A method for producing an ultra-high strength steel sheet having a narrow thickness tolerance

Abstract

The application discloses a production method of an ultrahigh-strength narrow-thickness-tolerance steel plate, and the process steps comprise the following steps: a, the narrow-thickness-tolerance steel plate is arranged in the early stage of the rolling period of a roller, 3-5 steel plates with the same specification are arranged in advance to adjust the thickness deviation control, and the rolling length of a mother plate is controlled to be less than or equal to 40 m; b, a walking beam heating furnace is adopted, the slab discharging temperature is greater than or equal to 1180 DEG C, and the temperature difference between the upper surface and the lower surface is controlled to be within 20 DEG C; c, double-stand rolling is adopted, a SmartCrown roller is adopted for a finishing mill, the plate crown is controlled to be less than 0.1 mm, the cooling water of a rough rolling table, a finishing rolling table and an intermediate roller table is turned off, the opening amount of the cooling water in the middle part of the working roller body is adjusted to be 60%-70%, and the opening amount of the cooling water on both sides is adjusted to be 30%-40%; d, the rough rolling and the finishing rolling are both controlled to be 7-9 passes, the biting speed is 1.2-1.6 m / s, and the rolling speed is 3-7 m / s. The steel plate with the thickness deviation controlled within 0.7 mm is obtained, and the stable control of the ultrahigh-strength narrow-thickness-tolerance steel plate is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of medium-thickness steel plate production and relates to a production method of ultra-high-strength narrow-thickness-tolerance steel plate. BACKGROUND

[0002] The narrow-thickness-tolerance steel plate is a finished product whose thickness is controlled within the tolerance range of national standards or enterprise standards, and the deviation of the target thickness is small, and the thickness deviation of the same plate is also small. The narrow-thickness-tolerance steel plate is beneficial to the lightweight of large equipment and is widely used in the field of engineering machinery, such as the application of the yield strength 1100 MPa grade ultra-high-strength steel in large-tonnage truck cranes, heavy-load crawler cranes, large-scale concrete pump trucks and other high-end engineering machinery equipment.

[0003] The existing technology can control the average thickness of the steel plate within the allowed tolerance range by using the AGC (Automatic Gauge Control) system, but the head and tail of the steel plate cannot be controlled within the range. Because the temperature of the head of the steel plate drops quickly during rolling, the rolling force rises, the actual rolling force is greater than the set rolling force, and the thickness is rolled; after the AGC system is self-adaptive, the actual rolling force decreases, and the thickness becomes thin. The tail of the steel plate also drops quickly, but due to the short time of the tail, only the rolling force decreases, so the thickness becomes thin.

[0004] Chinese patent CN 107030120 B discloses a "precise control method for thickness tolerance of ship steel plate", which realizes the precise control of the thickness tolerance of the ship steel plate by optimizing from the aspects of billet design, rolling thickness setting, rolling mill calibration, billet heating and rolling process. However, the strength level produced by the method is low, and the thickness precision is only the deviation of the average thickness of the steel plate after rolling from the set target thickness, and does not involve the control of the thickness deviation of the same plate.

[0005] Chinese patent CN 111389927 B discloses a "single-stand thin-gauge steel plate narrow-thickness-tolerance control method", which realizes the stable production of 0.2mm narrow-thickness-tolerance steel plate by single-stand thin-gauge steel plate. However, the single-stand thin-gauge steel plate rolling method is not suitable for the rolling method of the double-stand reversible four-roll rolling mill. SUMMARY

[0006] The application aims to provide a production method of ultra-high-strength narrow-thickness-tolerance steel plate, which realizes the stable control of the ultra-high-strength steel plate ≤0.7mm narrow-thickness-tolerance.

[0007] The technical scheme of the application is as follows:

[0008] A production method of ultra-high-strength narrow-thickness-tolerance steel plate, the thickness of the steel plate is 10-25mm, which comprises the following process steps:

[0009] a narrow thickness tolerance steel plate is arranged in the early stage of the rolling mill roll period, and the rolling mileage is ≤50 kilometers; 3-5 steel plates of the same specification are arranged to transition and adjust the thickness deviation control before production, and the thickness is preferentially transitioned from thick to thin, and then the width is transitioned from narrow to wide; the rolling length of the mother plate is controlled to be ≤40 m.

[0010] b a walking beam heating furnace is used, the slab casting temperature is ≥1180℃, the temperature difference between the upper and lower surfaces is controlled to be within 20℃, and there is no obvious water beam mark.

[0011] c double-stand rolling is used, the SmartCrown roller is used for the finishing mill, the plate crown is controlled to be <0.1mm; the cooling water of the rough and finishing mill roller and the intermediate roller is turned off; the middle cooling water of the work roller is adjusted to be 60-70%, and the cooling water on both sides is adjusted to be 30-40%.

[0012] Further, in step d, the rough rolling is controlled to be 7-9 passes; the finishing rolling is controlled to be 7-9 passes, the biting speed is 1.3-1.6m / s, and the rolling speed is 3-7m / s; the first pass of the finishing mill is descaled at the inlet, and the other odd passes are descaled at the outlet.

[0013] Further, the steel plate of the same specification is a steel plate with a thickness deviation ≤2mm and a width deviation ≤500mm.

[0014] In order to reduce the influence of the roll eccentricity on the thickness, preferably, in step c, the roundness of the roller is controlled to be within 50µm, and the roundness of the roller system is controlled to be within 250µm after on-machine calibration.

[0015] In order to reduce the temperature drop of the rolled piece head and tail during rolling, preferably, in step d, the ejection distance of the finishing mill inlet and outlet is controlled to be 3.2-3.5m.

[0016] The present application has the following beneficial effects: the present application optimizes the planning arrangement, slab heating and rolling process and the like, realizes the stable control of the ultra-high strength narrow thickness tolerance steel plate, narrows the allowed tolerance range of the steel plate thickness, and the thickness deviation of the same steel plate is controlled to be within 0.7mm, which meets the user demand of the product thickness tolerance requirement. DETAILED DESCRIPTION

[0017] The content of the present application will be further illustrated below in combination with examples.

[0018] Example 1:

[0019] The production method of the ultra-high strength narrow thickness tolerance steel plate. The order steel grade is Q1100E, the thickness is 12mm, the thickness tolerance is -0.2-0.5mm, and the width is 4200mm; the key process steps are:

[0020] a The length of the rolling mother plate is about 31.9 m, and the rolling starts at the beginning of the rolling period of 10.6 km. Five plates with a thickness of 12 / 14 mm and a width of 3700-4200 mm are arranged before production as a transition to adjust the thickness deviation.

[0021] b The step beam heating furnace is used, the slab casting temperature is 1242℃, the upper surface temperature is 1250℃, the lower surface temperature is 1243℃, the temperature difference is 7℃, and there is no obvious water beam mark.

[0022] c The double-stand rolling is used, the SmartCrown roller is used in the finishing mill, the plate crown is controlled to be less than 0.1 mm; the cooling water of the roughing and finishing roller ways and the intermediate roller way is turned off; the cooling water opening amount of the middle part of the work roller body is adjusted to 65%, and the cooling water opening amount of the two sides is adjusted to 35%.

[0023] d The rough rolling is 9 passes, and the 9th pass is skipped; the finishing rolling is 9 passes, the biting speed is 1.5 m / s, and the rolling speed is 3-7 m / s.

[0024] In order to reduce the temperature drop of the rolled piece head and tail during rolling, further control the biting speed, rolling speed and descaling mode, the throwing distance of the finishing mill exit and entrance is controlled to be 3.2-3.5 m; the first pass of the finishing mill is descaled at the entrance, and the other odd passes are descaled at the exit. The thickness of the rolled piece, the biting speed, the rolling speed and the descaling mode of each pass during rolling are shown in Table 1.

[0025] The thickness of the middle and edge parts of the head, middle and tail of the mother plate rolled in the above example is measured, and the results are shown in Table 3. The results show that: after removing the arc of the head and tail of the rolled piece, the cutting amount is reduced from more than 1000 mm to 500 mm, the thickness of the rolled piece is within the allowable range of the tolerance, and the thickness deviation of the rolled piece is 0.25 mm, which meets the product thickness tolerance requirement of the user with small demand, and can reduce the material quantity and improve the yield of the steel plate.

[0026] Example 2:

[0027] Production method of ultra-high strength narrow thickness tolerance steel plate. The order steel grade is Q1100E, the thickness is 17 mm, the thickness tolerance is -0.2-0.5 mm, and the width is 4500 mm; the key process steps are:

[0028] a The length of the rolling mother plate is about 31.9 m, and the rolling starts at the beginning of the rolling period of 10.6 km. Five plates with a thickness of 12 / 14 mm and a width of 3700-4200 mm are arranged before production as a transition to adjust the thickness deviation.

[0029] b The slab was heated in a walking beam furnace, the slab temperature was 1213℃, the upper surface temperature was 1227℃, the lower surface temperature was 1215℃, the temperature difference was 12℃, and there was no obvious water beam mark.

[0030] c Double-stand rolling was adopted, the Smart Crown roller was used in the finishing mill to control the plate crown <0.1mm; the cooling water of the roughing and finishing roller and the intermediate roller was turned off; the middle part of the work roller was adjusted to 65% and the two sides were adjusted to 35%.

[0031] d The rough rolling was 9 passes, the 9th pass was skipped; the finishing rolling was 11 passes, the last pass was skipped, the biting speed was 1.3-1.5m / s, and the rolling speed was 3-7m / s.

[0032] In order to reduce the temperature drop of the head and tail of the rolled piece during rolling, further control the biting speed, rolling speed and descaling mode, the throwing distance of the finishing mill was controlled to be 3.2-3.5m; the first pass of the finishing mill was descaled at the entrance, and the other odd passes were descaled at the exit; the thickness of the rolled piece, the biting speed, the rolling speed and the descaling mode of each pass during rolling were as shown in Table 2.

[0033] The thickness of the middle and edge of the head, middle and tail of the above-mentioned example was measured, and the results were as shown in Table 3. The results showed that the cutting amount of the head and tail of the rolled piece after removing the arc was reduced from more than 1000mm to 500mm, the thickness of the rolled piece was within the allowable range of the thickness, and the thickness deviation of the rolled piece was 0.27mm, which met the requirements of the user with small thickness tolerance, and the feeding amount was reduced and the yield of the steel plate was improved.

[0034] Table 1 Rolling process parameters of the steel plate of Example 1

[0035] .

[0036] Table 2 Rolling process parameters of the steel plate of Example 2

[0037] .

[0038] Table 3 Thickness measurement results of the steel plate of the example

[0039] .

Claims

1. A method for producing ultra-high strength narrow thickness tolerance steel plate with a thickness of 10 to 25 mm, characterized in that The process steps include: a. Narrow thickness tolerance steel plates are arranged to be rolled in the early stage of the rolling period, with the rolling mileage ≤ 50 kilometers; before production, 3 to 5 pieces of steel plates of the same specification are arranged to adjust the thickness deviation control, with the thickness transition from thick to thin and then the width transition from narrow to wide; the mother plate rolling length is controlled to be ≤ 40m; b. Using a walking beam heating furnace, the slab tapping temperature is ≥1180℃, and the temperature difference between the upper and lower surfaces is controlled within 20℃; c. Double-stand rolling is adopted, and the finishing mill adopts SmartCrown rolls to control the steel plate crown to less than 0.1mm; the cooling water of the roughing, finishing and intermediate roller tables is turned off; the cooling water opening of the middle part of the work roll barrel is adjusted to 60% to 70%, and the cooling water opening of the two sides is adjusted to 30% to 40%; d. Rough rolling is controlled for 7 to 9 passes; finishing rolling is controlled for 7 to 9 passes, the steel biting speed is 1.2 to 1.6 m / s, and the rolling speed is 3 to 7 m / s; the finishing mill is descaled at the entrance in the first pass, and the other odd-numbered passes are descaled at the exit; the thickness deviation of the same plate is controlled within 0.7 mm.

2. The method for producing ultra-high strength narrow thickness tolerance steel plate according to claim 1, characterized in that: In step a, the steel plates of the same specification are steel plates with a thickness deviation of ≤2 mm and a width deviation of ≤500 mm.

3. The method for producing ultra-high strength narrow thickness tolerance steel plate according to claim 1, characterized in that: In step c, the roundness of the roller is controlled within 50µm, and after calibration on the machine, the roundness of the roller system is controlled within 250µm.

4. The method for producing ultra-high strength narrow thickness tolerance steel plate according to claim 1, characterized in that: In step d, the steel throwing distances at the entrance and exit of the finishing mill are both 3.2 to 3.5 m.