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CN-117300086-B - Method for pre-judging casting blank longitudinal crack risk before production and continuous casting method based on pre-production

CN117300086BCN 117300086 BCN117300086 BCN 117300086BCN-117300086-B

Abstract

The invention discloses a method for prejudging casting blank longitudinal crack risk and a continuous casting method based on preproduction prejudgment, wherein the state of casting equipment is rated, rating rules are respectively rated from A, B, C, D grades, crystallizer vibration is that longitudinal deflection is less than or equal to +/-0.2 mm and transverse deflection is less than or equal to +/-0.05 mm and is A grade, longitudinal deflection is less than or equal to +/-0.2 mm and transverse deflection is less than or equal to +/-0.05 mm and is less than or equal to +/-0.2 mm and is B grade, longitudinal deflection is less than or equal to +/-0.25 mm and transverse deflection is less than or equal to +/-0.2 mm and is C grade, and longitudinal deflection is less than or equal to +/-0.25 mm and transverse deflection is less than or equal to +/-0.3 mm and is less than or equal to +/-0.2 mm is D grade. The method can effectively avoid the generation of longitudinal crack defects on the surface of the casting blank and the risk of the casting blank flowing into the next working procedure by establishing the equipment rating rule for pre-production, improves the surface quality of the casting blank on the basis of not increasing the production cost, and achieves the effects of high efficiency and high quality.

Inventors

  • JIANG LIMEI
  • HAN JIAN
  • LI SHOUHUA
  • CHENG DI
  • ZHANG CUIDUAN
  • MENG LINGFENG
  • Han Chuangchuang
  • WU WEI

Assignees

  • 邯郸钢铁集团有限责任公司
  • 河钢股份有限公司邯郸分公司

Dates

Publication Date
20260505
Application Date
20230905

Claims (6)

  1. 1.A method for prejudging casting blank longitudinal crack risk is characterized in that the state of casting machine equipment is rated, and the rating rules are respectively evaluated from A, B, C, D four grades; the vibration of the crystallizer is that the longitudinal deflection is < +/-0.2 mm and the transverse deflection is < +/-0.05 mm, the longitudinal deflection is < +/-0.2 mm and the transverse deflection is less than or equal to 0.05mm and less than or equal to 0.2mm and is B, the longitudinal deflection is less than or equal to 0.2mm and the transverse deflection is less than or equal to 0.25mm and less than or equal to 0.2mm and is C, and the longitudinal deflection is less than or equal to 0.3mm and the transverse deflection is less than or equal to 0.2mm and is D; the outer arc deviation of the sector section is A level, 1-3 point deviations of +/-0.5 mm less than or equal to the outer arc line are less than or equal to +/-1.0 mm, other deviations are all less than or equal to +/-0.5 mm and are B level, 4-5 point deviations of +/-0.5 mm less than or equal to the outer arc line are less than or equal to +/-1.0 mm, other deviations are all less than or equal to +/-0.5 mm and are C level, 6-8 point deviations of +/-0.5 mm less than or equal to the outer arc line are less than or equal to +/-1.0 mm, and no more than 2 point deviations are all less than or equal to +/-0.5 mm and are D level; the spray state is that the blocking rate before the straightening section is less than or equal to 3 percent and is A grade, the blocking rate is less than or equal to 5 percent and is B grade, the blocking rate is less than or equal to 8 percent and is C grade, and the blocking rate is 8 percent and is D grade; the equipment rating is pre-judged to be a short plate, the worst grade of the vibration, the outer arc deviation of the sector section and the spraying state of the crystallizer is used as a comprehensive evaluation standard, and the casting blank surface longitudinal crack risk is pre-judged, wherein the comprehensive evaluation grade A is minimum in longitudinal crack risk, the comprehensive evaluation grade B and the comprehensive evaluation grade C are maximum in longitudinal crack risk.
  2. 2. A continuous casting method based on pre-production pre-judgment is characterized in that the method of claim 1 is adopted for pre-production pre-judgment, and is characterized in that casting machine equipment comprehensively evaluates class A to produce sensitive steel with carbon equivalent of 0.3-0.6, class B to produce acid-washed steel and structural steel with carbon equivalent of 0.1-0.3, and class C and class D to produce ultra-low carbon steel and low carbon steel with carbon equivalent of 0.1.
  3. 3. The continuous casting method based on prenatal pre-judgment according to claim 2, wherein the pulling speed of the continuous casting is controlled by passing through the lower opening of the crystallizer at a pulling speed of 0.4m/min after starting, then rising to 0.8m/min at a rising acceleration of 0.3-0.4 m/min 2 , and rising to the target pulling speed at a rising reference of 0.2m/min 2 after holding for 2-3 minutes.
  4. 4. The continuous casting method based on prenatal pre-judgment according to claim 2, wherein in the continuous casting process, the thickness of the slag layer is controlled to be 8-15 mm, and the consumption of the protective slag is calculated according to a formula (I); Q=0.8(1/A 0.3 )(60/f)(nV 2 ) -0.5 +0.13 (I) Wherein Q is the consumption of the mold flux, kg/m 2 , A is the vibration amplitude of the crystallizer, mm, f is the vibration frequency of the crystallizer, times/min, n is the viscosity of the mold flux, pa.s, and V is the target pulling speed, m/min.
  5. 5. The continuous casting method based on prenatal pre-judgment according to claim 2, wherein in the continuous casting process, the heat flow ratio of the wide side and the narrow side of the crystallizer is controlled to be 1.1-1.25, and the superheat degree of molten steel is controlled to be 15-30 ℃.
  6. 6. The continuous casting method based on prenatal prediction according to any one of claims 2-5, wherein the mold vibration during the continuous casting process adopts a smooth sawtooth negative slip mode, the deflection rate is 60%, the smoothness is 25%, the negative slip time is controlled to be 0.12-0.15 s, and the negative slip time rate is controlled to be 39-43%.

Description

Method for pre-judging casting blank longitudinal crack risk before production and continuous casting method based on pre-production Technical Field The invention belongs to the technical field of continuous casting, and particularly relates to a method for pre-judging casting blank longitudinal crack risk before production and a continuous casting method based on the pre-judging before production. Background Casting blank longitudinal cracking is a common surface defect in the production process of continuous casting slabs, and occurs on the surface and subsurface of the casting blank. Aiming at the continuous casting billet longitudinal crack defect, students at home and abroad also do a great deal of research, the root of the research is initiated in a crystallizer, and the secondary cooling zone is expanded and deteriorated. The surface longitudinal cracks of the casting blank can be found through thermal inspection or cold inspection of the casting blank, can be eliminated through finishing manual gun pulling treatment, do not affect subsequent rolling, but can cause steel material loss and labor cost increase, and meanwhile, planning and arrangement are also affected. The casting blank longitudinal crack is a typical defect generated in a crystallizer, and is reflected to the casting blank, the casting blank is shorter than a few millimeters, the casting blank can be 3-4 meters long, and serious defects even penetrate through the whole surface of the casting blank. The root cause of the casting blank longitudinal cracking is that in the meniscus area of the crystallizer, the molten steel is subjected to volume shrinkage in the process of solidifying to form a blank shell, so that an air gap is generated between the blank shell and the wall of the crystallizer, the thermal resistance is increased, and the heat transfer efficiency is reduced. Because the air gap generated in the crystallizer is nonuniform, the uniformity of heat transfer from the blank shell to the crystallizer is affected, the thickness of the blank shell and the internal stress distribution of the blank shell are further uneven, and fine microcracks are formed at the weak part of the blank shell under the action of the ferrostatic pressure. If the precision state of the casting machine is poor, the cooling intensity of the casting blank entering the secondary cooling area is uneven, and the micro cracks formed by the crystallizer can be further expanded and extended, so that the longitudinal crack defect on the surface of the casting blank is formed. Therefore, the casting blank longitudinal cracking prevention is closely related to the casting powder performance, the heat flow of the crystallizer, the superheat degree of molten steel, the constant-pull-rate casting, the immersion nozzle insertion depth, the abrasion of the surface of a copper plate of the crystallizer and the like, and the precision of casting equipment and the secondary cooling strength are also important to pay attention. At present, research at home and abroad mainly analyzes and researches the cause of the longitudinal crack defect on the surface of a casting blank and rapidly identifies on-line detection, but in order to avoid the longitudinal crack risk, classification production of different steel grades by combining a casting machine arc line and a spraying state classification, pre-production fresh judgment is reported. The Chinese patent application with publication number of CN114346193A discloses a process method for preventing longitudinal cracks and bonding steel leakage in the starting process of a slab caster, which reduces the longitudinal cracks and steel leakage rate of casting blanks by controlling the pulling rate after the emergence of a tundish, automatically sets the pulling rate to 0.28m/min, and increases the pulling rate by 0.03m/min every 30 seconds after the maintaining for 2 minutes, and increases the pulling rate to normal pulling rate by 40 seconds instead of manual control after the pulling rate reaches 0.70 m/min. The method is not related to other technological parameters affecting longitudinal fracture. The Chinese patent application with publication number of CN101985166A discloses a continuous casting slab longitudinal crack steel leakage prediction method, which is characterized in that analysis and judgment are carried out according to temperature data detected by thermocouples, the transverse temperature difference, the longitudinal temperature change rule and the amplitude of the thermocouples are comprehensively considered, the occurrence of longitudinal cracks is determined by combining the characteristics of steel types, the limitation of single transverse temperature difference or single longitudinal thermocouple temperature change rate is overcome, but the related influence factors such as casting powder performance, crystallizer taper, liquid level steady state control and the like are not studied. The Chinese patent ap