CN101775557B - Low-carbon boron-containing mild steel and preparation method thereof - Google Patents
Low-carbon boron-containing mild steel and preparation method thereof Download PDFInfo
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- CN101775557B CN101775557B CN201010105024.5A CN201010105024A CN101775557B CN 101775557 B CN101775557 B CN 101775557B CN 201010105024 A CN201010105024 A CN 201010105024A CN 101775557 B CN101775557 B CN 101775557B
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Abstract
The invention discloses a low-carbon boron-containing mild steel which comprises the following components: 0.001-0.012 percent of C, 0.002-0.10 percent of Si, 0.01-0.25 percent of Mn, 0.025-0.075 percent of Al, 0.001-0.006 percent of B, not more than 0.025 percent of P, not more than 0.025 percent of S, not more than 0.040 percent of N, not more than 0.15 percent of Cu, Cr and Ni and the balance of iron and unavoidable impurity elements. The preparation method comprises the following steps of: smelting steel, namely converter blowing, RH vacuum decarburization, steel ladle aluminum deoxidation, boron-containing core-spun thread feeding in a steel ladle, steel ladle soft stirring and continuous casting; and rolling the steel, namely continuous casting blank heating, steel blank rough rolling, fine rolling, steel strip layer flow cooling, steel strip coiling and finished product acquiring. A metal pipe made of the low-carbon boron-containing mild steel can be used as a heat exchange pipe of an air conditioner and a refrigerator and has low production cost, good mechanical performance during processing, convenient bending and ideal heat exchange effect.
Description
Technical field
The invention belongs to metallurgical technology field, relate to a kind of production technology of low-carbon boron-containing mild steel.
Background technology
The household electric appliances such as air-conditioning and refrigerator will consume a large amount of copper pipes every year, due to the in short supply and Market Reasons of copper resource, are badly in need of the ordinary substitute to copper, to reduce production costs.At air-conditioning cooling tube, electric heating tube aspect people have started to substitute copper pipe with steel pipe.The most important performance that can steel pipe substitute copper pipe use is its bending property.In other words, steel pipe must be enough soft, can not ftracture in tube bending moulding with in using.Hot-rolled coil → pickling and cold-rolling → bundling → cold rolling → annealing → smooth → (copper facing) → open bar → high-frequency resistance welded pipe → thermal treatment.For the hot-rolled coil of processing welded tube require to there is low-down tensile strength (Rm ≈ 300MPa) and high unit elongation (A50 >=50%), can only adopt at present carbon and nitrogen respectively at 15ppm and the ULTRA CLEAN Non-intermittent atom steel below 20ppm as the raw material of processing welded tube.
Summary of the invention
The object of the present invention is to provide one can substitute copper pipe, be used as the low-carbon boron-containing mild steel of the heat exchanger tube of the industries such as air-conditioning, refrigerator.
Another object of the present invention is to provide a kind of preparation method of the low-carbon boron-containing mild steel for the preparation of heat exchanger tube.
For realizing object of the present invention, a kind of composition of low-carbon boron-containing mild steel comprises: carbon C:0.001～0.012%, silicon Si:0.002～0.10%, manganese Mn:0.01～0.25%, aluminium Al:0.025～0.075%, boron: 0.001～0.006, P≤0.025%, S≤0.025%, N≤0.0040%, Cu+Cr+Ni≤0.15, all the other are iron and inevitable impurity element.
For realizing another object of the present invention, a kind of preparation method of low-carbon boron-containing mild steel, its basic step comprises steel-making: bessemerize → RH vacuum decarburization → ladle aluminium deoxidation → ladle is fed with the soft stirring → continuous casting of boron cored-wire → ladle; Detailed process is as follows:
1. in converter, add and account for the steel scrap that total metal batch is less than 20%, all the other carry out pure oxygen blowing for after blast-melted, add lime, and control the basicity (CaO/SiO2)=3.5～4.5 of slag in converting process; The temperature of converter terminal tapping is 1680～1740 ℃, molten steel component C :≤0.07%, P≤0.020%, S≤0.018%; Converter tapping process adds 2.5～3.5 kilograms of lime of ton steel, and must avoid converter to roll inflow ladle;
2. the complete ladle of converter tapping enters RH and carries out vacuum-treat, after molten steel is processed more than 10 minutes under the vacuum tightness that is less than 2mBar, adds aluminium block carry out deoxidation to molten steel, then carries out 5 minutes above molten steel and only circulates; Complete after RH processing, the content of carbon, nitrogen and oxygen in molten steel is controlled at respectively 0.001%, below 0.0035% and 0.0035%, the content of silicon, manganese and aluminium is respectively and is less than 0.10%, 0.25% and 0.025～0.075%, the content of sulphur and squama is all less than 0.025%, and molten steel temperature is controlled at 1580～1600 ℃ (continuous casting even waters stove) and 1590～1610 ℃ (continuous casting is opened and watered the → stove);
3. complete after RH processing, to molten steel feeding ferro-boron cored-wire; After feeding cored-wire, in molten steel, content is controlled at 0.001～0.006%;
4. ladle stirs at the bottom of adopting Argon, and after the feeding of ferro-boron line, ladle must adopt the soft stirring of low argon flow amount more than 5 minutes; Molten steel top adopts ashing rice husk thermal insulation;
5. molten steel continuous casting adopts large bag long nozzle, tundish covering flux, crystallizer submersed nozzle, argon gas-sealed and covering slag to carry out full guard cast; Tundish control temperature: 1540～1570 ℃; Crystallizer must adopt low carbon protective slag.
Steel rolling method comprises: continuously cast bloom heating → rough rolling of steel billets → finish rolling → steel band laminar flow is cooling → and steel strip coiling → finished product;
1. continuous blank heating temperature: 1250～1300 ℃; Intermediate slab temperature after roughing: 1050～1110 ℃, thickness: 30～40mm; 2. finish to gauge finishes temperature of steel strips: 870～930 ℃, and thickness: 2.0～8.0mm;
3. laminar flow steel band cooling after, the curling temperature of steel band: 620～740 ℃.
Advantage of the present invention is: the metal tube that adopts low-carbon boron-containing soft iron to make can be used for the heat exchanger tube of air-conditioning, refrigerator, and this pipe production cost is low, and good mechanical property when processing is bending convenient, and heat transfer effect ideal.
Accompanying drawing explanation
Fig. 1 is the metallographic structure photo of the 1st heat steel band in table 2;
Fig. 2 is the metallographic structure photo of the 2nd heat steel band in table 2;
Fig. 3 is the metallographic structure photo of the 3rd heat steel band in table 2;
Fig. 4 is the metallographic structure photo of the 4th heat steel band in table 2.
Embodiment
Below low-carbon boron-containing soft iron of the present invention and preparation method thereof is described in further detail:
Boron is to be positioned at the element being positioned at second cycle before carbon in periodictable, and boron dissolves in iron-based, forms interval type and displaced type sosoloid; Boron and nitrogen, oxygen have very strong avidity, form compound.The boron dissolving in steel can significantly improve the hardening capacity of steel, improves mechanical property, particularly impelling strength.But in soft steel, boron has precedence over free nitrogen combination in high temperature austenite in aluminium and steel and forms thick boron nitride particle, has weakened the pinning effect of aluminium nitride to crystal boundary, makes ferrite crystal grain generation alligatoring; Separate out remaining boron meeting segregation at austenite grain boundary, suppressed the forming core of ferrite at austenite grain boundary, reduced ferritic nucleation rate, thereby increased ferrite grain size; The interpolation of boron effectively reduces free nitrogen in steel, thus the intensity of reduction steel etc.Visible, in soft steel, add a certain amount of boron and can form the ferritic structure of large-size, thereby reduce significantly the intensity of steel and the plasticity of raising steel.
The present invention is intended to utilize the effect of boron alligatoring soft steel grain fineness number, in ultra low-carbon steel (C≤120ppm), add boron, produce composition C:0.001 ~ 0.012% in general converter-RH-continuous casting Ultra-low carbon steel-making condition, Si:0.002 ~ 0.10%, Mn:0.1 ~ 0.25%, Al:0.025 ~ 0.075%, B:0.001 ~ 0.006%, P≤0.025%, S≤0.025%, N≤0.0040%, Cu+Cr+Ni≤0.15, all the other are the continuous casting steel billet of iron and inevitable impurity element, and by suitable hot continuous rolling process, obtain lower yield strength≤200MPa, tensile strength≤300MPa, unit elongation A50 >=50%, the coils of hot-rolled steel of hardness HB10≤100.
1, the composition of steel: C:0.001 ~ 0.012%, Si:0.002 ~ 0.10%, Mn:0.1 ~ 0.25%, Al:0.025 ~ 0.075%, B:0.001 ~ 0.006, P≤0.025%, S≤0.025%, N≤0.0040%, Cu+Cr+Ni≤0.15, all the other are iron and inevitable impurity element.
2, the performance of steel: lower yield strength≤200MPa, tensile strength≤300MPa, unit elongation A50 >=50%, hardness HB10≤100.
(1) metallographic structure of steel: the matrix of steel is ferrite, grain fineness number is 7 ~ 8 grades.
Method for making steel
Bessemerize → RH vacuum decarburization → ladle aluminium deoxidation → ladle is fed with the soft stirring → continuous casting of boron cored-wire → ladle.
1. in converter, add and account for the steel scrap that total metal batch is less than 20%, all the other carry out pure oxygen blowing for after blast-melted, add lime, and control the basicity (CaO/SiO2)=3.5 ~ 4.5 of slag in converting process.The temperature of converter terminal tapping is 1680 ~ 1740 ℃, molten steel component C :≤0.07%, P≤0.020%, S≤0.018%.Converter tapping process adds 2.5 ~ 3.5 kilograms of lime of ton steel, and must avoid converter to roll inflow ladle.
2. the complete ladle of converter tapping enters RH and carries out vacuum-treat, after molten steel is processed more than 10 minutes under the vacuum tightness that is less than 2mBar, adds aluminium block carry out technique deoxidation to molten steel, then carries out 5 minutes above molten steel and only circulates.Complete after RH processing, the content of carbon, nitrogen and oxygen in molten steel is controlled at respectively 0.001%, below 0.0035% and 0.0035%, the content of silicon, manganese and aluminium is respectively and is less than 0.10%, 0.25% and 0.025 ~ 0.075%, and the content of sulphur and squama is all less than 0.025%., molten steel temperature is controlled at 1580 ~ 1600 ℃ (continuous casting even waters stove) and 1590 ~ 1610 ℃ (continuous casting is opened and watered the first stove).
3. complete after RH processing, to molten steel feeding ferro-boron cored-wire.After feeding cored-wire, in molten steel, content is controlled at 0.001 ~ 0.006%.
4. ladle stirs at the bottom of adopting Argon, and after the feeding of ferro-boron line, ladle must adopt the soft stirring of low argon flow amount more than 5 minutes.
Molten steel top adopts ashing rice husk thermal insulation.
5. molten steel continuous casting adopts large bag long nozzle, tundish covering flux, crystallizer submersed nozzle, argon gas-sealed and covering slag to carry out full guard cast.Tundish control temperature: 1540 ~ 1570 ℃.Crystallizer must adopt low carbon protective slag.
Steel rolling method
Continuously cast bloom heating → rough rolling of steel billets → finish rolling → steel band laminar flow is cooling → steel strip coiling → finished product.
1. continuous blank heating temperature: 1250 ~ 1300 ℃; Intermediate slab temperature after roughing: 1050 ~ 1110 ℃, thickness: 30 ~ 40mm;
2. finish to gauge finishes temperature of steel strips: 870 ~ 930 ℃, and thickness: 2.0 ~ 8.0mm;
3. laminar flow steel band cooling after, the curling temperature of steel band: 620 ~ 740 ℃.
Embodiment
1, the chemical composition of finished product steel belt
Table 1 is according to the chemical composition of the typical 4 heat steel bands of above-described process for making production.
Table 1. chemical composition, weight percent
| No | C | Si | Mn | P | S | Al | Cu+Cr+Ni | B | O | N |
| 1 | 0.0045 | 0.0062 | 0.1126 | 0.0159 | 0.0122 | 0.0708 | 0.0793 | 0.0029 | 0.0026 | 0.0014 |
| 2 | 0.0053 | 0.0045 | 0.0303 | 0.0121 | 0.0078 | 0.0553 | 0.0334 | 0.0030 | 0.0027 | 0.0034 |
| 3 4 | 0.0107 0.001 | 0.0062 0.0022 | 0.1383 0.0152 | 0.013 0.0162 | 0.0154 0.0125 | 0.0351 0.0605 | 0.0987 0.0452 | 0.0036 0.0056 | 0.0021 0.0028 | 0.0021 0.0025 |
2, steel band performance
Table 2 is thickness and mechanical properties that in the table 1 of producing according to above-described steel rolling process, 4 heats represent steel band.The tension specimen of steel band adopts longitudinal test piece consistent with rolling direction, and sample marking distance is 50mm, gauge length partial width 25mm.
Table 2. finished product thickness and mechanical property
| Heat (batch) number | Thickness mm | Lower yield strength MPa | Tensile strength MPa | Elongation, % | HV 10Hardness |
| 1 | 2.75 | 183 | 278 | 54 | 87 |
| 2 | 2.75 | 179 | 285 | 52 | 86 |
| 3 | 2.90 | 209 | 296 | 50 | 91 |
| 4 | 2.75 | 175 | 272 | 54 | 85 |
3, steel band metallographic structure
Fig. 1,2,3 and 4 is respectively the metallographic structure photo that in table 2,4 heats represent steel band.
Claims (1)
1. the preparation method of low-carbon boron-containing mild steel, the composition of described low-carbon boron-containing mild steel comprises: carbon C:0.001～0.012%, silicon Si:0.002～0.10%, manganese Mn:0.01～0.25%, aluminium Al:0.025～0.075%, boron: 0.001～0.006%, P≤0.025%, S≤0.025%, N≤0.0040%, Cu+Cr+Ni≤0.15%, all the other are iron and inevitable impurity element, it is characterized in that: this preparation method's basic step comprises method for making steel and steel rolling method, wherein:
(1) step of method for making steel comprises: bessemerize → RH vacuum decarburization → ladle aluminium deoxidation → ladle is fed with the soft stirring → continuous casting of boron cored-wire → ladle; Detailed process is as follows:
1. in converter, add and account for the steel scrap that total metal batch is less than 20%, all the other carry out pure oxygen blowing for after blast-melted, add lime, and control the basicity (CaO/SiO2)=3.5～4.5 of slag in converting process; The temperature of converter terminal tapping is 1680～1740 ℃, molten steel component C :≤0.07%, P≤0.020%, S≤0.018%; Converter tapping process adds 2.5～3.5 kilograms of lime of ton steel, and must avoid converter slag to flow into ladle;
2. the complete ladle of converter tapping enters RH and carries out vacuum-treat, after molten steel is processed more than 10 minutes under the vacuum tightness that is less than 2mBar, adds aluminium block carry out deoxidation to molten steel, then carries out 5 minutes above molten steel and only circulates; Complete after RH processing, the content of carbon, nitrogen and oxygen in molten steel is controlled at respectively 0.001%, below 0.0035% and 0.0035%, the content of silicon, manganese and aluminium is respectively and is less than 0.10%, 0.25% and 0.025～0.075%, the content of sulphur and phosphorus is all less than 0.025%, continuous casting connects the molten steel temperature that waters stove and is controlled at 1580～1600 ℃, and continuous casting is opened the molten steel temperature that waters the first stove and is controlled at 1590～1610 ℃;
3. complete after RH processing, to molten steel feeding ferro-boron cored-wire; After feeding cored-wire, in molten steel, content is controlled at 0.001～0.006%;
4. ladle stirs at the bottom of adopting Argon, and after the feeding of ferro-boron line, ladle must adopt the soft stirring of low argon flow amount more than 5 minutes; Molten steel top adopts ashing rice husk thermal insulation;
5. molten steel continuous casting adopts large bag long nozzle, tundish covering flux, crystallizer submersed nozzle, argon gas-sealed and covering slag to carry out full guard cast; Tundish control temperature: 1540～1570 ℃; Crystallizer must adopt low carbon protective slag;
(2) step of steel rolling method comprises: continuously cast bloom heating → rough rolling of steel billets → finish rolling → steel band laminar flow is cooling → and steel strip coiling → finished product; Wherein:
1. continuous blank heating temperature is controlled at 1250～1300 ℃; After roughing, intermediate slab temperature is controlled at 1050～1110 ℃, and thickness is at 30～40mm;
2. finish to gauge finishes temperature of steel strips and is controlled at 870～930 ℃, and thickness is at 2.0～8.0mm;
3. laminar flow steel band cooling after, the coiling temperature of steel band is controlled at 620～740 ℃.
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| CN104525884A (en) * | 2014-12-22 | 2015-04-22 | 营口东邦冶金设备耐材有限公司 | Continuous casting method capable of increasing yield of easily oxidized alloy and equiaxial crystal rate of casting blank |
| CN107630172B (en) * | 2016-07-18 | 2019-04-26 | 鞍钢股份有限公司 | A method of preventing low-carbon boron-containing steel surface crackle |
| CN107475615B (en) * | 2017-09-23 | 2019-01-25 | 武钢集团昆明钢铁股份有限公司 | A kind of 160MPa grades of weather-proof low-yield point damper steel plate and strip production methods |
| CN109652745A (en) * | 2019-03-01 | 2019-04-19 | 江苏建中新材料科技有限公司 | A kind of acidproof heat exchanger tube steel and its processing technology |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2608508B2 (en) * | 1992-07-06 | 1997-05-07 | 新日本製鐵株式会社 | Manufacturing method of cold rolled steel sheet with excellent deep drawability |
| CN1213011A (en) * | 1997-07-28 | 1999-04-07 | 日本钢管株式会社 | Flexible cold-rolled plate and its manufacture method |
| CN101397626A (en) * | 2007-12-07 | 2009-04-01 | 江苏沙钢集团有限公司 | High intensity and high-toughness hot-rolled steel sheet and method for producing the same |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2608508B2 (en) * | 1992-07-06 | 1997-05-07 | 新日本製鐵株式会社 | Manufacturing method of cold rolled steel sheet with excellent deep drawability |
| CN1213011A (en) * | 1997-07-28 | 1999-04-07 | 日本钢管株式会社 | Flexible cold-rolled plate and its manufacture method |
| CN101397626A (en) * | 2007-12-07 | 2009-04-01 | 江苏沙钢集团有限公司 | High intensity and high-toughness hot-rolled steel sheet and method for producing the same |
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| Title |
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| JP第2608508B2 1997.05.07 |
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Inventor after: Zhang Xiaobing Inventor after: Bao Dezhi Inventor after: Li Ran Inventor after: Wang Zhifu Inventor after: Song Yongfu Inventor before: Zhang Xiaobing Inventor before: Bao Dezhi Inventor before: Li Ran Inventor before: Wang Zhifu Inventor before: Song Yongfu |
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