A method for stepwise cooling of a laminar flow cooling system of a plate mill

Abstract

The present application relates to the technical field of steel metallurgy, and particularly relates to a kind of progressive cooling method of laminar flow cooling system of medium plate furnace roll mill, suitable for the steel plate and steel coil produced by roll rolling mode, the rolling piece is placed on laminar flow roller way and moves, the top and bottom of laminar flow roller way are sequentially arranged with multiple groups of laminar flow upper header and laminar flow lower header along the length direction of laminar flow roller way, to form laminar flow cooling area, the number of groups of cooling water of laminar flow cooling system is selected to be opened, according to the length of the current rolling rolling piece and the finish rolling temperature curve condition of the mill, the length of the rolling piece and the number of groups of water are set to be opened progressively, and all laminar flow headers are closed after the rolling piece leaves the laminar flow cooling area.The present application simultaneously determines the length and number of groups of laminar flow water to be opened progressively in combination with the finish rolling temperature curve of the rolling piece leaving the mill, can effectively control the red temperature of the rolling piece leaving the laminar flow to meet the process performance requirements, greatly reduces the incidence of product performance rejudgment, and improves the qualified rate of product.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, and in particular to a step-by-step cooling method for a laminar flow cooling system in a medium-thick plate hot roll mill. Background Technology

[0002] The medium and heavy plate hot roll mill production line consists of a four-high mill, two coiling furnaces before and after the mill, and subsequent thickness gauges, flying shears, and laminar flow cooling systems. The hot roll mill production line has four production modes: flat-rolled plates, flat-rolled coils, rolled plates, and rolled coils, with the appropriate mode selected based on the plan. After being heated in the furnace, the rolled pieces are descaled by the descaling system to remove surface iron oxide scale, then transported via roller conveyors to the hot roll mill area. Through multiple rolling passes in the hot roll mill, the final finished product thickness and length are achieved. After being sheared into mother plates by the flying shear, the plates enter the laminar flow cooling system and subsequent processes.

[0003] There are two main water-cooling modes for laminar flow cooling systems: 1. Automatic water-cooling mode where the number of laminar flow groups activated for the current rolled piece remains unchanged; 2. Water-cooling mode where the laminar flow cooling system automatically calculates the number of groups to be activated. Modes 1 and 2 are applicable to the production of flat-rolled plates and flat-rolled coils.

[0004] Plates or coils produced by flat rolling have a final rolling temperature curve that is high at the beginning and low at the end. Using conventional laminar flow cooling and accelerating the process by throwing steel at the end can effectively control the temperature of the rolled piece after laminar flow cooling to achieve a stable temperature and meet the required temperature after cooling.

[0005] Plates or coils produced by coil rolling have varying temperature distributions along their length due to the presence of a coiling furnace during the rolling process. This results in a final rolling temperature curve that is low at both ends and high in the middle. When rolling thin sections of pipeline steel or other specialty steels, production is typically organized using tail-rolling, leading to a final rolling temperature curve that is low at the beginning and high at the end. Even with conventional laminar flow cooling systems using boiling water, the reflow temperature curve after exiting the laminar flow also sometimes corresponds to the final rolling temperature curve, exhibiting low temperatures at the head, moderate temperatures in the body, and high temperatures at the tail. This significantly impacts the final comprehensive mechanical properties of the rolled piece, failing to meet product requirements. The first two boiling water cooling methods are no longer sufficient for on-site cooling needs, as the reflow temperature curve after exiting the laminar flow fluctuates considerably. A novel boiling water cooling method is urgently needed to overcome this phenomenon. Therefore, we propose a staged cooling method for a laminar flow cooling system in medium-thick plate furnace coil rolling mills. Summary of the Invention

[0006] This invention addresses the aforementioned technical problems and overcomes the shortcomings of existing technologies by providing a step-by-step cooling method for a laminar flow cooling system in a medium-thick plate hot rolling mill. This method is applicable to steel plates and coils produced by coil rolling. The rolled piece is placed on a laminar flow roller table and moved there. Multiple sets of upper and lower laminar flow manifolds are arranged sequentially above and below the laminar flow roller table along its length, forming a laminar flow cooling zone. The method also includes the following steps:

[0007] When producing steel plates or coils using rolling mills, select the appropriate number of cooling water base groups to be turned on in the laminar flow cooling system.

[0008] Based on the current length of the rolled piece and the final rolling temperature curve of the mill, set the distance from the head of the laminar cooling water to be added in stages.

[0009] After the rolled piece exits the laminar flow cooling zone, all laminar flow manifolds are shut off.

[0010] The technical solution further defined in this invention is:

[0011] Furthermore, the number of cooling water base activation groups is 7.

[0012] Furthermore, the additional cooling water units consist of 3 groups.

[0013] Furthermore, in the additional cooling water units, the first unit is located 15m from the head, the second unit is located 40m from the head, and the third unit is located 73m from the head. The head refers to the position where the head of the rolled piece passes through the laminar flow first unit manifold.

[0014] Furthermore, the dimensions of the rolled piece are 10.3×2890×96000mm.

[0015] The beneficial effects of this invention are:

[0016] (1) Based on the original laminar flow cooling system, the present invention has logically rearranged the control mode of the laminar flow cooling system. At the same time, it determines the length and number of laminar flow cooling water groups by combining the final rolling temperature curve of the rolled piece exiting the mill. This can effectively control the red temperature of the rolled piece exiting the laminar flow to meet the process performance requirements, greatly reduce the occurrence rate of product performance reversal, improve the product qualification rate, and enhance the market competitiveness of the enterprise's products.

[0017] (2) This invention is mainly aimed at steel plate and steel coil products produced by rolling. In practical applications, it involves steel grades with similar final rolling temperature curves, such as pipeline steel, rolled plate / coil, and special steel grades. It is simple and convenient to maintain, flexible to operate, and the length and number of cooling water groups can be controlled and adjusted. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the laminar flow cooling system of the heavy plate hot roll mill production line of the present invention;

[0019] Figure 2 This is a schematic diagram of the final rolling temperature curve of pipeline steel produced by tail-end rolling in the medium-thick plate furnace rolling mill of the present invention.

[0020] Figure 3 This is the operation interface of the laminar flow cooling system for the medium-thick plate hot roll mill of the present invention (red box area);

[0021] Figure 4 This is a schematic diagram of the staged cooling segment of the final rolling temperature curve of pipeline steel produced by tail-end rolling in the medium-thick plate furnace coil mill of the present invention;

[0022] In the diagram: 1. Laminar flow cooling upper manifold crossbeam; 2. Laminar flow upper manifold; 3. Laminar flow lower manifold; 4. Laminar flow roller conveyor; 5. Rolled workpiece. Detailed Implementation

[0023] Example

[0024] In this embodiment, the dimensions of the rolled billet are 150×2890×6523mm, and the dimensions of the rolled piece are 10.3×2890×96000mm.

[0025] This embodiment mainly targets steel plates and coils produced by coil rolling. In practical applications, it involves steel grades with similar final rolling temperature curves, such as pipeline steel, coiled plates / coils, and special steel grades. Based on the thickness of the rolled piece of 10.3mm and the length of 96m, a single-pass coil rolling production method is adopted, with a step-by-step hot water method executed in a 7+1+1+1 mode.

[0026] 1. When producing steel plates using coil rolling, according to process requirements, at the interface of the laminar flow system of this invention ( Figure 3 (Check the box in the lower left corner) Select the number of 7 groups of cooling water base opening manifolds for the laminar flow cooling system (laminar flow upper manifold 2 and laminar flow lower manifold 3 are opened in pairs). The number of base groups is determined according to the process parameters in the work instruction book for the steel grade. Finally, ensure the compliance of the process parameters. Cooling pipes can be opened continuously from 1 to 7.

[0027] 2. Based on the current length of rolled piece 5 (96m) and the final rolling temperature curve of the mill exiting the mill ( Figure 2 , Figure 4 As shown), the length of the rolled piece 5 is set to gradually increase the laminar flow cooling water (corresponding positions are as follows). Figure 4(Arrow-marked locations) and the number of additional cooling water units (length calculated from the beginning of the first group of manifolds in laminar flow at the head of the rolled piece). Currently, the first (8th) group of additional cooling water units for rolled piece 5 is located 15m from the head; the second (9th) group is located 40m from the head; and the third (10th) group is located 73m from the head. Based on the basic number of laminar flow units, combined with the rolled piece length and final rolling temperature curve, the rolled piece length is set with the first group of manifolds as the reference. The number of manifold units activated is tracked step-by-step on-site according to the rolled piece position; the specific location can be adjusted based on the on-site temperature.

[0028] 3. After the rolled piece 5 exits the laminar flow cooling zone, all laminar flow manifolds (upper laminar flow manifold 2 and lower laminar flow manifold 3 open in pairs) automatically close. The number of additional laminar flow cooling manifolds (upper laminar flow manifold 2 and lower laminar flow manifold 3 open in pairs) groups 8, 9, and 10 are automatically reset to zero. The laminar flow system interface ( Figure 3 ④ Restore the laminar flow basic activation group to 7 groups. When using the flat rolling production method, simply remove the "√" from the corresponding position on the laminar flow system interface of this invention.

[0029] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for stepwise cooling of a plate mill laminar cooling system, characterized in that, The application relates to a steel plate and a steel coil produced by the rolling method, wherein the rolling piece is arranged on a laminar flow roller way to move, a plurality of laminar flow upper headers and laminar flow lower headers are arranged above and below the laminar flow roller way along the length direction of the laminar flow roller way, a laminar flow cooling area is formed, and the application further comprises the following steps: When the steel plate or the steel coil is produced by the rolling method, the number of the cooling water basic opening groups of the laminar flow cooling system is selected; According to the length of the current rolling piece and the final rolling temperature curve of the rolling mill, the position distance of the gradually opened laminar flow cooling water from the head is set; After the rolling piece leaves the laminar flow cooling area, all the laminar flow headers are closed; The number of the cooling water basic opening groups is 7.

2. The laminar cooling system stepwise cooling method according to claim 1, characterized in that, The size of the rolling piece is 10.3*2890*96000mm.

3. The laminar cooling system stepwise cooling method according to claim 1, characterized in that, ​

Images