CN110904318B - Controlled rolling and controlled cooling method for improving ferrite proportion of medium-carbon cold heading steel wire rod - Google Patents
Controlled rolling and controlled cooling method for improving ferrite proportion of medium-carbon cold heading steel wire rod Download PDFInfo
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- CN110904318B CN110904318B CN201911179037.4A CN201911179037A CN110904318B CN 110904318 B CN110904318 B CN 110904318B CN 201911179037 A CN201911179037 A CN 201911179037A CN 110904318 B CN110904318 B CN 110904318B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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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
Abstract
The invention belongs to the technical field of rolling, and relates to a controlled rolling and controlled cooling method for improving the ferrite proportion of a medium-carbon cold heading steel wire rod. Heating the steel billet at the temperature of not higher than 1050 ℃ for 1.5-2 hours to ensure that the cast structure in the steel is completely austenitized without causing obvious growth of austenite grains; the finishing mill group and the reducing sizing mill group adopt ultra-low temperature rolling at the temperature of not higher than 720 ℃ to generate more deformation induced ferrite in the wire rod structure; the spinning temperature adopts the ultra-low temperature which is not higher than 720 ℃, so that the wire rod enters the ferrite transformation temperature after spinning; and closing all the heat-insulating covers on the cooling control line, and increasing gaps among the asbestos cloth sealed heat-insulating covers to ensure that the cooling speed of the wire rod on the cooling control line is not higher than 0.15 ℃/s. The process effectively improves the ferrite proportion of the wire rod, obviously reduces the hardness and the strength of the wire rod, and obtains higher plasticity and cold heading performance.
Description
Technical Field
The invention belongs to the technical field of rolling, relates to a method for rolling and cooling a medium carbon cold heading steel wire rod, and particularly relates to a production process of annealing-free medium carbon cold heading steel wire rod cold heading steel. Further relates to a controlled rolling and controlled cooling method for improving the ferrite proportion of the medium-carbon cold heading steel wire rod.
Background
Cold heading steel is also called cold heading and cold extrusion steel, and refers to steel for manufacturing fasteners such as bolts, nuts, screws, rivets and the like by using cold heading and cold extrusion processing methods, and is commonly called rivet and screw steel in China. The cold heading forming is a processing technology of plastic forming by utilizing metal at normal temperature, and the fastener is manufactured by adopting the cold heading technology, so that the efficiency is high, the quality is good, the material consumption is saved, and the cost is low. But the cold heading process has higher requirements on the quality of raw materials, and the cold heading performance is one of the important properties of cold heading steel. The cold forging steel has the main properties of good cold formability; as little resistance as possible and as high deformability as possible are required for the cold-heading steel deformation. For this reason, it is generally required that the strength and hardness of the cold heading steel should be low and the yield ratio should be low. Meanwhile, in order to avoid surface cracking during cold heading, it is required that the surface quality of the steel is good and surface decarburization of the steel is as small as possible. The related standards stipulate that the steel material should be subjected to a cold heading test, and the ratio of the heights of the sample after cold heading and before cold heading is required to be high; 1/4, respectively; higher level; 1/3, respectively; a normal stage; 1/2, generally Standard designation 1/2. The cold forging steel has good cold forming performance, and the cold drawing replaces the cold cutting machining of hot rolled materials in the machining industry, so that the process has the advantages that a large amount of working hours are saved, the metal consumption can be reduced by 10% -30%, the size precision of products is high, the surface smoothness is good, the productivity is high, and the process is an advanced machining process.
At present, the output scale of the fastener industry in China reaches 800 ten thousand tons per year, the strength grades of the fasteners produced in China are mainly divided into 4.8-6.8 grades, 8.8 grades, 10.9 grades, 12.9 grades and four strength grades, wherein the 8.8 grade fastener is a grade with more demand and wider product application. In order to meet the requirements of downstream fastener production enterprises, the mainstream cold heading steel wire rods produced by domestic steel mills can be classified into four types, namely low-carbon high-quality carbon structural steel, medium-carbon high-quality carbon structural steel, low-carbon alloy structural steel and medium-carbon alloy steel according to different chemical components. In the cold heading steel industry, cold heading steel with the C content of less than 0.25% is generally changed into low-carbon cold heading steel, and cold heading steel with the C content of 0.25-0.45% is called medium-carbon cold heading steel.
The 8.8-grade fastener is widely applied to industries such as automobiles, trains, aviation, household appliances, mechanical equipment and the like, and the product demand is large and stable. In order to meet the production of 8.8-grade fasteners by downstream users, domestic steel mills mostly provide medium-carbon high-quality carbon structural steel (representative brands comprise SWRCH35K, ML35, SWRCH45K and the like) and low-carbon alloy structural steel (representative brands comprise ML20CrMo, ML20Cr, 10B21 and the like). The fastener industry is large in scale, the facing competitive pressure is continuously increased, most of the fastener production enterprises in China are always in micro-profit operation, and the fastener industry is further required to reduce the production cost. Under the industrial background, the 8.8-grade fastener is generally made of medium-carbon high-quality structural carbon steel with lower price and more sufficient supply, and is most popular with the carbon content of 0.30-0.38%. The carbon content is the most important element influencing cold plastic deformation of the cold heading steel wire rod, and the cold heading performance of the wire rod is obviously reduced along with the higher carbon content; however, if the carbon content is less than 0.30%, the strength of the steel cannot meet the requirements of 8.8-grade fasteners; this also becomes an important factor in restricting the use of medium carbon high quality carbon structural steel for the production of class 8.8 fasteners.
At present, the cold heading steel wire rod without annealing is produced by combining a cold heading steel wire rod low-temperature deformation rolling technology and a cooling and heat preservation control technology, and the hardness is reduced compared with that of the conventional wire rod and the reduction of area is improved by improving the proportion of ferrite. In the known method, the proportion of the ferrite structure in the cold forging steel can be increased only to about 65%, which has reached the limit value at present, and it is difficult to obtain a higher proportion (more than 80%) and the ferrite size is large. In the current medium carbon cold heading steel process, cold upsetting performance and processing application are not researched.
Therefore, intensive research on the controlled rolling and controlled cooling process of the medium carbon cold heading steel wire rod is needed, the proportion of ferrite is further improved, the strength, hardness and yield ratio of the wire rod are effectively reduced, and the cold upsetting performance of the wire rod is improved, which is a technical problem to be solved urgently at present.
Disclosure of Invention
The invention aims to provide a controlled rolling and controlled cooling method for improving the ferrite proportion of a medium-carbon cold heading steel wire rod, which can obviously improve the ferrite proportion of a microstructure of the medium-carbon cold heading steel wire rod in a hot rolling state, further effectively reduce the strength, hardness and yield ratio of the wire rod, improve the cold upsetting performance of the wire rod and solve the problems of high cold heading cracking rate and high die loss in the process of using medium-carbon high-quality carbon structural steel for producing 8.8-grade fasteners.
A controlled rolling and controlled cooling method for improving the ferrite proportion of a medium carbon cold heading steel wire rod comprises the following steps: heating by a heating furnace, rolling by a finishing mill group, rolling by a reducing sizing mill group, spinning and slow cooling by a stelmor controlled cooling line, and the method comprises the following steps:
(1) heating the steel billet by a heating furnace at the temperature of not higher than 1050 ℃ for 1.5-2 hours;
further, the preferable heating temperature is 1000-1050 ℃;
(2) rolling the rolled piece in a finishing mill group, wherein the rolling temperature of the finishing mill group is not higher than 720 ℃;
further, the preferable rolling temperature is 700-720 ℃;
(3) rolling the rolled piece rolled by the finishing mill group into a reducing and sizing mill group to be rolled into the specification of a finished wire rod product, wherein the rolling temperature of the reducing and sizing mill group is not higher than 720 ℃, and the final rolling temperature is not higher than 750 ℃;
further, the preferable rolling temperature is 700-720 ℃, and the finishing temperature is 730-750 ℃;
(4) after finishing rolling, the wire rod is looped by a wire laying machine, and the wire laying temperature is not higher than 720 ℃;
further, the preferable spinning temperature is 690-720 ℃;
(5) after spinning and looping, controlling cooling on a stelmor cooling control line, closing all heat preservation covers on the cooling control line, and increasing gaps among asbestos cloth sealed heat preservation covers to ensure that the cooling speed of the wire rod on the cooling control line is not higher than 0.15 ℃/s;
further, the preferred cooling method is: the cooling speed is 0.10-0.15 ℃/s, the heat preservation time is 21-31 minutes, and the air cooling is carried out when the temperature is cooled to be below 500 ℃.
The wire rod comprises the following chemical components in percentage by mass: 0.32 to 0.38%, Si: 0.10 to 0.35%, Mn: 0.30-0.80%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.20%, Cu is less than or equal to 0.20%, Al: 0.010-0.030%, and the balance of iron and inevitable impurities.
The main process control process of the present invention will be described in detail below with respect to the effect of increasing the ferrite proportion of the medium carbon cold heading steel wire rod.
Heating a steel billet: the continuous casting square billet with the section of 160mm x 160mm is heated by a regenerative heating furnace, wherein the heating time of the billet at the temperature of 1000-1050 ℃ is ensured to be 1.5-2 hours, so that the cast structure in steel is completely austenitized, the rolling requirement of a high-speed wire rod steel rolling production line is met, and the austenite grains are not obviously grown. If the heating temperature is lower than 1000 ℃, the steel cannot be completely austenitized, and hot rolling conditions are not met; if the temperature is higher than 1050 ℃ or the heating time exceeds 2 hours, the growth rate of austenite grain size increases, and the coarsening of austenite grain size is not favorable for the precipitation of deformation-induced ferrite and the increase of the final ferrite ratio.
Rough and medium rolling and pre-finishing rolling mill set rolling: and the heated steel billet enters a rough and medium rolling mill set for continuous rolling so as to ensure that the rolled piece is in a sufficient austenitizing state in the rolling process of the rough and medium rolling mill set and ensure that the rolling process is smoothly carried out. The coarse and medium rolling is the basic deformation stage, and the proportion of the ferrite of the wire rod is not influenced.
Rolling by a finishing mill group: and cooling the rolled piece rolled by the rough and medium mill set through water, then, rolling the rolled piece by the finish mill set, and controlling the temperature of the rolled piece entering the finish mill set to be 700-720 ℃.
Under the temperature condition of 700-720 ℃, the rolled piece deforms along with the rolling of the finishing mill group, and a large amount of deformation induced ferrite can be precipitated in the microstructure of the rolled piece. If the rolling temperature is higher than 720 ℃, the deformation induced ferrite separated out along with the rolling deformation can be obviously reduced, and if the rolling temperature is lower than 700 ℃, the deformation resistance is too large, and a finishing mill group in the industry can not roll.
Rolling by a reducing sizing mill set: the rolled piece after finish rolling enters a reducing sizing mill set to be rolled into a finished product specification of a wire rod, the rolling temperature of the reducing sizing mill set is controlled to be 700-720 ℃, the temperature is higher than 720 ℃, deformation induced ferrite separated out along with rolling deformation can be obviously reduced, the temperature is lower than 700 ℃, the deformation resistance is too large, and the reducing sizing mill set in the industry can not be rolled. By adopting the scheme of rolling by combining the finishing mill group and the reducing and sizing mill group, the temperature rise of the rolled piece caused by continuous rolling can be reduced due to the fact that the finishing mill group and the reducing and sizing mill group are provided with the cooling water tanks, so that the rolling temperature of the rolled piece in the process can meet the temperature requirement, and the problem of overhigh temperature of the core of the rolled piece caused by continuous rolling can be solved.
The finishing mill group and the reducing sizing mill group are both produced by Morgan company in America, and the minimum rolling temperature is 700 ℃. The cumulative reduction rate of the rolled piece is more than or equal to 50 percent.
During the rolling process of the reducing sizing mill set, deformation induced ferrite can be further precipitated from the microstructure of a rolled piece, so that conditions are provided for ensuring that high proportion of ferrite is obtained from the microstructure of the wire rod; meanwhile, the final rolling temperature is controlled to be 730-750 ℃, so that the deformation induced ferrite is prevented from being austenitized again, and the deformation induced ferrite is ensured to enter a controlled cooling stage.
Spinning: after finish rolling, the wire rod is coiled by a wire laying machine, the wire laying temperature is controlled to be 690-720 ℃ through water cooling of a water tank, and the temperature just reaches the ferrite transformation temperature, so that favorable conditions are provided for subsequent control cooling.
And (3) cooling control: and after rolling, the controlled cooling of the wire rod is realized on a stelmor controlled cooling line, all heat preservation covers on the controlled cooling line are closed, gaps among asbestos cloth sealed heat preservation covers are added, the cooling speed of the wire rod on the controlled cooling line is controlled to be 0.10-0.15 ℃/s, ferrite can be fully separated out and grow under the condition of the cooling speed, supercooled austenite in the microscopic structure of the wire rod is converted to ferrite as much as possible, and finally a pseudo eutectoid structure with the ferrite proportion higher than that of a balance phase is realized. The lower the cooling speed, the more favorable the precipitation and growth of ferrite, but the limit of slow cooling under the stelmor controlled cooling line condition is 0.10 ℃/s, and the slower the cooling speed is difficult; when the cooling speed exceeds 0.15 ℃/s, the precipitation quantity and the growth speed of the coil rod ferrite are reduced, and finally, the proportion of the ferrite in the coil rod microstructure is reduced.
The invention has the advantages that: the method has the advantages that alloy does not need to be added, the production process route does not need to be changed, the rolling deformation at the temperature of less than 750 ℃ is realized by optimizing the controlled rolling and controlled cooling process, the slower cooling rate (not higher than 0.15 ℃/s) is combined, meanwhile, the temperature for the wire rod to go out of the heat preservation cover and enter the air cooling is required to be lower (below 500 ℃), and the ferrite proportion is finally higher than that of the existing process and can reach the ferrite structure of more than 80% through the cooperation of process conditions. The microstructure of the wire rod is improved. The improvement of the microstructure of the wire rod improves the cold heading performance and reduces the strength and the hardness. The problems of low proportion of ferrite in the structure, high strength and hardness and poor cold heading performance of medium-carbon high-quality carbon structural steel due to high carbon content are solved, the application range of processing 8.8-grade fasteners by medium-carbon cold heading steel is expanded, and the production cost of the 8.8-grade fasteners is reduced. The wire rod obtains the qualification rate of 1/4 cold upsetting 100% in a hot rolling state, achieves better cold upsetting performance, and further meets the requirement that downstream fastener enterprises do not anneal to produce fasteners with large deformation such as flange bolts, flange nuts and the like.
Drawings
Fig. 1 is a microstructure view of a medium carbon cold-heading steel wire rod produced in example 1.
Fig. 2 is a microstructure view of a medium carbon cold-heading steel wire rod produced in example 2.
Fig. 3 is a microstructure view of a medium carbon cold-heading steel wire rod produced in comparative example 1.
Fig. 4 is a microstructure view of a medium carbon cold-heading steel wire rod produced in comparative example 2.
Detailed Description
The production of medium carbon cold heading steel ZT35KM wire rod (phi 12.0mm) is taken as an example:
ZT35KM comprises the following specific components:
Wt，％
| number plate | C | Si | Mn | P | S | Cr | Ni | Cu | Al |
| ZT35KM | 0.32-0.38 | 0.10-0.35 | 0.30-0.80 | ≤0.030 | ≤0.030 | ≤0.20 | ≤0.20 | ≤0.25 | 0.010-0.030 |
The steel rolling process flow comprises the following steps: the method comprises the following steps of a heat accumulating type heating furnace, a rough and medium rolling and pre-finishing rolling unit, a reducing and sizing unit, a wire laying head, a stelmor controlled cooling line, closing a heat insulation cover, slowly cooling and bundling. The conditions not limited thereto are conventional conditions.
(1) Heating the steel billet by a heating furnace at the temperature of not higher than 1050 ℃ for 1.5-2 hours;
further, the preferable heating temperature is 1000-1050 ℃;
(2) rolling the rolled piece in a finishing mill group, wherein the rolling temperature of the finishing mill group is not higher than 720 ℃;
further, the preferable rolling temperature is 700-720 ℃;
(3) rolling the rolled piece rolled by the finishing mill group into a reducing and sizing mill group to be rolled into the specification of a finished wire rod product, wherein the rolling temperature of the reducing and sizing mill group is not higher than 720 ℃, and the final rolling temperature is not higher than 750 ℃;
further, the preferable rolling temperature is 700-720 ℃, and the finishing temperature is 730-750 ℃;
(4) after finishing rolling, the wire rod is looped by a wire laying machine, and the wire laying temperature is not higher than 720 ℃;
further, the preferable spinning temperature is 690-720 ℃;
(5) after spinning and looping, controlling cooling on a stelmor cooling control line, closing all heat preservation covers on the cooling control line, and increasing gaps among asbestos cloth sealed heat preservation covers to ensure that the cooling speed of the wire rod on the cooling control line is not higher than 0.15 ℃/s;
further, the preferred cooling method is: the cooling speed is 0.10-0.15 ℃/s.
The wire rod comprises the following chemical components in percentage by mass: 0.32 to 0.38%, Si: 0.10 to 0.35%, Mn: 0.30-0.80%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.20%, Cu is less than or equal to 0.20%, Al: 0.010-0.030%, and the balance of iron and inevitable impurities.
Example 1
1. Heating a steel billet:
the steel billet comprises the following components: 0.35%, Si: 0.18%, Mn: 0.50%, P: 0.015%, S: 0.012%, Cr: 0.10%, Ni: 0.09%, Cu: 0.05%, Al: 0.023 percent.
And heating the continuous casting square billet with the section of 160mm x 160mm at the temperature of 1010-1045 ℃ for 1.8 hours.
2. Controlled rolling
The initial rolling temperature of rough rolling is 930-950 ℃, the rolled piece enters a finishing mill group for rolling, the rolling temperature of the finishing mill group is 705-720 ℃, the rolled piece after rolling of the finishing mill group enters a reducing and sizing mill group for rolling into a wire rod finished product with the specification of phi 12.0mm, the rolling temperature of the reducing and sizing mill group is 701-720 ℃, and the final rolling temperature is 733-750 ℃.
3. Spinning
And (3) after finishing rolling, coiling the wire rod by a wire laying machine, wherein the wire laying temperature is 700-718 ℃.
4. Controlled cooling
After spinning and looping, cooling is controlled on a stelmor cooling control line, all heat preservation covers on the cooling control line are closed, gaps among the heat preservation covers are sealed by asbestos cloth, and the actual cooling speed of the wire rod on the cooling control line is 0.12 ℃/s.
Fig. 1 is a microstructure view of a medium carbon cold-heading steel wire rod produced in example 1. As can be seen from FIG. 1, the wire rod structure is mainly composed of ferrite, and the proportion reaches 88%. The grain size of ferrite is 9-10 grades.
Example 2
1. Heating a steel billet:
the steel billet comprises the following components: 0.37%, Si: 0.26%, Mn: 0.51%, P: 0.018%, S: 0.015%, Cr: 0.12%, Ni: 0.06%, Cu: 0.03%, Al: 0.022 percent.
And heating the continuous casting square billet with the section of 160mm x 160mm at the temperature of 1012-1046 ℃ for 2.0 hours.
2. Controlled rolling
The initial rolling temperature of rough rolling is 932-950 ℃, the rolled piece enters a finishing mill group for rolling, the rolling temperature of the finishing mill group is 710-720 ℃, the rolled piece after rolling of the finishing mill group enters a reducing and sizing mill group for rolling into a wire rod finished product with the specification of phi 12.0mm, the rolling temperature of the reducing and sizing mill group is 705-720 ℃, and the final rolling temperature is 738-750 ℃.
3. Spinning
And (3) after finishing rolling, coiling the wire rod by a wire laying machine at the wire laying temperature of 702-718 ℃.
4. Controlled cooling
After spinning and looping, cooling is controlled on a stelmor cooling control line, all heat preservation covers on the cooling control line are closed, gaps among the heat preservation covers are sealed by asbestos cloth, and the actual cooling speed of the wire rod on the cooling control line is 0.14 ℃/s.
Fig. 2 is a microstructure view of a medium carbon cold-heading steel wire rod produced in example 2. As can be seen from FIG. 2, the coil structure is mainly composed of ferrite, and the proportion is 85%. The grain size of ferrite is 9-10 grades.
Comparative example 1
Comparative example 1 differs from example 1 mainly in that: the rolling temperature of a finishing mill group in the step 2 controlled rolling in the embodiment 1 is replaced by 780-800 ℃, and other conditions are the same as the embodiment 1.
Fig. 3 is a microstructure view of a medium carbon cold-heading steel wire rod produced in comparative example 1. The ferrite proportion of the wire rod structure obtained in comparative example 1 is 77%. Ferrite grain size is 7-8 grades.
Comparative example 2
Comparative example 2 differs from example 1 mainly in that: the rolling temperature of the reducing and sizing mill set in the step 2 of the embodiment 1 is replaced by 780-800 ℃ under the same conditions as the embodiment 1.
Fig. 4 is a microstructure view of a medium carbon cold-heading steel wire rod produced in comparative example 2. The ferrite ratio of the wire rod structure obtained in comparative example 2 was 71%. The grain size of ferrite is 6-8 grades.
Comparative example 3
Comparative example 3 compared to example 1, the main differences are: the spinning temperature in step 3 of the embodiment 1 is changed to be 800-820 ℃ instead of 702-718 ℃, and the other conditions are the same as the embodiment 1. The coil structure obtained in comparative example 3 had a ferrite ratio of 70%. The grain size of ferrite is 6-8 grades.
Comparative example 4
Comparative example 4 compared to example 1, the main differences are: the actual cooling speed of the wire rod on the cooling control line in the step 4 of the example 1 is replaced by 0.12 ℃/s to 0.50 ℃/s, and other conditions are the same as the example 1.
The ferrite ratio of the wire rod structure obtained in comparative example 4 was 67%. The grain size of ferrite is 6-7 grades.
The proportion of ferrite in the wire rod microstructures of the example 1 and the example 2 of the invention and the comparative example 1, the comparative example 2, the comparative example 3 and the comparative example 4 is detected, the detection standard is GB/T13299, and the comparison is shown in the following table 1:
TABLE 1
| Categories | Ferrite ratio | 1/4 percent pass of cold upsetting | Hardness HRB | Tensile strength, Mpa |
| Example 1 | 88％ | 100％ | 72/72.5 | 516/518 |
| Example 2 | 85％ | 100％ | 73/73.5 | 520/523 |
| Comparative example 1 | 77％ | 75％ | 74.5/76 | 538/540 |
| Comparative example 2 | 71％ | 50％ | 75.5/77 | 549/552 |
| Comparative example 3 | 70％ | 45％ | 78/78.5 | 552/556 |
| Comparative example 4 | 67％ | 30％ | 79/81 | 562/570 |
Compared with the proportion of ferrite in the medium carbon cold heading steel wire rod produced by the traditional process, the proportion of the ferrite obtained by the invention is higher, the proportion of the ferrite reaches more than 80%, the size is small, and the ferrite has higher molding plasticity, so that the cold upsetting performance of the medium carbon cold heading steel wire rod is improved.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified. The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all modifications of the above embodiments made according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (1)
1. A controlled rolling and controlled cooling method for improving the ferrite proportion of a medium-carbon cold heading steel wire rod is characterized by comprising the following steps: heating by a heating furnace, rolling by a finishing mill group, rolling by a reducing sizing mill group, spinning and slow cooling by a stelmor controlled cooling line, and the method comprises the following steps:
(1) heating the steel billet by a heating furnace at the temperature of 1000-1050 ℃ for 1.5-2 hours;
(2) rolling in a finishing mill set, wherein the rolling temperature of the finishing mill set is 700-720 ℃;
(3) rolling the rolled piece rolled by the finishing mill group into a wire rod finished product specification in a reducing and sizing mill group, wherein the rolling temperature of the reducing and sizing mill group is 700-720 ℃, and the final rolling temperature of the reducing and sizing mill group is 730-750 ℃;
(4) after finishing rolling, coiling the wire rod by a wire laying machine, wherein the wire laying temperature is 690-720 ℃;
(5) after spinning and looping, controlling cooling on a stelmor cooling control line, so that the cooling speed of the wire rod on the cooling control line is 0.10-0.15 ℃/s;
the wire rod comprises the following chemical components in percentage by mass: 0.32 to 0.38%, Si: 0.10 to 0.35%, Mn: 0.30-0.80%, P is less than or equal to 0.030%, S is less than or equal to 0.030%, Cr is less than or equal to 0.20%, Ni is less than or equal to 0.20%, Cu is less than or equal to 0.20%, Al: 0.010-0.030%, and the balance of iron and inevitable impurities.
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| CN111349856B (en) * | 2020-03-26 | 2021-09-03 | 邢台钢铁有限责任公司 | Cold heading steel wire rod for ultrahigh-strength lock rivet and preparation method thereof |
| CN111363975B (en) * | 2020-04-08 | 2021-11-02 | 中天钢铁集团有限公司 | Controlled rolling and controlled cooling method for medium-carbon CrMo steel wire rod capable of being directly drawn and processed in hot rolling state |
| CN111647794B (en) * | 2020-04-17 | 2021-09-24 | 江阴兴澄特种钢铁有限公司 | Steel wire rod and wire rod packing steel wire and manufacturing method thereof |
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| CN113789478B (en) * | 2021-09-16 | 2022-12-30 | 湖南华菱湘潭钢铁有限公司 | Production method of cold heading steel bar |
| CN114231840A (en) * | 2021-11-24 | 2022-03-25 | 邯郸钢铁集团有限责任公司 | Wire rod for high-hardenability medium-carbon cold heading steel and production process thereof |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61250111A (en) * | 1985-04-26 | 1986-11-07 | Nippon Steel Corp | Rolling method of steel strip for fe-cr-co alloy magnet |
| CN1799717A (en) * | 2004-12-31 | 2006-07-12 | 马鞍山钢铁股份有限公司 | Hot-rolling anneal-free coil rod production method for 8.8 grade high-strength cold forging steel |
| CN1858284A (en) * | 2005-05-01 | 2006-11-08 | 马鞍山钢铁股份有限公司 | Super fine crystal microalloyed medium carbon steel coil and its producing method |
| CN101045238A (en) * | 2007-04-30 | 2007-10-03 | 马鞍山钢铁股份有限公司 | Online softening rolling method for medium carbon alloy cold forging steel |
| CN103785695B (en) * | 2014-01-21 | 2015-09-30 | 首钢总公司 | A kind of control method reducing low-carbon cold heading steel yield tensile ratio |
| CN104984995A (en) * | 2015-07-09 | 2015-10-21 | 首钢总公司 | High-speed wire rolling method of boron-bearing non-quenched-and-tempered biphase cold forging steel |
| CN108330390A (en) * | 2018-02-13 | 2018-07-27 | 鞍钢股份有限公司 | A kind of the Alloy Cold Heading Steel wire rod and its production method of delayed fracture resistance |
-
2019
- 2019-11-27 CN CN201911179037.4A patent/CN110904318B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61250111A (en) * | 1985-04-26 | 1986-11-07 | Nippon Steel Corp | Rolling method of steel strip for fe-cr-co alloy magnet |
| CN1799717A (en) * | 2004-12-31 | 2006-07-12 | 马鞍山钢铁股份有限公司 | Hot-rolling anneal-free coil rod production method for 8.8 grade high-strength cold forging steel |
| CN1858284A (en) * | 2005-05-01 | 2006-11-08 | 马鞍山钢铁股份有限公司 | Super fine crystal microalloyed medium carbon steel coil and its producing method |
| CN101045238A (en) * | 2007-04-30 | 2007-10-03 | 马鞍山钢铁股份有限公司 | Online softening rolling method for medium carbon alloy cold forging steel |
| CN103785695B (en) * | 2014-01-21 | 2015-09-30 | 首钢总公司 | A kind of control method reducing low-carbon cold heading steel yield tensile ratio |
| CN104984995A (en) * | 2015-07-09 | 2015-10-21 | 首钢总公司 | High-speed wire rolling method of boron-bearing non-quenched-and-tempered biphase cold forging steel |
| CN108330390A (en) * | 2018-02-13 | 2018-07-27 | 鞍钢股份有限公司 | A kind of the Alloy Cold Heading Steel wire rod and its production method of delayed fracture resistance |
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