Production method for improving qualified rate of 5Ni steel

Abstract

This invention discloses a production method for improving the yield of 5Ni steel. The method includes adjusting the heating process, optimizing cooling water management, precisely controlling the descaling process, increasing the tapping speed, and increasing the number of water channel passes during fine descaling. This method can significantly reduce the phenomenon of iron oxide indentation on the lower surface of 5Ni steel. This method not only effectively improves the product quality of 5Ni steel but also significantly saves production costs, bringing significant economic benefits to enterprises. The implementation of this invention optimizes the production process, improves production efficiency, reduces the defect rate, and enhances the market competitiveness of the product. Furthermore, the widespread application of this method will help promote the extensive use of 5Ni steel in building structures, bridges, ships, vehicles, and other fields, providing strong support for the development of related industries.

Description

Technical Field

[0001] This invention belongs to the field of alloy steel preparation technology, specifically relating to a production method for improving the yield of 5Ni steel. Background Technology

[0002] In the field of steel materials, with the continuous advancement of industrial technology and the increasing demands on material performance in engineering structures, low-alloy high-strength structural steel has been widely used due to its excellent comprehensive performance. Among them, 5Ni steel, as a typical low-alloy high-strength structural steel, possesses unique physical and chemical properties due to its nickel content, making it play an important role in building structures, bridges, ships, vehicles, and other fields.

[0003] The chemical composition of 5Ni steel mainly includes elements such as carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), and nickel (Ni). The reasonable configuration of these elements gives 5Ni steel high strength, good plasticity and toughness, thus meeting the material performance requirements of various complex engineering structures.

[0004] However, in actual production, the high alloy content of 5Ni steel makes it prone to surface iron oxide formation during processing and manufacturing. The formation of surface iron oxide not only affects the appearance quality of 5Ni steel, but more importantly, it can adversely impact the material's performance. Especially in fields requiring strict surface quality control, such as precision machinery and electronic components, the presence of surface iron oxide can lead to decreased product performance and even safety hazards.

[0005] Furthermore, the presence of surface iron oxide indentation in 5Ni steel during production further complicates the removal of this oxide. While some methods exist for removing surface iron oxide, they are often inefficient and fail to completely remove all oxides. Consequently, some products are deemed defective due to surface iron oxide indentation, leading to a lower yield rate and hindering improvements in overall quality.

[0006] In conclusion, although 5Ni steel has broad application prospects in many fields, the problem of iron oxide on its surface remains a technical challenge that urgently needs to be solved. Therefore, researching and developing a technology that can effectively remove iron oxide from the surface of 5Ni steel is of great significance for improving product quality, reducing production costs, and promoting the widespread application of 5Ni steel. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a production method for improving the yield of 5Ni steel. By optimizing the production plan, the phenomenon of iron oxide on the lower surface is significantly reduced. Occasionally, a small amount of iron oxide may exist, but it can be removed by grinding and then stored in the warehouse, thereby improving the yield and saving production costs.

[0008] This invention is achieved through the following technical solution:

[0009] A production method for improving the yield of 5Ni steel includes the following steps:

[0010] Step 1) Furnace operation process: Low temperature furnace operation is adopted. The temperature of the first heating stage is set to 1130±10℃, the temperature of the second heating stage is set to 1140±10℃, and the temperature of the soaking stage is set to 1140±10℃, ensuring that the 5Ni steel is in the furnace for less than 500 minutes.

[0011] Step 2) Cooling water control: Before rolling, shut off the cooling water of the No. 1 furnace tapping roller table, reduce the cooling water of the rolling mill roller table, and shut off the cooling water of the inlet and outlet rotary roller tables;

[0012] Step 3) Coarse descaling: Set the coarse descaling speed to 0.5 m / s to ensure effective descaling of the lower surface;

[0013] Step 4) Fine descaling: High-pressure water jet descaling is used in the first 1-3 passes of rough rolling, and high-pressure water jet descaling is used in the first 1, 2, 5 and 6 passes of finish rolling.

[0014] Step 5) Steel plate rolling: The steel plate is rolled using conventional rolling technology, then straightened and cooled, and then finished to complete the operation.

[0015] Preferably, the furnace time in step 1) is 380–420 min.

[0016] Preferably, in step 1), if the 5Ni steel has been in the furnace for more than 500 minutes, it needs to be reheated.

[0017] Preferably, in step 5), the cutting allowance of the steel plate is set to 7.5cm.

[0018] Preferably, the process also includes step 6), which is as follows: the steel plate that has completed the finishing process is promptly sent to a heat treatment shot blasting process to check whether there are any defects on the surface of the steel plate.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention optimizes the heating process, eliminating the original conventional upper limit of 1200℃ and instead employing a low-temperature furnace operator with an upper limit of 1150℃. This improvement effectively reduces the oxidation of the steel billet during heating, thus reducing the formation of iron oxide. Simultaneously, by limiting the time spent in the furnace, it further ensures uniform heating and control of oxidation, thereby improving the overall product quality. Regarding cooling water management, this invention effectively avoids the scouring effect of cooling water on the steel billet surface by promptly shutting off the cooling water from the tapping and rotary roller conveyors, reducing iron oxide formation. This measure not only improves the surface quality of the product but also reduces energy consumption, achieving the goal of energy conservation and emission reduction. In terms of descaling control, this invention further improves the descaling effect and reduces the risk of iron oxide intrusion by increasing the number of fine descaling water passes and adding fine descaling passes. This measure ensures the cleanliness of the steel billet surface and improves the product qualification rate. Furthermore, this invention also increases the tapping speed, allowing the slab to pass through the rough descaling box as quickly as possible, reducing the residence time of the steel billet during descaling and further reducing iron oxide formation. This measure not only improved production efficiency but also reduced production costs, bringing economic benefits to the enterprise. In summary, by optimizing the production plan, this invention has achieved significant results in reducing the iron oxide indentation phenomenon on the lower surface of 5Ni steel, improving product quality, and saving production costs. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1

[0023] A production method for improving the yield of 5Ni steel includes the following steps:

[0024] (1) Furnace operation process: Low temperature furnace operation is adopted. The temperature of the first heating stage is set at 1130±10℃, the temperature of the second heating stage is set at 1140±10℃, and the temperature of the soaking stage is set at 1140±10℃. Ensure that the 5Ni steel is in the furnace for 380~420min. It is forbidden to exceed 500min. If the 5Ni steel is in the furnace for more than 500min, it must be returned to the furnace and must not be rolled.

[0025] (2) Cooling water control: Before rolling, the cooling water of the No. 1 furnace tapping roller table is turned off, the cooling water of the rolling line roller table is reduced, and the cooling water of the inlet and outlet rotary roller table is turned off.

[0026] (3) Coarse descaling: The coarse descaling speed is set to 0.5m / s to ensure the descaling effect on the lower surface.

[0027] (4) Fine descaling: High-pressure water jet descaling is used in the first to third passes of rough rolling, and high-pressure water jet descaling is used in the first, second, fifth and sixth passes of fine rolling.

[0028] (5) Steel Plate Rolling: The steel plates are rolled using conventional processes, which are strictly followed and meet the specified process temperature requirements. Quality issues such as camber and warping are controlled during rolling to ensure a smooth and stable process. Considering that the steel plates will be thinner after secondary quenching during heat treatment, rolling is performed according to the thickness of the assembled plates, taking into account both the overall plate thickness and the sample dimensions for each small plate. Simultaneously, to ensure the steel plates can be sheared from the shearing machine, a cutting allowance of 7.5cm for the large plates must be maintained.

[0029] After the steel plate is rolled, it needs to undergo MULPIC accelerated cooling, straightening, and cooling bed cooling according to the process, and then enter the subsequent finishing process, which includes flaw detection, sampling, head cutting, double-sided cutting, length setting, spraying and marking, and finally being sent to the finished product warehouse.

[0030] 5Ni steel heat-treated products, after finishing and entering the finished product warehouse, need to be transported by freight to the heat treatment workshop for subsequent heat treatment processes. The first heat treatment process is shot blasting, which allows for clear inspection of surface defects. In special cases, to quickly understand the surface condition, the rolling mill directly rolls the product off the production line after length setting and transports it by truck for direct shot blasting.

[0031] (6) Effect verification: After finishing, the surface was promptly sent for heat treatment and shot blasting inspection. The surface quality was verified to be good, with only a small amount of slight iron oxide in some parts. It can be put into storage after grinding.

[0032] Before adopting this process, the pass rate of 5Ni steel rolling was consistently around 80%. After adopting the above process, the pass rate increased to over 90%, an improvement of approximately 11%.

[0033] Example 2

[0034] A type of marine-grade 5Ni steel, grade X12Ni5, plate number B4218128000, is rolled according to DNV classification society material specifications and EN10028-4:2017 standard, with a target plate thickness of 8-50mm. It is produced according to the process described in Example 1, and the specific processing flow is shown in Table 1 below:

[0035] Table 1. Control parameters for each process of 5Ni (B4218128000)

[0036]

[0037] As shown in Table 1, the control of each process in the production of large board B4218128000 meets the requirements, and the surface quality is normal after inspection.

[0038] Example 3

[0039] A type of marine-grade 5Ni steel, grade X12Ni5, plate number B4218136000, is rolled according to DNV classification society material specifications and EN10028-4:2017 standard, with a target plate thickness of 8-50mm. It is produced according to the process described in Example 1, and the specific processing flow is shown in Table 2 below.

[0040] Table 2 Control parameters for each process of 5Ni B4218136000

[0041]

[0042] As shown in Table 2, the control of each process in the production of large board B4218136000 meets the requirements, and the surface quality is normal after inspection.

[0043] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A production method for improving the yield of 5Ni steel, characterized in that, Includes the following steps: Step 1) Furnace operation process: Low temperature furnace operation is adopted. The temperature of the first heating stage is set to 1130±10℃, the temperature of the second heating stage is set to 1140±10℃, and the temperature of the soaking stage is set to 1140±10℃, ensuring that the 5Ni steel is in the furnace for less than 500 min. Step 2) Cooling water control: Before rolling, shut off the cooling water of the No. 1 furnace tapping roller table, reduce the cooling water of the rolling mill roller table, and shut off the cooling water of the inlet and outlet rotary roller tables; Step 3) Coarse descaling: Set the coarse descaling speed to 0.5 m / s to ensure effective descaling of the lower surface; Step 4) Descaling: High-pressure water jet descaling is used in the first 1-3 passes of rough rolling, and high-pressure water jet descaling is used in the first 1, 2, 5 and 6 passes of finish rolling. Step 5) Steel plate rolling: The steel plate is rolled, then straightened and cooled, and then finished to complete the operation.

2. The production method for improving the yield of 5Ni steel according to claim 1, characterized in that, Step 1) The furnace time is 380~420 min.

3. The production method for improving the yield of 5Ni steel according to claim 1, characterized in that, In step 1), if the 5Ni steel is in the furnace for more than 500 minutes, it needs to be returned to the furnace.

4. The production method for improving the yield of 5Ni steel according to claim 1, characterized in that, In step 5), the cutting allowance of the steel plate is set to 7.5 cm.

5. The production method for improving the yield of 5Ni steel according to claim 1, characterized in that, It also includes step 6), which is as follows: the steel plate that has completed the finishing process is promptly sent for heat treatment shot blasting to check whether there are any defects on the surface of the steel plate.

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