Production method of invar alloy 4J36 hot-rolled coil

Abstract

The invention provides a production method of an invar alloy 4J36 hot-rolled coil, belongs to the technical field of invar alloy 4J36 hot rolling, and solves the problem that the invar alloy 4J36 hot-rolled coil needs to be efficiently produced. The plate blank is preheated and then heated after being ground, and the heated plate blank is subjected to high-pressure water descaling; and the descaled plate blank is rolled into an intermediate blank through seven-pass rough rolling, the intermediate blank is rolled into a black coil through five-pass steckel mill finish rolling, and the black coil is rolled into an invar alloy 4J36 hot-rolled black coil finished product. The method comprises the steps of slab component control, slab preheating and heating, rough rolling to obtain an intermediate slab, steekle mill rolling, coiling and the like, and surface oxidation generated in the heating process is reduced by adjusting the heating process; and through rolling of the steekle mill, dynamic recrystallization is fully carried out, the surface quality of the produced invar alloy 4J36 hot-rolled coil meets the product requirement, and the yield and the production efficiency are both remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hot rolling of Invar alloy 4J36, and in particular relates to a production method of a hot rolled coil of Invar alloy 4J36. Background Art

[0002] Invar alloy, also known as low expansion alloy, is a typical high nickel iron-based alloy. The thermal expansion coefficient of this alloy decreases significantly near the magnetic temperature, i.e., Curie point, and the so-called abnormal thermal expansion phenomenon (negative anomaly) occurs, so that a very small or even close to zero expansion coefficient can be obtained in a wide temperature range near room temperature. Therefore, this alloy is also called a low expansion alloy.

[0003] At the same time, Invar alloy contains a high nickel content, which improves the hardenability and hardenability of the steel, and improves the steel's gas resistance, corrosion resistance and wear resistance. It is widely used in precision laser equipment, important components of instruments and meters, fixed components, LNG storage tanks and transport ships, as well as high-tech products such as aerospace and laser.

[0004] Invar alloy requires high nickel and low carbon. Due to its special composition requirements and production process, it is difficult to produce and has long relied on imports, which has seriously restricted the application of this product in China and made it subject to foreign restrictions. With the rapid development of technology in the aerospace field, it is particularly urgent to study hot rolling technology to achieve the best performance of materials and meet industrial batches. Summary of the invention

[0005] The object of the present invention is to provide a method for producing an Invar 4J36 hot-rolled coil, so as to solve the problem that the Invar 4J36 hot-rolled coil needs to be produced efficiently.

[0006] The technical solution of the present invention is: a method for producing an Invar 4J36 hot-rolled coil, comprising the following steps: Step 1: Produce Invar alloy 4J36 slabs through steelmaking and continuous casting processes, the chemical composition percentages of the slabs are: C: ≤0.05%, Si: 0.10-0.40%, Mn: 0.20-0.46%, P: ≤0.015%, S: ≤0.01%, Ni: 35.00-36.50%, Al: 0.01-0.03%, and the rest are Fe and residual elements; Step 2: After grinding, the slab is preheated and then heated, and the heated slab is descaled with high-pressure water; Step 3: The descaled slab is rough-rolled into an intermediate slab by 7 passes, the intermediate slab is finish-rolled into a black coil by 5 passes of a furnace coil mill, and the black coil is coiled to produce an Invar alloy 4J36 hot-rolled black coil finished product.

[0007] As a further improvement of the present invention, in step 1, the size of the Invar alloy 4J36 slab is (160-220) mm×(950-1600) mm×(5000-12000) mm.

[0008] As a further improvement of the present invention, in step 2, the preheating temperature is 550-800°C, and the heating time is 120-320 min; the heating temperature is 950-1250°C, and the heating time is 120-320 min.

[0009] As a further improvement of the present invention, in step 2, the descaling system pressure is ≥15 MPa.

[0010] As a further improvement of the present invention, in step three, the thickness of the intermediate blank is 20-30 mm.

[0011] As a further improvement of the present invention, in step three, the finishing rolling time is 6-8 minutes, the furnace temperature of the coiling furnace at the entrance and exit of the Steckel mill is 800-1200° C., and the thickness of the rolled black coil is 4.5 mm.

[0012] As a further improvement of the present invention, in step three, the coiling temperature is 500-750°C.

[0013] The beneficial effects of the present invention are as follows: 1. The present invention uses a Steckel mill to reciprocate rolling to give the strip sufficient dynamic recrystallization time, reduce the anisotropy of the strip, and significantly reduce the performance difference of the strip. After annealing, the austenite equiaxed crystal rate is high, and the yield strength, tensile strength and elongation of the hot-rolled black coil are high, which provides a guarantee for the high strength and high toughness of the finished product.

[0014] 2. The present invention adopts Jiugang's unique series production process of preheating furnace and heating furnace. In view of the characteristics of this steel type with high alloy composition and low thermal conductivity, low-temperature slow heating is adopted to avoid the internal structural stress and temperature stress of the slab from being too high and causing fracture; the double-furnace series technology is adopted to ensure the heating uniformity of this steel type; the heating time and heating temperature are reasonably controlled to avoid the pressure-in of the primary oxide scale due to excessive thickness during rolling.

[0015] 3. The finishing rolling of the present invention ensures forced rapid cooling after high-temperature rolling through coiling furnace temperature control and reasonable cooling method, further refines the grains and improves the strength of the black coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The microstructure diagram of the hot-rolled black coil after annealing obtained in Example 1 of the method; Figure 2 This is the microstructure diagram of the hot-rolled black coil after annealing obtained in Example 2 of the method. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to the embodiments.

[0018] Embodiment 1, Step 1: Produce Invar alloy 4J36 slab through steelmaking and continuous casting process, the chemical composition percentage of the slab is: C: 0.05%, Si: 0.10%, Mn: 0.20%, P: 0.015%, S: 0.01%, Ni: 35.00%, Al: 0.01%, and the rest are Fe and residual elements; the size of the Invar alloy 4J36 slab is 160mm×950mm×5000mm.

[0019] Step 2: After grinding, preheat the slab and then heat it again. The preheating temperature is 550°C and the heating time is 120 minutes. The heating temperature is 950°C and the heating time is 120 minutes. The heated slab is descaled with high-pressure water. The descaling system pressure is 15MPa.

[0020] Step 3: The descaled slab is rough-rolled for 7 passes to form an intermediate billet. There is no limit on the descaling of the rough rolling stand. The vertical roller cooling water is selected in automatic mode or manually set to a reasonable speed during the rolling process. The thickness of the intermediate billet is 20 mm; the intermediate billet is finished-rolled by the furnace coil mill for 5 passes to form a black coil. The finishing time is 6 minutes. The furnace temperature of the coiling furnace at the inlet and outlet of the furnace coil mill is 800°C, and the thickness of the rolled black coil is 4.5 mm; laminar cooling is put into use, and the automatic cooling mode is adopted. The head and tail of the black coil are completely cooled. The coiling temperature is 500°C, and the black coil is coiled into the finished product of Invar alloy 4J36 hot-rolled black coil.

[0021] Embodiment 2, Step 1: Produce Invar alloy 4J36 slab through steelmaking and continuous casting process, the chemical composition percentage of the slab is: C: 0.04%, Si: 0.25%, Mn: 0.33%, P: 0.014%, S: 0.009%, Ni: 35.70%, Al: 0.02%, and the rest are Fe and residual elements; the size of the Invar alloy 4J36 slab is 190mm×1250mm×8500mm.

[0022] Step 2: After grinding, the slab is preheated and then heated, the preheating temperature is 720°C, and the heating time is 220 minutes; the heating temperature is 1100°C, and the heating time is 220 minutes; the heated slab is descaled with high-pressure water, and the descaling system pressure is 16MPa.

[0023] Step 3: The descaled slab is rough-rolled for 7 passes to form an intermediate billet. There is no limit on the descaling of the rough rolling stand. The vertical roller cooling water is selected in automatic mode or manually set to a reasonable speed during the rolling process. The thickness of the intermediate billet is 25mm; the intermediate billet is finished-rolled by the furnace coil mill for 5 passes to form a black coil. The finishing time is 7min. The furnace temperature of the coiling furnace at the inlet and outlet of the furnace coil mill is 1000℃, and the thickness of the rolled black coil is 4.5mm. Laminar cooling is put into use, and the automatic cooling mode is adopted. The head and tail of the black coil are completely cooled. The coiling temperature is 620℃, and the black coil is coiled into the finished product of Invar alloy 4J36 hot-rolled black coil.

[0024] Embodiment 3, Step 1: Produce Invar alloy 4J36 slab through steelmaking and continuous casting process, the chemical composition percentage of the slab is: C: 0.03%, Si: 0.40%, Mn: 0.46%, P: 0.013%, S: 0.008%, Ni: 36.50%, Al: 0.03%, and the rest are Fe and residual elements; the size of Invar alloy 4J36 slab is 220mm×1600mm×12000mm.

[0025] Step 2: After grinding, the slab is preheated and then heated, the preheating temperature is 800°C, and the heating time is 320 minutes; the heating temperature is 1250°C, and the heating time is 320 minutes; the heated slab is descaled with high-pressure water, and the descaling system pressure is 17MPa.

[0026] Step 3: The descaled slab is rough-rolled for 7 passes to form an intermediate billet. There is no limit on the descaling of the rough rolling stand. The vertical roller cooling water is selected in automatic mode or manually set to a reasonable speed during the rolling process. The thickness of the intermediate billet is 30 mm; the intermediate billet is finished-rolled by the furnace coil mill for 5 passes to form a black coil. The finishing time is 8 minutes. The furnace temperature of the coiling furnace at the inlet and outlet of the furnace coil mill is 1200°C, and the thickness of the rolled black coil is 4.5 mm; laminar cooling is put into use, and the automatic cooling mode is adopted. The head and tail of the black coil are completely cooled. The coiling temperature is 750°C, and the black coil is coiled into the finished product of Invar alloy 4J36 hot-rolled black coil.

[0027] The parameters of the finished black coils obtained in Examples 1-3 are shown in Table 1 below. From the data comparison in Table 1, it can be seen that the finished products made by this production process meet the customer requirements in terms of yield strength, tensile strength, elongation, HV hardness and elastic modulus, and are also significantly higher than the industry standards. In addition, the organization is uniform and the grain size is small. Figure 1-2This process method controls the heating process system reasonably to make the continuous casting billet reach a uniform heating temperature during the heating process. The finished product has the advantages of high strength, rigidity and toughness, high flatness, and excellent precision rolling performance. It is suitable for the production of precision instruments and aerospace precision components.

[0028] According to the above method, embodiments 1-3 realize the production of 4.5*1250mm Invar 4J36 hot-rolled coils, with a single coil weight of more than 12 tons and a coil metal yield rate of more than 98%. The method reduces the oxidation of hot-rolled black coils by adjusting the heating process, and avoids the rough surface caused by the pressing of oxide scale; through the furnace coil rolling mill, dynamic recrystallization is fully carried out, and the Invar alloy 4J36 hot-rolled coils produced have a maximum yield strength of 440MPa, a tensile strength of 535MPa, a HV hardness of 175, and an elastic modulus of more than 145GPa. The product performance meets the requirements of finished product processing, the grain size reaches 5-6 after annealing, the pickling efficiency is high, and the surface roughness after pickling is about 6.0μm, which greatly improves the production efficiency of Invar 4J36 hot-rolled coils. The Invar 4J36 hot-rolled coils produced have the characteristics of straight plate shape, small width control range, high yield rate, and low cost. At the same time, the quality of the finished product also fully meets the use requirements.

Claims

1. A method for producing an Invar 4J36 hot rolled coil, characterized in that: The following steps are involved: Step 1: Produce Invar alloy 4J36 slabs through steelmaking and continuous casting processes, the chemical composition percentages of the slabs are: C: ≤0.05%, Si: 0.10-0.40%, Mn: 0.20-0.46%, P: ≤0.015%, S: ≤0.01%, Ni: 35.00-36.50%, Al: 0.01-0.03%, and the rest are Fe and residual elements; Step 2: After grinding, the slab is preheated and then heated, and the heated slab is descaled with high-pressure water; Step 3: The descaled slab is rough-rolled into an intermediate slab by 7 passes, the intermediate slab is finish-rolled into a black coil by 5 passes of a furnace coil mill, and the black coil is coiled to produce an Invar alloy 4J36 hot-rolled black coil finished product.

2. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step 1, the size of the Invar alloy 4J36 slab is (160-220) mm×(950-1600) mm×(5000-12000) mm.

3. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step 2, the preheating temperature is 550-800°C, and the heating time is 120-320 minutes; the heating temperature is 950-1250°C, and the heating time is 120-320 minutes.

4. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step 2, the descaling system pressure is ≥15MPa.

5. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step three, the thickness of the intermediate billet is 20-30 mm.

6. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step three, the finishing rolling time is 6-8 minutes, the furnace temperature of the coiling furnace at the entrance and exit of the Steckel mill is 800-1200°C, and the thickness of the rolled black coil is 4.5 mm.

7. The method for producing an Invar 4J36 hot rolled coil according to claim 1, characterized in that: In step 3, the coiling temperature is 500-750°C.

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