Production method for improving yield of nickel-series steel

Abstract

The invention discloses a production method for improving the yield of nickel steel. The steel comprises the following alloy components in percentage by mass: 0.03-0.07% of C, 0.10-0.30% of Si, 0.60-0.90% of Mn, less than or equal to 0.005% of P, less than or equal to 0.002% of S, less than or equal to 0.020% of Nb, less than or equal to 0.010% of V, less than or equal to 0.030% of Ti, less than or equal to 0.30% of Cr, less than or equal to 0.30% of Mo, 3.0-9.50% of Ni, less than or equal to 0.05% of Cu, 0.020-0.050% of Al, less than or equal to 0.0045% of N and the balance of Fe and inevitable impurities. The production process comprises the steps of smelting and casting, plate blank surface pretreatment, plate blank heating, spraying and rolling, wherein the thickness of a plate blank is 180 mm / 220 mm / 260 mm; the size of the steel plate meets requirements, and the surface quality is qualified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel production and relates to a production method for improving the yield of nickel-based steel. BACKGROUND

[0002] With the continuous development of the world steel smelting technology, the production technology of nickel-based steel has been continuously broken through, covering all varieties from 9 nickel to 7 nickel, 5.5 nickel, 5 nickel and the like. Due to the influence of the supply and demand relationship, the competition of nickel-based steel has entered a white-hot stage. The production cost of nickel-based steel is high. In order to obtain orders in market competition, product quality is one aspect, and price is also a major factor. Therefore, in actual production, reducing the production cost through optimization of process control is an effective means to improve the price advantage of products. SUMMARY

[0003] The purpose of the application is to provide a production method for improving the yield of nickel-based steel. The surface of the nickel-based slab is treated by shot blasting instead of surface grinding, so as to reduce the metal consumption in the grinding process and improve the yield.

[0004] The technical scheme of the application is as follows: A production method for improving the yield of nickel-based steel, the alloy composition of the steel is C=0.03%~0.07%, Si=0.10%~0.30%, Mn=0.60%~0.90%, P≤0.005%, S≤0.002%, Nb≤0.020%, V≤0.010%, Ti≤0.030%, Cr≤0.30%, Mo≤0.30%, Ni=3.0%~9.50%, Cu≤0.05%, Al=0.020%~0.050%, N≤0.0045%, and the rest is Fe and inevitable impurities; the slab thickness is 180mm / 220mm / 260mm; the key process steps include: (1) smelting and casting: after the molten iron is treated by a converter and LF / RH refining, clean molten steel with few inclusions and sufficient removal of harmful gases is obtained, and after continuous casting, a slab with qualified composition, macrostructure and surface quality is obtained; (2) slab surface treatment: the slab temperature is cooled to below 50℃, and the upper and lower surfaces are shot blasted 2~3 times by a shot blasting machine to completely remove the surface iron oxide scale; (3) spraying: high-temperature anti-oxidation paint is sprayed on the upper and lower surfaces of the shot blasted slab, and the paint film thickness is 200~400μm; after spraying, the slab is packed with hard paper shell; (4) slab heating: the hearth temperature of the heating furnace is ≤1200℃, the core temperature of the slab after leaving the furnace is controlled at 1150~1200℃, and the slab heating time is not more than 200min; (5) Rolling: the slab is coarsely rolled, finely rolled, and the intermediate slab thickness is ≥3H, H is the order thickness of the steel plate; the fine rolling and finish rolling temperature is controlled at 740~820℃, to obtain the steel plate with the required size and qualified surface quality.

[0005] Innovations and benefits of the present application: 1) Because the nickel steel has high Ni content, the slab is prone to crack during the heating process, so the surface of the slab needs to be pretreated, and the general production method in the steel plant is to mechanically grind the surface of the slab by 2~4mm, polish it to be smooth, and then paint it. The present application adopts the production method of replacing the grinding with the shot blasting of the slab surface, reduces the metal consumption in the slab grinding process, and the yield can be increased by 1.3%~1.5%. 2) The slab heating temperature and heating time are strictly limited, the hearth temperature of the heating furnace is ≤1200℃, the core temperature of the slab after discharging is controlled at 1150~1200℃, and the slab heating time is not more than 200min, to ensure that the high-temperature oxidation-resistant coating plays a protective role and avoids the quality defects on the surface of the slab caused by heating. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 The surface quality effect diagram of the 260mm thick slab after shot blasting of example 1.

[0007] Figure 2 The surface quality effect diagram of the 180mm thick slab after shot blasting of example 2. DETAILED DESCRIPTION

[0008] The present application will be further described below in combination with specific examples. Example 1

[0009] The slab thickness is 260mm, and the chemical composition is shown in Table 1. The production process includes smelting casting, slab surface pretreatment, slab heating, spraying, and rolling, and the specific process steps and process parameters are as follows: Converter steelmaking-LF refining-VD refining-continuous casting, the slab thickness is 260mm, and the slab low-multiple center segregation C class is 1.0 level. The slab number is C500161, which is cooled to below 50℃, and the surface scale is removed clean after being shot blasted by the shot blasting machine for 3 times. The upper and lower surfaces of the shot blasted slab are sprayed with high-temperature oxidation-resistant coating, and the paint film thickness is 300~350μm. After spraying, the hard paper shell is used for packaging treatment. The slab is heated in the furnace, the core temperature after discharging is 1180℃, and the time in the furnace is 185min; the intermediate slab thickness is 65mm, the fine rolling and finish rolling temperature is 815℃, and the 30mm steel plate is rolled by rolling, and the size and surface quality of the steel plate meet the requirements.

[0010] In this embodiment, the slab is obtained by shot blasting for 3 times to remove the clean surface scale of the slab, as shown in Figure 1 . Example 2

[0011] The slab thickness is 180 mm, and the chemical composition percentage is shown in Table 1. The production process includes smelting casting, slab surface pretreatment, slab heating, spraying, and rolling. The specific process steps and process parameters are as follows: Oxygen converter steelmaking-LF refining-VD refining-continuous casting, slab thickness 180 mm, slab low-multiple center segregation C class 1.0 level. Slab number A500211, cooled to below 50℃, after 3 times of shot blasting by the shot blasting machine, the surface iron oxide scale is completely removed. After shot blasting, the upper and lower surfaces of the slab are sprayed with high-temperature anti-oxidation coating, and the paint film thickness is 280-310μm. After spraying, it is packaged with hard paper shell. The slab is heated in the furnace, the core temperature is 1160℃, the furnace time is 150min; the intermediate slab thickness is 60mm, the final rolling temperature is 795℃, and the 12mm steel plate is rolled by rolling. The size and surface quality of the steel plate meet the requirements.

[0012] In this embodiment, the slab is obtained by 3 times of shot blasting, and the upper and lower surfaces of the slab are cleaned of iron oxide scale, as shown in Figure 2 .

[0013] Table 1 Chemical composition of low-cost Ni-based steel produced in the embodiment (wt%) .

Claims

1. A production method for improving the yield of nickel-based steel, characterized in that: The alloy composition of the steel is as follows (mass percentage): C = 0.03%–0.07%, Si = 0.10%–0.30%, Mn = 0.60%–0.90%, P ≤ 0.005%, S ≤ 0.002%, Nb ≤ 0.020%, V ≤ 0.010%, Ti ≤ 0.030%, Cr ≤ 0.30%, Mo ≤ 0.30%, Ni = 3.0%–9.50%, Cu ≤ 0.05%, Al = 0.020%–0.050%, N ≤ 0.0045%, with the remainder being Fe and unavoidable impurities. Slab thickness: 180mm / 220mm / 260mm; Key process steps include: (1) Smelting and casting: After the molten iron is refined in a converter and LF / RH, clean molten steel with fewer inclusions and more harmful gases is obtained. After continuous casting, slabs with qualified composition, low magnification and surface quality are obtained. (2) Surface treatment of slab: After the slab temperature is cooled to below 50℃, the upper and lower surfaces are shot blasted 2 to 3 times to remove the iron oxide scale from the surface. (3) Spraying: The upper and lower surfaces of the slab after shot blasting are sprayed with high-temperature anti-oxidation coating with a film thickness of 200~400μm; after spraying, it is packaged with cardboard. (4) Slab heating: The furnace temperature of the heating furnace is ≤1200℃, the core temperature of the slab exiting the furnace is controlled at 1150~1200℃, and the slab heating time does not exceed 200min; (5) Rolling: The slab is rough rolled and finish rolled, with the intermediate slab thickness ≥3H, where H is the order thickness of the steel plate; the finishing and final rolling temperatures are controlled at 740~820℃ to obtain steel plates with satisfactory dimensions and qualified surface quality.

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