Method for controlled temperature rolling of medium thickness steel plates

Abstract

The application discloses a temperature control rolling method for a medium-thick steel plate, which comprises the following steps: moving an N-2th slab, which has completed first-stage rolling, from a front near-point track of a rolling mill to a rear far-point roller way behind the rolling mill to continue temperature holding, moving an N-1th slab, which has completed first-stage rolling, from a front far-point track of the rolling mill to a rear near-point roller way behind the rolling mill to continue temperature holding, performing first-stage rolling on an Nth slab, moving the Nth slab to the front far-point track to hold temperature after the first-stage rolling of the Nth slab is completed, moving the N-1th slab to the front near-point roller way to continue temperature holding, returning the N-2th slab to the rolling mill to perform second-stage rolling, and leaving the rolling process from the roller way behind the rolling mill after the second-stage rolling of the N-2th slab is completed. In the embodiment, two chain-type circulating rollings can be realized without setting a side roller way, the temperature holding time of the medium-thick steel plate is maintained, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medium-thick steel plate rolling, in particular to a medium-thick steel plate temperature control rolling method. BACKGROUND

[0002] In order to improve the microstructure of the medium-thick steel plate and improve the comprehensive mechanical properties thereof, the controlled rolling technology has been widely applied in the production of the medium-thick steel plate, and the medium-thick steel plate has been widely applied in many fields such as shipbuilding, construction, container and bridge. The controlled rolling technology needs to control the temperature of the intermediate blank to control the rolling temperature, which is currently mainly divided into two stages. The first stage is the high-temperature austenite recrystallization zone rolling of rough rolling, and then the temperature of the intermediate blank is controlled. The second stage is the austenite non-recrystallization zone temperature rolling of finish rolling, which is beneficial to obtain fine-grained structure and avoid mixed crystal structure in the partial recrystallization zone temperature range, so as to improve the comprehensive mechanical properties of the steel plate.

[0003] At present, when the plate process production needs to control the temperature of the steel plate, single block controlled rolling and two block controlled rolling are usually adopted. The single block controlled rolling mode is to stop after the first stage rolling of the slab is completed, and then the second stage rolling is started. The two block controlled rolling mode is to control the temperature of the first slab after the first stage rolling is completed, and then the temperature of the second slab is controlled after the first stage rolling is completed. Then the second stage rolling of the first slab is carried out until it is completed, and then the second stage rolling of the second slab is continued until it is completed. However, the rolling efficiency of this rolling mode is relatively low, which restricts the rolling efficiency of the steel plate.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a medium-thick steel plate temperature control rolling method to improve the rolling efficiency of the medium-thick steel plate.

[0006] The present application is realized as follows:

[0007] In a first aspect, the present application provides a medium-thick steel plate temperature control rolling method, comprising:

[0008] Two block chain type circulation rolling, the N-2 block slab which completes the first stage rolling is passed through the rolling mill from the front near point track to the rear far point roller to continue to wait for temperature, the N-1 block slab which completes the first stage rolling is passed through the rolling mill from the front far point track to the rear near point roller to continue to wait for temperature, if the N block slab has completed the previous process at this time, the first stage rolling of the N block slab is carried out, the N block slab is transferred to the front far point track to wait for temperature after the first stage rolling of the N block slab is completed, and the N-1 block slab is passed through the rolling mill to the front near point roller to continue to wait for temperature, the N-2 block slab returns to the rolling mill to carry out the second stage rolling, and the N-2 block slab leaves the rolling process from the rear roller after the second stage rolling of the N-2 block slab is completed;

[0009] wherein N≥3 and N is a positive integer, the distance between the far point orbit after the rolling mill and the rolling mill is greater than the distance between the near point orbit after the rolling mill and the rolling mill, and the distance between the far point orbit before the rolling mill and the rolling mill is greater than the distance between the near point orbit before the rolling mill and the rolling mill.

[0010] In an optional embodiment, the thickness of the medium-thick steel plate is greater than 40 mm.

[0011] In an optional embodiment, before the Nth slab is rolled, the method further comprises the following steps:

[0012] The first slab is subjected to the first-stage rolling, and if the first slab has completed the previous process when the second slab has completed the previous process, the first slab is transferred to the far point orbit after the rolling mill for temperature holding;

[0013] The second slab is subjected to the first-stage rolling, and if the second slab has completed the previous process when the third slab has completed the previous process, the second slab is transferred to the near point orbit after the rolling mill for temperature holding;

[0014] Then, the two-piece chain-type rolling is repeated.

[0015] In an optional embodiment, if the N-2th slab is transferred from the near point orbit before the rolling mill to the far point roller way after the rolling mill for temperature holding, and the N-1th slab is transferred from the far point orbit before the rolling mill to the near point roller way after the rolling mill for temperature holding, and the Nth slab has not completed the previous process, the N-1th slab is transferred from the rolling mill to the near point roller way before the rolling mill for temperature holding, and the N-2th slab is returned to the rolling mill for the second-stage rolling, and the N-2th slab is transferred from the roller way after the rolling mill out of the rolling process after the second-stage rolling of the N-2th slab is completed.

[0016] In an optional embodiment, if the Nth slab has completed the previous process after the second-stage rolling of the N-2th slab is completed, the Nth slab is subjected to the first-stage rolling, the Nth slab is transferred to the far point orbit before the rolling mill for temperature holding after the first-stage rolling of the Nth slab is completed, and the N-1th slab is transferred from the rolling mill to the near point roller way before the rolling mill for temperature holding, and then the two-piece chain-type rolling is repeated.

[0017] In an optional embodiment, if the Nth slab has not completed the previous process after the second-stage rolling of the N-2th slab is completed, the N-1th slab is returned to the rolling mill for the second-stage rolling, and the N-1th slab is transferred from the roller way after the rolling mill out of the rolling process after the second-stage rolling of the N-1th slab is completed.

[0018] In an optional embodiment, air cooling or natural cooling is used for temperature control during the temperature holding.

[0019] In an optional embodiment, there is no side temperature holding roller way before and after the rolling mill.

[0020] The present application has the following beneficial effects:

[0021] In the rolling process of the medium-thick steel plate, the temperature required for the first stage rolling, i.e. rough rolling, is relatively high, the temperature required for the second stage rolling, i.e. finish rolling, is relatively low, and in addition, the medium-thick steel plate has a large thickness and a slow cooling speed, so that the waiting time is relatively long, resulting in a low rolling efficiency. In the prior art, a side roller way is provided for waiting, so as to realize simultaneous rolling of multiple steel plates. However, the provision of the side roller way requires adjustment of the equipment, which increases the production cost and the floor area, and for some compact production environments, there is no condition to provide the side roller way. In the present embodiment, two pieces of chain type rolling can be realized without the provision of the side roller way, the waiting time of the medium-thick steel plate is maintained, and the production efficiency is improved.

[0022] In the rolling process of the medium-thick steel plate in the present application, the intermediate blank needs to be rolled through the rolling mill multiple times to wait for temperature at the rear or front of the rolling mill. The first stage rolling of other steel plates is effectively carried out during the waiting time of the intermediate blank. The control step of the rolling efficiency is changed from the waiting time to the rolling time, the utilization efficiency of the rolling mill is improved, and the rolling efficiency of the slab is improved.

[0023] In addition, on the basis of improving the rolling efficiency, the medium-thick steel plate rolling in the present application can be carried out according to the steel incoming sequence. The steel outgoing sequence is consistent with the steel incoming sequence, which facilitates marking or tracking of the slab. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 The flow chart for tracking the temperature control rolling of the medium-thick steel plate in the present application;

[0026] Figure 2 The queue flow chart for the temperature control rolling of the medium-thick steel plate in the present application;

[0027] Figure 3 The temperature condition of the intermediate blank in the present embodiment;

[0028] Figure 4 The temperature condition of the intermediate blank in the comparative example of the present application. DETAILED DESCRIPTION

[0029] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0030] The features and performances of the present application will be further described in detail below in combination with the embodiments.

[0031] In a first aspect, the present application provides a temperature control rolling method for a medium-thick steel plate, a tracking flowchart and a queue flowchart are shown in Figure 1 and Figure 2 , and include:

[0032] Two pieces of chain type circulation rolling, the N-2 piece of slab that has completed the first stage rolling is bypassed from the front near point track to the rear far point roller way of the rolling mill to continue to wait for temperature, the N-1 piece of slab that has completed the first stage rolling is bypassed from the front far point track to the rear near point roller way of the rolling mill to continue to wait for temperature, if the N piece of slab has completed the previous process at this time, the N piece of slab is subjected to the first stage rolling, after the first stage rolling of the N piece of slab is completed, the N piece of slab is transferred to the front far point track to wait for temperature, and the N-1 piece of slab is bypassed from the rolling mill to the front near point roller way to continue to wait for temperature, the N-2 piece of slab returns to the rolling mill to perform the second stage rolling, after the second stage rolling of the N-2 piece of slab is completed, the N-2 piece of slab leaves the rolling process from the rear roller way of the rolling mill;

[0033] wherein N≥3 and N is a positive integer, the distance between the rear far point track and the rolling mill is greater than the distance between the rear near point track and the rolling mill, and the distance between the front far point track and the rolling mill is greater than the distance between the front near point track and the rolling mill.

[0034] In the rolling process of the medium-thick steel plate, the temperature required for the first stage rolling, i.e. rough rolling, is relatively high, the temperature required for the second stage rolling, i.e. finish rolling, is relatively low, in addition, the thickness of the medium-thick steel plate is relatively large, the cooling speed is slow, so the waiting time is relatively long, so that the rolling efficiency is relatively low, in the prior art, a side roller way for waiting is also provided to realize the simultaneous rolling of multiple steel plates, but the setting of the side roller way requires the adjustment of the equipment, which increases the production cost and the floor area, and for some compact production environment, there is no condition to set the side roller way, in the present embodiment, two pieces of chain type circulation rolling can be realized without setting the side roller way, the waiting time of the medium-thick steel plate is maintained, and the production efficiency is improved.

[0035] In addition, the steps in the embodiment can be performed in the order described above, or the steps can be performed simultaneously if the later steps do not hinder the earlier steps, for example, the two steps of "passing the N-2 slab that has completed the first-stage rolling from the front near-point track to the rear far-point rollerway of the rolling mill to continue to wait for warming, and passing the N-1 slab that has completed the first-stage rolling from the front far-point track to the rear near-point rollerway of the rolling mill to continue to wait for warming" can be performed simultaneously, and after the first-stage rolling of the N slab is completed, the three slabs in "moving the N slab to the front far-point track to wait for warming, passing the N-1 slab to the front near-point rollerway of the rolling mill to continue to wait for warming, and returning the N-2 slab to the rolling mill for second-stage rolling" can be moved simultaneously, or the slabs can be moved sequentially if the conditions are met.

[0036] In the rolling process of the thick steel plate in the present application, the intermediate slab needs to be passed through the rolling mill multiple times to wait for warming at the rear or front of the rolling mill, and the first-stage rolling of other steel plates is effectively performed during the waiting time of the intermediate slab, the control step of rolling efficiency is changed from the waiting time to the rolling time, the utilization efficiency of the rolling mill is improved, and the rolling efficiency of the slab is improved.

[0037] In addition, on the basis of improving the rolling efficiency, the present application can perform tapping according to the steel sequence, the tapping sequence is consistent with the steel sequence, and the slabs are conveniently marked or tracked.

[0038] In the present application, the intermediate slab can be cooled in a natural cooling manner without cooling and temperature reduction through a cooling system, effectively solving the problems of uneven water cooling temperature of the intermediate slab and low temperature control efficiency of the intermediate slab, avoiding the large temperature difference between the head and tail of the intermediate slab after water cooling, causing serious upward bending or downward bending of the subsequent steel plate during rolling, and even causing rolling failure of the rolling piece, improving the stability of the rolling process in the finishing rolling stage of the temperature-controlled plate, and thus improving the rolling rhythm and rolling efficiency.

[0039] In an optional embodiment, the thickness of the thick steel plate is greater than 40 mm, and the rolling efficiency is improved more obviously when the thickness of the steel plate is greater than 40 mm.

[0040] In an optional embodiment, before the N slab is rolled, the following steps are further included:

[0041] The first-stage rolling of the first slab is performed, and if the first-stage rolling of the first slab is completed when the second slab has completed the previous process, the first slab is moved to the rear far-point track to wait for warming;

[0042] The first-stage rolling of the second slab is performed, and if the first-stage rolling of the second slab is completed when the third slab has completed the previous process, the second slab is moved to the rear near-point track to wait for warming;

[0043] Then, the two-piece chain cycle rolling step is repeated.

[0044] In the optional embodiment, if the N-2 piece of slab is rolled from the front near point track to the rear far point rollerway to continue to be tempered, the N-1 piece of slab is rolled from the front far point track to the rear near point rollerway to continue to be tempered, and the N piece of slab has not completed the previous process, then the N-1 piece of slab is rolled to the front near point rollerway to continue to be tempered, the N-2 piece of slab is returned to the rolling mill for the second stage rolling, and the N-2 piece of slab is rolled from the rear rollerway to exit the rolling process after the second stage rolling is completed.

[0045] In the optional embodiment, if the N-2 piece of slab has completed the previous process after the second stage rolling is completed, then the N piece of slab is rolled for the first stage rolling, the N piece of slab is transferred to the front far point track to be tempered after the first stage rolling is completed, and the N-1 piece of slab is rolled to the front near point rollerway to continue to be tempered, and then the two-piece chain cycle rolling step is repeated.

[0046] In the optional embodiment, if the N-2 piece of slab has not completed the previous process after the second stage rolling is completed, then the N-1 piece of slab is returned to the rolling mill for the second stage rolling, and the N-1 piece of slab is rolled from the rear rollerway to exit the rolling process after the second stage rolling is completed.

[0047] In the rolling process of the medium-thickness steel plate in the embodiment, when the previous sequence slab is tempered and the subsequent slab has not completed the previous process, the previous sequence slab can be rolled for the second time, and the adjustment can be flexibly made according to the condition of the incoming slab.

[0048] In the optional embodiment, the temperature is controlled by air cooling or natural cooling during the tempering process, and the temperature of each position of the intermediate slab before the second stage rolling in the embodiment is as shown in the table. Figure 3 As shown in the table, the temperature of the intermediate slab from the head to the tail is represented by the inverted U-shaped curve from left to right, and it can be seen from the figure that the temperature difference between the head and the tail of the intermediate slab is within 20℃, and the temperature difference is relatively small. Figure 3

[0049] In the optional embodiment, there is no side tempering rollerway in front of and behind the rolling mill.

[0050] Comparative Example:

[0051] ​The comparative example provides a controlled temperature rolling method of a medium-thick steel plate, including: after the first slab completes the first stage rolling, waiting for temperature after the mill, then after the second slab completes the first stage rolling, waiting for temperature before the mill, then the second stage rolling of the first slab is carried out, after the first slab completes the second stage rolling, leaving the roller way, then the second slab is transported to the mill to continue waiting for temperature, at this time, the first stage rolling of the third slab is carried out, after the third slab completes the first stage rolling, waiting for temperature before the mill, then the second stage rolling of the second slab is carried out until it is completed and leaves the roller way, and the like, forming a chain rolling mode.

[0052] The controlled temperature rolling method of the medium-thick steel plate provided by the comparative example has a relatively obvious improvement in rolling efficiency when rolling the plate with a thickness less than 40 mm in the single-block controlled rolling and two-block controlled rolling modes, but the waiting time of the intermediate slab is long when the thickness of the steel plate is greater than 40 mm, and the waiting time is a control step of the rolling efficiency, so the efficiency is not improved.

[0053] In the comparative example, in order to shorten the waiting time, the intermediate slab can be cooled by a cooling system to improve the rolling efficiency, but the cooling by the cooling system has the following problems:

[0054] 1. When the intermediate slab is air-cooled, the air-cooling temperature drop speed is small, the waiting time of the intermediate slab is not obviously shortened, and the rolling efficiency is not obviously improved.

[0055] 2. The intermediate slab is rapidly cooled by the pre-mill intermediate cooling system or the post-mill ultra-fast cooling system to achieve the purpose of controlling the second stage rolling, i.e., the roughing temperature of the finish rolling, but due to the limitation of the system model, the cooling schedule of the intermediate slab is mainly randomly water-cooled by the operator according to experience, and after water-cooling, most of the intermediate slabs have uneven temperature, and some of them also have head and tail buckling, which further affects the rolling in the finish rolling stage, and in severe cases, even causes the steel plate to be scrapped, resulting in a low utilization ratio.

[0056] The temperature of each position of the intermediate slab before the second stage rolling in the comparative example is shown in Figure 4 According to Figure 4 , the curve in the inverted U shape from left to right represents the temperature of the intermediate slab from the head to the tail, and from the figure it can be seen that the temperature difference between the head and the tail of the intermediate slab is about 50℃, and the temperature difference is relatively large compared with the example.

[0057] In the present application, the method of the example rolls the medium-thick plate, and when the thick specification plate is small, the number of blocks is increased from 7.5 blocks / hour in the comparative example to 10 blocks / hour, the cross-rolling efficiency is increased by more than 30%, the barrier of low waiting efficiency of the intermediate slab in the thick specification cross-rolling plate is broken, a new breakthrough in rolling efficiency is realized, the production cost is further reduced, and the market competitiveness of the plate product is also enhanced.

[0058] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for temperature-controlled rolling of medium-thick steel plates, characterized in that, include: Two-piece chain-type circulating rolling: the N-2 slab, having completed the first stage of rolling, passes through the mill from the near-point track before the mill to the far-point roller table after the mill to continue waiting for heating; the N-1 slab, having completed the first stage of rolling, passes through the mill from the far-point track before the mill to the near-point roller table after the mill to continue waiting for heating. If the Nth slab has already completed the previous process, then the Nth slab undergoes the first stage of rolling. After the first stage of rolling of the Nth slab is completed, the Nth slab is transferred to the far-point track before the mill to wait for heating, while the N-1 slab passes through the mill from the near-point roller table before the mill to continue waiting for heating. The N-2 slab returns to the mill for the second stage of rolling. After the second stage of rolling of the N-2 slab is completed, it leaves the rolling process from the rear roller table after the mill. Where N≥3 and N is a positive integer, the distance between the far point track behind the mill and the mill is greater than the distance between the near point track behind the mill and the mill, and the distance between the far point track in front of the mill and the mill is greater than the distance between the near point track in front of the mill and the mill. Before rolling the Nth slab, the following steps are also included: The first slab is rolled in the first stage. If the second slab has already completed the previous process when the first stage rolling of the first slab is completed, the first slab is transferred to the far end track behind the machine to wait for the temperature to rise. The second slab is rolled in the first stage. If the third slab has already completed the previous process when the first stage rolling of the second slab is completed, the second slab is transferred to the near-point track behind the machine to wait for the temperature to rise. Next, the two-piece chain-cycle rolling process is repeated.

2. The method for temperature-controlled rolling of medium-thick steel plates according to claim 1, characterized in that, The thickness of the medium-thick steel plate is greater than 40 mm.

3. The method for temperature-controlled rolling of medium-thick steel plates according to claim 1, characterized in that, If the N-2 slab is passed empty from the near-point track before the mill to the far-point roller table after the mill to continue waiting for heating, and the N-1 slab is passed empty from the far-point track before the mill to the near-point roller table after the mill to continue waiting for heating, and the N-2 slab has not yet completed the previous process, then the N-1 slab is passed empty from the mill to the near-point roller table before the mill to continue waiting for heating, and the N-2 slab is returned to the mill for the second stage of rolling. After the second stage of rolling of the N-2 slab is completed, it leaves the rolling process from the rear roller table of the mill.

4. The method for temperature-controlled rolling of medium-thick steel plates according to claim 3, characterized in that, If the Nth slab has completed the previous process after the second stage rolling of the N-2th slab, then the Nth slab is rolled in the first stage. After the first stage rolling of the Nth slab is completed, the Nth slab is transferred to the far end track in front of the mill to wait for heating, and the N-1th slab is passed empty through the mill to the near end roller table in front of the mill to continue to wait for heating. Then the two-piece chain cycle rolling steps are repeated.

5. The method for temperature-controlled rolling of medium-thick steel plates according to claim 3, characterized in that, If the second stage rolling of the N-2th slab is completed before the previous process of the Nth slab is completed, the N-1th slab is returned to the rolling mill for the second stage rolling. After the second stage rolling of the N-1th slab is completed, it leaves the rolling process from the rear roller table of the rolling mill.

6. The method for temperature-controlled rolling of medium-thick steel plates according to claim 1, characterized in that, The temperature is controlled by air cooling or natural cooling during the waiting process.

7. The method for temperature-controlled rolling of medium-thick steel plates according to claim 1, characterized in that, There are no side-warming rollers at the front and rear of the rolling mill.

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