CN-121988708-A - Method for improving solidification belt stability of thin belt continuous casting stainless steel

Abstract

The invention relates to the technical field of stainless steel strip continuous casting, and provides a method for improving the stability of a strip formed by solidifying strip continuous casting stainless steel, which comprises the steps of obtaining an initial parameter set of the strip; obtaining an initial technological parameter set, combining the obtained technological parameter set to conduct continuous casting of the thin strip, measuring the liquid level of a molten pool, the casting rolling force, the surface temperature of a casting roller and the surface temperature of the casting strip in the continuous casting process of the thin strip in real time, judging according to judging conditions, obtaining an adjusted technological parameter set if the adjustment is needed, returning, otherwise, entering the next step, and completing continuous casting of the thin strip to obtain a thin strip product. According to the scheme of the invention, the liquid level of a molten pool, the casting force, the surface temperature of the casting roller and the surface temperature of the casting belt in the continuous casting process of the thin belt are measured in real time and judged according to corresponding judging conditions, and the continuous stable production of the stainless steel casting belt with the ultra-thin specification of less than or equal to 2mm is ensured and the surface quality and the tissue uniformity are improved by establishing the real-time cooperative control of the liquid level, the heat transfer, the casting force and the roller gap.

Inventors

• Lv Peisheng
• LU JINGZHOU
• WANG WANLIN
• ZHOU LEJUN
• SUN YONGQI

Assignees

• 中南大学

Dates

Publication Date

20260508

Application Date

20260410

Claims (4)

1. 1. A method for improving the stability of a solidified strip of thin strip continuously cast stainless steel, comprising the steps of: Step one, obtaining an initial parameter set of a thin belt; step two, obtaining an initial parameter set of the thin strip based on the step one, wherein the initial process parameter set comprises a pull rate Vc, a cooling water flow rate Qw, a casting temperature T0, a predicted casting roller surface temperature Ttarget1, a predicted casting strip surface temperature Ttarget2, a set roll gap value Starget, a target liquid level Lset and a molten steel flow rate Qm; Step three, carrying out continuous casting of the thin strip by combining the obtained technological parameter set; measuring the liquid level L of a molten pool, the casting force actual, the surface temperature Tr of a casting roller and the surface temperature Ts of the casting belt in real time in the continuous casting process of the thin belt; Step five, judging according to judging conditions, if the process parameter set is required to be adjusted, obtaining an adjusted process parameter set, and returning to the step three, otherwise, entering the next step, wherein the judging conditions comprise judging the casting force actual, the liquid level L of a molten pool, the surface temperature Tr of a casting roll, the surface temperature Ts of a casting belt and dynamic compensation adjustment of a roll gap; and step six, completing continuous casting of the thin strip to obtain a thin strip product.
2. 2. The method for improving the solidification of thin strip cast stainless steel into strip according to claim 1, wherein the judging conditions in the fifth step are as follows: Conditions ①, aiming at casting force actual, increasing a roll gap value Startarget by 1% if actual-Fpredict is more than 2% multiplied by Fpredict, reducing the roll gap value Startarget by 1% if Fpredict-actual is more than 2% multiplied by Fpredict, wherein Fpredict is a casting force predicted value, fpredict =K multiplied by DeltaS, K is a coefficient determined by the attribute of the strip continuous casting equipment, and DeltaS is a spreading value of the roll gap value Startarget; The conditions ② are that the molten steel flow Qm is controlled by an electromagnetic stopper rod aiming at the molten pool liquid level L, specifically, if the molten pool liquid level L-target liquid level Lset is more than 1.0mm, the molten steel flow Qm is reduced by 5 percent, and if the target liquid level Lset-molten pool liquid level L is more than 1.0mm, the molten steel flow Qm is increased by 5 percent; Conditions ③, for the casting roll surface temperature Tr, if the casting roll surface temperature Tr-predicted casting roll surface temperature Ttarget1>5% x the predicted casting roll surface temperature Ttarget1, then the cooling water flow Qw is increased by 1%, the predicted casting roll surface temperature Ttarget 1-casting roll surface temperature Tr >5% x the predicted casting roll surface temperature Ttarget1, then the cooling water flow Qw is decreased by 1%; Conditions ④, regarding the cast strip surface temperature Ts, for the cast strip at the exit roll, if the cast strip surface temperature Ts-predicted cast strip surface temperature Ttarget2>5% x predicted cast strip surface temperature Ttarget2, decreasing the pull rate Vc by 1% until |the cast strip surface temperature Ts-predicted cast strip surface temperature Ttarget2| is less than or equal to 5% x predicted cast strip surface temperature Ttarget2, if the predicted cast strip surface temperature Ttarget 2-cast strip surface temperature Ts >5% x predicted cast strip surface temperature Ttarget2, increasing the pull rate Vc by 1% until |the cast strip surface temperature Ts-predicted cast strip surface temperature Ttarget2| is less than or equal to 5% x predicted cast strip surface temperature Ttarget2; And the conditions ⑤ and the roll gap dynamic compensation model compensate according to the following formula: Starget(i)=Starget(i-1)+ΔSthermal+ΔSshrink; wherein, the value of i is 1 or more, the value of i is the roll gap value Starget after the ith compensation, delta Sthermal is the thermal deformation compensation quantity, which is related to the casting roll thermal expansion coefficient alpha roll, the casting roll temperature rise delta Troll and the casting roll diameter Droll, delta Sthermal = alpha roll x delta Troll x Droll, the casting roll temperature rise delta Troll = the casting roll surface temperature Tr-room temperature TR, delta Sshrink is the solidification shrinkage compensation quantity, which is related to the line shrinkage coefficient beta, delta Sshrink = beta x (TL-TS) x Starget, TL is the liquidus temperature, and TS is the solidus temperature.
3. 3. The method for improving the solidification of thin strip cast stainless steel into strip stability of claim 1 or 2, wherein the obtaining of the initial set of parameters of the thin strip in step one specifically comprises: Inputting basic parameters including stainless steel physical parameters and casting temperature T0, wherein the stainless steel physical parameters comprise a density-temperature-dependent curve, a thermal conductivity-temperature-dependent curve, a specific heat capacity-temperature-dependent curve, latent heat of solidification, liquidus temperature, solidus temperature and line shrinkage coefficient, and are used for obtaining the predicted casting roll surface temperature Ttarget1, the predicted belt temperature Ttarget2, the solidification shrinkage compensation quantity delta Sshrink and the predicted heat flow density q0 through finite element calculation; the equipment process parameters include the diameter of the casting rolls, the materials of the casting rolls, the thermal expansion coefficient of the casting rolls, the cooling water flow rate Qw and the arc length Lh of the molten pool.
4. 4. The method for improving the solidification of thin strip cast stainless steel into strip stability of claim 2, wherein the target liquid level Lset is obtained according to a set roll gap value target by the following process: The cast strip one-sided solidification thickness d was calculated using the following: d = k×t (1/2) ; wherein t is the contact time of molten steel and a crystallization roller, t=the arc length Lh of a molten pool/the pull rate Vc; the set roll gap value Starget is calculated using the following formula: Starget=2d= 2k×(Lh/Vc) (1/2) ; The calculation formula for the bath arc length Lh is thus obtained as follows: Lh=Vc×(Starget/ 2k) 2 ; The target liquid level Lset is calculated based on the bath arc length Lh using the following formula: 。

Description

Method for improving solidification belt stability of thin belt continuous casting stainless steel Technical Field The invention relates to the technical field of stainless steel strip continuous casting, in particular to a method for improving stability of a strip formed by solidifying strip continuous casting stainless steel. Background The double-roll continuous casting technology (twin-roll STRIP CASTING, TRC) can directly manufacture molten steel into a thin strip with the thickness of 2-4mm, and can realize the integration of short-flow casting and rolling by combining hot rolling, thereby being beneficial to energy conservation, consumption reduction and material refinement. The technology for directly producing millimeter-grade thin strip by casting-rolling integrated stainless steel strip continuous casting technology is a key breakthrough for green and efficient transformation in the steel industry. The strip with the thickness of 1-2mm is directly produced by sub-fast solidification (cooling speed is 1000-1700 ℃ per second) of molten steel between counter-rotating crystallization rollers, a kilometer-level flow of traditional slab continuous casting and hot rolling is subverted, the energy consumption of ton steel is reduced by 80%, the carbon footprint is reduced by 90%, and the method is particularly suitable for producing high alloy stainless steel such as 304/316L. However, the technology faces a multi-factor coupling instability bottleneck, namely, thickness deviation, central shrinkage cavity and surface vibration mark of the casting belt caused by fluctuation of the liquid level (+/-3 mm) of a molten pool and thermal deformation of a casting roller, so that continuous and stable production of the ultrathin belt is severely restricted, and development of a liquid level-heat transfer-casting rolling force-roller gap cooperative control model is needed to break through the bottleneck of industrial mass production. The following schemes are disclosed in the prior art: The patent with the publication number of CN120079820B and the patent name of thin strip continuous casting process parameter determining method and device, medium and terminal discloses that a thin strip continuous casting process parameter full-coupling model is built in advance, casting process parameters required by a control casting machine are determined according to the thin strip continuous casting process parameter full-coupling model, initial casting process parameter values of the casting times are determined in an optimizing mode in casting process parameters recorded by historical casting secondary production data, and then correction values of solidification parameters, correction values of rolling parameters, set rolling force and set drawing speed are calculated according to period production data of a steady state period and the thin strip continuous casting process parameter full-coupling model, and initial casting process parameter values are adjusted based on the parameters. The invention application with the publication number of CN119282050A and the patent name of a double-roll thin-strip continuous casting method and a control system discloses setting continuous casting parameters of a casting process, at least comprising a casting force upper limit F- (upset), a casting force lower limit F- (downset), a target roll gap S- (target) and an initial roll surface speed V-0, starting casting, keeping the roll gap S at the target roll gap S- (target), monitoring a molten pool liquid level L and an actual casting force F- (actual) in real time, controlling the molten pool liquid level L to be stable in a target zone through a first closed-loop control loop related to casting flow Q after the molten pool liquid level L reaches a set value L- (set), and controlling the casting force F- (actual) to be stable in the target zone through a second closed-loop control loop formed by taking the casting force F- (actual) and the roll surface speed V- (actual) as variables. The casting method provided by the invention can avoid the problem of roll gap fluctuation caused by casting rolling force fluctuation, simplify the adjustment process of the system by decoupling liquid level closed-loop control and casting rolling force-speed closed-loop control, and improve the stability and control precision of the system. The invention patent with publication number CN114713780B and with the name of a method for improving the solidification stability of molten steel into a strip under the continuous casting process of a thin strip discloses that molten steel flows to a pair of casting rolls of a twin roll continuous casting machine through an overflow port at the bottom of a flow distributor, a molten pool is formed above a nip between the pair of casting rolls and above the casting surfaces of the casting rolls, the overflow port is immersed into the molten pool for a depth (d) which is selected from the range of 30mm to 50mm, wherei