CN115386788B - Cold bending cracking control process for HRB500E deformed steel bar - Google Patents
Cold bending cracking control process for HRB500E deformed steel bar Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 129
- 239000010959 steel Substances 0.000 title claims abstract description 129
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000005452 bending Methods 0.000 title claims abstract description 22
- 238000005336 cracking Methods 0.000 title claims abstract description 21
- 238000005096 rolling process Methods 0.000 claims abstract description 40
- 238000005266 casting Methods 0.000 claims abstract description 39
- 238000007670 refining Methods 0.000 claims abstract description 24
- 238000007664 blowing Methods 0.000 claims abstract description 22
- 238000009749 continuous casting Methods 0.000 claims abstract description 22
- 238000010079 rubber tapping Methods 0.000 claims abstract description 22
- 229910001199 N alloy Inorganic materials 0.000 claims abstract description 20
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 18
- 239000000956 alloy Substances 0.000 claims abstract description 18
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 14
- PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000003723 Smelting Methods 0.000 claims abstract description 8
- 238000009628 steelmaking Methods 0.000 claims abstract description 8
- 229910000628 Ferrovanadium Inorganic materials 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 229910052742 iron Inorganic materials 0.000 claims abstract description 7
- 238000004321 preservation Methods 0.000 claims abstract description 6
- 238000005275 alloying Methods 0.000 claims abstract description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 40
- 229910052786 argon Inorganic materials 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 229910000640 Fe alloy Inorganic materials 0.000 claims description 7
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 6
- 230000000149 penetrating effect Effects 0.000 claims description 6
- 229910006639 Si—Mn Inorganic materials 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 239000010955 niobium Substances 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- 229910018619 Si-Fe Inorganic materials 0.000 claims description 2
- 229910008289 Si—Fe Inorganic materials 0.000 claims description 2
- 238000005070 sampling Methods 0.000 claims description 2
- 238000001514 detection method Methods 0.000 claims 1
- 239000002344 surface layer Substances 0.000 abstract description 3
- 238000009851 ferrous metallurgy Methods 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000002893 slag Substances 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000903 blocking effect Effects 0.000 description 3
- 238000007667 floating Methods 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 2
- 230000003749 cleanliness Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000011112 process operation Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- 229910000592 Ferroniobium Inorganic materials 0.000 description 1
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
Classifications
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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
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/20—Controlling or regulating processes or operations for removing cast stock
-
- 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
- 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
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The application discloses a cold bending cracking control process for HRB500E deformed steel bar, which relates to the technical field of ferrous metallurgy steel making and steel rolling, and comprises the following steps: s1: controlling steelmaking components; s2: selecting a furnace body, and adding molten iron; s3: the converter smelting adopts a high-pulling repair blowing process, and molten steel is smelted at the end point; s4: the tapping of the converter adopts vanadium-nitrogen alloy and ferrovanadium alloy micro-alloying; s5: tapping through a converter, and entering a refining station; s6: the continuous casting machine 5 is used for 5-strand casting, and the superheat degree of the continuous casting steel is within the range of 10-25 ℃; s7: HRB500E continuous casting billets were each low-power rated for each flow in the early and middle stages of casting in the furnace; s8: and (3) producing the casting blank in the first 2 furnaces of each casting time without hot delivery, and cooling the casting blank to the surface temperature below 200 ℃ and then rolling the steel. According to the application, the dendritic tissue proportion of the surface layer of the deformed steel bar is reduced by adjusting the technological operations such as pouring and conveying time of a casting blank into a heating furnace, heat preservation time of the heating furnace before rolling and rolling start temperature.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy steel making and steel rolling, in particular to a cold bending cracking control process for HRB500E deformed steel bars.
Background
The HRB500E screw-thread steel has the characteristics of high strength, good performance and good earthquake resistance, and is widely applied to high-rise, large-span and earthquake-resistant buildings.
According to the requirements of national standard GB 1499.2-2018, HRB500E deformed steel bars with different specifications are required to be directly bent for 180 degrees by a bending pressure head with the diameter of 6-8 times, and cracks cannot be generated on the surface of the bent part of the deformed steel bar. However, in the production process of the HRB500E threaded steel, due to the influence of strength and specification effects, the plasticity and the technological performance of the steel bar are correspondingly deteriorated, and the problems of unstable mechanical property, large fluctuation, unqualified technological performance and the like of the steel bar are often caused, and the steel bar is mainly characterized by cold-bending cracking along the root of the transverse rib, especially the HRB500E threaded steel with the specification of more than 25 specifications, and the probability of cold-bending cracking is larger.
Reasons for HRB500E deformed steel bar cold-bending cracking:
1. When the converter is tapped, the HRB500E deformed steel bar is microalloyed by adding vanadium-nitrogen alloy into the ferrocolumbium alloy, so that the niobium element content of molten steel is increased, and the occurrence probability of cold bending cracking of the deformed steel bar is improved.
2. When tapping in the converter, a large amount of vanadium-nitrogen alloy is adopted for microalloying, so that the nitrogen element content in the molten steel is increased. When the nitrogen content in the molten steel exceeds 0.01%, nitrogen gas holes are liable to be formed, and these holes cause excessive segregation of nitrides at grain boundaries, increase brittleness of the steel, and deteriorate toughness of the steel, so that these holes are also one of sources of cold-bending cracking of HRB500E threaded steel.
3. The refining argon blowing time is insufficient. Due to the adoption of slag blocking balls for slag blocking and manual judgment of a tapping end point, slag discharging and slag leakage are caused by incomplete slag blocking and inaccurate judgment of the tapping end point, and in addition, the molten steel is insufficient in CAS refining time, so that large-particle inclusions in the molten steel do not float up enough time, the inclusions remain in the molten steel, the strength of the steel is reduced, meanwhile, the transverse extensibility of the steel is obviously influenced, and the occurrence probability of cold bending cracking of HRB500E threaded steel is increased.
4. The flow and pressure of bottom blowing argon are unstable in the refining process. In the refining process of molten steel, a refining operator only simply turns on an argon blowing switch and does not pay attention to the argon blowing effect in a molten steel tank, so that the phenomenon that inclusions float upwards difficultly due to small argon blowing and the phenomenon that molten steel is seriously oxidized due to large argon blowing exist, and the cleanliness of the molten steel is reduced.
5. The superheat degree of the molten steel is high. The highest superheat degree of the tundish is more than 30 ℃ and the ratio is more than 60%; the steel drawing speed is high, the average drawing speed of 155mm square billets is 4.2m/min, and the maximum drawing speed exceeds 4.5m/min. The high superheat degree and high drawing speed continuous casting production lead to the development of columnar crystals of casting blanks, increase the dendritic tissue ratio of the surface layer of the rolled deformed steel bar, and easily lead to cold bending cracking.
6. The degree of superheat of the furnace 2 before casting of HRB500E screw steel produced by continuous casting is high, coarse original austenite exists in the produced HRB500E hot blank, dynamic recrystallization in the rolling process is not facilitated by hot feeding into a heating furnace, and dendritic tissues are easy to generate on the surface of the screw steel to cause cold bending cracking.
7. The heat preservation time of the heating furnace is not enough before rolling, the heat preservation time is 65+/-5 minutes, the rolling start temperature of the heating furnace is controlled to 1040-1080 ℃, the grain size is larger due to the higher rolling start temperature control, and the dendritic tissue proportion on the surface of the steel bar is increased.
Based on the above, we propose a cold bending cracking control process for HRB500E deformed steel bar.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide a cold bending cracking control process for HRB500E deformed steel bars, wherein the steel tapping of a converter avoids the use of micro-alloying of niobium-containing alloy; the N element content of the molten steel is controlled within a proper range, so that the precipitation strengthening effect of the N element on the deformed steel bar is ensured, and the excessive N element content is prevented from increasing the crack generation probability; the refining time is prolonged, and longer floating time of inclusions in molten steel in the refining process is ensured; the argon pressure blown at the bottom of the ladle is stabilized within a stable range, so that the effect of removing impurities by blowing refining gas is ensured, and secondary oxidation of molten steel due to intense stirring is avoided; the superheat degree and the pulling speed of continuous casting molten steel are reduced, and the columnar crystal development of a continuous casting billet is avoided; the dendritic tissue proportion of the surface layer of the deformed steel bar is reduced by adjusting the technological operations such as pouring and conveying the casting blank into a heating furnace, preserving the heat of the heating furnace before rolling, rolling start rolling temperature and the like.
In order to achieve the technical purpose and the technical effect, the invention is realized by the following technical scheme:
a cold bending and cracking control process for HRB500E deformed steel bar comprises the following steps:
S1: controlling steelmaking components, and simultaneously avoiding microalloying of an alloy containing niobium element for converter tapping of the HRB500E screw-thread steel;
S2: selecting a furnace body, and adding molten iron;
S3: the converter smelting adopts a high-pulling repair blowing process, and molten steel is smelted at the end point;
s4: the tapping of the converter adopts vanadium-nitrogen alloy and ferrovanadium alloy micro-alloying;
s5: tapping steel from the converter, entering a refining station, and refining molten steel in CAS for argon blowing time of more than 10 minutes; argon pressure range of bottom blowing of the ladle is 0.5-1.2 MPa;
s6: the continuous casting machine 5 is used for 5-flow, the superheat degree of continuous casting steel is within the range of 10-25 ℃, and the capping and heat preservation of a molten steel tank are used for matching with the continuous casting steel with low superheat degree, so that the billet drawing speed is controlled to be no more than 4.0 m/min;
s7: HRB500E continuous casting billets were each low-power rated for each flow in the early and middle stages of casting in the furnace;
s8: the casting blank is produced in the first 2 furnaces of each casting time without hot delivery, and the casting blank is cooled to the surface temperature below 200 ℃ and then rolled; the rolling does not need any water penetrating equipment and any water penetrating cooling process;
s9: the casting blank is directly fed into a steel rolling heating furnace after being hot-fed by a hot-feeding rail, the heating time of the casting blank in the heating furnace is controlled according to 85+/-5 minutes, and the initial rolling temperature is controlled according to 950-1050 ℃; the rolling reduction rate of the first two passes is not less than 28% in the casting blank rolling process, and the rolling reduction rate of the second pass is not less than 32%;
s10: and (5) obtaining a steel product, and detecting each component to obtain a result.
Preferably, the steelmaking composition control criteria in step S1 are as follows: c:0.21% -0.25%; si:0.55% -0.8%; mn:1.45% -1.6%; p is less than or equal to 0.04 percent; s is less than or equal to 0.04 percent; v:0.056% -0.095%.
Preferably, the specific operation in step S4 is as follows: according to the test result of the vanadium-nitrogen alloy, the vanadium-nitrogen alloy is added into a single furnace by about 82kg according to the steel tapping amount of 120 tons of the single furnace and calculated by about 0.054 percent of vanadium addition of the vanadium-nitrogen alloy; and according to the analysis result of the ferrovanadium alloy components and the V element content standard requirements of HRB500E threaded steels of different specifications, the adding amount of ferrovanadium is flexibly controlled, so that the terminal V element content of molten steel is ensured to meet the steel grade control standard requirements, namely the terminal V element content is in the range of 0.056% -0.095%.
In summary, the present invention includes at least one of the following beneficial effects:
according to the application, the hot rolled ribbed deformed bar is used as a control object, and the processes of microalloying in steel making, refining process operation, continuous casting process operation, rolling temperature and the like are optimized, so that no water passing cooling equipment and water passing cooling process are used in the rolling process, and cold bending cracking of the deformed bar is avoided.
Secondly, the HRB500E screw thread steel avoids microalloying by using an alloy containing niobium element, and reduces the occurrence probability of cold bending cracking of the steel.
Thirdly, the HRB500E screw-thread steel of the application is regulated by tapping micro-alloying, namely, vanadium-iron alloy is used for partially replacing vanadium-nitrogen alloy, so that the screw-thread steel contains proper N element content range (90-120 ppm). Therefore, the reinforcing effect of N element on the mechanical property of the steel bar is fully utilized, and the increase of sensitivity and brittleness of threads split rings lines caused by the excessively high content of N element is avoided.
Fourthly, the HRB500E threaded steel does not need to be smelted in an LF furnace, but clearly requires that the argon blowing refining time of the CAS station is more than 10 minutes, reduces the production cost and is beneficial to floating removal of inclusions.
Fifthly, the HRB500E threaded steel has a definite argon blowing gas pressure control range in the argon blowing operation of the CAS station, has strong on-site production operability and is beneficial to improving the cleanliness of molten steel.
Sixth, the HRB500E threaded steel controls the columnar crystal ratio of the casting blank and improves the quality of the casting blank by defining the process parameters of the superheat degree and the drawing speed of the cast steel produced by continuous casting.
Seventh, the HRB500E screw-thread steel reduces the probability of cold bending cracking defect of the HRB500E screw-thread steel through definitely casting the technological parameters such as a 2-furnace billet forming mode before casting, casting blank heating time, casting blank rolling temperature, 2-channel rolling reduction before casting blank rolling and the like.
Detailed Description
The present invention will be described in further detail below.
Example 1
The invention discloses a cold bending cracking control process for HRB500E deformed steel bar, which comprises the following technical requirements:
1. The steel tapping of the HRB500E screw-thread steel converter avoids the use of niobium-containing alloy microalloying, and reduces the occurrence probability of cold bending cracking of the steel; the steelmaking ingredient control standards are as follows: c:0.21% -0.25%; si:0.55% -0.8%; mn:1.45% -1.6%; p is less than or equal to 0.04 percent; s is less than or equal to 0.04 percent; v:0.056% -0.095%.
2. The vanadium iron alloy is adopted to partially replace the vanadium nitrogen alloy composite micro-alloy mode to avoid high N element content in molten steel. The specific operation is that according to the vanadium-nitrogen alloy test result (the V element content of the vanadium-nitrogen alloy is about 78%), the single furnace is required to be added with about 82kg of the vanadium-nitrogen alloy according to the single furnace tapping amount of 120 tons and the vanadium addition of the vanadium-nitrogen alloy is about 0.054%; and according to the analysis result of the vanadium iron alloy component (the content of the V element of the vanadium iron alloy is about 50%), the vanadium iron addition amount is flexibly controlled according to the V element content standard requirements of HRB500E threaded steels of different specifications, and the terminal V element content of molten steel is ensured to meet the steel grade control standard requirements, namely the terminal V element content is in the range of 0.056% -0.095%.
3. HRB500E screw steel is produced without smelting in an LF furnace, but the argon blowing time of molten steel in CAS refining is longer than 10 minutes, and inclusions in the molten steel have longer floating time in the refining process of a CAS station.
4. The pressure range of argon blown by the bottom of the ladle is 0.5-1.2MPa, so that the effect of blowing air to remove impurities in refining is ensured, and secondary oxidation of molten steel due to intense stirring is avoided.
5. The superheat degree of continuous casting steel (155 mm square billet) is within the range of 10-25 ℃, and the steel ladle is used for capping and heat preservation to cooperate with continuous casting low superheat degree steel casting, so that the billet drawing speed is controlled to be no more than 4.0m/min, and the columnar crystal development of the casting blank is avoided.
6. And (3) producing the casting blank in the first 2 furnaces of each casting time without hot delivery, and cooling the casting blank to the surface temperature below 200 ℃ and then rolling the steel.
7. The heating time of the casting blank in the heating furnace is controlled according to 85+/-5 minutes, and the initial rolling temperature is controlled according to 950-1050 ℃.
8. The rolling reduction rate of the first two passes during casting blank rolling is not less than 28% in the first pass, and not less than 32% in the second pass. The effect of fully crushing austenite grains of the casting blank is achieved.
9. The rolling does not need any water penetrating equipment and any water penetrating cooling process.
Example two
Taking the production of HRB500E screw-thread steel with 25mm specification as an example:
Step 1, formulating the standard of components of the 25mm HRB500E anti-seismic reinforcing steel bar as follows: c:0.21% -0.25%; si:0.55% -0.65%; mn:1.45% -1.6%; p is less than or equal to 0.04 percent; s is less than or equal to 0.04 percent; v:0.064% -0.072%.
Step 2, furnace number 22103164, adding 100 tons of molten iron, and the components of the molten iron: c:0.42%; si:0.54%; mn:0.28%; p:0.148%; s: 0.023; the temperature of molten iron is 1299 ℃, and 20 tons of scrap steel is added.
Step 3, smelting the molten steel at the smelting end point by adopting a high-pulling repair blowing process in converter smelting: c:0.08%; si:0.0036%; mn:0.12%; p:0.015%; s:0.021%; the end point temperature is 1639 ℃.
And 4, microalloying the converter tapping by adopting vanadium-nitrogen alloy and vanadium-iron alloy. Adding into molten steel during tapping 1/4: 20kg of Si-Ca-Ba deoxidizer, 20kg of Si-Al-Ba deoxidizer, 120kg of carbon powder, 1350kg of Si-Mn alloy, 410kg of Si-Fe alloy, 82kg of V-N alloy and 23kg of V-Fe alloy.
Step 5, the tapping amount of the converter is 115.3 tons, and the components entering a refining station are as follows: c:0.224%; si:0.584%; mn:1.46%; p:0.017%; s:0.018%; v0.071%, feeding molten steel into refining station at 1583 ℃, adding 100kg of Si-Mn alloy at station: and (3) capping and pouring in the background before and after the molten steel tank is lifted, wherein the refining argon blowing time is 12 minutes, the argon pressure of the molten steel tank ranges from 0.5 MPa to 1.2MPa, the outlet temperature is 1556 ℃.
Step 6, 5 flows of a continuous casting machine 5, wherein the section size is 155mm square billets, the liquidus temperature of HRB500E is 1505 ℃, the tundish temperature is 1515-1525 ℃, and the requirements are met; the blank pulling speed is 3.8-4.0m/min, which meets the requirements; the steel drawing cycle is 32min. And (3) middle packet sampling results: c:0.233%; si:0.584%; mn:1.53%; p:0.018%; s:0.018%; v0.071%.
The ladle temperature after the ladle is opened and poured and the pulling speed of each stream are as follows:
And 7, respectively taking a piece of low-power grade of each flow of the HRB500E continuous casting blank in the early stage and the middle and late stage of casting in the furnace, wherein the low-power grade is as follows:
And 8, directly feeding the casting blank into a steel rolling heating furnace after hot feeding by using a hot feeding track, wherein the time of the heating furnace is 80-90min, the initial rolling temperature is 1020 ℃, the final rolling speed is 15m/s, the first pass rolling reduction is 29%, and the second pass rolling reduction is 32%.
Step 9, detecting the components of the steel product: c:0.236%; si:0.594%; mn:1.55%; p: 0.016; s:0.017%; v0.071%.
Step 10, detecting the content of gas elements in the steel product: the content of O element is 25ppm, the content of N element is 88ppm, and the content of H element is 0ppm.
Step 11, detecting the mechanical properties of the steel: yield strength, tensile strength, elongation after break, reduction of area, etc., as listed below.
And step 12, obtaining a cold-formed finished product.
The above embodiments are not intended to limit the scope of the present invention, so: all equivalent changes in structure, shape and principle of the invention should be covered in the scope of protection of the invention.
Claims (1)
1. A cold bending and cracking control process for HRB500E deformed steel bar comprises the following steps:
S1: the steelmaking components are controlled, and the standard of 25mm HRB500E earthquake-resistant steel bar components is formulated as follows: c:0.21% -0.25%; si:0.55% -0.65%; mn:1.45% -1.6%; p is less than or equal to 0.04 percent; s is less than or equal to 0.04 percent; v:0.064% -0.072%, and meanwhile, the converter tapping of the HRB500E screw steel avoids the microalloying of niobium-containing alloy;
s2: selecting a furnace body, adding 100 tons of molten iron, and adding the following components: c:0.42%; si:0.54%; mn:0.28%; p:0.148%; s: 0.023; the temperature of molten iron is 1299 ℃, and 20 tons of scrap steel is added;
S3: the converter smelting adopts a high-drawing and repair-blowing process, and the smelting endpoint molten steel comprises the following components: c:0.08%; si:0.0036%; mn:0.12%; p:0.015%; s:0.021%; the end point temperature is 1639 ℃;
S4: the converter tapping adopts vanadium-nitrogen alloy and ferrovanadium alloy micro-alloying, and is added into molten steel when tapping is 1/4: 20kg of Si-Ca-Ba deoxidizer, 20kg of Si-Al-Ba deoxidizer, 120kg of carbon powder, 1350kg of Si-Mn alloy, 410kg of Si-Fe alloy, 82kg of V-N alloy and 23kg of V-Fe alloy;
According to the test result of the vanadium-nitrogen alloy, the vanadium-nitrogen alloy is added into a single furnace according to the steel tapping amount of 120 tons of the single furnace and calculated by 0.054 percent of vanadium addition of the vanadium-nitrogen alloy; according to the analysis result of the ferrovanadium alloy components and the V element content standard requirements of HRB500E threaded steels of different specifications, the adding amount of ferrovanadium is flexibly controlled, and the terminal V element content of molten steel is ensured to meet the steel grade control standard requirements, namely the terminal V element content is in the range of 0.056% -0.095%;
s5: tapping steel from the converter, entering a refining station, and refining molten steel in CAS for argon blowing time of more than 10 minutes; argon pressure range of bottom blowing of the ladle is 0.5-1.2 MPa;
The tapping amount of the converter is 115.3 tons, and the components entering a refining station are as follows: c:0.224%; si:0.584%; mn:1.46%; p:0.017%; s:0.018%; v0.071%, feeding molten steel into refining station at 1583 ℃, adding 100kg of Si-Mn alloy at station: the refining argon blowing time is 12 minutes, the argon pressure of the molten steel tank ranges from 0.5 MPa to 1.2MPa, the outlet temperature is 1556 ℃, and the molten steel tank is capped before lifting and is poured in a background;
S6: the continuous casting machine 5 is used for 5-flow, the superheat degree of continuous casting steel is within the range of 10-25 ℃, and the capping and heat preservation of a molten steel tank are used for matching with the continuous casting steel with low superheat degree, so that the billet drawing speed is controlled to be no more than 4.0 m/min; the section size is 155mm square billet, the liquidus temperature of HRB500E is 1505 ℃, the tundish temperature is 1515-1525 ℃, and the requirements are met; the blank pulling speed is 3.8-4.0m/min, which meets the requirements; the steel pulling cycle is 32min, and the sampling result is that: c:0.233%; si:0.584%; mn:1.53%; p:0.018%; s:0.018%; v0.071;
s7: HRB500E continuous casting billets were each low-power rated for each flow in the early and middle stages of casting in the furnace;
s8: the casting blank is produced in the first 2 furnaces of each casting time without hot delivery, and the casting blank is cooled to the surface temperature lower than 200 ℃ and then rolled by steel rolling; the rolling does not need any water penetrating equipment and any water penetrating cooling process;
S9: the casting blank is directly fed into a steel rolling heating furnace after being hot-fed by a hot-feeding rail, the heating time of the casting blank in the heating furnace is controlled according to 85+/-5 minutes, and the initial rolling temperature is controlled according to 950-1050 ℃; the rolling reduction rate of the first two passes is not less than 28% in the casting blank rolling process, and the rolling reduction rate of the second pass is not less than 32%;
S10: obtaining a steel product, detecting each component to obtain a result, and detecting the components of the steel product to obtain a result: c:0.236%; si:0.594%; mn:1.55%; p: 0.016; s:0.017%; v is 0.071%, and the detection result of the gas element content of the steel product comprises: the content of O element is 25ppm, the content of N element is 88ppm, and the content of H element is 0ppm.
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