CN116855844A - Preparation method of Q345B alloy material with low porosity and high strength - Google Patents
Preparation method of Q345B alloy material with low porosity and high strength Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 15
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- 238000005096 rolling process Methods 0.000 claims abstract description 149
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- 239000000725 suspension Substances 0.000 claims description 14
- 229910052786 argon Inorganic materials 0.000 claims description 13
- 229910052748 manganese Inorganic materials 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 229910052727 yttrium Inorganic materials 0.000 claims description 12
- 229910052758 niobium Inorganic materials 0.000 claims description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims description 10
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- 238000005272 metallurgy Methods 0.000 abstract description 2
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- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
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- 229910011208 Ti—N Inorganic materials 0.000 description 1
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Classifications
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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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
-
- 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
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to the technical field of metallurgy, in particular to a preparation method of a Q345B alloy material with low porosity and high strength. Firstly smelting, nitrogen blowing process, homogenizing, continuous casting and forming to obtain a Q345B alloy ingot with specification, heating, rolling and cooling to obtain a Q345B alloy semi-finished product, and finally quenching and heat treatment to obtain the Q345B alloy, wherein the raw materials comprise 0.05-0.1% of C, 0.22-0.42% of Si, 0.8-1.5% of Mn, 0.15-0.25% of Ti, 0.001-0.002% of Ca, 0.01-0.02% of Nb, 0.02-0.06% of REE, less than or equal to 0.02% of P and less than or equal to 0.005% of S. Compared with the traditional process, the preparation method of the Q345B alloy material with low porosity and high strength improves the tensile strength and the yield strength performance of the Q345B alloy material, has the advantages of being outstanding, and is suitable for industrial popularization.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a preparation method of a Q345B alloy material with low porosity and high strength.
Background
The low-alloy high-strength steel Q345B is widely applied to the engineering fields of ships, bridges, engineering mechanical parts and the like because of good comprehensive properties such as strength, toughness and the like and easy welding and forming. Along with the development of smelting alloying and steel rolling processes, the alloy strengthening and cooling control process is commonly used for producing Q345B in the same industry at home and abroad. However, the existing rolling process cannot improve the comprehensive performance of the low alloy high strength Q345B in an unlimited amount, and the comprehensive performance of the low alloy high strength Q345B can only be limited in a certain range. The comprehensive performance of Q345B can be improved by adopting the principle of alloy smelting reinforcement, but the alloy cost is high, and the recovery and utilization rate of scrap steel is low.
At present, two steel types of conventional Q345B/C (GB/T1591-2008 low-alloy high-strength structural steel are used for manufacturing round pipes, square pipes or processing the round pipes and square pipes into various engineering structural members after flattening, and the main processing mode is welding), the smelting chemical components are designed to adopt high manganese components, the manganese content is generally about 1.3%, and the yield strength of the steel reaches more than 345MPa and the tensile strength reaches 470-630 MPa through solid solution strengthening of manganese. The defects are that a) the band-shaped structure is serious (grade 3.0), the carbon equivalent is high (about 0.4 percent), the subsequent welding performance is affected, and the bending and flattening test is extremely easy to crack; b) The cost is high, and the Mn content is high, so that the addition amount of the steelmaking alloy is large, and meanwhile, the steelmaking alloy needs to pass through an LF furnace, so that the alloy and working procedure cost is seriously high; c) The corrosion of the revolving furnace refractory is serious, the tapping temperature is required to be higher than 1680 ℃ in order to ensure the full melting of the alloy and the temperature drop in the tapping process, and the corrosion of the revolving furnace refractory is increased due to the overhigh tapping temperature, so that the service life of the revolving furnace is greatly influenced.
Abnormal growth of grains in a metal material can cause great changes in the properties of the bulk material, such as yield strength, fracture toughness, brittleness resistance, and magnetic properties, and the effect of grain boundary phase transformation on abnormal grain growth behavior is of particular importance in material processing. Grain growth is essentially a process of displacement of grain boundaries. In general, the growth of such grains is gradually and slowly performed, which is called normal growth. However, when certain factors (e.g., fine impurity particles, deformed texture, etc.) prevent the crystal grains from growing normally.
Through the prior art and document searching, the patent document (CN 112030058B) discloses a method for producing Ti microalloyed Q345B alloy seeds and Q345B alloy seeds by TMCP technology, wherein the method comprises the following steps of melting molten iron by a high-temperature furnace, preprocessing molten iron, smelting by a converter, LF refining, RH vacuum processing, continuous casting of sheet billet, casting blank slow cooling, heating by a heating furnace, rolling by a heavy and medium plate mill, quick cooling, inspection, finishing and warehousing; wherein, in the molten iron of the high-temperature furnace, the sheet billet is melted into high-temperature molten iron by the high-temperature smelting furnace, the temperature of the high-temperature molten iron is 1255 ℃, and [ S ] is 0.01%; in converter smelting, top-bottom combined blowing operation and argon blowing process are adopted to ensure that [ C ] at the end point of the converter is less than or equal to 0.07 percent and [ P ] at the end point of the converter is less than or equal to 0.025 percent; in the continuous casting of the sheet billet, the superheat degree of the ladle molten iron is controlled at 25-45 ℃, and the pulling speed is controlled at 3.7-4.0m/min.
Patent document (CN 111440982 a) discloses a Q345B alloy plate and a production method thereof, which belong to the field of structural steel. The chemical components of the Q345B alloy plate provided by the method are as follows, the mass percentage of C is 0.16-0.18%; si 0.22-0.32%; mn 0.3-0.4%; 0.012-0.015% of Ti; p is less than or equal to 0.016; s is less than or equal to 0.005%; 0.0012 to 0.0027 percent of Ca; als 0.015-0.030%; the balance of iron and unavoidable impurities.
The above method optimizes the properties of the Q345B alloy by adjusting the forming process of the Q345B alloy. In theory, the method has an improvement effect on the tensile strength and the yield strength of the Q345B alloy, but the improvement on the performance of the Q345B alloy is not obvious due to simple material adjustment through the simple process improvement; in the process from the smelting of the Q345B alloy to the forming, internal defects of the material can be reduced to a certain extent by controlling the forming temperature and cooling mode, and the growth of crystal grains is inhibited, but the effect of inhibiting the growth of the crystal grains of the Q345B alloy is not very outstanding, and the improvement of the uniformity of the material is not obvious. Aiming at the tensile strength and yield strength performance of the Q345B alloy, the method is used for obtaining the Q345B alloy with high tensile strength and yield strength through double improvements of the preparation process and components, and is suitable for large-scale industrial popularization.
Disclosure of Invention
The invention aims to provide a preparation method of a Q345B alloy material with low porosity and high strength, which has obvious gain effects on performances such as tensile strength, yield strength and the like of the Q345B alloy material under the improvement of related processes and raw materials.
The method has the key point 1 of ensuring that all raw materials are uniformly distributed in the material as much as possible, and reducing the generation of segregation and agglomeration as much as possible; 2. the influence of the size of the crystal grains on the material is obvious, the growth of the crystal grains in the material needs to be restrained by the related process and raw materials, and the reduction of the mechanical property of the material caused by the uneven growth of the crystal grains is reduced.
The invention relates to a preparation method of a Q345B alloy material with low porosity and high strength, which comprises the following specific embodiments:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.05-0.1% of C, 0.22-0.42% of Si, 0.8-1.5% of Mn, 0.15-0.25% of Ti, 0.001-0.002% of Ca, 0.01-0.02% of Nb, 0.05-0.08% of Mn, 0.02-0.06% of REE, less than or equal to 0.02% of P, less than or equal to 0.005% of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1250-1300 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1300-1400 ℃ for 20-40min under the vacuum degree of 1-50Pa before treatment;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 20-60um, and performing primary magnetic suspension smelting on the granulated powder to obtain homogenized molten steel solution, wherein the temperature is 1250-1300 ℃;
continuous casting, namely controlling the temperature to be 1275-1325 ℃ during continuous casting, and controlling the thickness of a continuous casting Q345B alloy ingot to be 10-20mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the semi-finished product of the Q345B alloy by a stepping heating furnace at 1200-1220 ℃ for 40-70min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 3-4 times in the first stage, the initial rolling temperature is 1100-1150 ℃, the final rolling temperature in the first stage is 1000-1050 ℃, and the single-pass rolling reduction rate in the first stage high-temperature extension rolling is 10-15%; the initial rolling temperature of the steel plate in the second stage is 950-980 ℃, and the final rolling temperature in the second stage is 780-820 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 800-850 ℃, the final cooling temperature is 650-700 ℃, and the cooling rate is controlled to be 30-50 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1000-1050 ℃ and preserving heat for 30-50min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 400-500 ℃ for heat preservation, wherein the heat preservation time is 60-100min, and then the Q345B alloy is obtained.
The beneficial effects are that:
(1) REE is added in the method designed by the invention, rare earth elements can obviously improve the casting blank segregation phenomenon of the structural steel Q345B, after rare earth elements are added in the Q345B alloy, molten steel can be effectively purified, grains are refined, in addition, the rare earth elements can obviously improve the plate belt core tissue segregation zone, so that the ferrite content in the Q345B alloy is increased;
(2) According to the method, the Ti content is improved, and after nitrogen blowing treatment, a large amount of nano-scale cubic Ti (C, N) precipitates are precipitated in a material grain boundary, so that the method has a good effect of inhibiting the growth of grains;
(3) The method of spray granulation and magnetic suspension smelting is designed to improve the uniformity of the material, the solid solution degree of the material can be improved after primary granulation, and the uniformity of the material solution is improved compared with the common smelting method after magnetic suspension smelting;
(4) The method of the invention adopts a quenching mode to carry out post-treatment on the steel piece after rolling, reduces uneven heating of the material, improves segregation products in material grains, has a gain effect on inhibiting the growth of the material grains, and can eliminate internal stress in the material after heat treatment so as to avoid the generation of inter-crystal cracks of the material.
Drawings
FIG. 1 is a preparation flow chart of a preparation method of a Q345B alloy material with low porosity and high strength.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a preparation method of a Q345B alloy material with low porosity and high strength, which mainly comprises the following steps:
s1, preparing a Q345B alloy raw material C, si, mn, ti, ca, nb, REE and the balance of Fe according to mass proportion;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
as an example, the following description of several specific examples of the preparation method of the Q345B alloy material with low porosity and high strength are given in the examples 1, 2, 3 and 1-7.
Example 1:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.05% of C, 0.22% of Si, 0.8% of Mn, 0.15% of Ti, 0.001% of Ca, 0.01% of Nb, 0.02% of REE, less than or equal to 0.02% of P, less than or equal to 0.005% of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1250 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1300 ℃ with the vacuum degree of 10Pa before treatment and the treatment time of 20min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein argon is used as the atmosphere during granulation, the granularity of the obtained granulated powder is 20um, and performing primary magnetic suspension smelting on the granulated powder to obtain homogenized molten steel solution, wherein the temperature is 1250 ℃;
continuous casting, wherein the control temperature is 1275 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 10mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely adopting a step heating furnace, wherein the heating temperature of the Q345B alloy semi-finished product is 1200 ℃, and the single-point effective heating time is 40min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 3 times in the first stage, the initial rolling temperature is 1100 ℃, the final rolling temperature in the first stage is 1000 ℃, and the single pass rolling reduction rate in the first stage high-temperature extension rolling is 10%; the initial rolling temperature of the steel plate in the second stage is 950 ℃, and the final rolling temperature in the second stage is 780 ℃;
cooling, namely cooling after rolling, wherein the cooling temperature is 800 ℃, the final cooling temperature is 650 ℃, and the cooling rate is controlled at 30 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1000 ℃ and preserving heat for 30min, and then rapidly cooling the rolled alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 400 ℃ for heat preservation, wherein the heat preservation time is 60 minutes, and then the Q345B alloy is obtained.
Example 2:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.1% of C, 0.42% of Si, 1.5% of Mn, 0.25% of Ti, 0.002% of Ca, 0.02% of Nb, 0.06% of REE, less than or equal to 0.02% of P, less than or equal to 0.005% of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1300 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1400 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 40min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein argon is used as the atmosphere during granulation, the granularity of the obtained granulated powder is 60 mu m, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1300 ℃;
continuous casting, wherein the control temperature is 1325 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 20mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the semi-finished product of the Q345B alloy by a stepping heating furnace at 1220 ℃ for 70min at a single-point effective heating time;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1150 ℃, the final rolling temperature is 1050 ℃, and the single pass rolling reduction rate is 15% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 980 ℃, and the final rolling temperature in the second stage is 820 ℃;
cooling, namely cooling after rolling is finished, wherein the opening cooling temperature is 850 ℃, the final cooling temperature is 700 ℃, and the cooling rate is controlled to be 50 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1050 ℃ and preserving heat for 50min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 500 ℃ for heat preservation, wherein the heat preservation time is 100min, and then the Q345B alloy is obtained.
Example 3:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
Comparative example 1:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.014 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
Comparative example 2:
s1, preparing a Q345B alloy raw material C, si, mn, ti, ca and Nb according to mass proportion, wherein the balance is Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
Comparative example 3:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
Comparative example 4:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling to obtain Q345B alloy after rolling, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
comparative example 5:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly carrying out oil cooling to room temperature to obtain the Q345B alloy.
Comparative example 6:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, quenching and heat-treating the Q345B alloy ingot subjected to continuous casting in the S2 to obtain a Q345B alloy semi-finished product;
quenching treatment, namely heating the Q345B alloy ingot to 1030 ℃ after continuous casting, preserving heat for 40min, and rapidly cooling oil to room temperature;
and (3) heat treatment, namely heating the quenched Q345B alloy ingot to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then obtaining a Q345B alloy semi-finished product.
S4, heating, rolling and cooling the semi-finished product of the Q345B alloy in the S3 to obtain a Q345B alloy;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
and cooling, namely cooling after rolling to obtain the Q345B alloy, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s.
Comparative example 7:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:2:4;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 200min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
Comparative example 8:
s1, preparing alloy raw materials C, si, mn, ti, ca, nb and REE of Q345B in mass proportion, and the balance being Fe:
0.08 percent of C, 0.32 percent of Si, 1.2 percent of Mn, 0.2 percent of Ti, 0.002 percent of Ca, 0.015 percent of Nb, 0.05 percent of REE, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, and the balance of Fe and unavoidable impurities;
wherein REE is a mixture of La, ce and Y, and the mass ratio is 4:1:1;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
smelting, namely smelting C, si, mn, ti, ca, nb, REE and Fe to obtain molten steel, wherein the smelting temperature is 1280 ℃;
nitrogen blowing process, in which molten steel is subjected to nitrogen blowing treatment at 1350 ℃, the vacuum degree before treatment is 10Pa, and the treatment time is 30min;
homogenizing, namely performing primary spray granulation on the molten steel subjected to nitrogen blowing treatment, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 30um, and performing primary magnetic suspension smelting on the granulated powder to obtain a homogenized molten steel solution, wherein the temperature is 1270 ℃;
continuous casting, wherein the control temperature is 1300 ℃ during continuous casting, and the thickness of the continuous casting Q345B alloy ingot is 15mm;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
heating, namely heating the Q345B alloy semi-finished product by a stepping heating furnace at the temperature of 1210 ℃ for 60min;
the rolling is carried out after the Q345B alloy semi-finished product is heated, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 4 times in the first stage, the initial rolling temperature is 1120 ℃, the final rolling temperature is 1030 ℃, and the single pass rolling reduction rate is 12% in the first stage high-temperature extension rolling; the initial rolling temperature of the steel plate in the second stage is 960 ℃, and the final rolling temperature in the second stage is 800 ℃;
cooling, namely cooling after rolling is finished, wherein the cooling temperature is 830 ℃, the final cooling temperature is 670 ℃, and the cooling rate is controlled at 40 ℃/s;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain a Q345B alloy;
quenching, namely heating the rolled Q345B alloy semi-finished product to 1030 ℃ and preserving heat for 40min, and then rapidly cooling the rolled Q345B alloy semi-finished product to room temperature by oil;
and (3) heat treatment, namely heating the quenched Q345B alloy semi-finished product to 450 ℃ for heat preservation, wherein the heat preservation time is 80 minutes, and then the Q345B alloy is obtained.
TABLE 1
Tensile strength test:
the tensile test is a test method for measuring the material characteristics under the condition of bearing axial tensile load, in the tensile test, the maximum tensile stress born by a sample until fracture is the tensile strength, and the tensile test method of the metal material can refer to national standard GB/T228.1-2010;
yield strength test:
the yield strength can be expressed by the following formula:
wherein a represents the yield strength of a simply supported beam or cantilever beam, in units of: kJ/m 2 (kilojoules per square meter); a represents the impact amount absorbed by the sample and is a unit J; b represents the width of the sample in mm; d representsThe thickness of the sample, in mm, is the thickness after subtracting the notch if notched impact.
Grain size test:
calculating the grain size grade number:
firstly, calculating the number of crystal grains in a sample, wherein the number of crystal grains is = a part of crystal grains which are 0.5 times of the number of complete crystal grains, and the grain boundaries of the complete crystal grains are observable;
secondly, calculating an actual area, wherein the actual area=picture length/magnification ratio×width/magnification ratio;
according to a calculation formula in an ASTM standard, N=2 (N-1), wherein N refers to the number of grains per square inch under 100 times magnification, N refers to the number of grain grades, the value of N can be obtained after unit conversion, and finally the number of grain grades N can be calculated;
bending properties:
the sample is placed on two supporting points with a certain distance, downward load is applied to the sample at the middle point of the two supporting points, three-point bending occurs when the 3 contact points of the sample form equal two moments, the sample is broken at the middle point, and the metal material bending test method can refer to national standard GB/T232-2010.
Comparative examples 1 to 7 in Table 1 are obtained by adjusting experimental processes or experimental parameters within experimental parameters of example 3, and comparing experimental data of examples 1, 2 and 3 and comparative example 1 in Table 1, it can be found that after Ti content in raw materials is reduced, tensile strength, yield strength and grain size are reduced, bending test is qualified, and it is demonstrated that Ti-N compounds formed by Ti during subsequent nitrogen blowing treatment are beneficial to inhibiting grain growth of materials and improving performance of materials;
as can be found from the comparison of the experimental data of examples 1, 2 and 3 and comparative example 2 in Table 1, after REE in the raw materials is removed, the tensile strength, the yield strength and the grain size are reduced, and the bending test is qualified, which proves that rare earth is beneficial to the influence of the materials, can improve the casting blank segregation phenomenon of structural steel Q345B, and can effectively purify molten steel and refine grains;
as can be seen from comparison of experimental data of examples 1, 2 and 3 and comparative example 3 in Table 1, after no homogenization treatment is performed in comparative example 3, tensile strength, yield strength and grain size are reduced, and a bending test is qualified, which shows that segregation phenomena with different degrees exist in the material after no homogenization treatment, the segregation can increase the non-uniformity of grains of the material and reduce the performance of the material;
as can be seen from comparison of experimental data of examples 1, 2 and 3 and comparative example 4 in Table 1, after no quenching and heat treatment in comparative example 4, tensile strength, yield strength and grain size are reduced, and bending test is qualified, which indicates that the quenching and heat treatment is beneficial to grain refinement of materials and performance improvement of the materials;
as can be seen from comparison of experimental data of examples 1, 2 and 3 and comparative example 5 in table 1, in comparative example 5, after the heat treatment is not performed on the sample, the tensile strength and the yield strength are reduced, the grain size is not obviously reduced, the bending test is disqualified, the heat treatment is favorable for releasing the internal stress of the material, after the heat treatment is not performed, the grains of the material cannot grow up due to the heat treatment, but the internal stress cannot be released, so that the material performance is obviously reduced;
as can be seen from comparison of experimental data of examples 1, 2, 3 and comparative example 6 in table 1, in comparative example 6, after the sequence of quenching+heat treatment and rolling operation is exchanged, the tensile strength, yield strength and grain size are all obviously reduced, and the bending test is qualified, which shows that when the material is quenched in advance, the difference of the material thickness causes the difference of internal temperature and external temperature of the material, the uneven grain growth between the interior and the exterior is caused, the internal stress is aggravated, and finally the material performance is reduced;
from comparison of the experimental data of examples 1, 2 and 3 and comparative example 7 in table 1, it can be found that the tensile strength, yield strength and grain size are reduced after the heating time is increased in comparative example 7, and the bending test is qualified, which indicates that the grain size of the material is increased and the performance of the material is reduced after the heat preservation time is increased at high temperature;
from comparison of experimental data of examples 1, 2 and 3 and comparative example 8 in table 1, it can be found that, after increasing the proportion of lanthanum in comparative example 8, tensile strength, yield strength and grain size are reduced, and the bending test is qualified, which shows that lanthanum is beneficial to the improvement of material performance in a reasonable range, but when the content of lanthanum is too high, excessive uneven distribution of reactive inclusions is formed in grain boundaries, resulting in the reduction of material performance.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (13)
1. The preparation method of the Q345B alloy material with low porosity and high strength is characterized by comprising the following steps:
s1, preparing a Q345B alloy raw material C, si, mn, ti, ca, nb, REE and the balance of Fe according to mass proportion;
s2, smelting the S1 raw material, carrying out nitrogen blowing process, homogenizing, and carrying out continuous casting molding to obtain an alloy ingot with the specification of Q345B;
s3, heating, rolling and cooling the Q345B alloy ingot in the S2 to obtain a Q345B alloy semi-finished product;
s4, quenching and heat-treating the rolled Q345B alloy semi-finished product in the S3 to obtain the Q345B alloy.
2. The preparation method according to claim 1, wherein in the step S1, the mass ratio of the alloy raw materials of Q345B is 0.05-0.1% C, 0.22-0.42% Si, 0.8-1.5% Mn, 0.15-0.25% Ti, 0.001-0.002% Ca, 0.01-0.02% Nb, 0.02-0.06% REE, less than or equal to 0.02% P, less than or equal to 0.005% S, and the balance Fe and unavoidable impurities.
3. The method according to claim 1, wherein in the step S1, REE is a mixture of La, ce and Y in a mass ratio of 4:2:4.
4. The method according to claim 1, wherein in step S2, the melting temperature of molten steel obtained by melting the raw material S1 is 1250 to 1300 ℃.
5. The method according to claim 1, wherein the nitrogen blowing process is performed on the molten steel in the step S2, wherein the treatment temperature is 1300-1400 ℃, the vacuum degree before the treatment is 1-50Pa, and the treatment time is 20-40min.
6. The method according to claim 1, wherein in the step S2, the molten steel is homogenized, which comprises the steps of spraying and granulating the molten steel after nitrogen blowing treatment once, wherein the atmosphere is argon during granulation, the granularity of the obtained granulated powder is 20-60um, and performing magnetic suspension smelting on the granulated powder once to obtain a homogenized molten steel solution, wherein the temperature is 1250-1300 ℃.
7. The method according to claim 1, wherein the step of continuously casting the molten steel in S2 in step S2 comprises controlling the temperature to 1275-1325 ℃ and the thickness of the Q345B alloy ingot to 10-20mm.
8. The method according to claim 1, wherein in the step S3, the step of heating the Q345B alloy ingot in the step S3 comprises the steps of adopting a step heating furnace, heating the Q345B alloy ingot at 1200-1220 ℃ for 40-70min.
9. The method according to claim 1, wherein in the step S3, the Q345B alloy ingot in the step S3 is rolled, the initial rolling thickness is the thickness of the continuous casting billet in the first stage, the rolling is carried out for 3-4 times in the first stage, the initial rolling temperature is 1100-1150 ℃, the final rolling temperature in the first stage is 1000-1050 ℃, and the single pass rolling reduction rate in the high-temperature extension rolling in the first stage is 10-15%; the initial rolling temperature of the second stage steel plate is 950-980 ℃, and the final rolling temperature of the second stage is 780-820 ℃.
10. The method according to claim 1, wherein in the step S3, the step of cooling the rolled Q345B alloy ingot comprises the steps of cooling at 800-850 ℃, final cooling at 650-700 ℃ and cooling at a rate of 30-50 ℃/S.
11. The method according to claim 1, wherein the step of quenching the cooled semi-finished product of the Q345B alloy in the step S4 comprises heating the rolled semi-finished product of the Q345B alloy to 1000-1050 ℃ and preserving the temperature for 30-50min, and then rapidly cooling the product to room temperature with oil.
12. The preparation method according to claim 1, wherein in the step S4, the step of heat-treating the quenched semi-finished product of the Q345B alloy comprises the steps of heating the quenched semi-finished product of the Q345B alloy to 400-500 ℃ for heat preservation for 60-100min to obtain the Q345B alloy.
13. The method according to claim 1, wherein the rolling operation in step S3 is performed before the quenching and heat treatment steps in step S4.
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