CN113025917A - Wire rod for low-strength high-plasticity annealing-free cold forging steel and manufacturing method thereof - Google Patents
Wire rod for low-strength high-plasticity annealing-free cold forging steel and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention relates to a wire rod for low-strength high-plasticity annealing-free cold forging steel and a manufacturing method thereof, wherein the wire rod comprises the following chemical components in percentage by mass: c: 0.20 to 0.26%, Si: less than or equal to 0.15 percent, Mn: 0.75-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 0.25 to 0.35%, Ti: 0.02-0.06%, Al 0.020-0.080%, Cu: less than or equal to 0.30 percent, B is 0.0008-0.0030 percent, H: less than or equal to 0.0002 percent, and the balance of Fe and inevitable impurity elements. The diameter of the produced wire rod ranges from 6mm to 16 mm. The production process flow comprises the following steps: converter or electric furnace smelting, LF refining, RH or VD degassing, continuous casting, blank surface treatment, wire temperature control rolling and stelmor cooling. The hot-rolled wire rod produced by the invention has fine ferrite and pre-spheroidized pearlite, has low tensile strength and high plasticity, can omit spheroidizing annealing, and can be directly used for fasteners with large deformation of cold heading flange surfaces. After heat treatment, the cold-headed fastener can meet the performance requirements of 8.8-grade and 10.9-grade products.
Description
Technical Field
The invention belongs to the technical field of preparation of wire rods for cold heading steel, and particularly relates to a wire rod for annealing-free cold heading steel with low strength and high plasticity and a manufacturing method thereof.
Background
The cold heading refers to a production process of cold extrusion or cold heading forming at room temperature by using a multi-station cold heading die by using a cold heading machine, and is widely applied to the production of products such as bolts, fasteners, sleeves and the like. The steel raw material adopted by cold heading is called cold heading steel. The cold heading steel wire rod generally needs to be subjected to spheroidizing annealing treatment, and the spheroidizing annealing not only reduces the tensile strength of the wire rod but also can improve the plasticity of the wire rod, particularly the plasticity, and is favorable for subsequent forming of complex parts and large-deformation workpieces. But the spheroidizing annealing heat treatment period is long, the energy consumption is large, the cost of a cold heading mill is increased, and the energy conservation and the environmental protection are not facilitated. If the cold heading steel can realize annealing-free direct cold heading, the production cost of the cold heading steel is greatly reduced, corresponding contribution is made to energy conservation and emission reduction of national calls, and the core competitiveness of a steel mill in the industry can be improved.
The mechanical property of the annealing-free cold heading steel after annealing needs to be achieved or is close to that of the annealing-free cold heading steel, the addition of alloy components in the steel is firstly considered to be reduced, and as described in the patent with the publication number of CN 105063481A, the annealing-free cold heading steel is designed to comprise the following components: the mass fraction of C is: 0.23-0.25% of Si, less than or equal to 0.07% of Mn, 0.80-1.00% of Mn, 0.025-0.040% of Ti, more than or equal to 0.020% of Al, less than 0.025% of P, less than 0.025% of S, 0.0010-0.0019% of B, and the balance of Fe and inevitable impurities. But the alloy components are reduced, the method can only be used for manufacturing 8.8 and 9.8-grade bolts, 10.9-grade high-strength bolts cannot be manufactured, the reduction of area is only 58-66%, and the requirement of large-deformation flange face bolts cannot be met. As described in patent publication No. CN 105543678A, the boron-containing high-strength annealing-free wire rod is designed to have the following components: the mass fraction of C is: 0.25-0.35%, the mass fraction of Si is less than or equal to 0.04%, the mass fraction of Mn is 0.50-0.70%, and the mass fraction of Cr is: 0.25-0.35 percent of Ti, 0.035-0.055 percent of Als, less than 0.012 percent of P, less than 0.004 percent of S, 0.0045-0.0060 percent of B, less than or equal to 0.0015 percent of O, less than or equal to 0.00015 percent of H, and the balance of Fe and inevitable impurities. The wire rod of this patent can reduce the strength of hot rolled wire rods, but is obtained by limiting the reduction of the Si content in steel and controlling the level of extremely severe non-metallic inclusions. Cr is added to increase hardenability to manufacture a high-strength 10.9-grade high-strength bolt, but the composition design has extremely high requirements on an original disc auxiliary material and a steelmaking process, the mass fraction of Si is less than or equal to 0.04%, molten iron needs to be subjected to Si removal treatment during smelting, and only ultralow Si alloy and low Si scrap steel can be added to prevent the Si content in the steelmaking process from exceeding the standard. The example of the non-metallic inclusion proposed in the patent requires that A, B, C, D types are all less than or equal to 0.5 grade, the requirement of the non-metallic inclusion is extremely strict, the requirement on raw and auxiliary materials such as refining slag is extremely high, and meanwhile, a complex smelting process needs to be matched. The actual production process increases the manufacturing cost of the hot rolled coil. But is not beneficial to cost reduction, energy conservation and environmental protection.
Disclosure of Invention
The invention aims to solve the technical problem of providing a steel wire rod for low-strength high-plasticity annealing-free cold heading and a manufacturing method thereof, aiming at the prior art, the wire rod is enabled to obtain fine ferrite and pre-spheroidized pearlite structures by properly adding alloy components and matching with a low-temperature rolling and stelmor slow cooling process, the steel wire rod has low tensile strength and high fracture shrinkage rate, the performance of the whole wire rod is good, and the requirement of a user on directly cold heading a large-deformation flange bolt after fine drawing is met. And then the bolts with 9.8-grade and 10.9-grade high strength grades are produced by heat treatment, the low cost of the wire rod production and the bolt manufacturing is realized in all directions in the whole process, and the purposes of energy conservation and consumption reduction are achieved.
The technical scheme adopted by the invention for solving the problems is as follows: the steel wire rod with low strength and high plasticity for annealing-free cold heading comprises the following chemical components in percentage by mass: 0.20 to 0.26%, Si: less than or equal to 0.15 percent, Mn: 0.75-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 0.25 to 0.35%, Ti: 0.02-0.06%, Al 0.020-0.080%, Cu: less than or equal to 0.30 percent, B is 0.0008-0.0030 percent, H: less than or equal to 0.0002 percent, and the balance of Fe and inevitable impurity elements.
The annealing-free cold heading steel has the following chemical components:
c, carbon is one of the main strengthening elements of steel. If the carbon content is too low, the strength and hardness of the cold forging steel after heat treatment are too low. The carbon content is too high, so that the heat treatment strength and hardness are increased, the hot rolling strength is also increased, the plasticity is reduced, and the service life of the cold heading die is greatly shortened. Therefore, the carbon content is controlled to be 0.20-0.26%;
si is a ferrite solid solution strengthening element and is also a deoxidizing element. Silicon can effectively strengthen ferrite, and the high silicon content can improve the hardening coefficient and hinder the plastic deformation of the cold forging steel. But to reduce the cost of steel making and to efficiently deoxidize. Therefore, the invention controls the silicon content in the steel to be less than or equal to 0.15 percent;
mn is an element for improving the hardenability of steel, and plays a role in solid solution strengthening to improve the strength of steel. Too low manganese can reduce the toughness of steel and plastic and simultaneously reduce the Mn/S ratio in steel, easily causes the segregation of continuous casting billets, and aims to achieve the matching of strength and plasticity of cold forging steel after heat treatment. Therefore, the manganese content in the steel is controlled to be 0.75-1.00 percent;
cr: chromium is an element for enhancing the hardenability of steel, and the addition of proper content can effectively increase the hardenability of medium and low carbon steel and improve the strength of the cold heading steel after heat treatment. However, if the chromium content is excessively added, the hot rolling strength is increased. Therefore, the chromium content in the steel is controlled to be 0.25-0.35%;
b: boron is the most obvious element for improving the hardenability of steel, the hardenability of the steel is improved by properly adding the boron to replace Cr, so that the hot rolling strength is reduced, the cost is reduced, and the boron content of the steel is controlled to be 0.0008-0.0030%;
ti: the titanium mainly plays a role in nitrogen fixation, can be combined with free nitrogen in steel in the early stage of solidification of a continuous casting billet to form TiN particles in the steel, so that the combination chance of the free nitrogen and boron is reduced, and the effect of improving hardenability by boron is fully exerted, so that the titanium content is controlled to be Ti: less than or equal to 0.06 percent;
al: the aluminum mainly plays roles of deoxidation and nitrogen fixation, and is added into the steel as a conventional deoxidizer, so that the oxygen content in the steel can be effectively reduced. Meanwhile, the aluminum and the nitrogen in the steel can form AlN particles, and crystal grains can be effectively refined. However, if the aluminum content is too high, the castability of the molten steel is deteriorated. The aluminum content of the steel is controlled to be 0.020-0.080%;
p, S, in principle, the lower the content of phosphorus and sulfur, the better, but the lower the content of phosphorus and sulfur, the higher the smelting cost, and the invention controls the content of phosphorus and sulfur below 0.015% under the condition of quality allowance.
Another object of the present invention is to provide a method for manufacturing the above hot rolled steel wire rod for low-strength high-plasticity annealing-free cold heading steel, which comprises the steps of:
smelting molten steel: the process comprises the steps of smelting raw materials, sequentially carrying out converter or electric furnace smelting, LF refining, RH or VD degassing to produce molten steel, controlling the tapping P to be less than or equal to 0.010% in the converter or electric furnace process, and adding slag charge, alloy and deoxidizer along the steel flow during tapping. And in the LF refining process, a titanium wire and ferroboron are fed by a wire feeder before refining is finished. And (5) after the refining is finished, standing the molten steel for 20 minutes, and then feeding the molten steel to a continuous casting machine for casting. Controlling the superheat degree of molten steel with qualified chemical components at 15-40 ℃, casting a continuous casting tundish into a steel billet under the protection of argon in the whole process, and cooling a continuous casting billet by a cold-piled pit or a lower slow cooling pit after hot cutting;
preparing a blank: removing the surface defects of the cooled blank;
rolling a steel billet: the rolling of the steel billet is divided into a heating process, a rolling process and a cooling process. The heating is carried out by adopting a stepping heating furnace, the temperature of the preheating section of the heating furnace is controlled to be less than or equal to 650 ℃, the temperature of the heating temperature equalizing section of the heating furnace is controlled to be 1000-1200 ℃, and the total heating time is controlled to be 90-160 min. And (3) heating the steel billet, descaling by high-pressure water, removing phosphorus with the pressure not less than 180bar, and rolling by a rolling mill after removing phosphorus. The rolling is divided into rough rolling, medium rolling, pre-finish rolling and finish rolling. The rough rolling temperature is controlled at 900-1000 ℃. The medium rolling temperature and the pre-finish rolling temperature are controlled at 850-950 ℃. Because the rolling speed of the wire rod is high, corresponding cooling water tanks are arranged after pre-finish rolling and before finish rolling to reduce the rolling temperature, and the length of the cooling wire is increased by using rolling return discs, and the length of the cooling wire is required to be more than 80 meters, so that the rolled red steel has enough time to carry out cooling and temperature equalization. The finish rolling adopts low-temperature rolling, the rolling temperature is controlled at 750-850 ℃, the rolling is carried out in a ferrite and austenite or an austenite non-recrystallization region, the total deformation amount of the low-temperature rolling is controlled at 30-50%, and the spinning temperature is controlled at 750-850 ℃; the rolled wire rod is cooled on a stelmor cooling line, the cooling line is fully covered with heat-insulating covers, and gaps between the heat-insulating covers are covered by heat-insulating cotton. The roller speed is 0.08-0.3m/s, the total slow cooling time is more than 500 seconds, the cover outlet temperature is 500-600 ℃, and the wire rod is uniformly cooled in the heat-insulating cover. During slow cooling, carbides are preferentially precipitated in a dotted or short rod-like shape on the basis of the deformed austenite. And collecting the coils and naturally cooling after the wire rods are taken out of the cover. The wire rod for the low-strength high-plasticity annealing-free cold forging steel can be obtained.
Furthermore, the hardenability and the heat treatment strength of the steel are improved by adding Cr and B elements on the basis of medium-low carbon steel. The cooling process of low-temperature large-deformation rolling and stelmor is utilized to refine ferrite grain size and increase ferrite phase proportion, so that the ferrite content can be increased to 75%, and meanwhile, the lamellar structure of lamellar pearlite can be broken or spherical and short rod-shaped carbides are directly precipitated from austenite to generate a pre-spheroidizing effect. The pre-spheroidized pearlite not only reduces the strength of the wire rod, but also improves the reduction of area, and is greatly beneficial to cold heading deformation. The low-temperature large deformation means that large deformation is carried out in a ferrite-austenite two-phase region or an austenite non-recrystallization region, so that austenite in steel obtains higher deformation energy storage and high dislocation density through low-temperature large deformation. Because the deformation temperature is lower, the austenite cannot recover and recrystallize after deformation, and the deformation state is still kept. The deformed wire rod is cooled in a slow mode, and carbide is preferentially nucleated from dislocation tangles in deformed austenite and is precipitated in a spherical or short rod shape. Meanwhile, the content of Si is properly controlled to ensure that the content of Si is less than 0.15 percent and the cold heading cracking caused by cold heading strengthening is avoided, and the Si element is properly added, wherein the target is controlled to be 0.08-0.12 percent. Therefore, the deoxidation of the molten steel is facilitated, the internal quality of the steel is improved, and the strength of the bolt after heat treatment can be improved. The content of impurity elements such as P, S is strictly controlled, the grain boundary purity of the steel is improved, and the grain boundary strength is improved.
Compared with the prior art, the invention has the advantages that:
the invention adopts a very small amount of alloy elements B and Ti to improve the hardenability of the steel, and a proper small amount of Cr element to ensure that the heat treatment performance reaches 8.8-10.9 levels. And properly reduces the requirements on the contents of Si, P and S elements, and obviously reduces the production cost. Tiny ferrite and pre-spheroidized pearlite structures are obtained through low-temperature large-deformation rolling and slow cooling, and the hot-rolled wire rod with low strength and high plasticity is obtained, has excellent cold heading deformability, can omit spheroidizing annealing of steel wires, and can directly meet the cold heading requirement of a fastener.
Drawings
FIG. 1 is a microstructure diagram of example 1 of the present invention.
FIG. 2 is a microstructure diagram of example 2 of the present invention.
Detailed Description
The invention will be further explained and illustrated by the following description and specific examples in conjunction with the accompanying drawings, which are not intended to unduly limit the technical scheme of the invention.
Example 1
The embodiment relates to the production of the non-annealing cold forging steel with low strength and high plasticity, which comprises the following components in percentage by weight: c: 0.24%, Si: less than or equal to 0.12 percent, Mn: 0.95%, P: less than or equal to 0.013%, S: less than or equal to 0.003 percent, Cr: 0.28%, Ti: 0.04%, Al 0.03%, Cu: 0.02%, B: 0.0022%, H: 0.00015 percent, and the balance of Fe and inevitable impurity elements. The diameter of the wire rod is 8mm, and the process flow is as follows: the main raw materials are sequentially subjected to converter smelting, LF + RH furnace number refining, and feeding of titanium wires and ferroboron for refining. And casting the molten steel into a continuous casting billet by adopting 15-30 ℃ low superheat degree whole-process argon protection, and performing surface treatment after the billet is slowly cooled. After treatment, the blank is heated to 1080 ℃ in a heating furnace, the temperature is kept for 120min, the blank is taken out of the furnace, the rolling temperature is 950 ℃, the finish rolling temperature is 780 ℃, and the spinning temperature is 860 ℃. Stelmor cooling was carried out at a roller speed of 0.10 m/s. The obtained hot-rolled wire rod has the tensile strength of 525MPa, the reduction of area of 70 percent and the actual grain size of 9 grades.
Example 2
The embodiment relates to the production of the non-annealing cold forging steel with low strength and high plasticity, which comprises the following components in percentage by weight: c: 0.23%, Si: less than or equal to 0.10 percent, Mn: 0.98%, P: less than or equal to 0.011 percent, S: less than or equal to 0.002%, Cr: 0.28%, Ti: 0.03%, Al 0.03%, Cu: 0.02%, B: 0.0022%, H: 0.00015 percent, and the balance of Fe and inevitable impurity elements. The diameter of the wire rod is 11mm, and the process flow is as follows: the main raw materials are sequentially subjected to converter smelting, LF + RH furnace number refining, and feeding of titanium wires and ferroboron for refining. And (3) casting the molten steel into a continuous casting blank by adopting 15-30 ℃ low superheat degree whole-process argon protection, and performing surface full treatment after the blank is slowly cooled. After treatment, the blank is heated to 1100 ℃ in a heating furnace, the temperature is kept for 140min, the blank is taken out of the furnace, the rolling temperature is 960 ℃, the finish rolling temperature is 800 ℃, and the spinning temperature is 860 ℃. Slow cooling with stelmor, full cover of heat insulating cover, and roller speed of 0.10 m/s. The tensile strength of the obtained hot-rolled wire rod is 510MPa, the reduction of area is 72 percent, and the actual grain size is 9 grade.
Example 3
The embodiment relates to the production of the non-annealing cold forging steel with low strength and high plasticity, which comprises the following components in percentage by weight: c: 0.22%, Si: less than or equal to 0.11 percent, Mn: 0.96%, P: less than or equal to 0.010 percent, S: less than or equal to 0.002%, Cr: 0.25%, Ti: 0.03%, Al 0.04%, Cu: 0.02%, B: 0.0020%, H: 0.0002 percent, and the balance of Fe and inevitable impurity elements. The diameter of the wire rod is 13mm, and the process flow is as follows: the main raw materials are sequentially subjected to converter smelting, LF + RH furnace number refining, and feeding of titanium wires and ferroboron for refining. And casting the molten steel into a continuous casting billet by adopting 15-30 ℃ low superheat degree whole-process argon protection, and performing surface treatment after the billet is slowly cooled. After treatment, the blank is heated to 1080 ℃ in a heating furnace, the temperature is kept for 110min, the blank is discharged from the furnace, the rolling temperature is 960 ℃, the finish rolling temperature is 790 ℃, and the spinning temperature is 860 ℃. Stelmor cooling was carried out at a roller speed of 0.15 m/s. The tensile strength of the obtained hot-rolled wire rod is 480MPa, the reduction of area is 73 percent, and the actual grain size is 10 grade.
The mechanical properties of the wire rod are shown in table 1 below:
TABLE 1 mechanical Properties of Low-Strength high-plasticity annealing-free Steel wire rod for Cold heading
In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.
Claims (6)
1. A wire rod with low strength and high plasticity for annealing-free cold heading is characterized in that the wire rod comprises the following chemical components in percentage by mass: 0.20 to 0.26%, Si: less than or equal to 0.15 percent, Mn: 0.75-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 0.25 to 0.35%, Ti: 0.02-0.06%, Al 0.020-0.080%, Cu: less than or equal to 0.30 percent, B is 0.0008-0.0030 percent, H: less than or equal to 0.0002 percent, and the balance of Fe and inevitable impurity elements.
2. The wire rod for the annealing-free cold heading with low strength and high plasticity as claimed in claim 1, wherein the wire rod has the tensile strength of 460-540MPa, the reduction of area is not less than 67%, the qualification rate of 1/3 in cold heading is 100%, and the actual grain size is 9-11 grade.
3. The wire rod for annealing-free cold heading with low strength and high plasticity according to claim 1, wherein the metallographic structure of the wire rod is ferrite + fragmented pearlite + spherical carbide.
4. A method for manufacturing a wire rod for annealing-free cold heading with low strength and high plasticity according to claim 1, wherein the method comprises the following steps:
1) smelting molten steel: smelting raw materials are sequentially subjected to converter or electric furnace smelting, LF refining and RH or VD degassing to produce molten steel, the converter or electric furnace process controls the tapping P to be less than or equal to 0.010%, slag, alloy and a deoxidizer are added along the steel flow during tapping, the superheat degree of the molten steel with qualified chemical components is controlled to be 15-40 ℃, a continuous casting tundish is cast into a steel billet under the protection of argon in the whole process, and a continuous casting billet is cooled by a dump cooling pit or a lower slow cooling pit after being subjected to flame cutting;
2) heating a continuous casting blank: heating by adopting a stepping heating furnace, controlling the temperature of a preheating section to be less than or equal to 650 ℃, controlling the temperature of a temperature equalizing section to be 1000-1200 ℃, controlling the total heating time to be 90-160min, descaling the steel billet by high-pressure water after heating, and removing phosphorus at a pressure of more than or equal to 180bar, and rolling by a rolling mill after removing phosphorus;
3) rolling a continuous casting blank: the rolling is divided into rough rolling, medium rolling, pre-finish rolling and finish rolling, wherein the rough rolling initial rolling temperature is 1000 ℃ in 900-;
4) cooling the wire rod: cooling the rolled wire rod on a stelmor cooling line, fully covering the cooling line heat-insulating covers, covering gaps among the heat-insulating covers by using heat-insulating cotton, wherein the speed of a roller way is 0.08-0.3m/s, the total slow cooling time is required to be more than 500 seconds, the cover outlet temperature is 500-600 ℃, uniformly cooling the wire rod in the heat-insulating covers, and collecting and naturally cooling the coil rod after the wire rod is out of the covers.
5. The method for manufacturing a wire rod for annealing-free cold heading with low strength and high plasticity as claimed in claim 1, wherein the intermediate rolling temperature and the pre-finish rolling temperature in the rolling stage of step 2) are controlled at 850 ℃ and 950 ℃, and corresponding cooling water tanks are arranged after the pre-finish rolling and before the finish rolling to reduce the rolling temperature, and the length of the cooling wire is increased by rolling back to the wire rod, and the length of the cooling wire is required to be more than 80 m.
6. The manufacturing method of a non-annealed wire rod for cold heading with low strength and high plasticity as claimed in claim 1, wherein the finish rolling in the rolling stage of step 2) is performed by low temperature rolling at a temperature of 750-850 ℃ in order to roll in a ferrite + austenite or austenite non-recrystallization region, and the total deformation amount of the low temperature rolling is controlled to be 30-50%.
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| CN116065099A (en) * | 2023-01-03 | 2023-05-05 | 包头钢铁（集团）有限责任公司 | Annealing-free cold heading steel wire rod and production process thereof |
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| CN116334469B (en) * | 2023-03-30 | 2024-01-23 | 新余钢铁股份有限公司 | ML40Cr spheroidizing-free annealed hot rolled wire rod and preparation method thereof |
| CN117327883A (en) * | 2023-12-01 | 2024-01-02 | 张家港荣盛特钢有限公司 | Non-quenched and tempered steel wire rod and production method thereof |
| CN117327883B (en) * | 2023-12-01 | 2024-02-20 | 张家港荣盛特钢有限公司 | Non-quenched and tempered steel wire rod and production method thereof |
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Application publication date: 20210625 |