Production method of 4J42 invar alloy hot continuous rolling plate strip

Abstract

The invention discloses a control method for producing a 4J42 alloy plate strip in a hot rolling process. After the method is implemented, the smooth production of the 4J42 alloy plate strip can be ensured and the abnormities such as waste steel and faults can be avoided through heating temperature adjustment, rough rolling upwarp control and finish rolling reduction load strategy control, so that the Taihi steel hot rolling variety is expanded, and the product benefit of special steel alloy is improved.

Description

Technical Field

[0001] The invention relates to the field of steel rolling in metallurgical science and technology, and in particular to a production method for a 4J42 Invar alloy hot-rolled strip. Background Art

[0002] The present invention is a hot rolling process technology invented for producing 4J42K alloy plates and strips by 1549 hot rolling production line of Taigang.

[0003] The equipment layout of the hot rolling line is divided into furnace area, rough rolling area, finishing rolling area, laminar cooling area and coiling area.

[0004] The main production process of the hot rolling production line is that the slab is first heated in a heating furnace according to the temperature specified by the process, and then enters the rough rolling mill for rolling after being heated to the target temperature. The rough rolling vertical roll controls the width, and the flat roll controls the thickness. Reversible rolling is performed in the rough rolling unit, generally for 5 to 7 passes.

[0005] After the roughing mill rolling, the strip reaches the preset target thickness, width and temperature. Then it enters the finishing mill for seven-stand flat roll continuous rolling to make the strip reach the preset target thickness and temperature. After that, the strip is controlled by laminar cooling to make the strip reach the target coiling temperature. Finally, the strip is formed into a coil by the coiler.

[0006] 4J42 alloy is an expansion alloy among precision alloys, containing about 42% nickel. It is widely used in aerospace, precision instruments, and electronics industries due to its small expansion coefficient, good thermal conductivity, and excellent mechanical properties.

[0007] After consulting the literature, it is found that the alloy wire manufacturing is relatively mature, but no literature on the use of continuous rolling for plate and strip production has been found. The market demand for 4J42 plates and strips is large, and most of them rely on imports. Through research and development, 4J42 die casting billets were successfully metallurgically produced and opened. Such billets need to be rolled into plates and strips through hot continuous rolling, but there is no such production experience in hot rolling.

[0008] Therefore, it is particularly important to develop and research a hot rolling production method for 4J42 alloy strip based on existing equipment and technology.

[0009] The purpose of the present invention is to develop a hot rolling production method for 4J42 alloy strips, thereby filling the gap in the production of 4J42 strips and expanding the variety structure that can be produced by hot rolling. Summary of the invention

[0010] The purpose of the present invention is to provide a production method for 4J42 Invar alloy hot-rolled strip in view of the above problems.

[0011] The object of the present invention is achieved as follows: A production method for a 4J42 Invar alloy hot-rolled strip comprises the following steps: Step 1: Heating furnace temperature control: The 4J42 slab is heated in a heating furnace, and the heating furnace is divided into three heating sections: a heating section, a second heating section, and a soaking section. The target furnace temperature of the first heating section is 1070±20°C, the target furnace temperature of the second heating section is 1150±20°C, and the target furnace temperature of the soaking section is 1170±20°C; the residence time of the first heating section is 60±10 minutes; the residence time of the second heating section is 70±10 minutes; the residence time of the soaking section is 50±10 minutes. Step 2: Rough rolling: The heated slab is subjected to one main descaling process and then rough rolled. Rough rolling is performed in seven passes without descaling. The thickness of the intermediate slab after rolling is 25-35mm. Step 3: After rough rolling, the intermediate slab is edge heated: during production, the edge power is given according to the maximum value of 1500-2300KW. Step 4: The reduction rate of the intermediate slab is controlled on each finishing rolling stand.

[0012] The calculation formula for the reduction rate in step 4 is as follows: eps(i)=RF(i)*GBZWK / MH(i) / nnfkorr(i) (1) Wherein, i represents the finishing mill stand number, when i is 0~6, it represents F0~F6 stands respectively, GBZWK represents the maximum rolling pressure of each finishing mill stand, i.e. 40000KN, MH(i) represents the hardness value of the steel of the i-th stand, nnfkorr(i) represents the pressure correction coefficient of the i-th stand.

[0013] The beneficial effect of the present invention is that after the implementation of the present invention, by adjusting the heating temperature, controlling the warping of the rough rolling and controlling the down-load strategy of the finishing rolling, the smooth production of the 4J42 alloy strip can be guaranteed, and abnormalities such as scrap steel and failures can be avoided, thereby expanding the hot-rolled varieties of TISCO and improving the product benefits of special steel alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings.

[0015] Figure 1 It is the alloy phase diagram of 4J42 of the present invention. DETAILED DESCRIPTION

[0016] The present invention develops a hot rolling production method for 4J42 slabs, and innovates a fixed deformation rate distribution method for rough rolling, that is, the first four passes have the same large deformation rate to maintain the deformation amount, and the deformation rate in the last three passes is gradually reduced to maintain the plate shape, so as to ensure the flatness of the intermediate slab. Through the present invention, the 4J42 plate and strip material can be smoothly passed through the plate, and the process is stable and controlled, which fills the gap in the 4J42k plate and strip rolling technology of Taigang Hot Rolling Plant, and at the same time, avoids the problem of low yield rate caused by abnormalities such as scrap steel, and has significant economic benefits.

[0017] The overall technical solution of the present invention is to creatively improve the control parameters and control strategies such as heating furnace temperature, rough rolling passes, and finishing rolling reduction rate for 4J42 incoming materials, thereby ensuring the successful rolling of 4J42.

[0018] The specific technical solutions are as follows: 1. Temperature control of the heating furnace: From the iron-nickel alloy phase diagram, the 4J42 alloy has an austenite structure at temperatures above 688°C; based on hot rolling experience, the alloy has an austenite structure throughout the hot rolling process without phase change problems.

[0019] TISCO has four heating furnaces, each of which is divided into four heating sections: preheating section, first heating section, second heating section, and soaking section. According to the laboratory pilot data, the 4J42 alloy has good thermoplasticity and transforms into austenite structure at temperatures above 700°C. According to the thickness of the ingot, the 4J42 heating process system is formulated as follows: The target furnace temperature of the first heating section is: 1070±20℃; the target furnace temperature of the second heating section is: 1150±20℃; the target furnace temperature of the soaking section is: 1170±20℃.

[0020] 2. Rough rolling: The thickness of the intermediate billet is 25-35mm. The difficulty of rough rolling of this steel grade lies in the control of the warping of the intermediate billet. To this end, a process control method specifically used to solve the warping of the 4J42 intermediate billet is invented, as follows: (1) Innovative fixed deformation rate distribution method. Traditional rolling adopts a load distribution method, that is, the reduction rate is adjusted with the load change. In order to ensure the control of the 4J42 plate shape, the present invention adopts seven rough rolling passes, and at the same time abandons the traditional load distribution method and changes to a fixed deformation rate control, that is, the first four passes have the same large deformation rate to maintain the deformation amount, and the deformation rate of the last three passes gradually decreases to maintain the plate shape, so as to ensure the flatness of the intermediate billet plate shape. (2) Rough rolling water management. Rough rolling does not involve descaling, and the cooling water of the rolling line is turned off during production to reduce the temperature drop on the upper and lower surfaces. (3) SKI value control. As an effective means to adjust the warping of the rough rolling buckle, when producing 4J42, production is carried out in accordance with the first five passes of micro buckle; the SKI values ​​of the sixth and seventh passes are not revised.

[0021] 3. Edge heater: This type of steel is prone to edge cracking, so the edge heater power is set at a maximum of 2000KW during production.

[0022] 4. Finishing rolling reduction rate control: According to the pilot test results, the rolling load of 4J42 is relatively large. In order to ensure the balance of the load of each frame and prevent a certain frame from having overcurrent, pressure over limit and other faults, the reduction rate control method adopts the "RF" load distribution method, that is, the dynamic reduction rate distribution method. The calculation formula of the initial reduction rate is as follows: eps ( i )= RF ( i )* GBZWK / MH (i ) / nnfkorr ( i ) (1) Among them, i Indicates the finishing mill frame number. i When it is 0~6, it indicates F0~F6 rack; GBZWK Indicates the maximum rolling pressure of each stand of finishing rolling, i.e. 40000KN; MH ( i ) indicates the i Hardness value of frame steel; nnfkorr ( i ) indicates the i Frame pressure correction factor.

[0023] The final calculated deformation rates of various thickness specifications of 4J42 in finishing rolling production are shown in Table 1 below.

[0024]

[0025] The implementation of the present invention can ensure the smooth production of 4J42 alloy strips, avoid abnormalities such as scrap steel and failures, thereby expanding the hot-rolled varieties of TISCO and improving the product benefits of special steel alloys.

[0026] Combined with the actual application of 1549 line in the hot rolling mill of TISCO in producing 4J42 stainless steel, the production guarantee of 4J42 after implementing the present invention is described in detail through examples. Example 1

[0027] The process parameters for producing 3.0mm thick 4J42 ingots are as follows: 1) Heating temperature: target furnace temperature of the first heating section: 1070±20℃; target furnace temperature of the second heating section: 1150±20℃; target furnace temperature of the soaking section: 1170±20℃.

[0028] 2) Rough rolling: The thickness of the intermediate billet is 26 mm, and the rolling is performed in seven passes. The deformation rates of passes 1-4 are 14%, pass 5 is 10%, pass 6 is 8%, and pass 7 is 6%. The rough rolling cooling water is turned off during production. The SKI value correction is set to -5 for passes 1-4, -10 for pass 5, and 0 for passes 6 and 7.

[0029] 3) Side addition: The power is given as 2000kw.

[0030] 4) The deformation rate of each pass of finishing rolling is shown in the following table.

[0031]

[0032] The process parameters for producing 4.0mm thick 4J42 ingots are as follows: 1) Heating temperature: target furnace temperature of the first heating section: 1070±20℃; target furnace temperature of the second heating section: 1150±20℃; target furnace temperature of the soaking section: 1170±20℃.

[0033] 2) Rough rolling: The intermediate billet thickness is 30 mm, and the rolling is performed in seven passes. The deformation rates of passes 1-4 are 14%, 9% for pass 5, 7% for pass 6, and 5% for pass 7. The rough rolling cooling water is turned off during production. The SKI value is corrected to -5 for passes 1-4, -10 for pass 5, and 0 for passes 6 and 7.

[0034] 3) Side addition: The power is given as 2000kw.

[0035] 4) The deformation rate of each pass of finishing rolling is shown in the following table.

[0036]

[0037] The process parameters for producing 5.0mm thick 4J42 ingots are as follows: 1) Heating temperature: target furnace temperature in the first heating section: 1070±20℃; target furnace temperature in the second heating section: 1150±20℃; target furnace temperature in the soaking section: 1170±20℃.

[0038] 2) Rough rolling: The intermediate billet thickness is 35mm, and the rolling is performed in seven passes. The deformation rates of passes 1-4 are 13.5%, pass 5 is 8%, pass 6 is 6%, and pass 7 is 5%. The rough rolling cooling water is turned off during production. The SKI value correction is set to -5 for passes 1-4, -10 for pass 5, and 0 for passes 6 and 7.

[0039] 3) Side addition: The power is given as 2000kw.

[0040] 4) The deformation rate of each pass of finishing rolling is shown in the following table.

[0041]

[0042] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for producing 4J42 Invar alloy hot-rolled strip, characterized in that: The following steps are involved: Step 1: Heating furnace temperature control: 4J42 slab is heated in the heating furnace, which is divided into three heating sections: heating section 1, heating section 2, and soaking section. The target furnace temperature of heating section 1 is 1070±20℃, the target furnace temperature of heating section 2 is 1150±20℃, and the target furnace temperature of soaking section is 1170±20℃; the residence time of heating section 1 is 60±10 minutes; the residence time of heating section 2 is 70±10 minutes; the residence time of soaking section is 50±10 minutes; Step 2: Rough rolling: The heated slab is subjected to one main descaling and then rough rolling, and seven rough rolling passes are adopted. No descaling is performed during the rough rolling, and the thickness of the intermediate slab after rolling is 25-35mm. Step 3: After rough rolling, the intermediate billet is heated at the edge: the edge heating power is given according to the maximum value of 1500-2300KW during production; Step 4: The reduction rate of the intermediate billet is controlled in each finishing rolling stand.

2. The method for producing a 4J42 Invar alloy hot-rolled strip according to claim 1, characterized in that: The calculation formula for the reduction rate in step 4 is as follows: eps(i)=RF(i)*GBZWK / MH(i) / nnfkorr(i) (1) Where i represents the finishing mill frame number. When i is 0 to 6, it represents F0 to F6 frames. GBZWK indicates the maximum rolling pressure of each finishing stand, which is 40000KN. MH(i) represents the hardness value of the i-th frame steel, nnfkorr(i) represents the pressure correction coefficient of the i-th rack.

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