CN101642774B - GCr15 bearing steel bloom continuous casting dynamic soft reduction process - Google Patents

GCr15 bearing steel bloom continuous casting dynamic soft reduction process Download PDF

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CN101642774B
CN101642774B CN2009100754031A CN200910075403A CN101642774B CN 101642774 B CN101642774 B CN 101642774B CN 2009100754031 A CN2009100754031 A CN 2009100754031A CN 200910075403 A CN200910075403 A CN 200910075403A CN 101642774 B CN101642774 B CN 101642774B
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China
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continuous casting
bearing steel
drafts
central
gcr15 bearing
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CN2009100754031A
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Chinese (zh)
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CN101642774A (en
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张永藏
祭程
田新中
施建强
刘敬军
钟保军
胡黎宁
赵忠义
董志强
薛正学
戴永刚
王立新
马富平
曹磊
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邢台钢铁有限责任公司
东北大学
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Abstract

The invention relates to a GCr15 bearing steel bloom continuous casting dynamic soft reduction process, which belongs to the technical field of metallurgical continuous casting and is used for solving the problems that the GCr15 bearing steel bloom continuous casting is easy to cause central segregation, central looseness, central parosity and other casting slab internal quality defects. The technical scheme is as follows: the reduction of a continuous casting soft reduction region is controlled through the change of central solid phase rate fs of a casting slab, and the relationship between the reduction of a soft reduction rack and the central solid phase rate of the casting slab is given out. The adoption of the soft reduction process of dynamic control can significantly reduce the central segregation of the GCr15 bearing steel casting slab, the central carbon segregation index of the casting slab is 0.95-1.08, and the average central segregation is 1.03; the process can also obviously improve the central looseness and the central parosity of the GCr15 bearing steel casting slab, the proportion of the central looseness of the casting slab which is not more than 1.0 grade is more than 90%, and the central parosity is not more than 0.5 grade.

Description

The GCr15 bearing steel bloom continuous casting dynamic soft reduction process

Technical field

The present invention relates to a kind of continuous casting process, particularly can eliminate or alleviate the GCr15 bearing steel bloom continuous casting dynamic soft reduction process of strand internal soundness defectives such as bloom center segregation, center porosity, central pipe, belong to the metallurgical continuous casting technical field.

Background technology

The GCr15 bearing steel is a high-carbon-chromium bearing steel, and carbon content and alloy content are higher, and the variations in temperature of freezing range is big, it is long to solidify gap length, mushy zone is wide, so forms easily serious center segregation in the process of setting, and is difficult to effectively be eliminated in the heating in later stage, the operation of rolling.The existence of high-carbon-chromium bearing steel center segregation causes that continuous-casting bearing steel is only suitable to be done lasso and can not make rolling element (ball, pearl, pin); And along with the aggravation of carbide strip segregation, heat treated sensitiveness strengthens, and the microhardness difference between the height carbon ribbon increases, and influences contact fatigue life.In addition, because the large square bland continuous-casting machine casting blank cross-section size is big, thereby the casting blank solidification time is longer, and the tendentiousness that strand produces central defects such as center segregation, center porosity, centre burst is bigger.Therefore, study and define rational GCr15 bearing steel continuous casting process, effectively solve comparatively serious technical barriers such as continuous casting billet center segregation, center porosity, for the hot-working character of the energy loss that reduces subsequent handling, raising product, produce high-quality most important with bearing steel high added value.

For the method that alleviates strand internal soundness defectives such as GCr15 bearing steel bloom center segregation, component segregation, center porosity, central pipe, the insider has done a large amount of research, once report that emerging clear special steel bearing steel 300mm * 340mm bloom continuous casting adopts omnidistance non-oxidation protection cast, M+F-EMS electromagnetic agitation technology, tundish metallurgy technology in August, 2008 as " Jiangsu metallurgy " magazine, thereby by adopting low overheat, the cast of control casting speed to improve center segregation and shrinkage cavity, strand center carbon segregation is 1.12; In February, 2009 reported that northern full special steel adopts passive light to depress technology and improves GCr15 bearing steel 240mm * 240mm bloom segregation by " special steel " magazine, the center porosity rank of GCr15 bearing steel bloom is reduced to 1.0~1.5 grades by 2.0~2.5 grades, strand center carbon segregation index is reduced to 1.07~1.13 by 1.17~1.26; In February, 2008 reported that the northeast special steel adopts end gently to depress technology and improves GCr15 bearing steel 240mm * 240mm bloom slab quality by " technology " magazine, putting enforcement simultaneously in one, two, three straightening seats in the plane gently depresses, drafts is 7~8mm, the distribution ratio of three frames was respectively 3: 3: 2,3: 2: 2.After implementing gently to depress, the horizontal segregation index of strand reduces to 1.00~1.18 by 1.06~1.28, and the vertical segregation index of strand reduces to 0.95~1.18 by 1.07~1.5.Above-mentioned research plays a role to solving problems such as GCr15 bearing steel center segregation, loose, shrinkage cavity, but still have following problems: (1) electromagnetic agitating technology can not effectively compensate molten steel solidification and shrink, when the solidification of molten steel terminal position changes, can not adjust mixing position, limit the realization of technical process; (2) the GCr15 bearing steel bloom continuous casting in the above-mentioned report is gently depressed all and is belonged to " passive light is depressed ", " passive light is depressed " its light depressing position, drafts, to depress speed be changeless in the continuous casting process, and the casting blank solidification end position is to determine gently to depress a whether rational important parameter of technology, therefore, when continuous casting pulling rate, the degree of superheat, intensity of cooling etc. change, adopt passive light to depress technology and be difficult to the central defects such as center segregation, center porosity that success alleviates continuous casting billet.In addition, a kind of dynamic soft reduction technologies for bloom continuous casting of heavy rail is disclosed in the national patent 200710048924.9, but because the carbon content and the alloying element content of GCr15 bearing steel and Properties of Heavy Rail Steel By have very big difference, and the non-constant of GCr15 bearing steel high-temp plastic, do not surpass 60% 1150 ℃ of contraction percentages of area the highest yet, high brittle zone is 950~1050 ℃ and 1250 ℃~fusing point, the GCr15 bearing steel belongs to the higher steel grade of carbon content, crack sensitivity is very strong, thus proposed in this patent dynamically gently depress technology and be not suitable for carbon content higher and contain and can improve strand intensity, the GCr15 bearing steel of the chromium element of hardness.

Summary of the invention

Technical problem to be solved by this invention is: a kind of GCr15 bearing steel bloom continuous casting dynamic soft reduction process that can significantly alleviate or eliminate defectives such as center segregation, center porosity, central pipe is provided.

The alleged problem of the present invention is solved by following technical scheme:

A kind of GCr15 bearing steel bloom continuous casting dynamic soft reduction process, its special feature is: gently depress the zone at continuous casting, drafts is controlled in variation by strand center solid rate fs, the pass of gently depressing frame drafts and strand center solid rate is: drafts is 0 when 0≤fs<0.4, drafts is 1.5mm when 0.40≤fs≤0.44, drafts is 2.5mm when 0.58≤fs≤0.62, drafts is 3.5mm when 0.73≤fs≤0.77, drafts is 3.0mm when 0.84≤fs≤0.88, drafts is 2.0mm when 0.92≤fs≤0.97, and drafts is 0 when 0.97<fs≤1.0; When gently depressing frame strand center solid rate and be in numerical value between above-mentioned two data segments, then adopt approach based on linear interpolation to calculate the pairing drafts of this frame according to its solid rate.

Above-mentioned GCr15 bearing steel bloom continuous casting dynamic soft reduction process, it is described that gently to depress regional casting blank solidification rate be 30%~100%, overall reduction is 7.66~12.5mm, the single maximum reduction≤3.5mm that gently depresses frame, maximum depression rate≤2.65mm/m.

Above-mentioned GCr15 bearing steel bloom continuous casting dynamic soft reduction process, GCr15 bearing steel continuous casting pulling rate 0.65~0.75m/min, 15~35 ℃ of tundish molten steel overheats, molten steel temperature in tundish is controlled at 1470~1490 ℃, the continuous casting ratio water yield is 0.18~0.28L/kg, gently depress regional casting blank surface temperature and be controlled at 780~950 ℃, the casting billet surface maximum speed≤20 ℃/m that rises again in the secondary cooling zone, maximum rate of temperature fall≤15 ℃/m.

Above-mentioned GCr15 bearing steel bloom continuous casting dynamic soft reduction process is characterized in that: described gently depress the zone to the distance of crystallizer meniscus in 16187mm~24649mm scope, gently depressing regional total length is 8462mm.

Above-mentioned GCr15 bearing steel bloom continuous casting dynamic soft reduction process, crystallizer electromagnetic agitation current strength is controlled to be 500A, and frequency is 2.4Hz, and rotation mode is unidirectional rotation.

The present invention is directed to GCr15 bearing steel bloom continuous casting is prone to strand internal soundness defect problems such as center segregation, center porosity, central pipe and improves, its crucial part is that the composition, continuous casting pulling rate, superheat of liquid steel, continuous casting intensity of cooling according to the GCr15 bearing steel etc. influences factors such as casting blank solidification end position, and what propose dynamically control gently depresses technology.Adopt this technology can significantly alleviate GCr15 bearing steel strand center segregation, strand center carbon segregation index 0.95~1.08, average 1.03; This technology also can obviously be improved GCr15 bearing steel strand center porosity and central pipe, and strand center porosity≤1.0 a grade ratio reaches more than 90%, central pipe≤0.5 grade.With the rolling bearing steel of continuous casting billet of the inventive method processing, can satisfy the specification requirement of making bearing roller (ball, pearl, pin).

The specific embodiment

The present invention is applicable to that C content is 0.95~1.05%, Cr content is 1.4~1.65%, Si content is that 0.15-0.35%, Mn content are 0.25-0.45%, and cross dimensions is greater than the GCr15 bearing steel continuous casting blooms of 220mm * 220mm.Technology of the present invention is determined a drafts of depressing frame according to casting parameters such as GCr15 bearing steel composition, pulling rate, the degree of superheat, intensities of cooling in good time, to alleviate defectives such as strand center segregation, center porosity, central pipe, can also improve simultaneously the uniformity of continuous casting billet bearing steel composition, stabilize and increase GCr15 bearing steel mechanical property and serviceability, reach the specification requirement of manufacturing rolling element.

Major technique measure of the present invention is as follows:

(1) formulate rational GCr15 bearing steel continuous casting pulling rate and molten steel temperature in tundish control system:

Continuous casting pulling rate 0.65~0.75m/min, 15~35 ℃ of tundish molten steel overheats, molten steel temperature in tundish is controlled at 1470~1490 ℃, guarantee that casting blank solidification end is positioned at and gently depress the zone, gently depress regional total length 8462mm, the variation flexible modulation that can adapt to continuous casting process such as steel grades, continuous casting pulling rate, the degree of superheat, intensity of cooling etc. is gently depressed zone length and drafts.

(2) gently depressing the solid rate control drafts of zone according to each strand center, straightening roller position, gently depress regional casting blank solidification rate 30%~100%, overall reduction is 7.66~12.5mm.Gently depress the zone, the single maximum reduction≤3.5mm that gently depresses frame, maximum depression rate≤2.65mm/m.Gently depress the relation such as the following table of frame drafts and strand solid rate:

Solid rate fs <0.40 0.40-0.44 0.58-0.62 0.73-0.77 0.84-0.88 0.92-0.97 >0.97 Drafts 0 1.5 2.5 3.5 3.0 2.0 0

When strand center solid rate less than 0.40 with greater than 0.97 the time, do not depress, when each frame strand center solid rate is in numerical value between table two data segment, then adopt known approach based on linear interpolation to calculate the pairing drafts of this frame according to its solid rate.

The control parameter of (3) two cool regions:

The continuous casting ratio water yield is 0.18~0.28L/kg, gently depress 780~950 ℃ of regional casting blank surface temperatures, guarantee that continuous casting gently depresses regional strand and have good high-temperature extension performance, and the two cold-zone casting billet surface maximums speed≤20 ℃/m that rises again, maximum rate of temperature fall≤15 ℃/m.

(4) adopt reasonable crystallizer electromagnetic agitation technological parameter, current strength is controlled to be 500A, and frequency is 2.4Hz, and rotation mode is unidirectional rotation.

Below provide several specific embodiments:

Described embodiment implements on the conticaster that is provided with 7 frame straightening machines, gently depresses the regional distance that arrives the crystallizer meniscus in 16187mm~24649mm scope, and gently depressing regional total length is 8462mm.

Embodiment 1: bearing steel GCr15 continuous casting blooms bloom cross dimensions is 280mm * 325mm, and the main chemical compositions (%) of cast heat is as shown in the table:

C Si Mn P S Cr 0.98 0.24 0.29 0.008 0.008 1.45

The main technologic parameters of cast heat continuous casting is as shown in the table:

Embodiment 2: bearing steel GCr15 continuous casting blooms cross dimensions is 280mm * 325mm, and the main chemical compositions (%) of cast heat is as shown in the table:

C Si Mn P S Cr 0.97 0.24 0.28 0.008 0.006 1.45

The main technologic parameters of cast heat continuous casting is as shown in the table:

Embodiment 3: bearing steel GCr15 continuous casting blooms cross dimensions is 280mm * 325mm, and the main chemical compositions (%) of cast heat is as shown in the table:

C Si Mn P S Cr 0.99 0.23 0.29 0.007 0.005 1.45

The main technologic parameters of cast heat continuous casting is as shown in the table:

Technology of the present invention is dynamically gently depressed by continuous casting billet, alleviates and has eliminated defectives such as strand center segregation, center porosity, central pipe, and strand center carbon segregation index reduces to 0.95~1.08 by 1.25~1.38, and average 1.03; Strand center porosity≤1.0 grade ratio increases to 100% by 28%, and central pipe≤0.5 grade increases to 100% by 45%, and satisfies the specification requirement of making rolling element (ball, pearl, pin) by the rolling bearing steel of continuous casting billet.

Claims (5)

1. GCr15 bearing steel bloom continuous casting dynamic soft reduction process, it is characterized in that: gently depress the zone at continuous casting, drafts is controlled in variation by strand center solid rate fs, the pass of gently depressing frame drafts and strand center solid rate is: drafts is 0 when 0≤fs<0.4, drafts is 1.5mm when 0.40≤fs≤0.44, drafts is 2.5mm when 0.58≤fs≤0.62, drafts is 3.5mm when 0.73≤fs≤0.77, drafts is 3.0mm when 0.84≤fs≤0.88, drafts is 2.0mm when 0.92≤fs≤0.97, and drafts is 0 when 0.97<fs≤1.0; When gently depressing frame strand center solid rate and be in numerical value between above-mentioned two data segments, then adopt approach based on linear interpolation to calculate the pairing drafts of this frame according to its solid rate, GCr15 bearing steel continuous casting pulling rate 0.65~0.75m/min, 15~35 ℃ of tundish molten steel overheats, molten steel temperature in tundish is controlled at 1470~1490 ℃, the continuous casting ratio water yield is 0.18~0.28L/kg, gently depress regional casting blank surface temperature and be controlled at 780~950 ℃, the casting billet surface maximum speed≤20 ℃/m that rises again in the secondary cooling zone, maximum rate of temperature fall≤15 ℃/m.
2. GCr15 bearing steel bloom continuous casting dynamic soft reduction process according to claim 1, it is characterized in that: described gently to depress regional casting blank solidification rate be 30%~100%, overall reduction is 7.66~12.5mm, single maximum reduction≤the 3.5mm that gently depresses frame, maximum depression rate≤2.65mm/m.
3. GCr15 bearing steel bloom continuous casting dynamic soft reduction process according to claim 1 and 2 is characterized in that: described gently depress the zone to the distance of crystallizer meniscus in 16187mm~24649mm scope, gently depressing regional total length is 8462mm.
4. GCr15 bearing steel bloom continuous casting dynamic soft reduction process according to claim 1 and 2 is characterized in that: crystallizer electromagnetic agitation current strength is controlled to be 500A, and frequency is 2.4Hz, and rotation mode is unidirectional rotation.
5. GCr15 bearing steel bloom continuous casting dynamic soft reduction process according to claim 3 is characterized in that: crystallizer electromagnetic agitation current strength is controlled to be 500A, and frequency is 2.4Hz, and rotation mode is unidirectional rotation.
CN2009100754031A 2009-09-15 2009-09-15 GCr15 bearing steel bloom continuous casting dynamic soft reduction process CN101642774B (en)

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Families Citing this family (12)

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Publication number Priority date Publication date Assignee Title
CN102310178A (en) * 2011-07-08 2012-01-11 南阳汉冶特钢有限公司 Method for solving center segregation of casting blank
CN102601331B (en) * 2011-12-09 2014-01-29 秦皇岛首秦金属材料有限公司 Method for improving center segregation of extra thick slab with thickness of 400mm
CN102601324B (en) * 2012-03-14 2013-07-17 北京科技大学 High-temperature experimental apparatus and method for research on mechanism of continuous casting soft-reduction
CN102653835B (en) * 2012-05-09 2013-08-21 东北大学 Method for reducing transverse cracks at corner of continuous casting billet of boron-steel-containing wide-thick plate
CN102990030B (en) * 2012-12-17 2014-09-03 南京钢铁股份有限公司 Continuous casting process for controlling semi-macroscopic segregation of H2S corrosion resisting steel casting blank
CN103128247A (en) * 2013-03-15 2013-06-05 北京科技大学 Method for producing 60 mm extra-thick steel plates with low compression ratio
CN104057051B (en) * 2013-09-13 2016-07-06 攀钢集团攀枝花钢铁研究院有限公司 A kind of production method of small square billet continuous casting bearing steel
CN104772444B (en) * 2014-01-15 2017-06-06 宝山钢铁股份有限公司 Reduce the control method of square billet afterbody shrinkage cavity
CN104308111B (en) * 2014-11-19 2016-05-18 河北工程大学 Reduce the method for bearing steel wire rod 1/2R place's gross segregation
CN104889354B (en) * 2015-06-05 2017-01-18 东北大学 Method for controlling torque of withdrawing and straightening machines for improving screw-down effects for solidification tail ends of continuous casting slabs
CN105127386A (en) * 2015-08-19 2015-12-09 河北钢铁股份有限公司 Continuous casting method for controlling center carbon segregation of small high-carbon hard-wire steel square billet
CN109396368A (en) * 2018-12-21 2019-03-01 南京钢铁股份有限公司 A method of improving high-carbon steel bloom continuous casting base internal soundness

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