Steel for photovoltaic pull rod with yield strength of 400 MPa and preparation method of steel

Abstract

The invention discloses steel for a photovoltaic pull rod with the yield strength of 400 MPa and a preparation method of the steel. The preparation method of the steel for the photovoltaic pull rod with the yield strength of 400 MPa comprises the steps that primary smelting, LF refining, RH vacuum treatment, continuous casting and wire rod rolling are conducted, and on the basis that the atmospheric corrosion index I is larger than or equal to 7, the chemical components of the steel for the photovoltaic pull rod with the yield strength of 400 MPa comprise, by mass, 0.06%-0.11% of C; 0.15% to 0.30% of Si; mn < = 0.70%; less than or equal to 0.020% of S; less than or equal to 0.020% of P; 0.50% or less of Ni; 2.50% to 3.50% of Cr; 0.23% to 0.35% of Cu; 0.10% or less of Ti; a certain amount of Cr and Cu corrosion-resistant weather-resistant elements are added on the basis of 0.10% of C and 0.5% of Mn on the basis that the atmospheric corrosion index I is larger than or equal to 7, meanwhile, Ti and Al components in steel are controlled in the smelting process, a structure with pearlite as the main part is obtained by controlling the wire rod rolling technology, good weather resistance is achieved, steel is effectively saved, and the production cost is reduced. And meanwhile, the strength of the steel for the photovoltaic pull rod is improved, and certain machining toughness is kept.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgy, and particularly relates to a yield strength 400 MPa level photovoltaic pull rod steel and a preparation method thereof. BACKGROUND

[0002] Solar energy is the cleanest, safest and most reliable energy in the future, and the photovoltaic industry is increasingly becoming a new industry after the IT and microelectronic industries with explosive development in the world, and the total output value of the industry has exceeded 1.7 trillion yuan. The photovoltaic support is a structural support for supporting a solar cell panel, and the pull rod is an important component for the stability of the support structure. Currently, Q235 steel material with surface galvanizing or galvanizing aluminum magnesium is used, which has the characteristics of low cost and easy processing, but has low strength, large material consumption, high corrosion maintenance cost in the later period, high pollution in the production process of galvanizing, and short service life. SUMMARY

[0003] To solve the above-mentioned technical problems in the prior art, the present application provides a yield strength 400 MPa level photovoltaic pull rod steel and a preparation method thereof.

[0004] The preparation method of the yield strength 400 MPa level photovoltaic pull rod steel of the present application comprises: rough smelting-LF refining-RH vacuum treatment-continuous casting-rod rolling. Under the benchmark of atmospheric corrosion index I≥7, the chemical composition of the yield strength 400 MPa level photovoltaic pull rod steel is controlled as follows in terms of mass percentage: C: 0.06%~0.11%; Si: 0.15%~0.30%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%~3.50%; Cu: 0.23%~0.35%; Ti≤0.10%; Al≤0.040%, and the rest is iron and unavoidable impurities; Rough smelting: molten iron and scrap steel are added into a converter to smelt into rough molten steel, and aluminum pellets 3.2~4.0 kg / ton of steel, lime 7.5~8 kg / ton of steel, synthetic slag 2.5~3.0 kg / ton of steel and dry alloy are added into the molten steel to obtain rough molten steel with the component content; LF refining: the rough molten steel is poured into an LF ladle refining furnace, low-C alloy is added for component fine adjustment, alkaline slag is adjusted after the other components are within the limit, Ti ferroalloy is added for Ti component adjustment, and refined molten steel with the outgoing component content is obtained; RH vacuum treatment: the refined molten steel with the outgoing component content is transferred into an RH refining furnace for vacuum treatment to obtain molten steel after smelting; Continuous casting: the molten steel after smelting is continuously cast into a continuous casting billet with a section of 220x220mm; Rod rolling: the continuous casting billet is heated to 1100-1150℃, the total heating time is >2h, and the rolling specification is φ7-20mm after rough rolling and finish rolling.

[0005] Further, in the above-mentioned yield strength 400MPa grade photovoltaic pull rod steel preparation method, in the rough refining step, the chemical composition of the rough molten steel is as follows in mass percent: C: 0.07%-0.10%; Si: 0.10%-0.25%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%-3.50%; Cu: 0.23%-0.35%; Ti≤0.10%; Al≤0.050%, and the rest is iron and inevitable impurities.

[0006] Further, in the above-mentioned yield strength 400MPa grade photovoltaic pull rod steel preparation method, in the LF refining step, the chemical composition of the refined molten steel is as follows in mass percent: C: 0.06%-0.12%; Si: 0.15%-0.30%; Mn: 0.2%-0.5%; S≤0.010%; P≤0.015%; Cr: 2.00%-2.50%; Al≤0.040%, and the rest is iron and inevitable impurities.

[0007] Further, in the above-mentioned yield strength 400MPa grade photovoltaic pull rod steel preparation method, in the RH vacuum treatment step, the RH vacuum degree is controlled to be ≤4mbar, the holding time is >10min, the on-line [H] after breaking the vacuum is ≤2.0ppm, the argon blowing soft stirring is controlled to be 10-15min, and the RH outlet temperature is controlled to be 1550-1560℃.

[0008] Further, in the above-mentioned yield strength 400MPa grade photovoltaic pull rod steel preparation method, in the continuous casting step, the tundish is baked to make the temperature >1150℃, the whole process is protected by argon during continuous casting, the temperature of the open pouring ladle is controlled to be 1555℃, the temperature of the open pouring tundish is controlled to be 1535-1550℃, the liquid level fluctuation of the crystallizer is ≤±3mm, the immersion depth of the crystallizer submerged entry nozzle is 120±5mm, the casting billet pulling speed is controlled to be 0.80-1.00m / min, the crystallizer cooling water amount is 1800L / min, the secondary cooling water amount is 0.2L / Kg, and the continuous casting billet is cooled in the natural air.

[0009] Further, in the above-mentioned yield strength 400MPa grade photovoltaic pull rod steel preparation method, the electromagnetic stirring is used for the crystallizer, the current is 200A, and the frequency is 3.5Hz; the current of the end electromagnetic stirring is 450A, the frequency is 4.5Hz, and the commutation is 15 seconds.

[0010] Further, in the preparation method of the yield strength 400 MPa grade photovoltaic pull rod steel, in the wire rod rolling step, the rough rolling opening rolling temperature is greater than 1050 DEG C, the finish rolling final rolling temperature is controlled to be 830-900 DEG C, the wire rod laying temperature is controlled to be 750-800 DEG C, and the wire rod is slowly cooled on a roller way after rolling, and the roller way speed is controlled to be 0.10-0.25 m / s.

[0011] In the second aspect of the present application, a yield strength 400 MPa grade photovoltaic pull rod steel is provided, which is produced by the preparation method of the yield strength 400 MPa grade photovoltaic pull rod steel.

[0012] The yield strength 400 MPa grade photovoltaic pull rod steel and the preparation method thereof have the following advantages and beneficial effects: The present application adds a certain amount of Cr and Cu corrosion resistant elements on the basis of 0.10% C and 0.5% Mn, controls the Ti and Al components in the steel during smelting, and obtains a structure mainly composed of pearlite by controlling the wire rod rolling process, so that the steel has good weather resistance, the steel material is effectively saved, the strength of the photovoltaic pull rod steel is improved, and the processing toughness is maintained, thereby providing performance guarantee for the subsequent cold processing of the finished product. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only used to further understand the present application and form a part of the present application. For those skilled in the art, other drawings can also be obtained without creative labor based on these drawings. In the drawings: Figure 1 The thermodynamic CCT curve diagram of the yield strength 400 MPa grade photovoltaic pull rod steel of the present application; Figure 2 The hot rolling wire rod structure diagram of the yield strength 400 MPa grade photovoltaic pull rod steel of the present application; Figure 3 The hot rolling wire rod structure enlarged diagram of the yield strength 400 MPa grade photovoltaic pull rod steel of the present application. DETAILED DESCRIPTION

[0014] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in combination with specific embodiments of the present application and corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0015] The preparation method of the yield strength 400 MPa level photovoltaic pull rod steel of the present application comprises: rough smelting-LF refining-RH vacuum treatment-continuous casting-wire rod rolling. Under the benchmark of atmospheric corrosion index I≥7, the chemical composition of the yield strength 400 MPa level photovoltaic pull rod steel is controlled as follows in mass percentage: C: 0.06%~0.11%; Si: 0.15%~0.30%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%~3.50%; Cu: 0.23%~0.35%; Ti≤0.10%; Al≤0.040%, and the rest is iron and inevitable impurities. Rough smelting: molten iron and scrap steel are added into a converter to smelt into rough molten steel, and aluminum pellets 3.2~4.0 kg / ton of steel, lime 7.5~8 kg / ton of steel, synthetic slag 2.5~3.0 kg / ton of steel and dry alloy are added into the molten steel to obtain rough molten steel meeting the component content; LF refining: the rough molten steel is poured into an LF ladle refining furnace, low-C alloy is added for component fine adjustment, alkaline slag is adjusted after other components are within the limit, Ti ferroalloy is added for Ti component adjustment, and refined molten steel meeting the outgoing component content is obtained; RH vacuum treatment: the refined molten steel meeting the outgoing component content is transferred into an RH refining furnace for vacuum treatment to obtain molten steel after smelting; Continuous casting: the molten steel after smelting is continuously cast into a continuous casting billet with a section of 220×220 mm specification; Wire rod rolling: the continuous casting billet is heated to 1100℃~1150℃, the total heating time is >2h, and the specification after rough rolling and finish rolling is φ7~20mm.

[0016] Further, in the above preparation method of the yield strength 400 MPa level photovoltaic pull rod steel, in the rough smelting step, the chemical composition of the rough molten steel is as follows in mass percentage: C: 0.07%~0.10%; Si: 0.10%~0.25%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%~3.50%; Cu: 0.23%~0.35%; Ti≤0.10%; Al≤0.050%, and the rest is iron and inevitable impurities.

[0017] Further, in the yield strength 400 MPa grade photovoltaic pull rod steel preparation method, in the LF refining step, the refining molten steel chemical composition is as follows in percentage by mass: C: 0.06%~0.12%; Si: 0.15%~0.30%; Mn: 0.2%~0.5%; S≤0.010%; P≤0.015%; Cr: 2.00%~2.50%; Al≤0.040%, the rest is iron and inevitable impurities.

[0018] Further, in the yield strength 400 MPa grade photovoltaic pull rod steel preparation method, in the RH vacuum treatment step, the RH vacuum degree is controlled at ≤4 mbar, the holding time is >10 min, the on-line [H] after breaking the vacuum is ≤2.0 ppm, the argon blowing soft stirring is controlled at 10~15 min, and the RH outlet temperature is controlled at 1550~1560℃.

[0019] Further, in the yield strength 400 MPa grade photovoltaic pull rod steel preparation method, in the continuous casting step, the tundish is baked to make the temperature >1150℃, the whole process is protected by argon during continuous casting, the temperature of the open ladle is controlled at 1555℃, the temperature of the open tundish is controlled at 1535~1550℃, the liquid level fluctuation of the crystallizer is ≤±3 mm, the crystallizer submerged entry nozzle insertion depth is 120±5 mm, the casting speed is controlled at 0.80~1.00 m / min, the crystallizer cooling water amount is 1800 L / min, the secondary cooling water amount is 0.2 L / Kg, and the continuous casting blank is cooled in the natural air.

[0020] Further, in the yield strength 400 MPa grade photovoltaic pull rod steel preparation method, the crystallizer uses electromagnetic stirring, the current is 200 A, and the frequency is 3.5 Hz; the terminal electromagnetic stirring current is 450 A, the frequency is 4.5 Hz, and the commutation is 15 seconds.

[0021] Further, in the yield strength 400 MPa grade photovoltaic pull rod steel preparation method, in the wire rod rolling step, the rough rolling open rolling temperature is >1050℃, the finish rolling final rolling temperature is controlled at 830~900℃, the wire drawing temperature is controlled at 750~800℃, and the wire rod is slowly cooled on the roller after rolling, and the roller speed is controlled at 0.10~0.25 m / s.

[0022] In the second aspect of the present application, a yield strength 400 MPa grade photovoltaic pull rod steel is provided, which is produced by the yield strength 400 MPa grade photovoltaic pull rod steel preparation method.

[0023] Example: The chemical composition of the yield strength 400 MPa grade photovoltaic pull rod steel of the embodiment is controlled according to mass percentage: C: 0.089%; Si: 0.22%; Mn: 0.35%; P: 0.018%; S: 0.005%; Cr: 2.65%; Cu: 0.27%; Ti: 0.03%; Al: 0.020%, and the rest is Fe and inevitable impurities.

[0024] Coarse smelting: 72.5 tons of molten iron and 13.5 tons of scrap steel are added to the converter, oxygen is blown, phosphorus is oxidized, and the molten steel is smelted into coarse molten steel. The chemical composition of the molten steel is: C: 0.05%; Si: 0.035%; Mn: 0.085%; P: 0.012%; S≤0.010%, the rest is Fe and inevitable impurities, and 300 kg of aluminum pellets, 250 kg of silicon-manganese alloy, 210 kg of low-manganese alloy, 550 kg of lime, and 210 kg of synthetic slag are added to the molten steel; LF refining: the coarse molten steel is poured into the LF ladle refining furnace for refining, the slag in the ladle refining furnace is adjusted to high basicity slag, the refining slag basicity is 1.82, the argon gas flow is 1100 liters / minute for stirring reduction, and then manganese iron, chromium iron, copper plate, and titanium iron are added for fine adjustment of the composition. The chemical composition of the refined molten steel is: C: 0.085%; Si: 0.20%; Mn: 0.30%; P: 0.015%; S: 0.005%; Cr: 2.63%; Cu: 0.26%; Ti: 0.030%; Al: 0.030%; the rest is Fe and inevitable impurities; RH refining: the refined molten steel meeting the outbound composition content is transferred into the RH refining furnace for vacuum pumping, reaching an ultimate vacuum degree of 4 mbar, and maintaining the vacuum degree for 15 min. The vacuum is broken, the online [H] is 0.7 ppm, and argon gas soft stirring is performed for 12 min. After adding the covering agent, the outbound temperature is 1564℃; Continuous casting: the cross-sectional specification of the continuous casting billet is 220x220mm, the tundish is baked at more than 1150℃, the whole process of continuous casting is protected by argon gas, the temperature of the starting ladle is 1555℃, the temperature of the starting tundish is 1550℃, the liquid level fluctuation of the crystallizer is ±3mm, the immersion depth of the crystallizer submerged entry nozzle is 120mm, the stable casting speed of the billet is 0.85m / min, the crystallizer cooling water quantity is 1800L / min, the secondary cooling water quantity is 0.2L / Kg, the crystallizer uses electromagnetic stirring, the current is 200A, and the frequency is 3.5Hz; the end electromagnetic stirring current is 450A, the frequency is 4.5Hz, and the commutation is 15 seconds. The continuous casting billet is naturally cooled in air (avoiding air cooling or water cooling); Rod rolling: billet heating 1130℃, total heating time 2.5h, soaking time at 1120℃ 60min. Rough rolling opening temperature 1080℃, finish rolling temperature 960℃, water quenching, finish rolling temperature 870℃, wire drawing temperature 780℃, rolling specification 8mm, wire rod after rolling is cooled on the roller bed.

[0025] In summary, compared with the prior art, the yield strength 400MPa level photovoltaic pull rod steel and the preparation method thereof have the following advantages and beneficial effects: based on the atmospheric corrosion index I≥7, on the basis of 0.10% C and 0.5% Mn, a certain amount of Cr and Cu corrosion resistant elements are added, Ti and Al components in the steel are controlled during smelting, and by controlling the wire rod rolling process, a structure mainly composed of pearlite is obtained, not only good weather resistance is obtained, but also the steel material is effectively saved, the strength of the photovoltaic pull rod steel is improved and a certain processing toughness is maintained, and the performance guarantee for the subsequent cold processing of the finished product is provided.

[0026] It should be noted that, in this document, unless otherwise explicitly specified and limited, the term "connection" or its synonyms should be understood broadly, for example, "connection" can be fixed connection, can also be detachable connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, and those skilled in the art can understand the specific meaning of the above-mentioned term in the present application according to the specific situation. Moreover, expressions such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. At the same time, the term "includes", "contains" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. In addition, "front", "back", "left", "right", "up", "down" in this document are referred to the placement state shown in the drawings.

[0027] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for manufacturing photovoltaic tie rod steel with a yield strength of 400 MPa, characterized in that, The method for preparing photovoltaic tie rod steel with a yield strength of 400MPa includes: roughing, LF refining, RH vacuum treatment, continuous casting, and wire rod rolling. Under the atmospheric corrosion index I≥7 benchmark, the chemical composition of the photovoltaic tie rod steel with a yield strength of 400MPa is controlled by mass percentage as follows: C: 0.06%~0.11%; Si: 0.15%~0.30%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%~3.50%; Cu: 0.23%~0.35%; Ti≤0.10%; Al≤0.040%, with the remainder being iron and unavoidable impurities. Rough smelting: Molten iron and scrap steel are added to a converter to smelt into crude steel. When tapping the steel, aluminum shot 3.2~4.0 kg / ton of steel, lime 7.5~8 kg / ton of steel, synthetic slag 2.5~3.0 kg / ton of steel and dry alloy material are added to obtain crude steel with the correct composition. LF refining: The crude steel is poured into the LF ladle refining furnace, and low C alloy is added for fine-tuning of the composition. After other components are added to the limit, basic slag is adjusted, and Ti ferroalloy is added to control the Ti composition, so as to obtain refined steel with the composition content that meets the requirements of the station exit. RH vacuum treatment: The refined molten steel that meets the composition requirements for leaving the station is transferred into the RH refining furnace for vacuum treatment to obtain the refined molten steel; Continuous casting: The process of continuously casting molten steel into a continuous casting billet with a cross-section of 220×220mm. Wire rod rolling: The continuously cast billet is heated to 1100℃~1150℃, with a total heating time of >2h, and then rolled to a specification of φ7~20mm by rough rolling and finish rolling.

2. The method for preparing photovoltaic tie rod steel with a yield strength of 400MPa as described in claim 1, characterized in that, In the roughing step, the chemical composition of the crude steel by mass percentage is as follows: C: 0.07%~0.10%; Si: 0.10%~0.25%; Mn≤0.70%; S≤0.020%; P≤0.020%; Ni≤0.50%; Cr: 2.50%~3.50%; Cu: 0.23%~0.35%; Ti≤0.10%; Al≤0.050%, with the remainder being iron and unavoidable impurities.

3. The method for preparing photovoltaic tie rod steel with a yield strength of 400MPa as described in claim 1, characterized in that, In the LF refining step, the chemical composition of the refined molten steel by mass percentage is as follows: C: 0.06%~0.12%; Si: 0.15%~0.30%; Mn: 0.2%~0.5%; S≤0.010%; P≤0.015%; Cr: 2.00%~2.50%; Al≤0.040%, with the remainder being iron and unavoidable impurities.

4. The method for preparing photovoltaic tie rod steel with a yield strength of 400MPa as described in claim 1, characterized in that, In the RH vacuum treatment step, the RH vacuum degree is controlled at ≤4mbar, the holding time is >10min, the [H] is determined online after rupture at ≤2.0ppm, the argon blowing and soft stirring is controlled at 10~15min, and the RH outlet temperature is controlled at 1550~1560℃.

5. The method for preparing photovoltaic tie rod steel with a yield strength of 400MPa as described in claim 1, characterized in that, In the continuous casting process, the tundish is baked to a temperature >1150℃, argon gas is used for protection throughout the continuous casting process, the temperature of the first pouring ladle is controlled at 1555℃, the temperature of the first pouring tundish is controlled at 1535~1550℃, the liquid level fluctuation in the crystallizer is ≤±3mm, the insertion depth of the immersion nozzle in the crystallizer is 120±5mm, the billet casting speed is controlled at 0.80~1.00m / min, the cooling water flow rate of the crystallizer is 1800 L / min, the secondary cooling water flow rate is 0.2 L / Kg, and the continuously cast billet is cooled in natural air.

6. The method for preparing photovoltaic tie rod steel with a yield strength of 400 MPa as described in claim 5, characterized in that, The crystallizer uses electromagnetic stirring with a current of 200A and a frequency of 3.5Hz; the end electromagnetic stirring has a current of 450A and a frequency of 4.5Hz, with a reversal time of 15 seconds.

7. The method for preparing photovoltaic tie rod steel with a yield strength of 400 MPa as described in claim 1, characterized in that, In the wire rod rolling process, the roughing rolling temperature is >1050℃, the finishing rolling temperature is controlled at 830~900℃, the wire drawing temperature is controlled at 750~800℃, and the wire rod is slowly cooled on the roller table after rolling, with the roller table speed controlled at 0.10~0.25m / s.

8. A photovoltaic tie rod with a yield strength of 400 MPa, characterized in that, The photovoltaic tie rod steel with a yield strength of 400MPa is produced using the method for preparing photovoltaic tie rod steel with a yield strength of 400MPa as described in any one of claims 1 to 7.

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