A method for producing hot-rolled strip of 4j42 invar alloy

Abstract

The application discloses a control method for producing 4J42 alloy plate strips in a hot rolling process. After the application is implemented, the smooth production of the 4J42 alloy plate strips can be ensured through heating temperature adjustment, rough rolling head control and finishing rolling load strategy control, and the abnormal conditions such as scrap steel and faults are avoided, so that the hot rolling varieties of TISCO are expanded, and the product benefits of the special steel alloy are improved.

Description

Technical Field

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

[0002] This invention is a hot rolling process technology for producing 4J42K alloy strip on the 1549 hot continuous rolling production line of Taiyuan Iron & Steel Group.

[0003] The hot strip mill line is divided into furnace area, roughing rolling area, finishing rolling area, laminar flow cooling area, and coiling area.

[0004] The main production process of this hot continuous rolling production line is as follows: the slab is first heated in a heating furnace at the temperature specified by the process. After being heated to the target temperature, it first enters the roughing mill for rolling. The vertical rolls control the width and the horizontal rolls control the thickness. Reversible rolling is carried out in the roughing mill, generally in 5 to 7 passes.

[0005] After being rolled on the roughing mill, the strip steel reaches the preset target thickness, width, and temperature. It then enters the finishing mill for seven-stand continuous rolling, achieving the same target thickness and temperature. Next, the strip steel undergoes laminar flow cooling to reach the target coiling temperature. Finally, it is coiled into a steel coil by a coiler.

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

[0007] Literature review revealed that the manufacturing process for this alloy wire is relatively mature, but no literature on continuous rolling for strip production was found. Meanwhile, the market demand for 4J42 strip is large, with most production relying on imports. Through research and development, a 4J42 die-cast billet was successfully produced and prepared. Such billets require hot continuous rolling to produce strip, but there is no prior experience with hot rolling in this production process.

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

[0009] The purpose of this invention is to develop a hot-rolling production method for 4J42 alloy strip, thereby filling the gap in the production of 4J42 strip and expanding the product range that can be produced by hot rolling. Summary of the Invention

[0010] The purpose of this invention is to address the above-mentioned problems by providing a method for producing 4J42 Invar alloy hot-rolled strip.

[0011] The objective of this invention is achieved as follows: A method for producing 4J42 Invar alloy hot-rolled strip, comprising the following steps: Step 1: Furnace temperature control: The 4J42 slab is heated in a furnace, which is divided into three heating sections: a first heating section, a second heating section, and a soaking section. The target furnace temperature for the first heating section is 1070±20℃, the target furnace temperature for the second heating section is 1150±20℃, and the target furnace temperature for the soaking section is 1170±20℃. The furnace dwell time for the first heating section is 60±10 minutes; the furnace dwell time for the second heating section is 70±10 minutes; and the furnace dwell time for the soaking section is 50±10 minutes. Step 2: Rough rolling: After the heated slab undergoes one main descaling pass, it is rough rolled in seven passes. No descaling is performed during rough rolling. The thickness of the intermediate slab after rolling is 25-35mm. Step 3: Edge heaters are installed on the intermediate slab after rough rolling. The edge heater power is set to the maximum value of 1500-2300KW during production. Step 4: The reduction rate of the intermediate slab is controlled on each stand of the finishing mill.

[0012] The formula for calculating the reduction rate in step four is as follows: eps(i)=RF(i)*GBZWK / MH(i) / nnfkorr(i)(1) Where i represents the finishing mill stand number, and when i is 0~6, it represents stands F0~F6 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 effects of this invention are: after implementing this invention, by adjusting the heating temperature, controlling the roughing roll head, and controlling the finishing roll load reduction strategy, the smooth production of 4J42 alloy strip can be guaranteed, and abnormalities such as scrap steel and malfunctions can be avoided, thereby expanding the hot-rolled varieties of Taiyuan Iron & Steel and improving the product benefits of special steel alloys. Attached Figure Description

[0014] The present invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is the alloy phase diagram of 4J42 of the present invention. Detailed Implementation

[0016] This invention develops a hot rolling production method for 4J42 slabs, innovating a fixed deformation rate distribution method in roughing rolling. This method maintains the deformation amount with equal large deformation rates in the first four passes, while gradually decreasing the deformation rate in the latter three passes to maintain slab shape, thus ensuring the flatness of the intermediate slab. Through this invention, 4J42 slabs and strips can be smoothly rolled, with a stable and controlled process, filling the gap in 4J42k slab and strip rolling technology at Taiyuan Iron & Steel's hot continuous rolling mill. Simultaneously, it avoids the low yield problem caused by scrap steel and other abnormalities, resulting in significant economic benefits.

[0017] The overall technical solution of this invention is to creatively improve the control parameters and control strategies of 4J42 feedstock by adjusting the furnace temperature, the number of roughing passes, and the finishing reduction rate, thereby ensuring the successful rolling of 4J42.

[0018] The specific technical solutions are as follows: 1. Furnace temperature control: According to the phase diagram of iron-nickel alloy, the microstructure of 4J42 alloy is austenitic at temperatures above 688℃; based on hot rolling experience, the alloy is austenitic throughout the hot rolling process and there is no phase transformation problem.

[0019] Taiyuan Iron & Steel Group (TISCO) has four heating furnaces, each divided into four heating sections: a preheating section, a first heating section, a second heating section, and a soaking section. Based on pilot-scale laboratory data, the 4J42 alloy exhibits good thermoplasticity, transforming into an austenitic structure above 700℃. Based on the billet thickness, the heating process for 4J42 is as follows: Target furnace temperature for heating section 1: 1070±20℃; Target furnace temperature for heating section 2: 1150±20℃; Target furnace temperature for soaking section: 1170±20℃.

[0020] 2. Rough rolling: The thickness of the intermediate billet is 25-35mm. The difficulty in rough rolling of this steel grade lies in the control of the intermediate billet head. To this end, a process control method specifically designed to solve the problem of the intermediate billet head of 4J42 has been 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. In order to ensure the plate shape control of 4J42, this invention adopts a seven-pass rough rolling process, and abandons the traditional load distribution method, and changes to 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, thus ensuring the flatness of the intermediate billet plate shape. (2) Rough rolling water management. No descaling is used in rough rolling, and the cooling water of the rolling line is turned off during production to reduce the temperature drop of the upper and lower surfaces. (3) SKI value control. As an effective means of adjusting the rough rolling head, when producing 4J42, production is carried out in the manner of slight reduction in the first five passes; the SKI value of the sixth and seventh passes is not revised.

[0021] 3. Edge heater: This steel grade is prone to edge cracking, so the edge heater power is given according to the maximum value of 2000KW during production.

[0022] 4. Finishing Roll Reduction Rate Control: Based on the pilot test results, the rolling load of 4J42 is relatively large. To ensure the load balance of each stand and prevent overcurrent, pressure over-limit, or other malfunctions from occurring on any stand, the reduction rate control method adopts the "RF" load distribution method, i.e., the dynamic reduction rate distribution method. The initial reduction rate is calculated using the following formula: eps ( i )= RF ( i )* GBZWK / MH (i ) / nnfkorr ( i (1) Among them, i Indicates the stand number of the finishing mill, when i When the range is 0 to 6, it represents racks F0 to F6 respectively; GBZWK This indicates the maximum rolling pressure of each stand in the finishing mill, which is 40,000 kN; MH ( i ) indicates the first i The hardness value of the frame steel; nnfkorr ( i ) indicates the first i Frame pressure correction factor.

[0023] The final deformation rates for various thicknesses of 4J42 produced by precision rolling are shown in Table 1 below.

[0024]

[0025] The implementation of this invention can ensure the smooth production of 4J42 alloy strip, avoid scrap steel and malfunctions, thereby expanding the range of hot-rolled products of Taiyuan Iron & Steel and improving the product benefits of special steel alloys.

[0026] Based on the practical application of the invention in the production of 4J42 stainless steel on the 1549 line of the hot rolling mill of Taiyuan Iron & Steel Group, the production guarantee of 4J42 after implementing the invention is described in detail through examples. Example 1

[0027] The process parameters for producing 3.0mm thick 4J42 billets 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 intermediate billet thickness is 26mm, and it is rolled in seven passes. The deformation rate is 14% for passes 1-4, 10% for pass 5, 8% for pass 6, and 6% for pass 7. The cooling water for rough rolling 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: Power is given according to 2000kw.

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

[0031]

[0032] The process parameters for producing 4J42 billets with a thickness of 4.0mm 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 30mm, and it is rolled in seven passes. The deformation rate is 14% for passes 1-4, 9% for pass 5, 7% for pass 6, and 5% for pass 7. The cooling water for rough rolling 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.

[0034] 3) Side addition: Power is given according to 2000kw.

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

[0036]

[0037] The process parameters for producing 5.0mm thick 4J42 billets 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℃.

[0038] 2) Rough rolling: The intermediate billet thickness is 35mm, and it is rolled in seven passes. The deformation rate is 13.5% for passes 1-4, 8% for pass 5, 6% for pass 6, and 5% for pass 7. The cooling water for rough rolling 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: Power is given according to 2000kw.

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

[0041]

[0042] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for producing 4J42 Invar alloy hot-rolled strip, characterized in that: Includes the following steps: Step 1: Furnace Temperature Control: The 4J42 slab is heated in the furnace, which consists of three heating sections: heating section 1, heating section 2, and soaking section. The target furnace temperature for heating section 1 is 1070±20℃, for heating section 2 it is 1150±20℃, and for soaking section it is 1170±20℃. The furnace dwell time for heating section 1 is 60±10 minutes; for heating section 2 it is 70±10 minutes; and for soaking section it is 50±10 minutes. Step 2: Rough rolling: After the heated slab undergoes one main descaling pass, it is rough rolled in seven passes. No descaling is performed during rough rolling. The thickness of the intermediate slab after rolling is 25-35mm. The first four passes have the same large deformation rate to maintain the deformation amount. The deformation rate of the last three passes gradually decreases to maintain the slab shape. Production is carried out in the same way as the first five passes with slight deflection. The SKI value of the sixth and seventh passes is not revised. Step 3: After rough rolling, the intermediate billet is heated at the edge using a heater: the edge heating power is given according to the maximum value of 2000KW during production; Step 4: The reduction rate of the intermediate billet is controlled on each stand of the finishing mill; The formula for calculating the reduction rate in step four is as follows: eps(i)=RF(i)*GBZWK / MH(i) / nnfkorr(i) (1) Where i represents the finishing mill stand number, and when i is 0~6, it represents stands F0~F6 respectively. GBZWK indicates the maximum rolling pressure of each stand in the finishing mill, which is 40000KN. MH(i) represents the hardness value of the steel of the i-th frame. nnfkorr(i) represents the pressure correction factor for the i-th rack.

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