阅读说明：本技术 一种减少VD工序结合组分优化生产低成本20CrMoA圆钢的方法 (Method for optimizing production of low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process and combining components ) 是由 寿先涛 陈振芳 张勇 于 2021-08-06 设计创作，主要内容包括：本发明属于圆钢生产技术领域,涉及一种减少VD工序结合组分优化生产低成本20CrMoA圆钢的方法；钢材成分：C：0.19～0.20％、Mn：0.60～0.63％、Si：0.23～0.25％、Mo：0.16～0.18％、Cr：0.92～1.00％、Ni：≤0.30％、P：≤0.020％、S：≤0.020％、Cu：≤0.20％,Alt：0.16～0.18％、余量为Fe及不可避免杂质；步骤包括转炉冶炼、LF精炼、连铸、堆冷、加热、高温剪切和热钢收集；本发明通过优化组分和工艺,保证钢材性能的同时降低吨钢成本；还有效避免连铸坯存在中心偏析及轧制过程中冷却工艺不当使钢材端部产生中心裂纹的问题,应用前景广阔。(The invention belongs to the technical field of round steel production, and relates to a method for optimizing and producing low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process combined components; the steel comprises the following components: c: 0.19 to 0.20%, Mn: 0.60 to 0.63%, Si: 0.23 to 0.25%, Mo: 0.16-0.18%, Cr: 0.92 to 1.00%, Ni: less than or equal to 0.30 percent, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cu: less than or equal to 0.20 percent, Alt: 0.16-0.18%, the balance being Fe and unavoidable impurities; the method comprises the steps of converter smelting, LF refining, continuous casting, heap cooling, heating, high-temperature shearing and hot steel collection; according to the invention, the components and the process are optimized, so that the ton steel cost is reduced while the steel performance is ensured; the method also effectively avoids the problems that the center segregation exists in the continuous casting billet and the center crack is generated at the end part of the steel due to improper cooling process in the rolling process, and has wide application prospect.)

1. A method for reducing VD procedure combined components and optimizing production of low-cost 20CrMoA round steel is characterized by comprising the following steps:

(1) smelting in a converter: the carbon content of the steel tapping is 0.06-0.12%, the phosphorus content P of the steel tapping is less than or equal to 0.015%, and the steel tapping temperature T is more than or equal to 1600 ℃;

(2) LF refining: aluminum particles and silicon carbide are used as deoxidizing agents, the white slag time is guaranteed to be more than or equal to 18min, the soft blowing strength is controlled to be 40-60 NL/min, and the time is more than or equal to 15 min;

(3) protective pouring is adopted in the whole continuous casting process, and the superheat degree and the specific water amount are controlled; electromagnetic stirring is adopted by a crystallizer in the continuous casting process; carrying out wind-shielding and stack cooling on the continuous casting billet obtained after continuous casting, wherein the stack cooling time is more than or equal to 36 h;

(4) heating: heating and preserving the heat of the continuously cast bloom after the heap cooling treatment, wherein the total heating time is more than or equal to 180min, and the heating section is divided into a preheating section, a heating section and a soaking section, wherein the preheating section is less than or equal to 650 ℃, the temperature of the heating section is 950-1000 ℃, the temperature of the heating section and the soaking section is controlled at 1160-1200 ℃, and the time of the heating section and the soaking section is more than or equal to 120 min;

(5) rolling: the initial rolling temperature is 1130 +/-50 ℃, the final rolling temperature is more than or equal to 850 ℃, and the shearing temperature is more than or equal to 450 ℃;

(6) carrying out wind-shielding stack cooling on the round steel, wherein the stack cooling time is more than or equal to 36h, and the stack cooling temperature is more than or equal to 200 ℃;

the 20CrMoA round steel comprises the following components in percentage by weight:

c: 0.19 to 0.20%, Mn: 0.60 to 0.63%, Si: 0.23 to 0.25%, Mo: 0.16-0.18%, Cr: 0.92 to 1.00%, Ni: less than or equal to 0.30 percent, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cu: less than or equal to 0.20 percent, Alt: 0.16-0.18%, and the balance of Fe and unavoidable impurities.

2. The method for producing low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process and optimizing the components according to claim 1, wherein the end point temperature in the step (1) is 1600-1610 ℃.

3. The method for producing the low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process and optimizing the components according to the claim 1, wherein no alloy element is added 10min before the ladle in the LF refining process in the step (2).

4. The method for producing 20CrMoA round steel by reducing VD procedure and optimizing components according to claim 1, wherein the electromagnetic stirring in step (3) adopts a first stirring process, wherein M-EMS parameter is I-400A, F-2 Hz, and no stirring process, and F-EMS parameter is I-300A, and F-10 Hz.

5. The method for optimizing and producing the low-cost 20CrMoA round steel by reducing the VD procedure and combining the components according to claim 1, wherein the control superheat degree is 22-30 ℃, and the specific water amount is 3.0L/kg.

6. The method for producing the low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process and optimizing the components according to the claim 1, wherein the continuous casting billet in the step (3) is a 220mm square billet; the heap cooling time is 36-38 h.

7. The method for producing the low-cost 20CrMoA round steel by reducing VD procedure combined component optimization according to claim 1, wherein the total heating time in the step (4) is 295-326 min; the total time of the heating second section and the soaking section is 125-135 min.

8. The method for producing the low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process combined component optimization according to claim 1, wherein the finish rolling temperature in the step (5) is 850-868 ℃; the shearing temperature is 450-472 ℃.

9. The method for producing the low-cost 20CrMoA round steel by reducing VD procedure combined component optimization according to claim 1, wherein the heap cooling time in the step (6) is 36-37 h, and the heap cooling temperature is 200-300 ℃.

Technical Field

The invention belongs to the technical field of round steel production, and particularly relates to a method for optimizing and producing low-cost 20CrMoA round steel by reducing VD (vacuum distillation) process and combining components.

Background

The 20CrMoA is common high-hardenability alloy structural steel, has higher strength and good toughness, good cold strain plasticity and no obvious temper brittleness. After quenching and tempering or carburizing treatment, the alloy has higher fatigue limit and impact resistance and good comprehensive mechanical property, and is widely applied to processing mechanical parts such as high-pressure pipelines, fasteners, gears, shafts and the like.

But the conventional method is followed in the current production of the 20CrMoA round steel, so that the production cost is always at a higher level; with the increasing market competition, reducing the cost of steel per ton is an urgent technical problem to be solved. Moreover, no corresponding technical report is found in the currently published documents.

Disclosure of Invention

The invention aims to overcome the technical defects in the prior art, and provides a method for optimizing and producing low-cost 20CrMoA round steel by reducing VD (vacuum degassing) process combined components.

In order to realize the purpose, the invention firstly provides a low-cost 20CrMoA round steel which comprises the following components in percentage by weight:

c: 0.17-0.24%, Mn: 0.40 to 0.70%, Si: 0.17 to 0.37%, Mo: 0.15 to 0.25%, Cr: 0.80-1.10%, Ni: less than or equal to 0.30 percent, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cu: less than or equal to 0.20 percent, Alt: 0.16-0.18%, and the balance of Fe and unavoidable impurities.

Further optimizing the component design:

c: 0.19 to 0.20%, Mn: 0.60 to 0.63%, Si: 0.23 to 0.25%, Mo: 0.16-0.18%, Cr: 0.92 to 1.00%, Ni: less than or equal to 0.30 percent, P: less than or equal to 0.020%, S: less than or equal to 0.020%, Cu: less than or equal to 0.20 percent, Alt: 0.16-0.18%, and the balance of Fe and unavoidable impurities.

And part of Mn and Cr are adopted to replace part of Mo alloy elements, so that the cost of each ton of steel is reduced. The cost of per ton steel is reduced; this seems to be a simple adjustment, which is a result that can be obtained through a large number of creative experiments, and the amount of the Mn and Cr components must be strictly controlled, which is not achieved by simple adjustment, and the Mn and Cr components are properly increased, and the Mo content is reduced, otherwise the performance of the steel is affected.

The carbon content has the most significant effect on the strength of the material. With the increase of the carbon content, the strength of the material increases, but the ductility and toughness decrease and the weldability also begins to deteriorate.

The manganese can be infinitely dissolved with the iron, and the influence on plasticity is small while the strength is improved. For the quenched and tempered steel, the manganese content is properly increased, so that the hardenability of the steel can be increased while the strength is improved. Chromium mainly improves hardenability and can improve strength in quenched and tempered steel.

Molybdenum belongs to a noble metal; molybdenum can obviously improve the hardenability of steel, and improve the tempering brittleness and the tempering stability.

Because manganese, chromium and molybdenum have certain consistency on the effects of hardenability and strength, the good synergistic effect can be exerted under the condition of proper dosage, and the use state of 20CrMo is a quenching and tempering state, the hardenability of the material and the tempering stability are ensured, so that the content of manganese, chromium, molybdenum and the like in the material is kept in a reasonable proportion, and the material has good use performance.

Meanwhile, a certain amount of aluminum is added into the alloy for refining grains, which is beneficial to the stable performance of the product and the processing of the product.

The conventional smelting mode comprises converter smelting, LF refining, VD vacuum treatment, continuous casting, wind shielding and stack cooling of casting blanks, heating, high-temperature shearing and hot steel collection. In order to further reduce the cost, the smelting mode is changed into converter smelting, LF refining, continuous casting, casting blank wind shielding and stack cooling, heating, high-temperature shearing and hot steel collection.

The alloy steel is sensitive to gas contents [ H ], [ O ] and [ N ]. The VD furnace can effectively remove [ H ], [ N ] and partial oxide inclusions in molten steel. The elimination of VD procedure increases the gas content of molten steel and the risk of improving the grade of non-metallic inclusions. The LF white slag time is increased to ensure the deoxidation effect, the aluminum content of the molten steel is reduced, and the soft blowing time is increased to reduce the risk of non-metallic inclusions. The superheat degree of the continuous casting molten steel is controlled, and the low-power quality of a casting blank can be improved; the low-power quality of the round steel can be improved by adjusting the heating temperature and time of the continuous casting billet and the cooling temperature of the round steel.

In order to reduce the production cost to the maximum extent, the method comprehensively starts from two aspects of adjusting components and reducing VD procedures.

The invention also provides a production method of the low-cost 20CrMoA round steel, which comprises the following steps:

the conventional smelting mode comprises converter smelting, LF refining, VD vacuum treatment, continuous casting, wind shielding and stack cooling of casting blanks, heating, high-temperature shearing and hot steel collection. In order to further reduce the cost, the smelting mode is changed into converter smelting, LF refining, continuous casting, casting blank wind shielding and stack cooling, heating, high-temperature shearing and hot steel collection.

(1) Smelting in a converter: the carbon content of the steel tapping is 0.06-0.12%, the phosphorus content P of the steel tapping is less than or equal to 0.015%, and the steel tapping temperature T is more than or equal to 1600 ℃;

(2) LF refining: aluminum particles and silicon carbide are used as deoxidizing agents, the white slag time is guaranteed to be more than or equal to 18min, the soft blowing strength is controlled to be 40-60 NL/min, and the time is more than or equal to 15 min;

(3) protective pouring is adopted in the whole continuous casting process, and the superheat degree and the specific water amount are controlled; electromagnetic stirring is adopted by a crystallizer in the continuous casting process; carrying out wind-shielding and stack cooling on the continuous casting billet obtained after continuous casting, wherein the stack cooling time is more than or equal to 36 h;

(4) heating: heating and preserving the heat of the continuously cast bloom after the heap cooling treatment, wherein the total heating time is more than or equal to 180min, the heating section is divided into a preheating section, a first heating section, a second heating section and a soaking section, the temperature of the first heating section is less than or equal to 650 ℃, the temperature of the second heating section and the soaking section is controlled to be 950-1000 ℃, the temperature of the second heating section and the soaking section is controlled to be 1160-1200 ℃, the total time of the second heating section and the soaking section is more than or equal to 120min, and the core temperature of the steel billet is guaranteed to reach the standard;

(5) rolling: the initial rolling temperature is 1130 +/-50 ℃, the final rolling temperature is more than or equal to 850 ℃, and the shearing temperature is more than or equal to 450 ℃;

(6) the round steel is subjected to wind-shielding and pile cooling, the pile cooling time is more than or equal to 36 hours, and the pile cooling temperature is more than or equal to 200 ℃.

Further, the end point temperature in the step (1) is 1600-1610 ℃.

Further, no alloy element is added 10min before ladle in the LF refining process in the step (2).

Further, the electromagnetic stirring in the step (3) adopts a process of stirring first, wherein the M-EMS parameter is I-400A, F is 2Hz, and stirring last, the F-EMS parameter is I-300A, and F is 10Hz, so that the columnar crystals can be broken, the isometric crystals can be increased, the growth of the columnar crystals can be effectively controlled, and the isometric crystal rate can be increased.

Further, in the step (3), the superheat degree is controlled to be 22-30 ℃, and the specific water amount is 3.0L/kg.

Further, the continuous casting billet in the step (3) is a 220mm square billet; the heap cooling time is 36-38 h.

Further, the total heating time in the step (4) is 295-326 min; the time of the hot second section and the soaking section is 125-135 min.

Further, the finishing temperature in the step (5) is 850-868 ℃; the shearing temperature is 450-472 ℃.

Further, in the step (6), the heap cooling time is 36-37 h, and the heap cooling temperature is 200-300 ℃.

The invention has the advantages and technical effects that:

part of Mn and Cr are adopted to replace part of Mo alloy elements, so that the cost of each ton of steel is reduced; the cost of per ton steel is reduced; the method seems to be simple adjustment, and is a result which can be obtained through a large amount of creative experiments, the dosage of the method needs to be strictly controlled, the method is not realized by simple adjustment, and otherwise, the performance of steel is influenced; the Mn and Cr components are properly improved, the Mo content is reduced, and the cost is saved on the basis of ensuring the qualified mechanical property; meanwhile, the production process provided by the invention adopts a non-VD procedure during steel making in combination with the improvement of the process steps, so that the cost is further saved while the performance of steel is not influenced.

The crystallizer in the continuous casting process adopts electromagnetic stirring; the electromagnetic stirring adopts initial stirring, the M-EMS parameter is that I is 400A, and f is 2 Hz; the process is not stirred, the F-EMS parameter is 300A, and the F is 10Hz, so that the columnar crystal can be broken, the isometric crystal can be increased, the growth of the columnar crystal can be effectively controlled, and the isometric crystal rate can be increased.

Through the simple and effective process flow design, the center segregation of the continuous casting billet is effectively avoided, and the central crack is generated at the end part of the steel material due to improper cooling process in the rolling process; the mechanical property of the round steel and the index requirement of ultrasonic flaw detection are ensured; the cost is saved by 85-120 yuan/ton, the cost of steel per ton is greatly reduced, and the method has a good application prospect.

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:

traditional components: c: 0.20%, Si: 0.25%, Mn: 0.55%, P: 0.016%, S: 0.005%, Cr: 0.90%, Ni: 0.01%, Mo: 0.19%, Cu: 0.02%, Alt: 0.22 percent; the balance being Fe and unavoidable impurities.

The steps are as follows: converter smelting, LF refining, VD vacuum treatment, continuous casting, wind shielding and stack cooling of casting blanks, heating, shearing and collection.

(1) Smelting in a converter: the carbon content of the steel tapping is 0.08 percent, and the phosphorus content of the steel tapping is P: 0.014%, tapping temperature T: 1607 deg.C;

(2) LF refining: aluminum beans and a silicon carbide deoxidizer are adopted, the white slag time is 15min, and the soft blowing strength is 40-60 NL/min; the flow rate of broken air argon is 120NL/min, and the flow rate of soft blowing gas is 20-40 NL/min, so as to cover the molten steel surface; the maximum vacuum degree is 53Pa, the vacuum time is 12min, and the soft blowing time is 15 min;

(3) the whole continuous casting process adopts protective pouring, the superheat degree is 28 ℃, and the specific water amount is 3.0L/kg. M-EMS parameter 400A/2HZ, F-EMS parameter 300A/10 HZ; carrying out wind shielding and pile cooling on the continuous casting billet for 36 hours; the continuous casting billet is a 220mm square billet;

(4) the total heating time of the casting blank is 300min, wherein the heating temperature of the second heating section is 1163 ℃ and the soaking temperature is 1170 ℃;

(5) the initial rolling temperature is 1130 ℃, and the final rolling temperature is 860 ℃;

(6) and (3) conducting wind-shielding and heap cooling on the round steel, wherein the heap cooling time is 36h, and the heap cooling temperature is 200 ℃.

Example 1:

the invention comprises the following components: c: 0.19%, Si: 0.24%, Mn: 0.60%, P: 0.015%, S: 0.001%, Cr: 0.95%, Ni: 0.02%, Mo: 0.16%, Cu: 0.02%, Alt: 0.18 percent; the balance being Fe and unavoidable impurities.

The method comprises the following steps: converter smelting, LF refining, continuous casting, wind shielding and pile cooling of casting blanks, heating, high-temperature shearing and hot steel collection.

(1) Smelting in a converter: tapping carbon content is 0.10%, tapping phosphorus content is P: 0.014%, tapping temperature T: 1606 deg.C;

(2) LF refining: aluminum beans and a silicon carbide deoxidizer are adopted to ensure that the white slag time is 22min, the soft blowing strength is 40-60 NL/min, and the soft blowing time is 15 min;

(3) protective pouring is adopted in the whole continuous casting process, the superheat degree is 30 ℃, and the specific water amount is 3.0L/kg; M-EMS parameters 400A/2HZ, F-EMS parameters 300A/10 HZ. Carrying out wind shielding and pile cooling on the continuous casting billet for 36 hours; the continuous casting billet is a 220mm square billet;

(4) the total heating time of the casting blank is 295 min; heating at 1175 deg.C for 72 min; the soaking section is 1170 ℃ for 60 min; the total time of the heating second section and the soaking section is 132 min;

(5) the initial rolling temperature is 1100 ℃, the final rolling temperature is 856 ℃, and the shearing temperature is 455 ℃;

(6) and (3) conducting wind-shielding and heap cooling on the round steel, wherein the heap cooling time is 38h, and the heap cooling temperature is 200 ℃.

Example 2:

the invention comprises the following components: c: 0.19%, Si: 0.25%, Mn: 0.63%, P: 0.016%, S: 0.002%, Cr: 0.92%, Ni: 0.02%, Mo: 0.18%, Cu: 0.02%, Alt: 0.18 percent; the balance being Fe and unavoidable impurities.

The method comprises the following steps: the method comprises the steps of converter smelting, LF refining, continuous casting, wind shielding and pile cooling of a casting blank, heating, high-temperature shearing and hot steel collection.

(1) Smelting in a converter: tapping carbon content of 0.09%, tapping phosphorus content P: 0.013%, tapping temperature T: 1600 ℃;

(2) LF refining: aluminum beans and a silicon carbide deoxidizer are adopted to ensure that the white slag time is 25min, the soft blowing strength is 40-60 NL/min, and the soft blowing time is 18 min;

(3) protective pouring is adopted in the whole continuous casting process, the superheat degree is 25 ℃, and the specific water amount is 3.0L/kg; M-EMS parameter 400A/2HZ, F-EMS parameter 300A/10 HZ; carrying out wind shielding and pile cooling on the continuous casting billet for 38 hours; the continuous casting billet is a 220mm square billet;

(4) the total heating time of the casting blank is 326 min; heating at 1170 deg.C for 80 min; the soaking section is 1170 ℃ for 55 min; the total time of the heating second section and the soaking section is 135 min;

(5) the initial rolling temperature is 1180 ℃, the final rolling temperature is 868 ℃, and the shearing temperature is 472 ℃;

(6) and (3) conducting wind-shielding and heap cooling on the round steel, wherein the heap cooling time is 37h, and the heap cooling temperature is 250 ℃.

Example 3:

the invention comprises the following components: c: 0.20%, S: 0.23%, Mn: 0.60%, P: 0.017%, S: 0.006%, Cr: 1.00%, Ni: 0.01%, Mo: 0.17%, Cu: 0.02%, Alt: 0.16 percent; the balance being Fe and unavoidable impurities.

The method comprises the following steps: converter smelting, LF refining, continuous casting, wind shielding and pile cooling of casting blanks, heating, high-temperature shearing and hot steel collection.

(1) Smelting in a converter: tapping carbon content is 0.12%, tapping phosphorus content P: 0.014%, tapping temperature T: 1610 ℃;

(2) LF refining: aluminum beans and a silicon carbide deoxidizer are adopted, the white slag time is 25min, the soft blowing strength is 40-60 NL/min, and the soft blowing time is 19 min;

(3) the whole continuous casting process adopts protective pouring, the superheat degree is controlled at 27 ℃, and the specific water amount is 3.0L/kg. M-EMS parameter 400A/2HZ, F-EMS parameter 300A/10 HZ; the wind shielding and pile cooling time of the continuous casting billet is 36h, and the continuous casting billet is a 220mm square billet;

(4) the total heating time of the casting blank is 310 min; heating the second section to 1165 deg.C for 50 min; the temperature of the soaking section is 1170 ℃, the time is 75min, and the total time of the second section and the soaking section is 125 min;

(5) the initial rolling temperature is 1160 ℃, the final rolling temperature is 850 ℃ and the shearing temperature is 450 ℃.

(6) And (3) conducting wind-shielding and heap cooling on the round steel, wherein the heap cooling time is 36h, and the heap cooling temperature is 300 ℃.

And (3) displaying effect data:

(1) cost-effectiveness:

(a) calculating according to the current alloy market price: the average cost per 0.01 wt% Mn is 1.0 yuan, Cr is 1.5 yuan, and Mo is 22.8 yuan. Calculated from the compositional comparisons of comparative example 1 and examples 1-3, only the alloy aspect:

example 1 saves 55.9 yuan/ton, example 2 saves 12.8 yuan/ton, and example 3 saves 25.6 yuan/ton.

(b) The VD procedure is simplified and cancelled in the process steps, and the cost is saved by 60 yuan/ton;

through the optimization of components and processes, the two items are summed up: the cost is reduced by 117.9 yuan/ton in the embodiment 1, 74.8 yuan/ton in the embodiment 2, and 87.6 yuan/ton in the embodiment 3, so that the cost is saved by 85-120 yuan/ton, and the method has a good popularization significance.

(2) Performance indexes are as follows:

performance requirements	Tensile strength measured/Mpa	Yield strength/Mpa	Elongation after break/%	Reduction of area/%)	Mean value of impact (J)	Ultrasonic flaw detection
							Standard of merit	≥885	≥685	≥12	≥50	≥78	GB/T4162B grade
Comparative example 1	932	785	16	54	180	Qualified
							Example 1	1021	949	15	52	132	Qualified
Example 2	1021	925	16	66	165	Qualified
							Example 3	920	780	17.5	68	174	Qualified

The results show that the 20CrMoA round steel with good strength and toughness is obtained; mn is a solid solution strengthening element and is beneficial to improving the strength and the toughness of the round steel; cr and iron form a continuous solid solution, an austenite phase region is reduced, the strength and the hardenability are obviously improved, the strength of the round steel is improved, and the round steel has good wear resistance; mo is dissolved in steel in a solid state and has the functions of eliminating temper brittleness, refining grains and improving the hardenability of the steel. The Mn and Cr components are properly improved, the Mo content is reduced, and the cost is saved on the basis of ensuring the qualified mechanical property; meanwhile, Al is added to play a role in refining grains and strengthening, electromagnetic stirring is combined, stable product performance is facilitated, and the cost of steel per ton is reduced, so that the steel has good strength and toughness.

The production process of the invention adopts a non-VD procedure for steel making in combination with the improvement of the process steps, thereby further saving the cost while not influencing the performance of steel.

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.