CN112195305A - Method for refining grain size of sulfur-containing non-quenched and tempered steel - Google Patents
Method for refining grain size of sulfur-containing non-quenched and tempered steel Download PDFInfo
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- CN112195305A CN112195305A CN202010978415.1A CN202010978415A CN112195305A CN 112195305 A CN112195305 A CN 112195305A CN 202010978415 A CN202010978415 A CN 202010978415A CN 112195305 A CN112195305 A CN 112195305A
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- 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
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
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- 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
- C21C7/0006—Adding metallic additives
Abstract
The invention discloses a method for refining the grain size of sulfur-containing non-quenched and tempered steel, which is characterized in that after VD or RH refining process finishes adjusting other components, a certain content of Mg element is added, MnS inclusion is modified by the Mg element to form fine and dispersedly distributed manganese sulfide and magnesium aluminum oxide composite inclusion which is used as a ferrite nucleation core to induce equiaxed ferrite to refine grains. Test data show that the method can effectively refine the crystal grains of the sulfur-containing non-quenched and tempered steel to obtain the fine-grain non-quenched and tempered steel, has excellent performance and low cost, is easy to realize industrial production, and improves the grain size control level of the sulfur-containing non-quenched and tempered steel.
Description
Technical Field
The invention relates to a method for refining the grain size of sulfur-containing non-quenched and tempered steel.
Background
The non-quenched and tempered steel is high-quality structural steel which achieves mechanical properties of the quenched and tempered steel by means of micro-alloying, controlled rolling, controlled cooling and other strong toughening methods and without quenching and tempering heat treatment. The non-quenched and tempered steel does not need to be subjected to heat treatment and straightening in the production process, so that the process operation is simplified, the product yield is improved, the energy consumption is reduced, and the pollution to the environment is reduced, so that the non-quenched and tempered steel is called green steel. The non-quenched and tempered steel is mainly used for parts such as connecting rods and crankshafts of automobile engines, and is also successfully applied to products such as N80 petroleum casings and seamless steel tubes, and the application range relates to the fields of bridges, machinery, automobiles and the like.
The research and development of microalloy non-quenched and tempered steel reach a certain level, but the production of high-quality non-quenched and tempered steel is still difficult in the aspects of steel grain size control, inclusion control and the like, and higher requirements are difficult to meet.
The Chinese patent with application publication number CN110791708A discloses a non-quenched and tempered steel for automobile parts and a production process thereof, wherein trace elements of Ni, Nb, Ti, N and the like are added to refine grains and improve the strength and toughness of the material, and the cooling-controlled and rolling-controlled technology is used to refine the grains and improve the strength, so that the comprehensive performance of the material is greatly improved.
The Chinese invention patent with application publication number CN111206191A discloses Ti-V composite microalloyed superfine bainite non-quenched and tempered steel and a forging and cooling control process and a production process thereof, and compared with common bainite non-quenched and tempered steel, the steel is obviously refined in bainite tissue, similar to a tempered sorbite tissue is obtained, and the toughness is greatly improved by the aid of high Ti content alloying design and V-N microalloying.
The Chinese patent with application publication No. CN107587076A discloses a method for producing a large-diameter ferrite + pearlite non-quenched and tempered steel bar for a crankshaft, which gives clear requirements on a continuous casting billet heating process parameter, a hot rolling deformation process parameter, a finish rolling temperature, a pre-eutectoid ferrite precipitation temperature interval cooling rate and a pit entering temperature. After the control method is adopted, the core structure of the rolled material is ferrite plus pearlite; the prior austenite grain size is not less than 6.0 grade, the ferrite proportion is not less than 25 percent, the banded structure is not more than 2.0 grade, the structure is uniform, and abnormal coarse grains are avoided.
In the prior art, the improvement of the steel structure and the performance is realized by adding micro alloy elements in the smelting process or adjusting the technological parameters during forging, but the non-quenched and tempered steel is obtained by adding micro alloy elements such as Nb, V, Ti and the like and controlling rolling and cooling and the like, and the quenching and tempering treatment is omitted. The technical means belongs to the conventional technology, and the requirements of high-quality non-quenched and tempered grain size and performance cannot be met at present.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects of the prior art, the invention provides a method for refining the grain size of sulfur-containing non-quenched and tempered steel, so that the grains are refined, and the quality and the performance of the non-quenched and tempered steel are improved.
The technical scheme is as follows: the method for refining the grain size of the sulfur-containing non-quenched and tempered steel comprises the following steps of: converter or electric furnace smelting, LF refining, VD or RH refining, and continuous casting; after the adjustment of other components in the VD refining or RH refining process is finished, controlling the active oxygen in the steel to be 5-15ppm, and adding magnesium element into the molten steel in the form of a magnesium-silicon cored wire to ensure that the mass percent of magnesium in the molten steel is 0.001-0.003%.
The added Mg element forms MgO-Al2O3Promoting the nucleation of ferrite, pinning crystal boundary, refining crystal grains and improving the quality and performance of non-quenched and tempered steel. MgO-Al2O3The inclusions are small in size, stable in components and dispersed in distribution in the high-temperature molten steel, and provide heterogeneous nucleation points for ferrite transformation. This is because MgO. Al2O3The Mg vacancy exists in the alloy, so that Mn element can be absorbed, poor Mn appears around the alloy, acicular ferrite nucleation is promoted, and the effect of refining grains is achieved. More Mg increases the cost of steel, so in order to guarantee the refining effect of the Mg on crystal grains and control the cost, the Mg content in the invention is 0.001-0.003%.
The thickness of the iron sheet of the magnesium-silicon cored wire is 0.45 +/-0.1 mm, and the weight of each meter is 390 g/m; the proportion of the core powder is as follows: mg: 8%, Si: 16 percent, and the balance of Fe and inevitable impurities. The feeding speed is 180 m/min.
After the core-spun yarn is fed, the carbonized rice hulls are thrown in for heat preservation, soft argon blowing (without blowing the liquid level to avoid oxygenation) is ensured for 15 minutes, and impurities in the steel are enabled to float sufficiently; and (5) carrying out ladle lifting after sampling and temperature measurement.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: the method for adding the magnesium element into the molten steel in the form of the magnesium-silicon cored wire is found out through experiments, not only overcomes the defects of difficult addition and high risk of the Mg element in the traditional process, but also can realize the refinement of the grain size of the sulfur-containing non-quenched and tempered steel at extremely low cost, and the process experiments prove that: on the basis of the conventional process, the invention can further refine the grain size of the sulfur-containing non-quenched and tempered steel and improve the control level of the grain size of the non-quenched and tempered steel, thereby improving the quality of the non-quenched and tempered steel and having higher economic value and practical value.
Drawings
FIG. 1 shows the grain size of a sample of example 1 of the present invention.
FIG. 2 shows the grain size of a sample of example 2 of the present invention.
FIG. 3 is a graph showing the grain size of a sample of example 3 of the present invention.
Fig. 4 is the grain size of the comparative example.
Detailed Description
The technical solution of the present invention is further explained below with reference to the examples and the accompanying drawings.
Example 1
Smelting in an electric furnace of 100 tons, and controlling the end point of the electric furnace: c: 0.10%, P: 0.0053% and the tapping temperature of 1639 ℃.
And adding 692kg of silicon-manganese alloy, 103kg of silicon-iron, 550kg of lime and 252kg of refining slag into the ladle in sequence after tapping for 1 minute and 30 seconds.
Blowing nitrogen in the LF furnace in the whole process, wherein the flow rate is 75.0L/min; 130kg of silicon carbide is used for deoxidizing the slag surface in the LF refining process, the element content is adjusted, sampling detection is carried out when the molten steel is taken out of an LF furnace, and the carbon element content is 0.705%, the silicon element content is 0.156%, the manganese content is 0.565%, the aluminum content is 0.004%, and the sulfur content is 0.0586%.
VD refining process, vacuum degree of 1.1mbar, high vacuum processing time of 12min, nitrogen as lifting gas in the whole process, and gas flow rate of 82.9L/min during vacuum maintaining.
Feeding a sulfur iron wire for 30 meters after the VD refining process finishes soft blowing, and adjusting the sulfur content to be 0.066%; after the adjustment of the sulfur content is finished, the 100 m magnesium-silicon core-spun yarn is fed by a yarn feeding machine, and the yarn feeding speed is 180 m/min.
After the core-spun yarn is fed, the carbonized rice hulls are thrown in for heat preservation, the sample is taken after static stirring for 15 minutes, and the suspension ladle is carried out after temperature measurement.
The smelting end point comprises the following components in percentage by mass: c: 0.70%, Si: 0.157%, Mn: 0.574%, P: 0.0117%, S: 0.065%, Al: 0.0038%, V: 0.0389%, Mg: 0.0011%, and the balance of Fe and inevitable impurities.
The continuous casting adopts 320-420 mm cross section pouring, improves the material compression ratio and reduces the macroscopic defect of the material, wherein the electromagnetic stirring current of the crystallizer is 450A-5, and the macroscopic defect level of the casting blank is reduced by adopting a 12mm large reduction mode under light reduction.
Example 2
Smelting in an electric furnace of 100 tons, and controlling the end point of the electric furnace: c: 0.083%, P: 0.0049 percent and the tapping temperature is 1642 ℃.
694kg of silicon-manganese alloy, 87kg of ferrosilicon, 550kg of lime and 254kg of refining slag are added into the ladle in sequence after tapping for 1 minute and 30 seconds.
Blowing nitrogen in the LF furnace in the whole process, wherein the flow rate is 75.0L/min; in the LF refining process, 70kg of silicon carbide is used for slag surface deoxidation, the element content components are adjusted, sampling detection is carried out when LF is obtained, and the mass ratio of C in molten steel is as follows: 0.689%, Si: 0.178%, Mn: 0.567%, Al: 0.005%, S: 0.0494 percent.
And a VD refining process, wherein the vacuum degree is 1.1mbar, the high vacuum treatment time is 12min, nitrogen is used as lifting gas in the VD refining process, and the gas flow is 71.2L/min when the vacuum is maintained.
After the VD refining process is finished and the soft blowing is finished, feeding a ferrosulfur wire for 100 meters, and adjusting the sulfur content to 0.0622%; after the adjustment of the sulfur content is finished, feeding 150 m magnesium-silicon core-spun yarns by using a yarn feeding machine, wherein the yarn feeding speed is 180 m/min.
After the core-spun yarn is fed, the carbonized rice hulls are thrown in for heat preservation, the sample is taken after static stirring for 18 minutes, and the suspension ladle is carried out after temperature measurement. The smelting end point comprises the following components in percentage by mass: c: 0.7059%, Si: 0.165%, Mn: 0.571%, P: 0.0108%, S: 0.0623%, Al: 0.0035%, V: 0.0378%, Mg: 0.0015%, the balance being Fe, and unavoidable impurities.
The continuous casting adopts 320-420 mm cross section pouring, improves the material compression ratio and reduces the macroscopic defect of the material, wherein the electromagnetic stirring current of the crystallizer is 450A-5, and the macroscopic defect level of the casting blank is reduced by adopting a 12mm large reduction mode under light reduction.
Example 3
Smelting in an electric furnace of 100 tons, and controlling the end point of the electric furnace: c: 0.071%, P: 0.0056% and the tapping temperature of 1635 ℃.
And adding 693kg of silicomanganese alloy, 91kg of ferrosilicon, 550kg of lime and 252kg of refining slag into the ladle in sequence after tapping for 1 minute and 30 seconds.
Blowing nitrogen in the LF furnace in the whole process, wherein the flow rate is 75.0L/min; in the LF refining process, 120kg of silicon carbide is used for slag surface deoxidation, the element content components are adjusted, sampling detection is carried out when LF is obtained, and the mass ratio of C in molten steel is as follows: 0.685%, Si: 0.182%, Mn: 0.546%, Alt: 0.0092%, S: 0.0611 percent.
VD refining process, vacuum degree of 1.3mbar, high vacuum processing time of 12min, RH or VD refining process using nitrogen as lifting gas, gas flow of 71.2L/min when vacuum is maintained.
Feeding a ferrosulfur wire for 120 m after VD refining treatment finishes soft blowing, and adjusting the sulfur content to be 0.069%; after the adjustment of the sulfur content is finished, 200 m of magnesium-silicon core-spun yarn is fed by a yarn feeding machine, and the yarn feeding speed is 180 m/min.
After the core-spun yarn is fed, the carbonized rice hulls are thrown in for heat preservation, the sample is taken after static stirring for 15 minutes, and the suspension ladle is carried out after temperature measurement.
The smelting end point comprises the following components in percentage by mass: c: 0.7206%, Si 0.171%, Mn 0.555%, P0.0075%, S0.069%, Al: 0.0036%, V: 0.0399%, Mg 0.0021%, and the balance Fe and inevitable impurities.
The continuous casting adopts 320-420 mm cross section pouring, improves the material compression ratio and reduces the macroscopic defect of the material, wherein the electromagnetic stirring current of the crystallizer is 450A-5, and the macroscopic defect level of the casting blank is reduced by adopting a 12mm large reduction mode under light reduction.
Comparative example
Smelting in an electric furnace of 100 tons, and controlling the end point of the electric furnace: c: 0.096%, P: 0.0044 percent and the tapping temperature of 1640 ℃.
613kg of silicon-manganese alloy, 91kg of ferrosilicon, 550kg of lime and 249kg of refining slag are added into a ladle in sequence after tapping for 1 minute and 30 seconds.
Blowing nitrogen in the LF furnace in the whole process, wherein the flow rate is 75.2L/min; in the LF refining process, 120kg of silicon carbide is used for slag surface deoxidation, the element content components are adjusted, sampling detection is carried out when LF is obtained, and the mass ratio of C in molten steel is as follows: 0.691%, Si: 0.151%, Mn: 0.555%, Al: 0.0072%, S: 0.0657%.
VD refining process, vacuum degree of 0.89mbar, high vacuum processing time of 12min, RH or VD using nitrogen gas as lifting gas in the whole course, and gas flow rate of 71.2L/min when vacuum is maintained.
Feeding a sulfur iron wire for 150 meters after VD refining finishes soft blowing, and adjusting the sulfur content to be 0.068%; after the adjustment of the sulfur content was completed, the stirring time was 10 minutes.
The smelting end point comprises the following components in percentage by mass: c: 0.7185%, Si: 0.203%, Mn: 0.559%, P: 0.0053%, S: 0.069%, Al: 0.0038%, V: 0.0385%, the balance being Fe and unavoidable impurities.
The continuous casting adopts 320-420 mm cross section pouring, improves the material compression ratio and reduces the macroscopic defect of the material, wherein the electromagnetic stirring current of the crystallizer is 450A-5, and the macroscopic defect level of the casting blank is reduced by adopting a 12mm large reduction mode under light reduction.
The contents of the elements of the examples 1, 2 and 3 and the comparative example are shown in the table below;
| element(s) | C | Si | Mn | P | S | Al | V | Mg |
| Example 1 | 0.70 | 0.157 | 0.574 | 0.0117 | 0.065 | 0.0038％ | 0.0389 | 0.0011 |
| Example 2 | 0.7059 | 0.165 | 0.571 | 0.0108 | 0.0623 | 0.0035 | 0.0378 | 0.0015 |
| Example 3 | 0.7206 | 0.171 | 0.555 | 0.0075 | 0.069 | 0.0036 | 0.0399 | 0.0021 |
| Comparative example | 0.7185 | 0.203 | 0.559 | 0.0053 | 0.069 | 0.0038 | 0.0385 |
The phase diagrams of the examples 1, 2 and 3 and the comparative example are shown in the attached drawings of the specification, and the grain size is continuously refined along with the increase of the content of the magnesium element. The method for refining the grain size of the sulfur-containing non-quenched and tempered steel adopted by the invention has obvious effect.
Claims (8)
1. A method for refining the grain size of sulfur-containing non-quenched and tempered steel is characterized by comprising the steps of converter or electric furnace smelting, LF refining, VD or RH refining and continuous casting; after the VD refining or RH refining step finishes adjusting other components, adding magnesium element into the molten steel.
2. The method for refining the grain size of the sulfur-containing non-quenched and tempered steel as claimed in claim 1, wherein in the smelting step of the converter or the electric furnace, the end point C is controlled to be less than or equal to 0.10%, the P is controlled to be less than or equal to 0.01%, the tapping temperature is 1610-1680 ℃, and alloy and slag charge are sequentially added into the ladle after the tapping is started.
3. The method for refining the grain size of sulfur-containing non-quenched and tempered steel as recited in claim 1, wherein the LF refining step is performed by blowing nitrogen throughout the refining step, deoxidizing the slag surface with silicon carbide, and adjusting the element content.
4. The method for refining the grain size of sulfur-containing non-quenched and tempered steel as recited in claim 1, wherein in the VD refining or RH refining step, the activity oxygen of steel grade is controlled to be 5-15 ppm.
5. The method for refining the grain size of sulfur-containing non-quenched and tempered steel as recited in claim 1, wherein the magnesium element is fed in the form of magnesium-silicon cored wire.
6. The method as claimed in claim 5, wherein the weight of the Mg-Si core-spun wire per meter is 380-390g/m, and the thickness of the sheet iron is about 0.45 ± 0.5 mm.
7. The method for refining the grain size of the sulfur-containing non-quenched and tempered steel as claimed in claim 5 or 6, wherein the ratio of the Mg-Si cored wire is, in mass percent, Mg: 7-8% of silicon, 15-16% of silicon, and the balance of industrial pure iron and inevitable impurities.
8. The method for refining the grain size of sulfur-containing non-quenched and tempered steel as recited in claim 1, wherein the magnesium content in the molten steel is ensured to be 0.001% -0.003%.
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Cited By (5)
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| CN112921238A (en) * | 2021-01-21 | 2021-06-08 | 南京钢铁股份有限公司 | Non-quenched and tempered steel for fine-grain crankshaft and smelting method thereof |
| CN113234889A (en) * | 2021-03-31 | 2021-08-10 | 南京钢铁股份有限公司 | Method for improving carbide form in bearing steel |
| CN113430465A (en) * | 2021-07-06 | 2021-09-24 | 南京钢铁股份有限公司 | Low alloy steel and smelting method thereof |
| CN113999951A (en) * | 2021-11-11 | 2022-02-01 | 攀钢集团攀枝花钢铁研究院有限公司 | Magnesium-containing cored wire for steel rail production, steel rail and production method thereof |
| CN114058784A (en) * | 2021-11-11 | 2022-02-18 | 攀钢集团攀枝花钢铁研究院有限公司 | Magnesium-containing composite cored wire for steel rail production, steel rail and production method thereof |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112921238A (en) * | 2021-01-21 | 2021-06-08 | 南京钢铁股份有限公司 | Non-quenched and tempered steel for fine-grain crankshaft and smelting method thereof |
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| CN113430465A (en) * | 2021-07-06 | 2021-09-24 | 南京钢铁股份有限公司 | Low alloy steel and smelting method thereof |
| CN113999951A (en) * | 2021-11-11 | 2022-02-01 | 攀钢集团攀枝花钢铁研究院有限公司 | Magnesium-containing cored wire for steel rail production, steel rail and production method thereof |
| CN114058784A (en) * | 2021-11-11 | 2022-02-18 | 攀钢集团攀枝花钢铁研究院有限公司 | Magnesium-containing composite cored wire for steel rail production, steel rail and production method thereof |
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Application publication date: 20210108 |