2022042730A1/en
Priority to KR1020237009927A priority patent/KR20230061413A/en
Publication of CN114107790A publication Critical patent/CN114107790A/en
Application granted granted Critical
Publication of CN114107790B publication Critical patent/CN114107790B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • 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
    • 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
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • 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

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

A980 MPa-level ultra-low carbon martensite high-reaming steel and a manufacturing method thereof are disclosed, and the steel comprises the following chemical components in percentage by weight: 0.03-0.06% of C, 0.5-2.0% of Si, 1.0-2.0% of Mn, less than or equal to 0.02% of P, less than or equal to 0.003% of S, 0.02-0.08% of Al, less than or equal to 0.004% of N, 0.1-0.5% of Mo, 0.01-0.05% of Ti, less than or equal to 0.0030% of O, and the balance of Fe and other inevitable impurities. Hair brushThe yield strength of the high-hole-expansion steel is more than or equal to 800MPa, the tensile strength is more than or equal to 980MPa, and the elongation percentage is transverse A50The cold bending property (d is less than or equal to 4a and 180 degrees) and the hole expanding rate is more than or equal to 50 percent, and the cold bending cold.

Description

980 MPa-grade ultra-low-carbon martensite high-reaming steel and manufacturing method thereof
Technical Field
The invention belongs to the field of high-strength steel, and particularly relates to 980 MPa-grade ultra-low-carbon martensite high-reaming steel and a manufacturing method thereof.
Background
With the development of national economy, the production of automobiles is greatly increased, and the use amount of plates is continuously increased. The original design requirements of parts of many vehicle types in the domestic automobile industry require the use of hot-rolled or pickled plates, such as chassis parts, torsion beams, auxiliary frames of cars, wheel spokes and rims, front and rear axle assemblies, body structural parts, seats, clutches, safety belts, truck box plates, protective nets, automobile girders and other parts of automobiles. Wherein, the proportion of the chassis steel to the total steel used by the car can reach 24 to 34 percent.
The light weight of passenger cars is not only a development trend in the automotive industry, but also a requirement of legal regulations. The fuel consumption is regulated by laws and regulations, the weight of a vehicle body is required to be reduced in a phase-changing manner, and the requirement reflected on materials is high strength, thinning and light weight. High strength subtracts heavy is the inevitable requirement of follow-up new motorcycle type, and this must lead to the fact with the steel grade higher, also must bring the change on the chassis structure: if the parts are more complex, the requirements on material performance, surface and the like and the forming technology are improved, such as hydraulic forming, hot stamping, laser welding and the like, and the performances of high strength, stamping, flanging, resilience, fatigue and the like of the material are further converted.
Compared with the foreign countries, the development of domestic high-strength high-hole-expansion steel has relatively lower strength level and poor performance stability. For example, high-expansion-hole steel used by domestic automobile part enterprises is basically high-strength steel with the tensile strength of below 600MPa, and high-expansion-hole steel with the tensile strength of below 440MPa competes for whitening. High hole expansion steel with 780 MPa-grade tensile strength is gradually used in batch at present, but higher requirements are provided for two important indexes of forming elongation and hole expansion rate. And 980 MPa-grade high-reaming steel is still in a research and development certification stage at present and does not reach a batch use stage. However, 980 h-bore steel with higher strength and higher hole expansion rate is a necessary development trend in the future. In order to better meet the potential future demands of users, 980MPa grade high hole-expanding steel with good hole-expanding performance needs to be developed.
At present, most of the related patent documents are high hole-expanding steel with the grade of 780MPa and below. Few documents are related to 980MPa grade high-hole-expansion steel. Chinese patent CN106119702A discloses 980 MPa-grade hot-rolled high-reaming steel, which is mainly characterized by low-carbon V-Ti microalloying design, wherein the microstructure is granular bainite and a small amount of martensite, and trace Nb and Cr are added. Are very different from the present invention in terms of composition, process, and organization.
As known from the literature, in general, the elongation of a material is in inverse proportion to the hole expansion rate, i.e., the higher the elongation, the lower the hole expansion rate; conversely, the lower the elongation, the higher the hole expansion ratio. It is very difficult to obtain high elongation high hole expansion steel having high strength. Further, the higher the strength of the material, the lower the hole expansion ratio, under the same or similar strengthening mechanisms.
In order to obtain a steel material having good plasticity and burring performance, a better balance between the two is required. Of course, the rate of hole enlargement of a material is closely related to many factors, the most important of which include uniformity of the structure, inclusion and segregation control levels, different structure types, and measurements of the rate of hole enlargement. Generally, a single homogeneous structure is advantageous for achieving higher porosities, while a bi-or multi-phasic structure is generally disadvantageous for increasing the porosities.
Disclosure of Invention
The invention aims to provide 980 MPa-grade ultra-low carbon martensite high-hole-expansion steel and a manufacturing method thereof, wherein the yield strength of the high-hole-expansion steel is more than or equal to 800MPa, the tensile strength is more than or equal to 980MPa, and the elongation percentage is transverse A50The cold bending property (d is less than or equal to 4a and 180 degrees) and the hole expanding rate is more than or equal to 50 percent, and the cold bending cold.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the invention adopts the lower C content in the component design, which can ensure that the welding performance is excellent when the welding tool is used by a user and the obtained martensite structure has good hole expanding performance and impact toughness; designing higher Si content, and matching with the process to obtain more residual austenite, thereby improving the plasticity of the material; meanwhile, the higher Si content is beneficial to reducing the non-recrystallization temperature of the steel, so that the steel can finish the dynamic recrystallization process within a wider finish rolling temperature range, thereby refining austenite grains and the final martensite grain size, and improving the plasticity and the hole expansion rate.
Specifically, the 980 MPa-grade ultra-low carbon martensite high-hole-expansion steel comprises the following chemical components in percentage by weight: 0.03-0.06% of C, 0.5-2.0% of Si, 1.0-2.0% of Mn, less than or equal to 0.02% of P, less than or equal to 0.003% of S, 0.02-0.08% of Al, less than or equal to 0.004% of N, 0.1-0.5% of Mo, 0.01-0.05% of Ti, less than or equal to 0.0030% of O, and the balance of Fe and other inevitable impurities.
Further, one or more elements of Cr less than or equal to 0.5 percent, B less than or equal to 0.002 percent, Ca less than or equal to 0.005 percent, Nb less than or equal to 0.06 percent, V less than or equal to 0.05 percent, Cu less than or equal to 0.5 percent and Ni less than or equal to 0.5 percent are also contained; wherein, the Cr content is preferably 0.2-0.4%, and the B content is preferably 0.0005-0.0015%; the content of Ca is preferably less than or equal to 0.002%; the content of Nb and V is preferably less than or equal to 0.03 percent respectively; the content of Cu and Ni is preferably less than or equal to 0.3 percent respectively.
In the composition design of the high hole expansion steel of the invention:
carbon is an essential element in steel and is also one of the important elements in the present invention. Carbon expands the austenite phase region and stabilizes austenite. Carbon, which is an interstitial atom in steel, plays a very important role in increasing the strength of steel, and has the greatest influence on the yield strength and tensile strength of steel. In the invention, because the microstructure to be obtained is low-carbon or ultra-low-carbon martensite, in order to obtain high-strength steel with the tensile strength reaching 980MPa, the content of carbon is required to be ensured to be more than 0.03 percent, otherwise, the content of carbon is less than 0.03 percent, and the tensile strength can not reach 980MPa even if the steel is completely quenched to the room temperature; but the carbon content cannot be higher than 0.06%. The carbon content is too high, the strength of the formed low-carbon martensite is too high, and the elongation and the hole expansion rate are both low. Therefore, the carbon content should be controlled to be between 0.03 and 0.06%, and preferably in the range of 0.04 to 0.055%.
Silicon is an essential element in steel and is also one of the important elements in the present invention. The Si content is increased, so that the solid solution strengthening effect is improved, and more importantly, the following two effects are achieved. Firstly, the non-recrystallization temperature of the steel is greatly reduced, and the dynamic recrystallization of the steel can be completed in a very low temperature range. Therefore, in the actual rolling process, rolling can be carried out within a relatively wider final rolling temperature range, such as the final rolling temperature range of 800-900 ℃, so that the anisotropy of the structure can be greatly improved, the anisotropy of the final martensite structure is reduced, the strength and the plasticity are favorably improved, and meanwhile, the good hole expansion rate is favorably obtained; the other important function of Si is to inhibit cementite precipitation, and a certain amount of retained austenite can be reserved under proper rolling process conditions, especially when a structure mainly comprising martensite is obtained, so that the elongation is favorably improved. It is known that the elongation of martensite is usually the lowest under the same strength class conditions, and that retention of a certain amount of stable retained austenite is an important measure in order to increase the elongation of martensite. This effect of Si generally begins to manifest when its content reaches above 0.5%; but the content of Si is not too high, otherwise, the rolling force load is too large in the actual rolling process, and the stable production of products is not facilitated. Therefore, the Si content in the steel is usually controlled to be between 0.5 and 2.0%, and preferably in the range of 0.8 to 1.4%.
Manganese, the most basic element in steel, is also one of the most important elements in the present invention. It is known that Mn is an important element for expanding the austenite phase region, and can reduce the critical quenching rate of steel, stabilize austenite, refine grains, and delay transformation of austenite to pearlite. In the invention, in order to ensure the strength of the steel plate and stabilize the retained austenite, the content of Mn is generally controlled to be more than 1.0%; meanwhile, the Mn content is generally not more than 2.0%, otherwise Mn segregation is likely to occur during steel making, and hot cracking is also likely to occur during slab continuous casting. Therefore, the Mn content in the steel is generally controlled to be 1.0 to 2.0%, preferably in the range of 1.4 to 1.8%;
the amount of phosphorus is such that,is an impurity element in steel. P is easy to be partially gathered on the grain boundary, and Fe is formed when the content of P in steel is higher (more than or equal to 0.1 percent)2P is precipitated around the crystal grains to reduce the plasticity and toughness of the steel, so the lower the content of the P is, the better the P content is generally controlled within 0.02 percent, and the steelmaking cost is not increased.
Sulfur, an impurity element in steel. S in steel is usually combined with Mn to form MnS inclusions, and particularly when the contents of S and Mn are high, the steel forms more MnS, and the MnS has certain plasticity, and the MnS deforms along the rolling direction in the subsequent rolling process, so that the transverse plasticity of the steel is reduced, the structural anisotropy is increased, and the hole expansion performance is not favorable. Therefore, the lower the S content in the steel, the better, considering that the Mn content in the present invention must be at a high level, the S content is strictly controlled in order to reduce the MnS content, and the S content is required to be controlled to be within 0.003%, and preferably to be within 0.0015%.
The role of aluminum in steel is mainly deoxidation and nitrogen fixation. In the presence of strong carbide forming elements such as Ti, Nb, V, etc., Al mainly functions to deoxidize and refine grains. In the invention, Al is taken as a common deoxidizing element and an element for refining grains, and the content of Al is usually controlled to be 0.02-0.08%; the Al content is lower than 0.02 percent, and the effect of refining grains is not achieved; similarly, when the Al content is higher than 0.08%, the effect of refining grains is saturated. Therefore, the Al content in the steel may be controlled to be 0.02 to 0.08%, and preferably 0.02 to 0.05%.
Nitrogen, which is an impurity element in the present invention, is preferably contained in a lower amount. Nitrogen is an unavoidable element in the steel making process. Although the content thereof is small, the formed TiN particles, in combination with a strong carbide forming element such as Ti or the like, have a very adverse effect on the properties of the steel, particularly on the hole expansibility. Because TiN is square, great stress concentration exists between the sharp corner and the substrate, and cracks are easily formed by the stress concentration between the TiN and the substrate in the reaming deformation process, so that the reaming performance of the material is greatly reduced. On the premise of controlling the nitrogen content as much as possible, the lower the content of the element forming strong carbide such as Ti, the better. In the present invention, a trace amount of Ti is added to fix nitrogen, and the adverse effect of TiN is minimized. Therefore, the nitrogen content should be controlled to 0.004% or less, and preferably 0.003% or less.
Titanium is one of important elements in the present invention. Ti plays two main roles in the present invention: firstly, the nitrogen-fixing agent is combined with impurity element N in steel to form TiN, and plays a part of the role of nitrogen fixation; secondly, a certain amount of TiN with fine dispersion is formed in the subsequent welding process of the material, thereby inhibiting the size of austenite grains, refining the structure and improving the low-temperature toughness. Therefore, the Ti content in the steel is controlled in the range of 0.01 to 0.05%, and preferably in the range of 0.01 to 0.03%.
Molybdenum, is one of the important elements in the present invention. The addition of molybdenum to the steel can greatly retard ferrite and pearlite transformation. The effect of the molybdenum is beneficial to adjusting various processes in the actual rolling process, such as sectional cooling after finishing the final rolling, air cooling before water cooling and the like. In the invention, a process of air cooling and then water cooling or direct water cooling after rolling is adopted, the addition of molybdenum can ensure that structures such as ferrite or pearlite and the like cannot be formed in the air cooling process, and meanwhile, deformed austenite can be dynamically restored in the air cooling process, thereby being beneficial to improving the uniformity of the structures; molybdenum has strong resistance to solder softening. Because the invention mainly aims to obtain the structure of single low-carbon martensite and a small amount of residual austenite, the low-carbon martensite is easy to soften after welding, and the addition of a certain amount of molybdenum can effectively reduce the softening degree of welding. Therefore, the content of molybdenum should be controlled between 0.1-0.5%, preferably in the range of 0.15-0.35%.
Chromium is one of the elements that can be added in the present invention. The addition of a small amount of chromium element is not for improving the hardenability of the steel, but for combining with B, which is beneficial to forming an acicular ferrite structure in a welding heat affected zone after welding, and can greatly improve the low-temperature toughness of the welding heat affected zone. Since the final application parts related by the invention are passenger car chassis products, the low-temperature toughness of the welding heat affected zone is an important index. Besides ensuring that the strength of the welding heat affected zone cannot be reduced too much, the low-temperature toughness of the welding heat affected zone also meets certain requirements. In addition, chromium itself has some resistance to solder softening. Therefore, the addition amount of the chromium element in the steel is generally less than or equal to 0.5 percent, and the preferred range is 0.2 to 0.4 percent;
boron is one of the elements that can be added in the present invention. Boron mainly has the function of being segregated at the original austenite grain boundary in the steel and inhibiting the formation of proeutectoid ferrite; boron added to steel can also greatly improve the hardenability of steel. However, in the present invention, the trace amount of boron is added not mainly for the purpose of enhancing hardenability but for the purpose of improving the structure of the weld heat affected zone in combination with chromium to obtain an acicular ferrite structure excellent in low-temperature toughness. The addition of boron in the steel is generally controlled below 0.002%, and the preferred range is 0.0005-0.0015%.
Calcium, an added element in the present invention. Calcium can improve the form of sulfides such as MnS, so that elongated sulfides such as MnS and the like are changed into spherical CaS, the inclusion form is favorably improved, the adverse effect of the elongated sulfides on the hole expanding performance is further reduced, but the addition of excessive calcium can increase the amount of calcium oxide, and is adverse to the hole expanding performance. Therefore, the addition amount of calcium in steel grades is usually less than or equal to 0.005%, and the preferable range is less than or equal to 0.002%.
Oxygen, which is an inevitable element in the steel making process, is an essential element in the present invention, and the content of O in steel after deoxidation is generally 30ppm or less, and does not cause significant adverse effects on the properties of the steel sheet. Therefore, the O content in the steel is controlled to be within 30 ppm.
Niobium, is one of the elements that may be added in the present invention. Niobium is similar to titanium and is a strong carbide element in steel, niobium is added into the steel to greatly improve the non-recrystallization temperature of the steel, deformed austenite with higher dislocation density can be obtained in the finish rolling stage, and the final phase change structure can be refined in the subsequent transformation process. However, the addition amount of niobium is not so large that the addition amount of niobium exceeds 0.06%, which tends to form relatively coarse carbonitrides of niobium in the microstructure, consume part of carbon atoms, and reduce the precipitation strengthening effect of carbides. Meanwhile, the niobium content is high, the anisotropy of hot-rolled austenite structures is easily caused, and the anisotropy is transmitted to final structures in the subsequent cooling phase change process, so that the reaming performance is not good. Therefore, the niobium content in the steel is usually controlled to 0.06% or less, and preferably in the range of 0.03% or less.
Vanadium, is an additive element in the present invention. Vanadium, like titanium and niobium, is also a strong carbide former. However, vanadium carbides are low in solid solution or precipitation temperature, and are usually all solid-dissolved in austenite in the finish rolling stage. Only when the temperature is lowered to start the phase transformation does vanadium start to form in the ferrite. Because the solid solubility of vanadium carbide in ferrite is larger than that of niobium and titanium, the vanadium carbide has larger size in ferrite, is not beneficial to precipitation strengthening and contributes far less to the strength of steel than titanium, but because certain carbon atoms are consumed in the formation of vanadium carbide, the steel strength is not beneficial to improvement. Therefore, the amount of vanadium added to the steel is usually 0.05% or less, preferably 0.03% or less.
Copper, which is an additive element in the present invention. The corrosion resistance of the steel can be improved by adding the copper into the steel, and the corrosion resistance effect is better when the copper and the P element are added together; when the addition amount of Cu exceeds 1%, an epsilon-Cu precipitated phase can be formed under certain conditions, and a strong precipitation strengthening effect is achieved. However, addition of Cu is likely to cause the phenomenon of "Cu embrittlement" during rolling, and in order to fully utilize the effect of Cu on improving corrosion resistance in some applications without causing significant "Cu embrittlement", the content of Cu element is usually controlled to be within 0.5%, preferably within 0.3%.
Nickel, which is an additive element in the present invention. The nickel added into the steel has certain corrosion resistance, but the corrosion resistance effect is weaker than that of copper, the nickel added into the steel has little influence on the tensile property of the steel, but the structure and the precipitated phase of the steel can be refined, and the low-temperature toughness of the steel is greatly improved; meanwhile, in the steel added with copper element, a small amount of nickel is added to inhibit the generation of Cu brittleness. The addition of higher nickel has no significant adverse effect on the properties of the steel itself. If copper and nickel are added simultaneously, not only can the corrosion resistance be improved, but also the structure and precipitated phase of the steel are refined, and the low-temperature toughness is greatly improved. However, both copper and nickel are relatively expensive alloying elements. Therefore, in order to reduce the alloy cost as much as possible, the amount of nickel added is usually 0.5% or less, and preferably 0.3% or less.
The invention relates to a method for manufacturing 980 MPa-grade ultra-low carbon martensite high-reaming steel, which comprises the following steps of:
1) smelting and casting
Smelting by adopting a converter or an electric furnace, secondarily refining by adopting a vacuum furnace, and then casting into a casting blank or an ingot;
2) the casting blank or the cast ingot is heated again at the temperature of 1100 ℃ and 1200 ℃, and the heat preservation time is 1-2 hours;
3) hot rolling
The initial rolling temperature: at 950-1100 ℃, under 3-5 times of large pressure above 950 ℃ and the accumulated deformation is more than or equal to 50 percent, and the main purpose is to refine austenite grains; then, the intermediate blank is heated to 920-950 ℃, and then the final 3-5 passes of rolling are carried out, and the accumulated deformation is more than or equal to 70 percent; the finishing temperature is 800 ℃ and 920 ℃;
4) cooling down
Firstly, air cooling for 0-10s to perform dynamic recovery and dynamic recrystallization, then cooling the strip steel to a certain temperature (between room temperature and Ms point) below the Ms point by water at a cooling speed of more than or equal to 50 ℃/s, coiling, and cooling to the room temperature after coiling;
5) acid pickling
The pickling operation speed of the strip steel can be adjusted within the range of 30-100 m/min, the pickling temperature is controlled within the range of 75-85 ℃, the withdrawal and straightening rate is controlled to be less than or equal to 2% so as to reduce the elongation loss of the strip steel, and then the strip steel is rinsed, dried on the surface of the strip steel and oiled.
Preferably, after the acid washing in the step 5), rinsing is carried out at the temperature range of 35-50 ℃ to ensure the surface quality of the strip steel, and surface drying and oiling are carried out at the temperature of 120-140 ℃.
The innovation points of the invention are as follows:
the invention adopts the lower C content in the component design, which can ensure that the welding performance is excellent when the welding tool is used by a user and the obtained martensite structure has good hole expanding performance and impact toughness; designing higher Si content, and matching with the process to obtain more residual austenite, thereby improving the plasticity of the material; meanwhile, the higher Si content is beneficial to reducing the non-recrystallization temperature of the steel, so that the steel can finish the dynamic recrystallization process within a wider finish rolling temperature range, thereby refining austenite grains and the final martensite grain size, and improving the plasticity and the hole expansion rate.
The low-carbon martensite design concept is adopted in the component design, higher silicon is added to inhibit and reduce cementite formation, meanwhile, the non-recrystallization temperature is reduced, rolling and air cooling are carried out in a relatively wider final rolling temperature range, original austenite grains with fine, uniform and equiaxial grains can be obtained, and martensite and retained austenite tissues with uniform tissues are finally obtained. The retained austenite endows the steel plate with higher plasticity and cold bending property, the martensite endows the steel plate with high strength, and the uniform and fine structure endows the steel plate with higher hole expansion property and low-temperature toughness.
In the design of the rolling process, the rhythm of the rolling process is required to be completed as fast as possible in the stages of rough rolling and finish rolling. After finishing rolling, air cooling is firstly carried out for a certain time. The main purposes of air cooling are as follows: because of the higher manganese and molybdenum content in the composition design, the manganese is an element for stabilizing austenite, and the molybdenum greatly delays ferrite and pearlite phase transformation. Therefore, during the air-cooling for a certain period of time, the rolled deformed austenite does not undergo phase transformation, i.e., ferrite structure, but dynamic recrystallization and relaxation processes. The deformed austenite is dynamically recrystallized to form nearly equiaxial austenite with uniform structure, the dislocation in the austenite grains is greatly reduced after relaxation, and the combination of the two can obtain martensite with uniform structure in the subsequent water-cooling quenching process. In order to obtain a martensite structure, the water cooling speed is higher than the critical cooling speed of the low-carbon martensite, in the invention, the critical cooling speed of the martensite is 30-50 ℃/s according to the difference of components and processes, and in order to ensure that the martensite can be obtained by all component designs, the water cooling speed of the strip steel is required to be more than or equal to 50 ℃/s.
Since the microstructure according to the present invention is low-carbon or ultra-low-carbon martensite, the strip steel may be cooled to a temperature not higher than the martensite transformation start point Ms at a cooling rate higher than the critical cooling rate after the finish rolling. The cooling and stopping temperatures are different, and the content of residual austenite at room temperature is different. There is usually an optimum quenching stop temperature range, which varies depending on the alloy composition, and is generally between 150 ℃ and 350 ℃. In order to obtain high-strength steel with good plasticity and hole expansion rate, the strip steel needs to be quenched to a certain temperature range below the Ms point, and the structure with excellent comprehensive performance can be obtained by quenching the strip steel to a temperature range of less than or equal to 400 ℃ according to theoretical calculation and actual test verification. When the quenching temperature is more than or equal to 400 ℃, although the quantity of the residual austenite is more, a bainite structure appears in the structure, and the strength requirement of over 980MPa cannot be met. For the above reasons, the coiling temperature needs to be controlled to be less than or equal to 400 ℃. Based on the innovative components and process design thought, 980 MPa-grade ultra-low-carbon martensite high-hole-expansion steel with excellent strength, plasticity, toughness, cold bending and hole expansion properties can be obtained.
The invention has the beneficial effects that:
(1) by adopting a relatively economic component design idea and an innovative cooling process path, 980MPa grade high-hole-expansion steel with excellent strength, plasticity, toughness, cold bending and hole expansion performance can be obtained;
(2) the steel coil or the steel plate has excellent matching of strength, plasticity and toughness, and simultaneously has good cold bending performance and hole expanding and flanging performance, the yield strength is more than or equal to 800MPa, the tensile strength is more than or equal to 980MPa, and simultaneously, the steel coil or the steel plate has good elongation (transverse A)50Not less than 8 percent), cold bending performance (d is not more than 4a and 180 degrees) and hole expanding performance (the hole expanding rate is not less than 50 percent), can be applied to the manufacture of parts requiring high-strength thinning and hole expanding flanging, such as automobile chassis, auxiliary frames and the like, and has very wide application prospect.
Drawings
FIG. 1 is a process flow diagram of a method for manufacturing 980MPa grade ultra-low carbon martensitic high-expansion steel according to the present invention;
FIG. 2 is a schematic view of a rolling process in the manufacturing method of 980MPa grade ultra-low carbon martensitic high-expansion steel according to the present invention;
FIG. 3 is a schematic view of a cooling process in the 980MPa grade ultra-low carbon martensitic high-hole-expansion steel manufacturing method of the present invention.
Detailed Description
Referring to fig. 1 to 3, the method for manufacturing 980MPa grade ultra-low carbon martensitic high-hole-expansion steel according to the present invention comprises the following steps:
1) smelting and casting
Smelting by adopting a converter or an electric furnace, secondarily refining by adopting a vacuum furnace, and then casting into a casting blank or an ingot;
2) the casting blank or the cast ingot is heated again at the temperature of 1100 ℃ and 1200 ℃, and the heat preservation time is 1-2 hours;
3) hot rolling
The initial rolling temperature: at 950-1100 ℃, under 3-5 times of large pressure above 950 ℃ and the accumulated deformation is more than or equal to 50 percent, then the intermediate billet is heated to 920 ℃ and 950 ℃, and then the final 3-5 times of rolling is carried out and the accumulated deformation is more than or equal to 70 percent; the finishing temperature is 800 ℃ and 920 ℃;
4) cooling down
Firstly, air cooling for 0-10s to perform dynamic recovery and dynamic recrystallization, then cooling the strip steel to a certain temperature (between room temperature and Ms point) below the Ms point by water at a cooling speed of more than or equal to 50 ℃/s, coiling, and cooling to the room temperature after coiling;
5) acid pickling
The pickling speed of the strip steel can be adjusted within the range of 30-100 m/min, the pickling temperature is controlled within the range of 75-85 ℃, the withdrawal and straightening rate is controlled to be less than or equal to 2%, the strip steel is rinsed within the temperature range of 35-50 ℃, and the surface of the strip steel is dried and oiled within the temperature range of 120-140 ℃.
The components of the high hole expansion steel embodiment of the invention are shown in table 1, and tables 2 and 3 are production process parameters of the steel embodiment of the invention, wherein the thickness of a billet in a rolling process is 120 mm; table 4 shows the mechanical properties of the steel sheets of examples of the present invention.
As can be seen from Table 4, the yield strength of the steel coil is more than or equal to 800MPa, the tensile strength is more than or equal to 980MPa, the elongation is usually between 8 and 13 percent, the impact energy is relatively stable, the low-temperature impact energy at minus 40 ℃ is stabilized at 150 plus 180J, the content of the residual austenite is changed along with different coiling temperatures, the total content is changed between 2 and 5 percent, and the hole expansion ratio is more than or equal to 50 percent.
The embodiment shows that the 980MPa high-strength steel has good matching of strength, plasticity, toughness and hole expansion performance, is particularly suitable for parts such as automobile chassis structures and the like which need high-strength thinning and hole expansion flanging forming, such as control arms and the like, and can also be used for parts such as wheels and the like which need hole expansion, and has wide application prospect.
Figure BDA0002658559880000111
Figure BDA0002658559880000121
Figure BDA0002658559880000131
Figure BDA0002658559880000141

Claims (14)

1. The 980 MPa-grade ultra-low carbon martensite high-hole-expansion steel comprises the following chemical components in percentage by weight: 0.03-0.06% of C, 0.5-2.0% of Si, 1.0-2.0% of Mn, less than or equal to 0.02% of P, less than or equal to 0.003% of S, 0.02-0.08% of Al, less than or equal to 0.004% of N, 0.1-0.5% of Mo, 0.01-0.05% of Ti, less than or equal to 0.0030% of O, and the balance of Fe and other inevitable impurities.
2. The 980 MPa-grade ultra-low carbon martensitic high-hole-expansion steel as claimed in claim 1, further comprising one or more elements selected from Cr 0.5% or less, B0.002% or less, Ca 0.005% or less, Nb 0.06%, V0.05% or less, Cu 0.5% or less, and Ni 0.5% or less; wherein, the content of Cr is preferably 0.2-0.4%, the content of B is preferably 0.0005-0.0015%, and the content of Ca is preferably less than or equal to 0.002%; the content of Nb and V is preferably less than or equal to 0.03 percent respectively; the content of Cu and Ni is preferably less than or equal to 0.3 percent respectively.
3. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the C content is 0.04-0.055%.
4. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the Si content is 0.8-1.4%.
5. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the Mn content is 1.4-1.8%.
6. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the S content is controlled to be below 0.0015%.
7. The 980 MPa-grade ultra-low carbon martensitic high bore steel of claim 1, wherein the Al content is 0.02-0.05%.
8. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the N content is controlled to be less than 0.003%.
9. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the Ti content is 0.01-0.03%.
10. The 980 MPa-grade ultra-low carbon martensitic high bore steel of claim 1, wherein the Mo content is 0.15-0.35%.
11. The 980MPa grade ultra-low carbon martensitic high bore steel of claim 1, wherein the microstructure of the high bore steel is ultra-low carbon martensite or ultra-low carbon tempered martensite.
12. The 980 MPa-grade ultra-low carbon martensitic high-hole-expansion steel as claimed in claim 1 or 11, wherein the yield strength of the high-hole-expansion steel is not less than 800MPa, the tensile strength is not less than 980MPa, and the elongation percentage is in the transverse direction A50More than or equal to 8 percent, cold bending performance (d is less than or equal to 4a and 180 degrees), and hole expanding rate is more than or equal to 50 percent.
13. The method for manufacturing 980MPa grade ultra-low carbon martensitic high-hole-expansion steel according to any of claims 1 to 12, wherein: the method comprises the following steps:
1) smelting and casting
Smelting by a converter or an electric furnace and performing secondary refining by a vacuum furnace according to the components of the alloy of claims 1-10, and then casting into a casting blank or an ingot;
2) the casting blank or the cast ingot is heated again at the temperature of 1100 ℃ and 1200 ℃, and the heat preservation time is 1-2 hours;
3) hot rolling
The initial rolling temperature: at 950-1100 ℃, under 3-5 times of large pressure above 950 ℃, the accumulated deformation is more than or equal to 50 percent; then, the intermediate blank is heated to 900 ℃ and 920 ℃, and then the final 3-5 passes of rolling are carried out, and the accumulated deformation is more than or equal to 70 percent; the finishing temperature is 800 ℃ and 920 ℃;
4) cooling down
Firstly, air cooling is carried out for 0-10s, then the strip steel is cooled to the room temperature to Ms point by water at the cooling speed of more than or equal to 50 ℃/s and is coiled, and then the strip steel is cooled to the room temperature after being coiled;
5) acid pickling
Adjusting the strip steel pickling operation speed within the range of 30-100 m/min, controlling the pickling temperature to be 75-85 ℃, controlling the withdrawal and straightening rate to be less than or equal to 2%, rinsing, drying the surface of the strip steel, and coating oil.
14. The method as claimed in claim 13, wherein the 980 MPa-grade ultra-low carbon martensitic high-hole-expansion steel is prepared by rinsing at 35-50 ℃ after acid pickling, drying at 120-140 ℃ and coating with oil.
CN202010896455.1A 2020-08-31 2020-08-31 980 MPa-grade ultralow-carbon martensitic high-reaming steel and manufacturing method thereof Active CN114107790B (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
CN202010896455.1A CN114107790B (en) 2020-08-31 2020-08-31 980 MPa-grade ultralow-carbon martensitic high-reaming steel and manufacturing method thereof
EP21860562.4A EP4206350A4 (en) 2020-08-31 2021-08-30 High-strength low-carbon martensitic high hole expansion steel and manufacturing method therefor
US18/043,217 US20230313332A1 (en) 2020-08-31 2021-08-30 High-strength low-carbon martensitic high hole expansion steel and manufacturing method therefor
JP2023513798A JP2023539649A (en) 2020-08-31 2021-08-30 High strength low carbon martensitic high hole expandability steel and its manufacturing method
PCT/CN2021/115431 WO2022042730A1 (en) 2020-08-31 2021-08-30 High-strength low-carbon martensitic high hole expansion steel and manufacturing method therefor
KR1020237009927A KR20230061413A (en) 2020-08-31 2021-08-30 High-strength low-carbon martensitic steel with high hole expandability and manufacturing method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010896455.1A CN114107790B (en) 2020-08-31 2020-08-31 980 MPa-grade ultralow-carbon martensitic high-reaming steel and manufacturing method thereof

Publications (2)

Publication Number Publication Date
CN114107790A true CN114107790A (en) 2022-03-01
CN114107790B CN114107790B (en) 2023-11-14

Family

ID=80359948

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010896455.1A Active CN114107790B (en) 2020-08-31 2020-08-31 980 MPa-grade ultralow-carbon martensitic high-reaming steel and manufacturing method thereof

Country Status (1)

Country Link
CN (1) CN114107790B (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105506494A (en) * 2014-09-26 2016-04-20 宝山钢铁股份有限公司 High-toughness hot-rolled high-strength steel with yield strength being 800 MPa and manufacturing method of high-toughness hot-rolled high-strength steel
CN110475889A (en) * 2017-03-31 2019-11-19 日本制铁株式会社 Hot rolled steel plate and steel forged part and its manufacturing method
CA3110823A1 (en) * 2018-09-20 2020-03-26 Arcelormittal Hot rolled steel sheet with high hole expansion ratio and manufacturing process thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105506494A (en) * 2014-09-26 2016-04-20 宝山钢铁股份有限公司 High-toughness hot-rolled high-strength steel with yield strength being 800 MPa and manufacturing method of high-toughness hot-rolled high-strength steel
CN110475889A (en) * 2017-03-31 2019-11-19 日本制铁株式会社 Hot rolled steel plate and steel forged part and its manufacturing method
CA3110823A1 (en) * 2018-09-20 2020-03-26 Arcelormittal Hot rolled steel sheet with high hole expansion ratio and manufacturing process thereof

Also Published As

Publication number Publication date
CN114107790B (en) 2023-11-14

Similar Documents

Publication Publication Date Title
CN114107791B (en) 980 MPa-grade full bainite type ultra-high reaming steel and manufacturing method thereof
WO2022042731A1 (en) 980 mpa-grade bainite high hole expansion steel and manufacturing method therefor
CN114107792A (en) 780 MPa-grade high-surface ultrahigh-hole-expansion steel and manufacturing method thereof
CN114107797A (en) 980 MPa-level bainite precipitation strengthening type high-reaming steel and manufacturing method thereof
CN114107789B (en) 780 MPa-grade high-surface high-performance stability ultrahigh-reaming steel and manufacturing method thereof
CN114107795B (en) 1180MPa low-temperature tempered martensite high-reaming steel and manufacturing method thereof
CN114921726A (en) Low-cost high-yield-ratio cold-rolled hot-galvanized ultrahigh-strength steel and production method thereof
CN114107788B (en) 980 MPa-grade tempered martensite type high-reaming steel and manufacturing method thereof
CN114107794B (en) 980 MPa-grade ultra-low carbon martensite and residual austenite ultra-high hole-enlarging steel and manufacturing method thereof
WO2022042730A1 (en) High-strength low-carbon martensitic high hole expansion steel and manufacturing method therefor
CN117305692A (en) High-reaming steel and manufacturing method thereof
CN114107793B (en) 1180 MPa-grade low-carbon martensitic high-reaming steel and manufacturing method thereof
CN114107790B (en) 980 MPa-grade ultralow-carbon martensitic high-reaming steel and manufacturing method thereof
CN117305690A (en) High-reaming ultrahigh-plasticity steel and manufacturing method thereof
CN116497266A (en) Hot-rolled high-strength high-plasticity steel and manufacturing method thereof
CN114107835A (en) 1180 MPa-grade high-plasticity high-hole-expansion steel and manufacturing method thereof
CN114107796A (en) 1180 MPa-grade high-plasticity high-hole-expansion steel and manufacturing method thereof
CN117305730A (en) High-surface high-reaming steel and manufacturing method thereof
CN117305731A (en) High-strength high-reaming steel and manufacturing method thereof
CN117305691A (en) Precipitation strengthening type tempered bainite high-reaming steel and manufacturing method thereof
CN117305688A (en) High-reaming ultrahigh-plasticity steel and manufacturing method thereof
CN117305687A (en) Precipitation strengthening type tempered martensite high-reaming steel and manufacturing method thereof
CN117305685A (en) High-strength ultrahigh-plasticity steel and manufacturing method thereof
CN116287991A (en) 780 MPa-grade hot rolled high-reaming steel with excellent welding performance and manufacturing method thereof

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant