CN115612913B - TiO (titanium dioxide) 2 Preparation method of nanoparticle reinforced hot rolled steel bar - Google Patents

Abstract

The invention discloses a method for preparing hot-rolled steel bars reinforced by TiO ₂ nanoparticles, which includes: weighing a certain amount of TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder, mixing them according to a certain mass ratio, and then performing ball milling treatment; The mixed powder after ball milling is put into a tube furnace for sintering, and the TiO ₂ nanocomposite material is obtained after the sample is cooled in the furnace. The scrap steel is loaded into the medium frequency induction furnace for smelting. In the later stage of smelting, the TiO ₂ nanocomposite material is added to the molten steel. After the temperature and composition are adjusted to meet the requirements, it is poured into steel ingots; the steel ingots are rolled into qualified steel bars; the present invention uses a master alloy to The carrier method overcomes the agglomeration phenomenon of TiO ₂ nanoparticles during storage and transportation, improves the wettability between TiO ₂ nanoparticles and the steel matrix, and solves the problem that TiO ₂ nanoparticles are easy to float and agglomerate in molten steel. This problem ensures a reasonable distribution of the second phase particles TiO ₂ and achieves the effect of strengthening the second phase of steel bars.

Description

A method for preparing TiO2 nanoparticle-reinforced hot-rolled steel bars

Technical field

The invention belongs to the field of steel materials and their manufacturing, and specifically relates to a preparation method of _TiO2 nanoparticle-reinforced hot-rolled steel bars.

Background technique

After the implementation of the new standard for threaded steel bars (GB/T1499.2-2018), the requirements for macroscopic metallographic structure (P+F) are added, and the post-rolling residual heat quenching process (strong water penetration process) is used to increase phase change strengthening and promote fineness. The method of crystal strengthening has been eliminated. In order to ensure that the mechanical properties of steel bars meet the requirements of national standards, precious metals niobium or vanadium are added. Through the precipitation of carbonitrides of niobium or vanadium after rolling, the steel bars can be improved while ensuring the structure (P+F) of the steel bars. Strength is currently the main process method commonly used in major steel plants, but the prices of precious metals such as niobium and vanadium remain high. Adding cheap nano-two-phase particles to improve the mechanical properties of steel bars is important to reduce steel bar production costs and improve the competitiveness of enterprises. meaning.

The type, size, shape and distribution of the second phase particles in the steel matrix will have a very important impact on the mechanical, physical and chemical properties of the steel. Nanoscale second phase particles with high hardness and high melting point can produce precipitation strengthening and fine grain strengthening effects on the steel matrix, thereby improving the comprehensive mechanical properties of the steel; among which, grain refinement includes nucleation refinement during solidification and crystallization and later stages. Recrystallization refinement during processing. However, when the second phase particles are larger (micron level), they serve as crack nucleation sources, leading to the formation and propagation of cracks, which have a destructive effect on the mechanical properties of steel. Introducing nanoscale second phase particles with high hardness and high melting point into the steel material can form pinning at the grain boundaries, prevent grain growth, and refine the grains, thus improving the mechanical properties of the steel material; In addition, it is believed that the added second phase particles can achieve multiple grain refinement effects of nucleation refinement and recrystallization refinement during the later rolling process when the molten steel solidifies and crystallizes. Compared with the internal precipitation of second phase particles, This method overcomes the uncertainty and difficulty in grasping the quantity and size of the second phase generated by the internal precipitation method. It is more controllable, does not have excessive requirements on the purity of the steel, and can be easily applied to industrial scale. of steel production. However, nanoparticles with high hardness and high melting point are easy to agglomerate during storage and transportation. After being added to molten steel, they are easy to float and agglomerate. Only by overcoming the above shortcomings can we truly realize the production of low-cost high-strength steel bars.

Contents of the invention

In order to solve the above technical problems, the technical solution provided by the present invention is: a preparation method of TiO ₂ nanoparticle-reinforced hot-rolled steel bars, which includes the following steps:

Step 1: Weigh the TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder respectively, and mix the TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder in a mass ratio of 1:2 to 20:5 to 30. The mixed powder is put into the ball mill tank. The ball-to-material ratio is 5 to 15:1. The total volume of the grinding ball and sample is no more than two-thirds of the ball mill tank volume. One-third of the ball mill tank volume is reserved. grinding space;

Step 2: Use a vacuum pump to evacuate the gas in the ball mill tank so that the ball mill tank is in a vacuum state; place the ball mill tank symmetrically into the planetary ball mill to mechanically alloy the sample;

Step 3: After the ball mill stops running, wait for the ball mill tank to cool down, take out the mixed powder and pour it into the crucible, and then perform high-temperature sintering in the tube furnace. Before the sintering starts, remove the air in the tube furnace. After sintering is completed, it is cooled in the furnace until the sample is taken out;

Step 4: Load the scrap steel bars into the experimental medium frequency induction furnace for smelting. When the temperature rises to above 1550°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the target composition, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust. The composition of the molten steel. When the composition is qualified and the temperature reaches 1560~1570°C, after two slag removals, the temperature is kept for 10 minutes. When the temperature of the molten steel drops to 1530~1550°C, let it stand for 1 minute and pour the molten steel into a control ingot. ;

Step 5: Put the scrap steel bars into the experimental medium frequency induction furnace for smelting. When the temperature rises to above 1560°C and the scrap steel is completely melted, samples are taken for spectral component analysis. According to the same target components as in step 4, the prepared TiO ₂ nanoparticles are composited. The materials are added to the molten steel. The prepared TiO ₂ nanoparticle composite material accounts for 0.01 to 0.15% of the total weight of the molten steel. After stirring for 5 to 10 minutes, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust the composition of the molten steel. When the ingredients When it is qualified and the temperature reaches 1560~1570℃, after two times of slag removal, keep the temperature for 10 minutes. When the temperature of the molten steel drops to 1530~1550℃, let it stand for 1 minute and pour the molten steel into a test sample ingot;

Step 6: Air-cool the control sample steel ingot and test sample steel ingot to room temperature, demold, and then cast them; after forging and forming, put them into a heating furnace for heating, roll them into steel bar samples, conduct mechanical testing on the samples, and compare TiO ₂ nanometers Effect of particles on mechanical properties of steel bars.

The advantage of the present invention compared with the prior art is that the TiO ₂ nanoparticles reinforced hot-rolled steel bars prepared by the present invention overcome the problem that the TiO ₂ nanoparticles are easily agglomerated during storage and transportation by using a master alloy as a carrier. It improves the wettability between TiO ₂ nanoparticles and the steel matrix, achieves a reasonable distribution of TiO ₂ nanoparticles in the steel, achieves the second phase strengthening effect, and improves the mechanical properties of steel bars.

Description of the drawings

Figure 1 is a schematic diagram of a scanning electron microscope (SEM) of the composite material prepared in Examples 1 and 2 of the present invention.

Figure 2 is a schematic diagram of a scanning electron microscope (SEM) of the steel bars prepared in Examples 1 and 2 of the present invention.

In the figure: (a) is Embodiment 1, (b) is Embodiment 2.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, rather than all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Example 1:

A method for preparing _TiO2 nanoparticle-reinforced hot-rolled steel bars, including the following steps:

Weigh a certain amount of TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder respectively. The particle size of the TiO ₂ nanoparticles is 20 nm and the purity is 99.9%; the particle size of the Al powder is 200 mesh and the purity is 99.9%; Mix TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder in a mass ratio of 1:5:10. Put the mixed powder into a cleaned and dried ball mill tank. The ball-to-material ratio is 7:1 , the volume of the grinding ball and sample should not be greater than two-thirds of the volume of the ball mill tank, and one-third of the volume of the ball mill tank should be used as the reserved grinding space.

Use a vacuum pump to evacuate the gas in the ball milling tank so that the ball milling tank is in a vacuum state; place the ball milling tank symmetrically into the planetary ball mill to mechanically alloy the sample. Set the speed of the ball mill to 200r/min, the ball milling time to 12 hours, run forward for 3 minutes, then pause for 2 minutes, then run in reverse for 3 minutes, repeat the cycle, and mix thoroughly until the end of the program.

After the ball mill stops running, wait for the ball mill tank to cool down, take out the mixed powder and pour it into the crucible, and put them together into the tube furnace for high-temperature sintering. Before sintering begins, remove the air from the tube furnace. From the beginning of the temperature rise to the completion of sintering The furnace was cooled until the sample was taken out, and argon gas was introduced as a protective gas throughout the process. The purity of the argon gas was 99.9%. The starting temperature was room temperature. The heating rate was 5°C/min. Heating to 660°C, holding for 30 minutes, and then followed by The furnace was cooled and the composite material was taken out after cooling to room temperature.

Load 145kg of scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1550°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the target composition, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust the steel. When the composition of the liquid steel is qualified and the temperature reaches 1560~1570°C, after two slag removals, the temperature is kept for 10 minutes. When the temperature of the molten steel drops to 1530~1550°C, let it stand for 1 minute. Then pour the molten steel into a control ingot. After air cooling to room temperature, demold.

Load 145kg of scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1560°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the same target composition as in step 4, 0.1kg of TiO ₂ nanoparticle composite material is added into the molten steel, stir for 6 minutes and then add ferrosilicon, ferromanganese and ferrovanadium as appropriate to adjust the composition of the molten steel. When the composition is qualified and the temperature reaches 1560~1570°C, after two slag removals, the liquid steel is kept warm for 10 minutes. Reduce the temperature to 1530~1550℃, let it stand for 1 minute, pour the molten steel into a test steel ingot, air-cool to room temperature and then demould.

After the above two steel ingots are forged into a certain shape according to the same process, they are heated in a heating furnace and rolled into steel bar samples. The samples are placed on a tensile testing machine for mechanical testing to compare the effects of TiO ₂ nanoparticles on the mechanical properties of the steel bars. .

The actual composition control of the test steel bars is shown in Table 1.

Table 1 Test steel bar composition control

The actual mechanical properties of the test steel bars (Φ20mm steel bars) are shown in Table 2.

Table 2 Mechanical properties of test steel bars

The above results show that under the same chemical composition and hot rolling process conditions, the post-break elongation of the steel bars remains basically unchanged, the yield strength increases by an average of 27MPa, and the tensile strength increases by an average of 31MPa.

Example 2:

A method for preparing _TiO2 nanoparticle-reinforced hot-rolled steel bars, including the following steps:

Weigh a certain amount of TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder respectively. The particle size of the TiO ₂ nanoparticles is 20 nm and the purity is 99.9%; the particle size of the Al powder is 200 mesh and the purity is 99.9%; TiO ₂ nanoparticles, Al powder, and silicon-manganese alloy powder are mixed in a mass ratio of 1:7:15. The mixed powder is put into a cleaned and dried ball mill tank. The ball-to-material ratio is 10:1 , the volume of the grinding ball and sample should not be greater than two-thirds of the volume of the ball mill tank, and one-third of the volume of the ball mill tank should be used as the reserved grinding space.

Use a vacuum pump to evacuate the gas in the ball milling tank so that the ball milling tank is in a vacuum state; place the ball milling tank symmetrically into the planetary ball mill to mechanically alloy the sample. Set the speed of the ball mill to 200 rad/min, the ball milling time to 12 hours, run forward for 3 minutes, then pause for 2 minutes, then run in reverse for 3 minutes, repeat the cycle, and mix thoroughly until the end of the program.

After the ball mill stops running, wait for the ball mill tank to cool down, take out the mixed powder and pour it into the crucible, and put them together into the tube furnace for high-temperature sintering. Before sintering begins, remove the air from the tube furnace. From the beginning of the temperature rise to the completion of sintering The furnace was cooled until the sample was taken out, and argon gas was introduced as a protective gas throughout the process. The purity of the argon gas was 99.9%. The starting temperature was room temperature. The heating rate was 5°C/min. Heating to 680°C, holding for 30 minutes, and then followed by The furnace was cooled and the composite material was taken out after cooling to room temperature.

Load 145kg of scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1550°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the target composition, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust the steel. When the composition of the liquid steel is qualified and the temperature reaches 1560~1570°C, after two slag removals, the temperature is kept for 10 minutes. When the temperature of the molten steel drops to 1530~1550°C, let it stand for 1 minute. Then pour the molten steel into a control ingot. After air cooling to room temperature, demold.

Load 145kg scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1560°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the same target composition as in step 4, 0.12kg TiO ₂ nanoparticle composite material is added into the molten steel, stir for 8 minutes and then add ferrosilicon, ferromanganese and ferrovanadium as appropriate to adjust the composition of the molten steel. When the composition is qualified and the temperature reaches 1560~1570°C, after two slag removals, the liquid steel is kept warm for 10 minutes. The temperature is lowered to 1530~1550°C, and after standing for 1 minute, the molten steel is poured into a test steel ingot, which is air-cooled to room temperature and then demolded.

After the above two kinds of steel ingots are forged into a certain shape, they are heated in a heating furnace and rolled into steel bar samples. The samples are placed on a tensile testing machine for mechanical testing to compare the effects of TiO ₂ nanoparticles on the mechanical properties of the steel bars.

The actual composition control of the test steel bars is shown in Table 3.

Table 3 Test steel bar composition control

The actual mechanical properties of the test steel bars (Φ18mm steel bars) are shown in Table 4.

Table 4 Mechanical properties of test steel bars

The above results show that under the same chemical composition and hot rolling process conditions, the post-break elongation of the steel bars remains basically unchanged, the yield strength increases by an average of 26MPa, and the tensile strength increases by an average of 30MPa.

Example 3:

A method for preparing _TiO2 nanoparticle-reinforced hot-rolled steel bars, including the following steps:

Weigh a certain amount of TiO2 nanoparticles, Al powder, and silicon-manganese alloy powder respectively. The particle size of TiO2 nanoparticles is 20nm and the purity is 99.9%; the particle size of Al powder is 200 mesh and the purity is 99.9%; put the TiO2 nanoparticles into Particles, Al powder, and silicon-manganese alloy powder are mixed according to a mass ratio of 1:10:15. The mixed powder is put into a cleaned and dried ball mill tank. The ball-to-material ratio is 10:1, and the grinding ball is The volume of the sample should not be greater than two-thirds of the ball mill tank volume, and one-third of the ball mill tank volume should be used as the reserved grinding space.

Use a vacuum pump to evacuate the gas in the ball milling tank so that the ball milling tank is in a vacuum state; place the ball milling tank symmetrically into the planetary ball mill to mechanically alloy the sample. Set the speed of the ball mill to 200 rad/min, the ball milling time to 12 hours, run forward for 3 minutes, then pause for 2 minutes, then run in reverse for 3 minutes, repeat the cycle, and mix thoroughly until the end of the program.

After the ball mill stops running, wait for the ball mill tank to cool down, take out the mixed powder and pour it into the crucible, and put them together into the tube furnace for high-temperature sintering. Before sintering begins, remove the air from the tube furnace. From the beginning of the temperature rise to the completion of sintering The furnace was cooled until the sample was taken out, and argon gas was introduced as a protective gas throughout the process. The purity of the argon gas was 99.9%. The starting temperature was room temperature. The heating rate was 5°C/min. Heating to 660°C, holding for 30 minutes, and then followed by The furnace was cooled and the composite material was taken out after cooling to room temperature.

Load 145kg of scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1550°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the target composition, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust the steel. When the composition of the liquid steel is qualified and the temperature reaches 1560~1570°C, after two slag removals, the temperature is kept for 10 minutes. When the temperature of the molten steel drops to 1530~1550°C, let it stand for 1 minute. Then pour the molten steel into a control ingot. After air cooling to room temperature, demold.

Put 145kg scrap steel bars into a 150kg experimental medium frequency induction furnace for smelting. When the temperature rises to above 1560°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the same target composition as in step 4, 0.08kg TiO ₂ nanoparticle composite material is added into the molten steel, stir for 10 minutes and then add ferrosilicon, ferromanganese and ferrovanadium as appropriate to adjust the composition of the molten steel. When the composition is qualified and the temperature reaches 1560~1570°C, after two slag removals, the liquid steel is kept warm for 10 minutes. Reduce the temperature to 1530~1550℃, let it stand for 1 minute, pour the molten steel into a test steel ingot, air-cool to room temperature and then demould.

After the above two kinds of steel ingots are forged into a certain shape, they are heated in a heating furnace and rolled into steel bar samples. The samples are placed on a tensile testing machine for mechanical testing to compare the effects of TiO ₂ nanoparticles on the mechanical properties of the steel bars.

The actual composition control of the test steel bars is shown in Table 5.

Table 5 Actual composition control of test steel bars

The actual mechanical properties of the test steel bars (Φ16mm steel bars) are shown in Table 6.

Table 6 Actual mechanical properties of test steel

The above results show that under the same chemical composition and hot rolling process conditions, the post-break elongation of the steel bars remains basically unchanged, the yield strength increases by an average of 21MPa, and the tensile strength increases by an average of 31MPa.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can, within the technical scope disclosed in the present invention, implement the technical solutions of the present invention. Equivalent substitutions or changes of the inventive concept thereof shall be included in the protection scope of the present invention.

Claims (1)

1. A method for preparing TiO ₂ nanoparticle-reinforced hot-rolled steel bars, which is characterized in that it includes the following steps: Step 1: Weigh the _TiO2 nanoparticles, Al powder, and silicon-manganese alloy powder respectively, and mix the _TiO2 nanoparticles, Al powder, and silicon-manganese alloy powder in a mass ratio of 1:2~20:5~30. The mixed powder is put into the ball mill tank. The ball-to-material ratio is 5~15:1. The total volume of the grinding ball and sample is no more than two-thirds of the ball mill tank volume. One-third of the ball mill tank volume is reserved. Grinding space; among them, the TiO2 nanoparticles have a particle size of 20~50 nm and a purity of 99.9%; the Al powder has a particle size of 200 mesh and a purity of 99.9%; the silicon-manganese alloy powder is a micron-sized powder with a particle size less than 100 μm ; The composition control ranges of the hot-rolled steel bars are: C is 0.22-0.25, Si is 0.50-0.60, Mn is 1.30-1.40, V is 0.01-0.02, P≤0.04, S≤0.04; Step 2: Use a vacuum pump to evacuate the gas in the ball mill tank so that the inside of the ball mill tank is in a vacuum state; place the ball mill tank symmetrically into the planetary ball mill to mechanically mix the sample; set the speed of the ball mill to 150~200 r/ min, the ball milling time is 6 to 12 hours, run forward for 3 minutes, pause for 2 minutes, then run reversely for 3 minutes, repeat the cycle, and mix thoroughly until the end of the program; Step 3: After the ball mill stops running, wait for the ball mill tank to cool down, take out the mixed powder and pour it into the crucible, and then perform high-temperature sintering in the tube furnace. Before the sintering starts, remove the air in the tube furnace. After the sintering is completed, the furnace is cooled until the sample is taken out; the crucible used is an alumina crucible, and the purity of the argon gas used is 99.9%; argon gas is introduced throughout the process as a protective gas, the starting temperature is room temperature, and the heating rate is 5 ℃/min, heat to 640~700℃, keep warm for 10~30 min, then cool in the furnace, take out the composite material after cooling to room temperature; Step 4: Load the scrap steel bars into the experimental medium frequency induction furnace for smelting. When the temperature rises to above 1550°C and the scrap steel is completely melted, samples are taken for spectral composition analysis. According to the target composition, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust. For the composition of molten steel, when the composition is qualified and the temperature reaches 1560~1570°C, after two slag removals, the temperature is kept for 10 minutes. When the temperature of the molten steel drops to 1530~1550°C, let it stand for 1 minute and pour the molten steel into a control sample. steel ingot; Step 5: Put the scrap steel bars into the experimental medium frequency induction furnace for smelting. When the temperature rises to above 1560°C and the scrap steel is completely melted, samples are taken for spectral component analysis. According to the same target components as in step 4, the prepared TiO ₂ nanoparticles are composited. The materials are added to the molten steel. The prepared TiO2 nanoparticle composite material accounts for 0.01~0.15% of the total weight of the molten steel. After stirring for 5~10 minutes, ferrosilicon, ferromanganese and ferrovanadium are added as appropriate to adjust the composition of the molten steel. When the ingredients When it is qualified and the temperature reaches 1560~1570℃, after two times of slag removal, keep the temperature for 10 minutes. When the temperature of the molten steel drops to 1530~1550℃, let it stand for 1 minute and pour the molten steel into a test steel ingot; Step 6: Air-cool the control sample steel ingot and test sample steel ingot to room temperature, demold, and then cast them; after forging and forming, put them into a heating furnace for heating, roll them into steel bar samples, conduct mechanical testing on the samples, and compare TiO ₂ nanometers Effect of particles on mechanical properties of steel bars.