CN113843299A - Production method of pickling-free high-carbon chromium bearing steel wire rod after spheroidizing annealing - Google Patents
Production method of pickling-free high-carbon chromium bearing steel wire rod after spheroidizing annealing Download PDFInfo
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Abstract
The invention belongs to the technical field of metal product production, and relates to a production method of a high-carbon chromium bearing steel wire rod free of acid pickling after spheroidizing annealing. The method comprises the following steps: obtaining a continuous casting billet after converter smelting, LF refining, VD vacuum treatment and continuous casting; then carrying out slow cooling on a continuous casting blank heat preservation pit, heating in a furnace, carrying out high-pressure water dephosphorization, controlled rolling, controlled cooling, collecting and packaging, finishing and inspecting, and finally carrying out spheroidizing annealing and drawing; wherein the annealing treatment comprises the following steps: heating the hot-rolled wire rod to 790-class 810 ℃, cooling to 690-class 720 ℃ after heat preservation, cooling to 600-650 ℃ again after heat preservation, wherein the cooling speed is less than or equal to 20 ℃/h, and finally discharging and air cooling; the obtained wire rod is drawn without surface treatment to obtain a wire rod product; the thickness of the iron scale of the wire rod is increased to more than 14 mu m, and Fe in the iron scale3O4The proportion is improved to over 30 percent from the original 15-20 percent, the performance is good, and abnormal phenomena such as uneven carbide and the like are not found.
Description
Technical Field
The invention belongs to the technical field of metal product production, and particularly relates to a production method of a pickling-free high-carbon chromium bearing steel wire rod after spheroidizing annealing.
Background
The carbon content of the bearing steel is about 1.0 percent, belongs to hypereutectoid steel, and is mainly used for processing and manufacturing rolling bodies (balls, rollers and needle rollers) and ferrules. The microstructure is constituted of lamellar pearlite and carbide, and is poor in plasticity and low in drawability. Therefore, before use, spheroidizing annealing treatment is needed to improve the processing performance. The production method of the conventional bearing steel wire rod is that after the hot rolled wire rod is treated by spheroidizing annealing, surface treatment (acid pickling and phosphorization) is required, and then wire drawing processing is carried out; the process has the characteristics of long production period, acid cleaning pollution, high cost and the like.
Therefore, it is urgently needed to research a new production method of the pickling-free bearing steel wire rod after spheroidizing annealing, the pickling surface treatment is omitted and the wire rod is directly drawn by optimizing the surface quality of the hot-rolled wire rod, the thickness and the structure of the iron scale, and the surface quality and the wire drawing performance can be ensured.
Disclosure of Invention
The invention aims to overcome the technical defects in the prior art and provides a production method of a pickling-free high-carbon chromium bearing steel wire rod after spheroidizing annealing; the surface quality and the iron scale control of the hot-rolled wire rod of the bearing steel are realized through a new methodThe manufacturing method comprises the steps that the thickness of the oxide scale of the bearing steel after spheroidizing annealing reaches more than 14 mu m, the FeO in the oxide scale accounts for 55-70%, and no Fe exists on the surface of the wire rod2O3Meanwhile, the inner and outer layers of iron scales on the surface of the wire rod are separated or have cracks, and the wire rod is easy to fall off during drawing.
The invention aims to solve the technical problems of improving the mechanical stripping rate of the iron scale of the bearing steel wire rod after being drawn, solving the problem of iron scale residue on the surface of the steel wire and improving the wire drawing performance and the surface quality. And descaling by high-pressure water to remove primary iron scale, and opening a proper spinning temperature, a proper roller speed, a proper fan air quantity and a proper heat-insulating cover to obtain the ideal surface quality of the wire rod and the thickness and the structure of the iron scale. And then spheroidizing annealing treatment is carried out, so that the separation of the inner and outer layer iron scales on the surface of the wire rod from the matrix or the appearance of cracks is ensured, the wire rod is easy to fall off during drawing, and the structure and the performance of the wire rod are not influenced.
In order to achieve the above object, the present invention provides a bearing steel, which comprises the following components by weight: c: 0.96-1.03%, Mn: 0.30-0.40%, Si: 0.20-0.30%, Cr: 1.42-1.52%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, Ni is less than or equal to 0.10%, Cu is less than or equal to 0.10%, Mo is less than or equal to 0.05%, Al: 0.008 to 0.015 percent, less than or equal to 0.0030 percent of Ti, less than or equal to 0.0009 percent of O, less than or equal to 0.0010 percent of Ca, less than or equal to 0.04 percent of As, less than or equal to 0.002 percent of Pb, and less than or equal to 0.03 percent of Sn; the balance being Fe and unavoidable impurities.
The invention also provides a production method of the pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing, which comprises the following steps:
the method comprises the steps of converter smelting, LF refining, VD vacuum treatment and continuous casting operation to obtain a 160-square continuous casting billet; then slowly cooling a continuous casting blank heat preservation pit, heating in a heating furnace, removing phosphorus by high-pressure water, controlling rolling, controlling cooling, collecting and packaging, finishing and inspecting, spheroidizing annealing and drawing. The specific operation steps and parameter settings are as follows.
(1) According to the control requirements of each component, carrying out converter smelting, LF refining, VD vacuum treatment and continuous casting operation to obtain a continuous casting billet (160 square);
(2) directly putting the continuous casting slab into a heat preservation pit for slow cooling for 48-72 hours based on the continuous casting slab obtained in the step (1), and after the continuous casting slab is cooled to be below 200 ℃, conveying the continuous casting slab to a storage yard for furnace charging and rolling;
(3) charging the continuous casting blank subjected to slow cooling in the step (2), and heating in a heating furnace, wherein the ratio of air to coal gas is 0.55-0.60; the temperature of the preheating section is 800 ℃ and 900 ℃, and the retention time is more than or equal to 40 minutes; the temperature of the second section is 1150-1230 ℃, and the retention time is more than or equal to 40 minutes; the temperature of the soaking section is 1190 ℃ and 1250 ℃, and the retention time is more than or equal to 40 minutes;
(4) after the heating and heat preservation operation based on the step (3), taking the continuous casting slab out of the heating furnace, and carrying out high-pressure water dephosphorization to thoroughly remove primary iron scale;
(5) based on the step (4), rolling is carried out after high-pressure water dephosphorization, the initial rolling temperature is 1090-;
(6) and (4) performing controlled cooling after rolling based on the step (5), wherein the conditions are as follows: the air quantity of the fan is 30-60%, the speed of the roller way is 0.3-0.5m/s, and the cooling speed of the wire rod and the thickness and structure of the oxide scale are controlled;
(7) collecting, surface inspecting, packaging, finishing and inspecting the wire rod subjected to hot rolling and cooling control in the step (6);
(8) performing spheroidizing annealing treatment on the hot-rolled wire rod collected in the step (7) in a pit furnace under a protective atmosphere (nitrogen gas); the specific treatment conditions are as follows: heating the hot-rolled wire rod to 790 ℃ and 810 ℃, preserving heat for 2-3 hours, then cooling to 690 ℃ and 720 ℃ along with the furnace at a cooling speed of less than or equal to 20 ℃/h, preserving heat for 3-5 hours, cooling to 600-650 ℃ along with the furnace at a cooling speed of less than or equal to 20 ℃/h, and finally discharging from the furnace for air cooling;
(9) and (4) based on the wire rod after spheroidizing annealing in the step (8), carrying out drawing processing by using a diamond wire drawing die and a wire drawing machine under the condition of no surface treatment to obtain the required wire rod product.
Preferably, the slow cooling time in the step (2) is 60 to 72 hours.
Preferably, the total residence time of the preheating section, the heating section and the soaking section in the step (3) is 120-160 minutes.
Preferably, the dephosphorization pressure in the step (4) is 23-25 MPa.
Preferably, the air volume of the fan in the step (6) is 50-60%, and the roller speed is 0.45-0.5 m/s.
Preferably, the hot-rolled wire rod in the step (8) is heated to 790-810 ℃, and the temperature is kept for 2 hours; cooling to 690 and 720 ℃, and keeping the temperature for 4 hours.
Preferably, the cooling rate in the step (8) is 15-20 ℃/h.
The invention has the advantages and technical effects that:
after spheroidizing annealing, the hot rolled wire rod obtains smooth surface quality, the thickness of the scale of the wire rod is increased to more than 14 mu m from the original 4-10 mu m, and Fe in the scale3O4The percentage of the iron wire rod is increased to more than 30 percent from the original 15-20 percent, and the outermost layer of the surface of the wire rod is free of Fe2O3. Meanwhile, the mechanical property and the structure of the wire rod meet the standard requirements, and abnormal phenomena such as uneven carbide and the like are not found. Under the condition of no surface treatment, the diamond die and the wire drawing machine are used for drawing, the iron oxide scale is in a block shape after being discharged from the die and falls off, the matrix basically has no residue, the surface of the wire rod has no drawing processing defect, and the quality of the die has no deterioration.
Compared with the conventional surface treatment process, the invention omits the processes of acidity, phosphorization and saponification, reduces the process cost and environmental pollution, and has no difference in product quality.
Drawings
FIG. 1 is a graph showing the morphology of hot-rolled scale in comparative example 1.
FIG. 2 is a topographic map of hot rolled scale in example 1.
Fig. 3 is a morphology of the oxide scale after the spheroidizing annealing in comparative example 1.
FIG. 4 is a graph of the morphology of the oxide scale after the spheroidizing annealing in example 1.
FIG. 5 is a graph showing the appearance of scale after drawing in comparative example 1.
FIG. 6 is a morphology of the scale after the drawing of example 1.
Detailed Description
The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
Comparative example 1:
conventional production
The components: c: 0.99%, Mn: 0.35%, Si: 0.25%, Cr: 1.46%, P: 0.008%, S: 0.003%, Ni: 0.02%, Cu: 0.02%, Mo: 0.01%, Al: 0.011%, Ti: 0.0013%, [ O ]: 0.0005%, Ca: 0.0001%, As: 0.004%, Pb: 0.0002%, Sn: 0.003%; the balance being Fe and unavoidable impurities.
The method comprises the following traditional steps: converter smelting, LF refining, VD vacuum treatment and continuous casting operation are carried out to obtain a 160-square continuous casting billet; then slowly cooling a continuous casting blank heat preservation pit, heating in a heating furnace, removing phosphorus by high-pressure water, controlling rolling, controlling cooling, collecting and packaging, finishing and inspecting, spheroidizing annealing, performing surface treatment (acid washing, phosphorization and saponification), and drawing.
(1) According to the control requirements of each component, 160-square continuous casting billets are obtained through converter smelting, LF refining, VD vacuum treatment and continuous casting operation;
(2) directly putting the continuous casting slab into a heat preservation pit for slow cooling for 72 hours, after the highest temperature of the continuous casting slab is cooled to be below 200 ℃, conveying the continuous casting slab to a storage yard, and waiting for furnace loading and rolling;
(3) charging the continuous casting billet into a furnace, and heating in a heating furnace, wherein the ratio of air to coal gas is 0.55; the temperature of the preheating section is 815 ℃, and the retention time is 45 minutes; heating the second section at 1180 deg.c for 45 min; the temperature of the soaking section is 1200 ℃, and the retention time is 40 minutes;
(4) taking the continuous casting slab out of the heating furnace, and removing phosphorus by high-pressure water at the phosphorus removal pressure of 18MPa to remove primary iron scale;
(5) the initial rolling temperature is 1120 ℃, the initial rolling temperature is 880 ℃, and the spinning temperature is 835 ℃ after the rough rolling, the intermediate rolling, the finish rolling and the reducing and sizing rolling;
(6) the cooling speed of the wire rod and the thickness and the structure of the oxide scale are controlled by adjusting the air volume (45%) of the fan and the speed (0.35m/s) of the roller way;
(7) collecting, surface inspecting, packaging, finishing and inspecting the hot rolled wire rod;
(8) and (3) carrying out spheroidizing annealing treatment on the hot-rolled wire rod in a pit furnace under a protective atmosphere (nitrogen). Heating the hot-rolled wire rod to 800 ℃, preserving heat for 2 hours, then furnace-cooling to 710 ℃ at a cooling speed of 20 ℃/h, preserving heat for 4 hours, furnace-cooling to 650 ℃ at a cooling speed of 18 ℃/h, and finally discharging from the furnace for air cooling;
(9) after surface treatment (acid washing, phosphating and saponification), a hard alloy wire drawing die and a wire drawing machine are used for drawing to obtain the required wire rod product.
Example 1:
the invention comprises the following components: c: 0.98%, Mn: 0.35%, Si: 0.24%, Cr: 1.47%, P: 0.010%, S: 0.002%, Ni: 0.02%, Cu: 0.02%, Mo: 0.03%, Al: 0.009%, Ti: 0.0015%, [ O ]: 0.0006%, Ca: 0.0001%, As: 0.004%, Pb: 0.0002%, Sn: 0.005 percent; the balance being Fe and unavoidable impurities.
The method comprises the following steps: converter smelting, LF refining, VD vacuum treatment and continuous casting operation are carried out to obtain a 160-square continuous casting billet; then slowly cooling a continuous casting blank heat preservation pit, heating in a heating furnace, removing phosphorus by high-pressure water, controlling rolling, controlling cooling, collecting and packaging, finishing and inspecting, spheroidizing annealing and drawing.
(1) According to the control requirements of each component, 160-square continuous casting billets are obtained through converter smelting, LF refining, VD vacuum treatment and continuous casting operation;
(2) directly putting the continuous casting slab into a heat preservation pit for slow cooling for 72 hours, after the highest temperature of the continuous casting slab is cooled to be below 200 ℃, conveying the continuous casting slab to a storage yard, and waiting for furnace loading and rolling;
(3) charging the continuous casting billet into a furnace, heating in a heating furnace, wherein the ratio of air to coal gas is 0.56; the temperature of the preheating section is 820 ℃, and the retention time is 44 minutes; heating the second section at 1180 deg.c for 45 min; the temperature of the soaking section is 1210 ℃, and the retention time is 42 minutes;
(4) taking the continuous casting slab out of the heating furnace, and carrying out high-pressure water dephosphorization under the dephosphorization pressure of 23MPa to thoroughly remove primary iron scale;
(5) the initial rolling temperature is 1110 ℃, the initial rolling temperature is 875 ℃ and the final rolling temperature is 840 ℃ after the rough rolling, the medium rolling, the finish rolling and the reducing and sizing rolling mill are carried out in sequence;
(6) on the original basis, the air volume of a fan is increased by 10 percent, the speed of a roller way is increased by 0.15m/s, and the cooling speed of a wire rod and the thickness and the structure of an oxide scale are controlled;
(7) collecting, surface inspecting, packaging, finishing and inspecting the hot rolled wire rod;
(8) and (3) carrying out spheroidizing annealing treatment on the hot-rolled wire rod in a pit furnace under a protective atmosphere (nitrogen). Heating the hot-rolled wire rod to 800 ℃, preserving heat for 2 hours, then cooling to 705 ℃ along with the furnace at a cooling speed of 20 ℃/h, preserving heat for 4 hours, then cooling to 650 ℃ along with the furnace at a cooling speed of 18 ℃/h, and finally discharging from the furnace for air cooling;
(9) and (3) carrying out drawing processing by using a diamond drawing die and a drawing machine without surface treatment to obtain the required wire rod product.
And (3) performance testing:
comparing the results of the cold charge introduced in the comparative example 1 with the results of the hot charge introduced in the example 1, and particularly referring to the attached drawings;
fig. 1 is a morphology of hot rolled scale in comparative example 1, from which it can be seen that the scale is separated from the matrix or adhered or partially separated and exhibits a jagged bond, and is divided into three layers: from the surface to the substrate, Fe2O3、Fe3O4FeO; wherein Fe2O3The thickness of the layer is from 1.69 μm to 4.54 μm, the total thickness reaches 10.72 μm, and the thickness of the iron scale is uneven.
FIG. 2 is a morphology of hot rolled scale in example 1, from which it can be seen that by increasing the phosphorus removal pressure with high pressure water and controlling rolling and cooling, the surface of the scale becomes smooth, in which Fe2O3The thickness of the layer is basically 1.8 to 2 mu m, the total thickness is 5.73 mu m, and the iron scale is uniform in thickness and is adhered to the matrix.
FIG. 3 is a morphology of the oxide scale after spheroidizing annealing in comparative example 1, and it can be seen that saw-tooth sharp corners and dense pits, or adhesion or partial separation, are present between the oxide scale and the substrate, and the thickness of the oxide scale is not uniform.
FIG. 4 is a graph showing the morphology of the oxide scale separated from the substrate and having a relatively uniform thickness after the spheroidizing annealing in example 1.
FIG. 5 is an operation diagram (left) of the drawing process of comparative example 1 and a morphology diagram (right) of the scale after drawing, wherein the scale is in a powdery state and is not completely peeled off.
FIG. 6 is a graph showing the appearance of scale after drawing in example 1, where the scale is stripped off in the form of strips and the surface of the matrix is smooth.
Compared with the surface treatment of the bearing steel wire, the invention avoids the surface treatment process after spheroidizing annealing by improving the dephosphorization pressure of high-pressure water, controlling the cooling of the hot-rolled wire rod and selecting the diamond wire drawing die. After spheroidizing annealing, the wire rod can be directly used for drawing processing, and the surface quality is not deteriorated. The invention has the advantages of shortening the production period, reducing the environmental pollution and reducing the energy consumption and the cost, and simultaneously, the product quality requirement of the wire rod product is also met.
Description of the drawings: the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; thus, while the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted; all such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
Claims (7)
1. A production method of a pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing is characterized by comprising the following steps:
(1) according to the control requirements of each component, carrying out converter smelting, LF refining, VD vacuum treatment and continuous casting operation to obtain a continuous casting billet;
(2) directly putting the continuous casting slab into a heat preservation pit for slow cooling for 48-72 hours based on the continuous casting slab obtained in the step (1), conveying the continuous casting slab to a storage yard after the continuous casting slab is cooled to be below 200 ℃, and loading into a furnace for rolling;
(3) charging the continuous casting blank subjected to slow cooling in the step (2), and heating in a heating furnace, wherein the ratio of air to coal gas is 0.55-0.60; the temperature of the preheating section is 800 ℃ and 900 ℃, and the retention time is more than or equal to 40 minutes; the temperature of the second section is 1150-1230 ℃, and the retention time is more than or equal to 40 minutes; the temperature of the soaking section is 1190 ℃ and 1250 ℃, and the retention time is more than or equal to 40 minutes;
(4) after the heating and heat preservation operation based on the step (3), taking the continuous casting slab out of the heating furnace, and carrying out high-pressure water dephosphorization;
(5) based on the step (4), rolling is carried out after high-pressure water dephosphorization, the initial rolling temperature is 1090-;
(6) and (4) performing controlled cooling after rolling based on the step (5), wherein the conditions are as follows: the air volume of the fan is 30-60%, and the speed of the roller way is 0.3-0.5 m/s;
(7) collecting, surface inspecting, packaging, finishing and inspecting the wire rod subjected to hot rolling and cooling control in the step (6);
(8) performing spheroidizing annealing treatment on the hot-rolled wire rod collected in the step (7) in a pit furnace under the nitrogen protection atmosphere; the specific treatment conditions are as follows: heating the hot-rolled wire rod to 790 ℃ and 810 ℃, preserving heat for 2-3 hours, then cooling to 690 ℃ and 720 ℃ with the furnace at a cooling speed of less than or equal to 20 ℃/h, preserving heat for 3-5 hours, then cooling to 600-650 ℃ with the furnace at a cooling speed of less than or equal to 20 ℃/h, and finally discharging from the furnace for air cooling;
(9) based on the wire rod after spheroidizing annealing in the step (8), drawing by using a diamond wire drawing die and a wire drawing machine without surface treatment to obtain a required wire rod product;
wherein the bearing steel comprises the following components in percentage by weight: c: 0.96-1.03%, Mn: 0.30-0.40%, Si: 0.20-0.30%, Cr: 1.42-1.52%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, Ni is less than or equal to 0.10%, Cu is less than or equal to 0.10%, Mo is less than or equal to 0.05%, Al: 0.008 to 0.015 percent, less than or equal to 0.0030 percent of Ti, less than or equal to 0.0009 percent of O, less than or equal to 0.0010 percent of Ca, less than or equal to 0.04 percent of As, less than or equal to 0.002 percent of Pb, and less than or equal to 0.03 percent of Sn; the balance being Fe and unavoidable impurities.
2. The method for producing a spheroidizing annealed pickling-free high-carbon chromium bearing steel wire rod according to claim 1, wherein the time for slow cooling in the step (2) is 60 to 72 hours.
3. The method for producing a pickling-free high-carbon chromium bearing steel wire rod after spheroidizing annealing as claimed in claim 1, wherein the total residence time of the preheating section, the heating second section and the soaking section in the step (3) is 160 minutes.
4. The production method of the pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing according to claim 1, wherein the dephosphorization pressure in the step (4) is 23-25 MPa.
5. The production method of the pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing according to claim 1, wherein the air volume of the fan in the step (6) is 50-60%, and the speed of a roller way is 0.45-0.5 m/s.
6. The method for producing the pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing as claimed in claim 1, wherein in the step (8), the hot-rolled wire rod is heated to the temperature of 790-810 ℃ and is subjected to heat preservation for 2 hours; cooling to 690 and 720 ℃, and keeping the temperature for 4 hours.
7. The method for producing the pickling-free high-carbon chromium bearing steel wire rod subjected to spheroidizing annealing according to claim 1, wherein the cooling rate in the step (8) is 15-20 ℃/h.
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