CN118166189A - 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof - Google Patents
12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof Download PDFInfo
- Publication number
- CN118166189A CN118166189A CN202410607547.1A CN202410607547A CN118166189A CN 118166189 A CN118166189 A CN 118166189A CN 202410607547 A CN202410607547 A CN 202410607547A CN 118166189 A CN118166189 A CN 118166189A
- Authority
- CN
- China
- Prior art keywords
- wire rod
- steel wire
- temperature
- cold heading
- molten salt
- 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
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 122
- 239000010959 steel Substances 0.000 title claims abstract description 122
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 62
- 150000003839 salts Chemical class 0.000 claims abstract description 123
- 238000010791 quenching Methods 0.000 claims abstract description 90
- 230000000171 quenching effect Effects 0.000 claims abstract description 90
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 63
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 56
- 238000005496 tempering Methods 0.000 claims abstract description 41
- 238000010583 slow cooling Methods 0.000 claims abstract description 38
- 238000009987 spinning Methods 0.000 claims abstract description 24
- 239000000126 substance Substances 0.000 claims abstract description 10
- 238000005096 rolling process Methods 0.000 claims description 86
- 238000000034 method Methods 0.000 claims description 45
- 238000001816 cooling Methods 0.000 claims description 42
- 230000009467 reduction Effects 0.000 claims description 24
- 238000003723 Smelting Methods 0.000 claims description 23
- 238000010438 heat treatment Methods 0.000 claims description 22
- 238000007670 refining Methods 0.000 claims description 21
- 238000009749 continuous casting Methods 0.000 claims description 18
- 238000004321 preservation Methods 0.000 claims description 14
- 239000002131 composite material Substances 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 10
- 238000002791 soaking Methods 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 239000002893 slag Substances 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 238000004886 process control Methods 0.000 claims 1
- 230000009466 transformation Effects 0.000 abstract description 13
- 238000013461 design Methods 0.000 abstract description 10
- 238000005516 engineering process Methods 0.000 abstract description 5
- 229910052748 manganese Inorganic materials 0.000 abstract description 4
- 229910052804 chromium Inorganic materials 0.000 abstract description 3
- 230000008569 process Effects 0.000 description 33
- 230000000052 comparative effect Effects 0.000 description 17
- 229910001566 austenite Inorganic materials 0.000 description 14
- 230000000694 effects Effects 0.000 description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 13
- 239000011159 matrix material Substances 0.000 description 13
- 238000005336 cracking Methods 0.000 description 11
- 238000000137 annealing Methods 0.000 description 10
- 238000012545 processing Methods 0.000 description 10
- 229910000859 α-Fe Inorganic materials 0.000 description 9
- 239000011651 chromium Substances 0.000 description 8
- 230000001276 controlling effect Effects 0.000 description 8
- 229910001562 pearlite Inorganic materials 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 238000005265 energy consumption Methods 0.000 description 7
- 239000011572 manganese Substances 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 7
- 230000000630 rising effect Effects 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 238000005266 casting Methods 0.000 description 6
- 239000013078 crystal Substances 0.000 description 6
- 230000001105 regulatory effect Effects 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000005482 strain hardening Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000003009 desulfurizing effect Effects 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- 150000003568 thioethers Chemical class 0.000 description 4
- 230000003313 weakening effect Effects 0.000 description 4
- 208000010392 Bone Fractures Diseases 0.000 description 3
- 206010017076 Fracture Diseases 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000011143 downstream manufacturing Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000005728 strengthening Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000006032 tissue transformation Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- 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
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
-
- 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
- C21D2211/001—Austenite
-
- 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
- C21D2211/002—Bainite
-
- 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
- C21D2211/004—Dispersions; Precipitations
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod and a manufacturing method thereof, which adopts the low-cost and low-hardenability chemical component design of reducing Cr and Mn content and containing no microalloy components such as Mo and the like, combines the molten salt super-fast quenching and isothermal technology after spinning, promotes the transformation of an austenitic structure to a bainite and martensite mixed structure, regulates and controls the cold heading steel wire rod structure to a tempering state, promotes the further toughening of the wire rod structure and the spheroidization of carbide, and finally carries out roller way slow cooling to obtain the complex-phase structure composed of tempered bainite as a main part, a small amount of tempered martensite and the rest of quasi-spheroidized carbide.
Description
Technical Field
The invention belongs to the technical field of cold heading steel hot rolled wire rods, and particularly relates to a 12.9-grade annealing-free hot rolled composite cold heading steel wire rod and a manufacturing method thereof.
Background
The 12.9 grade and above ultra-high strength fastener is usually manufactured by medium carbon, high hardenability such as Mn, cr and the like and noble metal alloy component systems such as Mo, V, nb and the like, and because of high alloy content, the raw material hot rolled wire rod needs to be sequentially subjected to the procedures such as spheroidizing annealing, drawing, cold heading and the like in the processing and manufacturing process of a fastener factory, and the spheroidizing annealing procedure aims to soften tissues to improve the drawing and cold heading performances and reduce the drawing broken wire and cold heading cracking risks of the wire rod. Because spheroidizing annealing is often subjected to high-temperature heat treatment at 750-780 ℃ for 10-24 hours, the production period is long, and meanwhile, the problems of high manufacturing cost and high energy consumption are brought, the 12.9-grade annealing-free hot-rolled cold heading steel wire rod needs to be developed, and the efficient green manufacturing of the ultra-high strength fastener bolt is realized. The hot-rolled cold heading steel wire rod in the prior art is difficult to meet the technical difficulty and the cause of the manufacturing application requirement of the 12.9-grade annealing-free fastener are as follows:
(1) The addition of the alloy element can improve the hardenability of steel, the mechanical properties of the fastener are improved through integral reinforcement, for example, cr is helpful for improving the strength grade of a bolt, but the cold working performance of the wire rod is reduced, work hardening and cold heading cracking are easy to generate, meanwhile, the addition of the high alloy element increases the material cost of the cold heading steel wire rod, on the basis, the cold heading steel wire rod is mainly manufactured through a Sitermo air cooling line after spinning, due to the limited cooling capacity of the Sitermo air cooling line, the high hardenability component aggravates martensite and bainite hard brittle phases under the strong air cooling condition, and further causes the wire rod to have extremely poor increase, plastic degradation and risk of cold heading cracking, so the cold heading performance of the wire rod is generally improved by adopting a process of reducing the spinning temperature and slow cooling after rolling as much as possible, for example: according to the annealing-free cold heading steel and the manufacturing method thereof as well as the fastener obtained by the annealing-free cold heading steel disclosed by the patent CN117265408A, C-SI-Mn-Al-Cr-Mo-B-Mg composition design is adopted, a low-temperature rolling spinning and a Steyr heat preservation cooling process are combined to obtain ferrite tissues with the volume percentage of 60% -70% and pearlite with the volume percentage of 30% -40% degenerated, rm is less than or equal to 650MPa, and the surface shrinkage Z is more than or equal to 53%, on one hand, the low-temperature rolling increases the wear load of a rolling line rolling mill, the low-temperature spinning is easy to cause spinning difficulty, the rolling and the spinning temperature are increased for the purpose of improving rolling efficiency, so that the hard and brittle phase precipitation risk is aggravated, and meanwhile, the prolonged heat preservation on-line time can seriously damage the production efficiency; on the other hand, only a soft phase structure mainly comprising ferrite and pearlite can be obtained, the strength of the wire rod is damaged by increasing the proportion of the ferrite structure, the strength grade after tempering is achieved by large drawing processing strengthening strength during the manufacture of the fastener, the plastic loss is large in the process, the work hardening is easy to generate, the cold heading cracking is caused, the application range is too narrow, and meanwhile, the material cost is high and the strength improvement of the cold heading steel wire rod is limited by adding micro alloy elements.
(2) Because the original structure is ferrite and pearlite, cementite is slowly dissolved and the spheroidizing time is longer, and the aim of shortening the spheroidizing annealing period is achieved, the cold heading steel wire rod is made into a design thought of all bainite or bainite and martensite composite structures, and a fast cooling and slow cooling combination process after rolling is mainly adopted, for example: according to the production method of the bainite cold heading steel wire rod disclosed in the patent CN109023103B, a C-Si-Mn-Cr-Mo component design is adopted, and a water tank quick cooling, low-temperature spinning, air cooling quick cooling and heat preservation slow cooling process design after rolling are combined to form a large amount of bainite, a small amount of ferrite and a small amount of martensite structure, but on one hand, martensite and a bainite hard and brittle phase can seriously damage the plasticity of the wire rod, and the martensite and bainite hard and brittle phase can easily cause breakage in the process of processing and unreeling a coil downstream from a steelworks, even in the process of coiling the wire rod of the steelworks, so that the yield is affected; on the other hand, although the spheroidizing annealing difficulty is reduced and the production period is shortened to some extent, the structure of the ceramic material also needs to undergo spheroidizing degradation at least once in order to reach the 12.9 grade performance grade, and the production period is still long, and the manufacturing cost and the energy consumption are high.
Disclosure of Invention
The invention aims to solve at least one of the technical problems to a certain extent, and provides a 12.9-grade annealing-free hot-rolled composite cold heading steel wire rod and a manufacturing method thereof, which can reduce material cost, improve cold processing performance of the cold heading steel wire rod and are used for the annealing-free high-efficiency green manufacturing of a 12.9-grade high-strength cold heading steel fastener.
The technical scheme adopted for solving the technical problems is as follows:
A manufacturing method of a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.37% -0.43%, si:0.20% -0.35%, mn:0.50% -0.75%, cr: 0.32-0.47%, P is less than or equal to 0.015%, S is less than or equal to 0.008%, and the balance is Fe and unavoidable impurities; the manufacturing method comprises the following steps:
The wire rod produced by wire spinning in the rolling control procedure is firstly subjected to molten salt ultra-fast quenching, so that the wire rod is cooled to a temperature zone which is mainly in a bainitic phase zone at a cooling speed of more than or equal to 30 ℃/s, an austenitic structure is converted into a mixed structure of quenched bainite and quenched martensite, then the wire rod is subjected to online molten salt heating tempering, isothermal tempering is carried out to convert the quenched bainite into tempered bainite, the quenched martensite is converted into tempered martensite, meanwhile, carbide is promoted to be converted into a spheroidized structure, and finally the wire rod is subjected to roller way slow cooling, so that the cold heading steel wire rod with a multiphase structure consisting of tempered bainite which is mainly, a small amount of tempered martensite and the balance of quasi-spheroidized carbide is manufactured.
The design basis of the chemical components and the mass percentage of the cold heading steel wire rod comprises:
(1) Carbon: the element C is the most basic and cheap strengthening element in steel, the tensile strength and hardenability of the steel can be improved along with the increase of the carbon content, the transformation from austenite to quenched bainite is facilitated, but the ductility and cold heading performance of the steel are reduced due to the fact that the content is too high, and the decarburization risk is increased, so that the cold heading steel wire rod can reach the final strength grade through tempering under the annealing-free process, meanwhile, the plasticity and the cold heading performance of the steel are both considered, and the mass percentage of the element C is controlled to be 0.37% -0.43%.
(2) Silicon: si is the main deoxidizing element in steel, and can be dissolved in austenite to improve the strength and hardness of steel; however, excessive silicon promotes columnar crystal growth in the continuous casting steel, reduces wire rod plasticity, and increases cold heading forming difficulty, so that the mass percentage of Si is controlled to be 0.20% -0.35%.
(3) Manganese: mn is a strong hardenability element, can promote the transformation of quenched bainite and quenched martensite, and the poor deoxidation and the increase of smelting difficulty are caused by the too low Mn content, but the segregation in the solidification process of a steel billet is easily aggravated by the too high Mn content, so that the uniformity of the steel is poor, and the Mn content is properly reduced, and the mass percentage of Mn is controlled to be 0.50% -0.75%.
(4) Chromium: the Cr element can obviously improve the hardenability of the steel, strongly delay the transformation of pearlite and bainite, ensure that the steel has good comprehensive mechanical property after hardening and tempering, reduce the Cr content and facilitate control of the bainite content of the matrix, and meanwhile, the Cr element is a medium-strength carbide forming element, if the content is too high, the drawing and cold heading properties of the wire rod are deteriorated, so that the Cr content is properly reduced, and the mass percentage of the Cr is controlled to be 0.32% -0.47%.
(5) Phosphorus, sulfur: the lower the P element and the S element are, the better, so that the P is less than or equal to 0.015 percent and the S is less than or equal to 0.008 percent.
The Mo element is ferrite forming element, can strongly improve the hardenability, but has extremely high cost, and is based on the medium carbon component design of the invention, so the invention is used for reducing the hardenability of the material and effectively controlling the matrix complex phase structure through the component design without Mo element; on the basis of the low hardenability and low-cost chemical composition design of the C-Si-Mn-Cr, by combining with the molten salt ultra-fast quenching and isothermal technology, the wire rod subjected to wire spinning is subjected to molten salt ultra-fast quenching by utilizing the high heat exchange capacity of the molten salt, and by utilizing the Xiang Jiaosi T mole heat preservation slow cooling technology, the phase transition temperature interval of ferrite and pearlite can be skipped rapidly, soft-phase ferrite and pearlite are avoided from being generated in a tissue, meanwhile, compared with the Steyr mole air cooling fast cooling, the wire rod is cooled to the molten salt temperature from high temperature wire spinning temperature more rapidly, the high temperature austenite in the wire rod is controlled to perform quenching transformation in the temperature interval mainly comprising the bainite phase area, the hardenability loss on components is compensated by using the ultra-fast cooling, the hardenability of steel types is improved, the high temperature austenite structure of the wire rod subjected to wire spinning is promoted to be transformed into the mixed structure of most quenching bainite and a small part quenching martensite after ultra-fast quenching, the matrix strength is provided, and the excessive formation of quenching martensite is avoided, and the plastic content in the subsequent structure is reduced due to excessive tempering martensite; because the wire rod passes through the molten salt and can exchange heat with the molten salt uniformly, compared with the air quantity in forced cooling, the temperature difference of the wire rod is smaller, and therefore the performance of the wire rod is extremely poor.
Compared with the mixed structure of all bainite or martensite and bainite obtained through heat preservation and slow cooling after the stelmor air cooling, the invention further carries out online molten salt heating tempering on the wire rod subjected to molten salt ultra-fast cooling quenching, so that the quenched bainite and the quenched martensite structure are subjected to high-temperature isothermal transformation, and are transformed into tempered bainite and tempered martensite for toughening, the strength characteristics of the quenched bainite and the quenched martensite can be reserved, the strength loss caused by low-cost components for reducing the alloy content is compensated, and the plasticity of the quenched structure is obviously improved by using the tempering structure; meanwhile, compared with continuous slow cooling, the wire rod can keep consistent with the molten salt temperature to carry out high-temperature isothermal, the wire rod has a longer-time high-temperature state, after the wire rod is converted into a tempering structure, the matrix structure can be further softened at high temperature for a long time, and carbide in the structure is promoted to be converted into a spheroidized structure, so that the strength and plasticity of the wire rod are ensured to be matched, and the problem of breakage caused by a hard and brittle phase in the process of unreeling a downstream processing coil, in the process of transporting the wire rod from a steel mill to the downstream, and even in the process of coiling the wire rod of the steel mill is effectively avoided; similarly, the further roller way slow cooling can utilize the high temperature state of the wire rod molten salt to continue the softening effect of the later stage of the online heating tempering stage, the slow cooling promotes the wire rod tissue to be further toughened and the carbide to be further spheroidized, the wire rod softening effect is improved, and compared with the process of prolonging the high temperature isothermal time, the roller way slow cooling energy consumption is smaller and more economical, so that the strong plasticity matching of the cold heading steel wire rod can be regulated and controlled by regulating and controlling the hot rolled cold heading steel wire rod tissue to the tempering state, and the roller way slow cooling device is used for manufacturing 12.9-level annealing-free high-strength fastener bolts and other application fields.
Preferably, the converter smelting, refining and continuous casting are used for producing the steel billet before controlled rolling, and the alkalinity of the covering slag is controlled to be 1.5-5 in the converter smelting, so that the cleanliness of molten steel is improved, the S content in the smelting process can be reduced, meanwhile, the influence of the excessive alkalinity of the covering slag on the fluidity of slag is avoided, the brittleness caused by segregation or solidification precipitation due to the excessive S content is avoided, and the risk of cold processing cracking caused by sulfide is weakened.
Preferably, the initial rolling temperature is controlled to be 1000-1050 ℃ and the initial rolling reduction is controlled to be 35-45%; because the wire rod has higher cooling speed through molten salt ultra-fast quenching, the low-temperature wire-spinning and rolling requirements caused by limited stelmor cooling capacity and process requirements do not need to be considered, and therefore, higher blooming temperature can be adopted for reducing the abrasion of a rolling mill and improving the rolling efficiency, and columnar crystals are crushed as much as possible with larger blooming reduction, so that preparation is made for grain refinement.
Preferably, the rolling control procedure controls the final rolling temperature to be 850-900 ℃ and the final rolling reduction to be 26-36%; the rolling mill wear is reduced by using higher final rolling temperature, the rolling efficiency is improved, austenite grains are thinned as much as possible by using larger final rolling reduction, the dispersity is large, austenite is easier to homogenize, the quenching degree of the cold heading steel wire rod is improved, the nucleation rate can be increased, and the transformation of carbide to a spheroidized structure is promoted.
Preferably, the soaking time of the billet is controlled to be less than or equal to 2 hours before rolling in the rolling control process, and the oxygen content in the furnace is controlled to be less than or equal to 1.5 percent; on the basis of improving the initial rolling temperature, the homogenizing of the steel billet components can be promoted by adopting higher soaking temperature, soaking time and low oxygen content in the furnace are further controlled, and decarburization risk can be reduced.
Preferably, the quenching temperature of the molten salt ultra-fast quenching is controlled to be 375-415 ℃, and the quenching treatment time is 8-20 s; in the quenching temperature range of molten salt ultra-fast quenching, the lower the quenching temperature is and the longer the quenching treatment time is, the more the ratio of quenched martensite in the mixed structure is, so that the content of tempered martensite in the complex phase structure is increased, and the strength and plasticity of the cold heading steel wire rod are improved; conversely, the higher the quenching temperature is and the shorter the quenching treatment time is, the more the proportion of quenching bainite in the mixed structure is, so that the content of tempering bainite in the complex phase structure is increased, and the strength and the plasticity of the cold heading steel wire rod are reduced; however, when the quenching temperature is too high, the quenching temperature is close to a ferrite-pearlite phase transition temperature range, which is unfavorable for transformation of an austenite structure to quenched bainite and quenched martensite, and when the quenching temperature is too low, the quenching temperature is close to a quenching martensite phase transition temperature range, which is unfavorable for transformation of the austenite structure to a mixed structure, so that the quenching temperature can be controlled to be in a temperature range with the bainite phase range as a main temperature range, the quenching treatment time is further controlled, the ratio of quenched bainite to quenched martensite in the mixed structure is regulated, and the preparation on the structure is realized for subsequent online molten salt heating tempering.
Preferably, the molten salt ultra-fast quenching controls the temperature rise of the molten salt to be less than or equal to 8 ℃; because the temperature difference from the wire rod spinning temperature to the quenching temperature is large, the molten salt circulation quantity can be controlled to further control the molten salt temperature rise, and the quenching control precision is improved.
Preferably, the temperature of the online molten salt is controlled to be 550-615 ℃ by heating and tempering, and the isothermal time of the molten salt is 380-580 s; in the online molten salt temperature rising tempering temperature range, the higher the isothermal temperature is, the longer the molten salt isothermal time is, the more obvious the softening effect is, the higher the proportion of quasi-spheroidized carbide is, the higher the plasticity of the cold heading steel wire rod is, the larger the strength loss is, and the higher the energy consumption and the production cost are simultaneously; on the contrary, the lower the isothermal temperature is, the shorter the molten salt isothermal time is, the weaker the softening effect is, and even when the isothermal temperature is too low and the molten salt isothermal time is too short, the quenched martensite and the quenched bainite can not finish tempering transformation, so that the plasticity of the cold heading steel wire rod is obviously reduced.
Preferably, the online molten salt temperature rise tempering control molten salt temperature rise is less than or equal to 5 ℃; the temperature difference of the wire rod from the quenching temperature to the isothermal temperature is relatively small, so that the temperature difference is easier to control, the molten salt circulation quantity can be controlled, the molten salt temperature rise is further controlled, and the isothermal tempering precision is improved.
Preferably, the roller way is used for conveying the wire rods into a heat insulation cover by adopting the roller way, so that the wire rods are slowly cooled to below 350 ℃ at a cooling speed of 0.5-1.2 ℃/s for collecting the coils; the higher the cooling speed is, the weaker the softening effect of the roller way slow cooling for promoting the toughening and spheroidization of the wire rod tissue is, the slower the cooling speed is, the better the softening effect is, but the longer the online time is, the lower the production efficiency is, so that the cooling speed of the wire rod can be further controlled, and the strength and plasticity matching of the wire rod is promoted on the basis of economic production.
A 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod obtained according to the manufacturing method of the 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod described in any one of the above.
Preferably, the volume percentage of the tempered bainite is 55% -60%, and the volume percentage of the tempered martensite is 35% -40%; the tempered bainite has obviously improved plasticity compared with the quenched bainite, the tempered martensite has better plasticity compared with the tempered martensite, the tempered martensite has obviously improved plasticity compared with the quenched martensite, and the tempered bainite has better strength compared with the tempered bainite, so that the ratio of tempered bellevil and tempered martensite is controlled on the basis of the quasi-spheroidized carbide in the complex phase structure, and the strength-plasticity matching of the wire rod can be further regulated and controlled by regulating and controlling the cold heading steel wire rod structure.
In the preferred process, the diameter of the cold heading steel wire rod is 6.0-12.0 mm, the tensile strength is 1012-1063 MPa, the reduction of area is 55% -59%, compared with the traditional air-cooled cold heading steel wire rod, the high tensile strength is maintained, the strength is further strengthened through a large drawing amount, the strength grade of a 12.9-level fastener can be achieved through tempering without annealing, the drawing fracture and cold heading fracture risk caused by overlarge plastic loss in the manufacturing process is reduced, on the basis, the cold heading steel wire rod has obviously improved plasticity, namely high reduction of area, further has lower deformation resistance, can bear larger deformation without crack, and is suitable for annealing-free production.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention aims at least one annealing when the existing cold heading steel wire rod is used for manufacturing a 12.9-grade fastener, not only has long production period, but also brings the problems of high manufacturing cost and high energy consumption.
(2) Aiming at the problems of mill wear and difficult wire-laying caused by the adoption of low-temperature wire-laying and low-temperature rolling processes of the cold heading steel wire rod for the existing 12.9-level fastener, the invention combines controlled rolling control on the aspects of molten salt ultrafast cold quenching and isothermal technology, improves the initial rolling and finishing rolling temperature, reduces the mill wear, improves the rolling efficiency, refines austenite grains as much as possible with large reduction, improves the hardenability of steel types, and promotes the transformation of carbide to spheroidized tissues.
(3) Aiming at the current situation that the existing cold heading steel wire rod is used for manufacturing the 12.9-grade fastener without annealing and has a narrow application range, the invention successfully develops the 12.9-grade hot-rolled composite cold heading steel wire rod without annealing, can reduce the material cost, improve the cold processing performance of the cold heading steel wire rod, can reach the tensile strength of 1012-1063 MPa, has the area reduction rate of 55-59 percent, can effectively improve the problems of work hardening and cold heading cracking caused by large drawing, can be used for manufacturing the 12.9-grade high-strength fastener bolt without annealing and other application fields, and has good industrial adaptability and application prospect.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a metallographic structure diagram of example 1 of the present invention;
FIG. 2 is a metallographic structure diagram of comparative example 2 of the present invention;
FIG. 3 is a metallographic structure diagram of example 2 of the present invention;
FIG. 4 is a metallographic structure of example 4 of the present invention.
Detailed Description
The embodiments described below are exemplary only and are not intended to limit the description of the features and characteristics of the invention, in order to set forth the best mode of carrying out the invention, intended to illustrate it and to enable those skilled in the art to practice it, without any limitation to its scope, which is defined solely by the claims appended hereto.
Example 1:
The invention relates to a preferred embodiment of a manufacturing method of a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which comprises the following chemical components in percentage by mass: c:0.42%, si:0.2%, mn:0.5%, cr:0.41%, P:0.013%, S:0.008% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following technological processes of converter smelting, refining, continuous casting, rolling control, wire laying, molten salt ultra-fast quenching and isothermal, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The converter smelting is used for smelting molten iron raw materials into primary molten steel through a blast furnace, controlling the alkalinity of the covering slag to be 1.5, reducing the S content in the smelting process and weakening the cold processing cracking risk caused by sulfides; the refining is used for further adjusting components, deoxidizing, desulfurizing and removing impurities of the primary molten steel in a refining station; the continuous casting is used for casting molten steel obtained by refining in a continuous casting machine, and continuous casting is carried out to produce steel billets with the specification of 220mm multiplied by 220 mm; the controlled rolling is used for heating a billet into a high-temperature billet with rolling plasticity through a heating furnace, rolling the billet coming out of the heating furnace into a wire rod with the specification of 10mm through a rolling line, crushing columnar crystals as much as possible by high-temperature and high-pressure reduction, and preparing for refining grains, and is particularly suitable for the rolling of the billet: the soaking time of the billet is controlled to be 1.8 hours, the oxygen content in the furnace is 1.4 percent, the initial rolling temperature is 1020 ℃, the initial rolling reduction is 38 percent, the final rolling temperature is 860 ℃ and the final rolling reduction is 29 percent; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to 844 ℃, austenitizing becomes the preparation on the follow-up structure, and the wire rod is dispersed on the roll table and conveyed along the roll table.
The molten salt ultra-fast quenching and isothermal use two sections of salt baths with molten salt arranged therein, wire rods after spinning pass through the first section of salt baths through a roller way, and are rapidly cooled to the molten salt temperature for molten salt ultra-fast quenching, so that the wire rods are cooled to a temperature interval which is mainly in a bainite phase region at a cooling speed of 33 ℃/s, an austenite structure is transformed into a quenching bainite and quenching martensite mixed structure, and the matrix strength is provided; the wire rod is conveyed through a second section of salt bath through a roller way, the temperature is quickly increased to the molten salt temperature for online molten salt temperature rising tempering, isothermal tempering enables quenched bainite to be converted into tempered bainite, quenched martensite to be converted into tempered martensite for toughening, meanwhile carbide is promoted to be converted into spheroidized tissue, matrix tissue is softened for a long time at high temperature, so that strength and plasticity of the wire rod are guaranteed to be matched, and the wire rod is concrete: the quenching temperature of the molten salt ultra-fast quenching is controlled to be 388 ℃, the quenching treatment time is 18s, and the temperature rise of the molten salt is controlled to be less than or equal to 8 ℃; the temperature of the online molten salt is controlled to be 615 ℃, the isothermal time of the molten salt is 580s, and the temperature of the molten salt is controlled to be less than or equal to 5 ℃.
The wire rod that the process of roll table slow cooling will come out from the second section salt bath carries into the heat preservation cover with the roll table and carries out slow cooling treatment, and the slow cooling promotes the further toughening of wire rod tissue and the further spheroidization of carbide, improves wire rod softening effect, and is specific: slowly cooling the wire rod to 325 ℃ at a cooling speed of 1.2 ℃/s until the wire rod is coiled; the coil collecting procedure is used for collecting and coiling the wire rods into coils through the coil collecting drum, and obtaining cold heading steel wire rod finished products after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished products is shown in figure 1.
Comparative example 1:
A manufacturing method of a cold heading steel wire rod, which is different from example 1 in that: the manufacturing method comprises the following steps of low temperature hot rolling, spinning, stelmor heat preservation slow cooling and coil collection, and specifically comprises the following steps of: the initial rolling temperature of the low-temperature hot rolling process is controlled to be 925 ℃ and the final rolling temperature is controlled to be 800 ℃; the spinning process controls the spinning temperature to be 780 ℃; the Steyr heat preservation slow cooling adopts the steps that the wire rods after spinning pass through a Steyr air cooling line, all fans and a heat preservation cover are closed, the wire rods are subjected to phase change in the cover at a cooling speed of 1.5 ℃/s, and a cold heading steel wire rod finished product is obtained after coil collection and coil discharging.
Comparative example 2:
A manufacturing method of a cold heading steel wire rod, which is different from example 1 in that: the manufacturing method comprises the following steps of low-temperature hot rolling, wire laying and molten salt ultra-fast cold quenching, and specifically comprises the following steps of: the molten salt ultra-fast quenching adopts two sections of salt baths with molten salt arranged therein, the quenching temperature is 250 ℃, the quenching treatment time is 30s, and the finished cold heading steel wire rod product is obtained after offline, and the metallographic structure diagram is shown in figure 2.
Example 2:
The invention relates to a preferred embodiment of a manufacturing method of a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which comprises the following chemical components in percentage by mass: c:0.43%, si:0.35%, mn:0.58%, cr:0.47%, P:0.015%, S:0.007% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following technological processes of converter smelting, refining, continuous casting, rolling control, wire laying, molten salt ultra-fast quenching and isothermal, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
the converter smelting is used for smelting molten iron raw materials into primary molten steel through a blast furnace, controlling the alkalinity of the covering slag to be 3.5, reducing the S content in the smelting process and weakening the cold processing cracking risk caused by sulfides; the refining is used for further adjusting components, deoxidizing, desulfurizing and removing impurities of the primary molten steel in a refining station; the continuous casting is used for casting molten steel obtained by refining in a continuous casting machine, and continuous casting is carried out to produce steel billets with the specification of 220mm multiplied by 220 mm; the controlled rolling is used for heating a billet into a high-temperature billet with rolling plasticity through a heating furnace, rolling the billet coming out of the heating furnace into a wire rod with the specification of 12mm through a rolling line, crushing columnar crystals as much as possible by high-temperature and high-pressure reduction, and preparing for refining grains, and is particularly suitable for the rolling of the billet: the soaking time of the billet is controlled to be 2 hours, the oxygen content in the furnace is 1.5 percent, the initial rolling temperature is 1000 ℃, the initial rolling reduction is 35 percent, the finishing temperature is 850 ℃, and the finishing rolling reduction is 26 percent; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to be 830 ℃, austenitizing is the preparation on the follow-up structure, and the wire rod is scattered on the roll table and is conveyed along the roll table.
The molten salt ultra-fast quenching and isothermal use two sections of salt baths with molten salt arranged therein, wire rods after spinning pass through the first section of salt baths through a roller way, and are rapidly cooled to the molten salt temperature for molten salt ultra-fast quenching, so that the wire rods are cooled to a temperature interval which is mainly in a bainite phase region at a cooling speed of 33 ℃/s, an austenite structure is transformed into a quenching bainite and quenching martensite mixed structure, and the matrix strength is provided; the wire rod is conveyed through a second section of salt bath through a roller way, the temperature is quickly increased to the molten salt temperature for online molten salt temperature rising tempering, isothermal tempering enables quenched bainite to be converted into tempered bainite, quenched martensite to be converted into tempered martensite for toughening, meanwhile carbide is promoted to be converted into spheroidized tissue, matrix tissue is softened for a long time at high temperature, so that strength and plasticity of the wire rod are guaranteed to be matched, and the wire rod is concrete: the quenching temperature of the molten salt ultra-fast quenching is controlled to be 375 ℃, the quenching treatment time is 20s, and the temperature rise of the molten salt is controlled to be less than or equal to 8 ℃; the online molten salt temperature rise tempering control isothermal temperature is 565 ℃, the molten salt isothermal time is 436s, and the molten salt temperature rise is controlled to be less than or equal to 5 ℃.
The wire rod that the process of roll table slow cooling will come out from the second section salt bath carries into the heat preservation cover with the roll table and carries out slow cooling treatment, and the slow cooling promotes the further toughening of wire rod tissue and the further spheroidization of carbide, improves wire rod softening effect, and is specific: slowly cooling the wire rod to 335 ℃ at a cooling speed of 0.7 ℃/s until the wire rod is coiled; the coil collecting procedure is used for collecting and coiling the wire rods into coils through the coil collecting drum, and obtaining cold heading steel wire rod finished products after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished products is shown in figure 3.
Comparative example 3:
A manufacturing method of a cold heading steel wire rod, which is different from example 2 in that: the quenching temperature is controlled to be 310 ℃, the quenching treatment time is 25s, and the finished cold heading steel wire rod is obtained after coil collection and offline.
Comparative example 4:
A manufacturing method of a cold heading steel wire rod, which is different from example 2in that: the quenching temperature is controlled to be 430 ℃, the quenching treatment time is 5s, and the finished cold heading steel wire rod is obtained after coil collection and offline.
Example 3:
The invention relates to a preferred embodiment of a manufacturing method of a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which comprises the following chemical components in percentage by mass: c:0.39%, si:0.2%, mn:0.66%, cr:0.38%, P:0.013%, S:0.006% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following technological processes of converter smelting, refining, continuous casting, rolling control, wire laying, molten salt ultra-fast quenching and isothermal, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The converter smelting is used for smelting molten iron raw materials into primary molten steel through a blast furnace, controlling the alkalinity of the mold flux to be 5, reducing the S content in the smelting process and weakening the cold processing cracking risk caused by sulfides; the refining is used for further adjusting components, deoxidizing, desulfurizing and removing impurities of the primary molten steel in a refining station; the continuous casting is used for casting the refined molten steel into a continuous casting machine, and continuously casting steel billets with the specification of 160mm multiplied by 160 mm; the controlled rolling is used for heating a billet into a high-temperature billet with rolling plasticity through a heating furnace, rolling the billet coming out of the heating furnace into a wire rod with the specification of 8mm through a rolling line, crushing columnar crystals as much as possible by high-temperature and high-pressure reduction, and preparing for refining grains, and is particularly suitable for the rolling of the billet: the soaking time of the billet is controlled to be 1.7 hours, the oxygen content in the furnace is 1.4 percent, the initial rolling temperature is 1030 ℃, the initial rolling reduction is 42 percent, the final rolling temperature is 880 ℃, and the final rolling reduction is 33 percent; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to 862 ℃, austenitizing becomes the preparation on the follow-up structure, and the wire rod is scattered on the roll table and is conveyed along the roll table.
The molten salt ultra-fast quenching and isothermal use two sections of salt baths with molten salt arranged therein, wire rods after spinning pass through the first section of salt baths through a roller way, and are rapidly cooled to the molten salt temperature for molten salt ultra-fast quenching, so that the wire rods are cooled to a temperature interval mainly comprising a bainite phase region at a cooling speed of 34 ℃/s, an austenite structure is transformed into a quenching bainite and quenching martensite mixed structure, and the matrix strength is provided; the wire rod is conveyed through a second section of salt bath through a roller way, the temperature is quickly increased to the molten salt temperature for online molten salt temperature rising tempering, isothermal tempering enables quenched bainite to be converted into tempered bainite, quenched martensite to be converted into tempered martensite for toughening, meanwhile carbide is promoted to be converted into spheroidized tissue, matrix tissue is softened for a long time at high temperature, so that strength and plasticity of the wire rod are guaranteed to be matched, and the wire rod is concrete: the quenching temperature of the molten salt ultra-fast quenching is controlled to be 403 ℃, the quenching treatment time is 12s, and the temperature rise of the molten salt is controlled to be less than or equal to 8 ℃; the temperature of the online molten salt is controlled to be 585 ℃, the isothermal time of the molten salt is 515s, and the temperature of the molten salt is controlled to be less than or equal to 5 ℃.
The wire rod that the process of roll table slow cooling will come out from the second section salt bath carries into the heat preservation cover with the roll table and carries out slow cooling treatment, and the slow cooling promotes the further toughening of wire rod tissue and the further spheroidization of carbide, improves wire rod softening effect, and is specific: slowly cooling the wire rod to 330 ℃ at a cooling speed of 1 ℃/s until the wire rod is coiled; the coil collecting procedure is used for collecting and winding the coil rod into coils through the coil collecting drum, and obtaining a cold heading steel coil rod finished product after packaging and warehousing.
Comparative example 5:
a manufacturing method of a cold heading steel wire rod, which is different from example 3 in that: and the online molten salt temperature rise tempering control isothermal temperature is 625 ℃, the molten salt isothermal time is 300s, and the cold heading steel wire rod finished product is obtained after coil collection and offline.
Comparative example 6:
A manufacturing method of a cold heading steel wire rod, which is different from example 3 in that: and the online molten salt temperature rising tempering is carried out to control the isothermal temperature to be 500 ℃, the molten salt isothermal time is 600s, and the cold heading steel wire rod finished product is obtained after coil collection and offline.
Example 4:
The invention relates to a preferred embodiment of a manufacturing method of a 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which comprises the following chemical components in percentage by mass: c:0.37%, si:0.32%, mn:0.75%, cr:0.32%, P:0.015%, S:0.007% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following technological processes of converter smelting, refining, continuous casting, rolling control, wire laying, molten salt ultra-fast quenching and isothermal, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The converter smelting is used for smelting molten iron raw materials into primary molten steel through a blast furnace, controlling the alkalinity of the covering slag to be 2.5, reducing the S content in the smelting process and weakening the cold processing cracking risk caused by sulfides; the refining is used for further adjusting components, deoxidizing, desulfurizing and removing impurities of the primary molten steel in a refining station; the continuous casting is used for casting the refined molten steel into a continuous casting machine, and continuously casting steel billets with the specification of 160mm multiplied by 160 mm; the controlled rolling is used for heating a billet into a high-temperature billet with rolling plasticity through a heating furnace, rolling the billet coming out of the heating furnace into a wire rod with the specification of 6mm through a rolling line, crushing columnar crystals as much as possible by high-temperature and high-pressure reduction, and preparing for refining grains, and is particularly suitable for the rolling of the billet: the soaking time of the billet is controlled to be 1.5 hours, the oxygen content in the furnace is 1.3 percent, the initial rolling temperature is 1050 ℃, the initial rolling reduction is 45 percent, the final rolling temperature is 900 ℃, and the final rolling reduction is 36 percent; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to 880 ℃, austenitizing becomes the preparation on the follow-up structure, and the wire rod is dispersed on the roll table and is transported along the roll table.
The molten salt ultra-fast quenching and isothermal use two sections of salt baths with molten salt arranged therein, wire rods after spinning pass through the first section of salt baths through a roller way, and are rapidly cooled to the molten salt temperature for molten salt ultra-fast quenching, so that the wire rods are cooled to a temperature interval mainly comprising a bainite phase region at a cooling speed of 34 ℃/s, an austenite structure is transformed into a quenching bainite and quenching martensite mixed structure, and the matrix strength is provided; the wire rod is conveyed through a second section of salt bath through a roller way, the temperature is quickly increased to the molten salt temperature for online molten salt temperature rising tempering, isothermal tempering enables quenched bainite to be converted into tempered bainite, quenched martensite to be converted into tempered martensite for toughening, meanwhile carbide is promoted to be converted into spheroidized tissue, matrix tissue is softened for a long time at high temperature, so that strength and plasticity of the wire rod are guaranteed to be matched, and the wire rod is concrete: the quenching temperature of the molten salt ultra-fast quenching is controlled to be 415 ℃, the quenching treatment time is 8s, and the temperature rise of the molten salt is controlled to be less than or equal to 8 ℃; the online molten salt temperature rise tempering control isothermal temperature is 550 ℃, the molten salt isothermal time is 380s, and the molten salt temperature rise is controlled to be less than or equal to 5 ℃.
The wire rod that the process of roll table slow cooling will come out from the second section salt bath carries into the heat preservation cover with the roll table and carries out slow cooling treatment, and the slow cooling promotes the further toughening of wire rod tissue and the further spheroidization of carbide, improves wire rod softening effect, and is specific: slowly cooling the wire rod to 340 ℃ at a cooling speed of 0.5 ℃/s until the wire rod is coiled; the coil collecting procedure is used for collecting and coiling the wire rods into coils through the coil collecting drum, and obtaining cold heading steel wire rod finished products after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished products is shown in figure 4.
Comparative example 7:
A manufacturing method of a cold heading steel wire rod, which is different from example 4 in that: the manufacturing method comprises the steps of converter smelting, refining, continuous casting, rolling control, wire spinning, molten salt ultra-fast quenching, isothermal, air cooling and coil collecting, wherein the air cooling is realized by opening a heat preservation cover, conveying a coil rod coming out of a second section of salt bath by a roller way, and controlling the coil rod to be slowly cooled to 340 ℃ at a cooling speed of 3.3 ℃/s until the coil rod is collected, and obtaining a cold heading steel coil rod finished product after coil collecting and discharging.
The cold heading steel wire rods obtained in the examples and the comparative examples are subjected to structure and performance detection: tensile testing was performed using the metal material tensile test section 1 of GB-T228.1-2021: room temperature test method, to obtain tensile strength and reduction of area, and to perform tissue detection according to the metal microstructure detection method of GB/T13298 standard, the comparison results obtained are shown in table 1 below:
TABLE 1 comparison of the composition of the steel wire rods of the different Cold heading and the properties of the wire rod structure of the manufacturing method
As can be seen from the comparison results of examples 1-4 and comparative example 1, compared with the existing low-temperature wire laying and stelmor slow cooling processes, the invention adopts the design of low-cost and low-hardenability chemical components which reduce Cr and Mn content and do not contain microalloy components such as Mo and the like, and directly carries out molten salt ultra-fast quenching and isothermal technology after wire laying, firstly promotes the transformation of a high-temperature austenitic structure to a mixed structure of bainite and martensite after ultra-fast quenching in a temperature range taking a bainite phase region as a main temperature range, can avoid soft-phase pearlite and ferrite structure generated by stelmor slow cooling, can provide matrix strength, compensates the hardenability loss on the components by ultra-fast cooling, and improves the hardenability of steel types; compared with the comparative example 2, the comparative example 1-4 shows that compared with the transformation from high-temperature austenite structure in the wire rod to needle-shaped martensite through molten salt ultra-fast cold quenching in the martensite phase region, the invention regulates and controls the cold heading steel wire rod structure to a tempering state on the basis of obtaining the mixed structure of bainite and martensite, promotes the further toughening of the wire rod structure and the spheroidization of carbide, and obtains the multiphase structure composed of tempered bainite as a main component, a small amount of tempered martensite and the rest of quasi-spheroidized carbide, thereby remarkably improving the plasticity of the cold heading steel wire rod, realizing the strong plasticity matching of the cold heading steel wire rod, achieving the tensile strength of 1012-1063 MPa, effectively improving the work hardening and cold heading cracking problems caused by large drawing, avoiding the fracture problems caused by hard and brittle phases in the process of unreeling of downstream processing coil, the downstream transportation process of steel mill and even in the coiling process of steel mill coil, being applicable to the manufacture of 12.9-grade annealing-free high-strength fasteners, and the like, and having good industrial application prospect.
From the comparison of examples 1 to 4, the comparison results of example 2 and comparative example 3 show that the lower the quenching temperature is, the longer the quenching treatment time is, the more the ratio of quenched martensite in the mixed structure is, so that the content of tempered martensite in the complex phase structure is increased, and the strength and plasticity of the cold heading steel wire rod are improved; from the comparison of examples 1 to 4, the comparison result of example 2 and comparative example 4 shows that the higher the quenching temperature is, the shorter the quenching treatment time is, the more the ratio of quenching bainite in the mixed structure is, the content of tempering bainite in the complex phase structure is increased, and the strength and plasticity of the cold heading steel wire rod are reduced; the quenching temperature and the quenching treatment time can be controlled, so that the preparation on the structure is performed for the subsequent online molten salt heating tempering.
As can be seen from the comparison results of examples 1-4 and example 3 and comparative example 5, when the isothermal temperature is too high and the molten salt isothermal time is too short, part of quenched bainite is not completely converted into tempered martensite, the softening effect is reduced, and the plasticity of the cold heading steel wire rod is obviously reduced; from the comparison of examples 1-4, the comparison results of example 3 and comparative example 6 show that the wire rod strength and plasticity loss is larger and the energy consumption is larger when the isothermal temperature is too low and the isothermal time of molten salt is too long; therefore, the wire molten salt temperature rising tempering isothermal temperature and molten salt isothermal time can be further controlled, the wire rod tissue transformation is promoted, the softening effects of tissue toughening and spheroidization are regulated and controlled, and the strength and plasticity matching of the wire rod is promoted on the basis of economic production.
As can be seen from the comparison results of examples 1-4 and comparative example 7, the roller way slow cooling can utilize the high temperature state of the molten salt of the wire rod to extend the softening effect of the later stage of the online heating tempering stage, the slow cooling promotes the further toughening of the wire rod tissue and the further spheroidization of carbide, the softening effect of the wire rod is improved, and compared with the prolonging of the high temperature isothermal time, the roller way slow cooling energy consumption is smaller and more economical.
The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent embodiments or modifications that do not depart from the spirit of the present invention should be included in the scope of the present invention.
Claims (10)
1. The manufacturing method of the 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod is characterized by comprising the following chemical components in percentage by mass: c:0.37% -0.43%, si:0.20% -0.35%, mn:0.50% -0.75%, cr: 0.32-0.47%, P is less than or equal to 0.015%, S is less than or equal to 0.008%, and the balance is Fe and unavoidable impurities; the manufacturing method comprises the following steps:
The wire rod produced by wire spinning in the rolling control procedure is firstly subjected to molten salt ultra-fast quenching, so that the wire rod is cooled to a temperature zone which is mainly in a bainitic phase zone at a cooling speed of more than or equal to 30 ℃/s, an austenitic structure is converted into a mixed structure of quenched bainite and quenched martensite, then the wire rod is subjected to online molten salt heating tempering, isothermal tempering is carried out to convert the quenched bainite into tempered bainite, the quenched martensite is converted into tempered martensite, meanwhile, carbide is promoted to be converted into a spheroidized structure, and finally the wire rod is subjected to roller way slow cooling, so that the cold heading steel wire rod with a multiphase structure consisting of tempered bainite which is mainly, a small amount of tempered martensite and the balance of quasi-spheroidized carbide is manufactured.
2. The manufacturing method of the 12.9-grade annealing-free hot-rolled composite cold heading steel wire rod, which is characterized in that a billet before controlled rolling is produced by converter smelting, refining and continuous casting, and the alkalinity of covering slag is controlled to be 1.5-5 in the converter smelting.
3. The method for manufacturing a 12.9-grade annealing-free hot-rolled composite cold heading steel wire rod according to claim 1, wherein the rolling control process controls the initial rolling temperature to be 1000-1050 ℃, the initial rolling reduction to be 35-45%, the final rolling temperature to be 850-900 ℃ and the final rolling reduction to be 26-36%.
4. The method for manufacturing a 12.9-grade annealing-free hot-rolled composite cold heading steel wire rod according to claim 3, wherein the soaking time of the steel billet is controlled to be less than or equal to 2 hours before rolling in the rolling control procedure, and the oxygen content in a furnace is controlled to be less than or equal to 1.5 percent.
5. The manufacturing method of the 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which is characterized in that the quenching temperature is controlled to be 375-415 ℃ by molten salt ultra-fast quenching, and the quenching treatment time is 8-20 s; the temperature of the online molten salt is controlled to be 550-615 ℃ by heating and tempering, and the isothermal time of the molten salt is 380-580 s.
6. The manufacturing method of the 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which is characterized in that the molten salt ultra-fast cold quenching controls the molten salt temperature rise to be less than or equal to 8 ℃; and the online molten salt temperature rise tempering controls the molten salt temperature rise to be less than or equal to 5 ℃.
7. The manufacturing method of the 12.9-grade annealing-free hot-rolled complex-phase cold heading steel wire rod, which is characterized in that the roller way slow cooling adopts the roller way to convey the wire rod into a heat preservation cover, so that the wire rod is slowly cooled to below 350 ℃ at a cooling speed of 0.5-1.2 ℃/s for coil collection.
8. A 12.9 grade annealing-free hot-rolled composite cold-heading steel wire rod, characterized in that it is obtained by the manufacturing method of a 12.9 grade annealing-free hot-rolled composite cold-heading steel wire rod according to any one of claims 1 to 7.
9. The 12.9 grade annealing-free hot rolled multi-phase cold heading steel wire rod of claim 8, wherein the tempered bainite is 55% -60% by volume and the tempered martensite is 35% -40% by volume.
10. The 12.9-grade annealing-free hot-rolled composite cold heading steel wire rod of claim 8, wherein the diameter of the cold heading steel wire rod is 6.0-12.0 mm, the tensile strength is 1012-1063 mpa, and the reduction of area is 55% -59%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410607547.1A CN118166189B (en) | 2024-05-16 | 2024-05-16 | 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410607547.1A CN118166189B (en) | 2024-05-16 | 2024-05-16 | 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN118166189A true CN118166189A (en) | 2024-06-11 |
| CN118166189B CN118166189B (en) | 2024-10-01 |
Family
ID=91355065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202410607547.1A Active CN118166189B (en) | 2024-05-16 | 2024-05-16 | 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118166189B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118360553A (en) * | 2024-06-20 | 2024-07-19 | 江苏永钢集团有限公司 | 9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof |
| CN118497622A (en) * | 2024-07-19 | 2024-08-16 | 江苏永钢集团有限公司 | 12.9-Grade annealing-free hot-rolled high-carbon cold heading steel wire rod and manufacturing method thereof |
| CN118621220A (en) * | 2024-08-14 | 2024-09-10 | 江苏永钢集团有限公司 | Cold heading steel high-carbon wire rod for 14.9-grade bolt and manufacturing method thereof |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0372029A (en) * | 1989-08-14 | 1991-03-27 | Topy Ind Ltd | Austempering treatment for fastener product |
| CN115710676A (en) * | 2023-01-10 | 2023-02-24 | 北京科技大学 | Low-cost high-strength and high-toughness bainite/martensite multiphase steel |
| CN116121511A (en) * | 2022-12-20 | 2023-05-16 | 青岛特殊钢铁有限公司 | Production method for improving structural performance uniformity of SCM435 cold heading steel wire rod |
| CN116121512A (en) * | 2023-01-18 | 2023-05-16 | 江苏省沙钢钢铁研究院有限公司 | Cold heading steel wire rod for high-strength fastener and production method thereof |
| CN118007026A (en) * | 2024-04-09 | 2024-05-10 | 江苏永钢集团有限公司 | Hot-rolled 1300 MPa-level B-containing spring steel wire rod and production process thereof |
-
2024
- 2024-05-16 CN CN202410607547.1A patent/CN118166189B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0372029A (en) * | 1989-08-14 | 1991-03-27 | Topy Ind Ltd | Austempering treatment for fastener product |
| CN116121511A (en) * | 2022-12-20 | 2023-05-16 | 青岛特殊钢铁有限公司 | Production method for improving structural performance uniformity of SCM435 cold heading steel wire rod |
| CN115710676A (en) * | 2023-01-10 | 2023-02-24 | 北京科技大学 | Low-cost high-strength and high-toughness bainite/martensite multiphase steel |
| CN116121512A (en) * | 2023-01-18 | 2023-05-16 | 江苏省沙钢钢铁研究院有限公司 | Cold heading steel wire rod for high-strength fastener and production method thereof |
| CN118007026A (en) * | 2024-04-09 | 2024-05-10 | 江苏永钢集团有限公司 | Hot-rolled 1300 MPa-level B-containing spring steel wire rod and production process thereof |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118360553A (en) * | 2024-06-20 | 2024-07-19 | 江苏永钢集团有限公司 | 9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof |
| CN118360553B (en) * | 2024-06-20 | 2024-09-13 | 江苏永钢集团有限公司 | 9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof |
| CN118497622A (en) * | 2024-07-19 | 2024-08-16 | 江苏永钢集团有限公司 | 12.9-Grade annealing-free hot-rolled high-carbon cold heading steel wire rod and manufacturing method thereof |
| CN118497622B (en) * | 2024-07-19 | 2024-10-01 | 江苏永钢集团有限公司 | 12.9-Grade annealing-free hot-rolled high-carbon cold heading steel wire rod and manufacturing method thereof |
| CN118621220A (en) * | 2024-08-14 | 2024-09-10 | 江苏永钢集团有限公司 | Cold heading steel high-carbon wire rod for 14.9-grade bolt and manufacturing method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN118166189B (en) | 2024-10-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112981235B (en) | Hardened and tempered steel plate with yield strength of 420MPa grade for building structure and production method thereof | |
| CN118166189B (en) | 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof | |
| CN118007026B (en) | Hot-rolled 1300 MPa-level B-containing spring steel wire rod and production process thereof | |
| CN118166190B (en) | Hot-rolled wire rod for 12.9-grade low-chromium fire-reducing bolt and manufacturing method thereof | |
| CN118186310B (en) | 12.9-Grade quenching-free high-hardenability hot-rolled multiphase cold heading steel wire rod and manufacturing method thereof | |
| CN118166286B (en) | 10.9-Grade non-adjustable cold heading steel hot rolled wire rod and manufacturing method thereof | |
| US20210079491A1 (en) | Wire rod for cold heading, processed product using same, and manufacturing method therefor | |
| CN118166191B (en) | Manufacturing method of 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod | |
| CN118345307B (en) | 10.9-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof | |
| CN118497622B (en) | 12.9-Grade annealing-free hot-rolled high-carbon cold heading steel wire rod and manufacturing method thereof | |
| CN118207405B (en) | 10.9-Grade high Cr annealing-free cold heading steel hot rolled wire rod and manufacturing method thereof | |
| CN114000056A (en) | Marine steel plate with yield strength of 960MPa grade and low yield ratio and preparation method thereof | |
| CN100560772C (en) | The preparation method of granule carbonide reinforced ferritic steel | |
| CN118497633A (en) | 12.9-Grade non-quenched and tempered hot-rolled high-carbon cold heading steel wire rod and manufacturing method thereof | |
| CN104451446B (en) | Thick-gauge, high-strength and high-toughness bainite engineering steel and production method thereof | |
| CN103614637A (en) | Rack steel wire rod for carding and production method thereof | |
| CN100545290C (en) | A kind of thermal treatment ultra-fine crystal D grade sucker rod sucker rod of exempting from is with steel and production method | |
| CN114000068B (en) | Low-nitrogen ultrahigh-strength hot-rolled steel strip with thickness of 4-10mm and production method thereof | |
| CN115161440A (en) | Hot-rolled heavy H-shaped steel with yield strength of 560MPa and production method thereof | |
| CN106222547B (en) | A kind of 1200MPa grades of high-strength plasticity reinforcing bar and heat treatment method | |
| CN115181899A (en) | 980 MPa-grade low-carbon low-alloy TRIP steel and rapid heat treatment manufacturing method thereof | |
| CN118360553B (en) | 9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof | |
| CN118086782B (en) | High-plasticity hot-rolled wire rod for 8.8-grade non-adjustable bolt and manufacturing method thereof | |
| CN118086785B (en) | Fire-reducing cold heading steel wire rod for 8.8-grade bolt and manufacturing method thereof | |
| CN118360552B (en) | 10.9-Grade hot-rolled carbon fire-reducing cold heading steel wire rod 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 |