Method for preventing water ripples on surface of Q960E steel plate

Abstract

The invention relates to a method for preventing water ripples from being generated on the surface of a Q960E steel plate. A plate blank is machined according to a rough rolling procedure, a through water cooling procedure, a swing temperature holding procedure and a finish rolling procedure in sequence. Wherein in the through-water cooling process, the through-water amount is 900-1000 m < 3 > / h, the through-water pressure is 0.1-0.2 Mpa, and the water cooling speed is 2-3 DEG C / s; in the swinging temperature holding process, the swinging temperature holding time is 150-210 s, and the swinging temperature holding cooling mode is natural air cooling. Through water cooling between rough rolling and finish rolling, the slab temperature holding time is shortened, secondary oxide scale formed by an intermediate slab is extremely easy to remove in the subsequent finish rolling stage, the pitted surface of the high-alloy steel plate Q960E is effectively prevented, and the product yield is increased.

Description

Technical Field

[0001] The invention relates to the technical field of steel plate surface treatment in the metallurgical industry, and in particular to a method for preventing water ripples from being generated on the surface of a Q960E steel plate. Background Art

[0002] The whole process of medium and thick plate production, from billet to steel plate that meets the target size, steel plate surface and customer performance requirements, needs to go through heating, descaling, rolling, cooling, straightening and cutting, until it is shipped after passing the spraying and engraving inspection. In the above process, the surface treatment of the steel plate is the key. How to avoid the occurrence of pockmarks on the surface of the steel plate is the eternal pursuit of every steel rolling worker.

[0003] Steel plate water ripples, commonly known as "pitted surface", are a common surface defect of steel materials. It is characterized by irregular, rough, concave and convex textures on the surface of the steel plate, similar to pockmarks. This defect not only affects the appearance quality of the steel plate, but may also have a serious impact on the performance and service life of the steel plate. The following are the main hazards caused by the pitted surface of the steel plate: (1) Reduce the corrosion resistance of steel plates The rough surface of the steel plate increases the contact area with corrosive media such as air and moisture, thereby accelerating the corrosion process of the steel plate. Corrosion not only makes the steel plate thinner, affecting its structural strength and bearing capacity, but may also cause safety problems.

[0004] (2) Impact on the processing performance of steel plates The rough surface makes the steel plate surface uneven, which brings difficulties to the subsequent processing such as cutting, welding, coating, etc. During the processing, problems such as increased tool wear, unstable welding quality, and poor coating adhesion may occur, thus affecting product quality and production efficiency.

[0005] (3) Reduce the fatigue life of steel plates When the steel plate surface is subjected to stress, stress concentration is likely to occur, resulting in excessive local stress. Under long-term action, these stress concentration points may become the source of crack initiation, thereby accelerating the fatigue fracture of the steel plate. Fatigue fracture is a sudden failure mode with great safety hazards.

[0006] (4) Affecting the appearance quality of steel plates The rough surface of steel plate seriously affects its appearance and reduces the market competitiveness of products. Especially in the fields that require high-precision appearance requirements, such as construction and decoration, rough surface defects may cause products to fail to meet customer needs and bring economic losses to enterprises.

[0007] (5) Increased maintenance costs Due to the corrosion and processing difficulties caused by the rough surface of the steel plate, enterprises may need to increase the frequency of maintenance and repair during use, thereby increasing maintenance costs. This not only affects the economic benefits of the enterprise, but may also affect the stable operation of the production line.

[0008] In short, the pitting of steel plates brings many hazards to the performance, processing, appearance and service life of steel plates. Therefore, in the production and use of steel plates, the generation of pitting defects should be strictly controlled and effective preventive measures should be taken to improve the quality and performance of steel plates. As a typical representative of alloy steel, it is of practical significance to study the prevention methods of pitting of Q960E. Summary of the invention

[0009] The purpose of the present invention is to provide a method for preventing water ripples from being generated on the surface of a Q960E steel plate, which can effectively prevent water ripples from being generated on the surface of the steel plate and improve the production quality of the steel plate.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a method for preventing water ripples from being generated on the surface of a Q960E steel plate, comprising: processing the slab in sequence according to a rough rolling process, a water cooling process, a swinging temperature waiting process and a finishing rolling process; Wherein, in the water-penetrating cooling process, the water-penetrating water volume is 900-1000 m3 / h, the water-penetrating water pressure is 0.1-0.2Mpa, and the water cooling speed is 2-3℃ / s; In the swing waiting process, the swing waiting time is 150-210 s, and the swing waiting cooling method is natural air cooling; the chemical composition of the slab is calculated by mass percentage as follows: C: 0.08-0.12%; Si: 0.2-0.4%; Mn: 1.6-1.8%; P<0.015%; S<0.008%; Cr: 0.7-1.0%; Ni: 1.0-1.2%; Cu<0.2%; Mo<0.2%; Ti: 0.01-0.02%; V: 0.05-0.1%; Nb: 0.03-0.04%; B: 0.003-0.005%, and the remainder is Fe and unavoidable impurities.

[0011] Furthermore, in the rough rolling process, the inlet temperature is 1020-1050°C, and the outlet temperature is 950-980°C.

[0012] Furthermore, in the rough rolling process, the rough rolling passes are 5 to 7 passes.

[0013] Furthermore, in the finishing rolling process, the inlet temperature is 860-880°C, and the outlet temperature is 800-820°C.

[0014] Furthermore, in the finishing rolling process, the finishing rolling passes are 5 to 6 passes.

[0015] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The present invention shortens the air-cooling time of the slab by water-cooling after rough rolling, thereby greatly shortening the exposure time of the slab in the air, reducing the degree of surface oxidation, and greatly weakening the adhesion of the formed secondary oxide scale to the substrate, which can be easily removed in the subsequent finishing rolling process, thereby effectively preventing the occurrence of pitting on the high-alloy steel plate Q960E. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 A schematic diagram of the production process of a method for preventing water ripples from forming on the surface of a Q960E steel plate according to the present invention; Figure 2 The invention discloses a steel plate without pitting defects which is manufactured according to a method for preventing water ripples from being generated on the surface of a Q960E steel plate. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The present invention provides a method for preventing water ripples from forming on the surface of a Q960E steel plate, which comprises a rough rolling process, a water cooling process, a swinging temperature waiting process and a finishing rolling process performed in sequence.

[0019] In the embodiments of the present invention, a slab with a certain thickness is rolled into a finished steel plate that meets the requirements and has qualified quality through the above-mentioned process.

[0020] In the embodiment of the present invention, a 260 mm slab is selected to be rolled into a 45 mm finished steel plate.

[0021] Specifically, the chemical composition of the above-mentioned slab is, by mass percentage, C: 0.08~0.12%; Si: 0.2~0.4%; Mn: 1.6~1.8%; P<0.015%; S<0.008%; Cr: 0.7~1.0%; Ni: 1.0~1.2%; Cu<0.2%; Mo<0.2%; Ti: 0.01~0.02%; V: 0.05~0.1%; Nb: 0.03~0.04%; B: 0.003~0.005%, and the remainder is Fe and unavoidable impurities.

[0022] In the aforementioned rough rolling process, the inlet temperature is set at 1020~1050℃, and the outlet temperature is set at 950~980℃. At this temperature, the rolling pass is controlled at 5~7 times. Then, when the rough rolling reaches the 6th~8th pass, the slab is sent for water cooling. The water flow is controlled at 900~1000m3 / h, the water pressure is 0.1~0.2 Mpa, and the water cooling rate is 2~3℃ / s. Thus, the water cooling process is used to replace the conventional natural air cooling process, thereby shortening the total slab cooling residence time. After the rough rolling process, the slab generally needs natural air cooling for about 380 s under normal conditions before it can be sent to the next finishing process for subsequent operations. However, if the natural air cooling time is too long, it is easy to make the iron oxide scale generated during the rolling process difficult to remove in the subsequent finishing process, which will cause defects similar to pitting to appear on the surface of the steel plate after finishing rolling. In the embodiment of the present invention, water-penetrating cooling of the slab rolled piece is adopted, so that the swing waiting cooling time after water cooling can be shortened to 150-210s, thereby greatly shortening the exposure time of the slab rolled piece in the air, reducing the degree of oxidation on the surface of the slab, and greatly weakening the adhesion between the formed secondary oxide scale and the substrate, which can be easily removed in the subsequent finishing rolling stage, thereby improving the production quality of the steel plate and the yield of the finished product.

[0023] After the swing temperature is completed, the slab is sent to the next finishing process. Specifically, the finishing entrance temperature is set at 860~880℃, and the exit temperature is set at 800~820℃. The finishing passes are controlled at 5~6 passes, so that the slab can be rolled into a steel plate product of the target thickness.

[0024] Example 1 In this embodiment, Q960E billet is used as raw material to roll and produce a finished steel plate with a specification of Φ45mm. The chemical composition of the aforementioned Q960E billet is calculated as follows by mass percentage: C: 0.1%; Si: 0.3%; Mn: 1.7%; P<0.015%; S<0.008%; Cr: 0.9%; Ni: 1.1%; Cu<0.2%; Mo<0.2%; Ti: 0.015%; V: 0.08%; Nb: 0.035%; B: 0.004%, and the remainder is Fe and unavoidable impurities.

[0025] In this embodiment, a method for preventing water ripples from forming on the surface of a Q960E steel plate includes a rough rolling process, a water cooling process, a swinging temperature waiting process, and a finishing rolling process performed in sequence.

[0026] In the rough rolling process, the inlet temperature is 1035°C, the outlet temperature is 960°C, and the rough rolling is performed for 7 passes; In the water cooling process, the water volume is controlled at 1000m3 / h, the water pressure is controlled at 0.015Mpa, and the cooling rate is 2℃ / s; In the swing waiting process, the swing waiting method is natural air cooling, and the swing waiting time is 190s; In the finishing rolling process, the inlet temperature was 870°C, the outlet temperature was 810°C, and the finishing rolling was performed for 5 passes.

[0027] Example 2 In this embodiment, Q960E billet is used as raw material to roll and produce a finished steel plate with a specification of Φ45mm. The chemical composition of the aforementioned Q960E billet is calculated as follows by mass percentage: C: 0.1%; Si: 0.3%; Mn: 1.7%; P<0.015%; S<0.008%; Cr: 0.9%; Ni: 1.1%; Cu<0.2%; Mo<0.2%; Ti: 0.015%; V: 0.08%; Nb: 0.035%; B: 0.004%, and the remainder is Fe and unavoidable impurities.

[0028] In this embodiment, the only difference from Example 1 is that the water cooling process is not performed. After the rough rolling of the slab, the conventional natural air cooling method is selected for swinging and waiting for temperature. The specific swinging and waiting time is 380s, and a Q960E steel plate finished product can also be prepared.

[0029] The surface quality of the target steel plate rolled from the Q960E billet was checked, and the mechanical properties were also tested. Figure 2 During the inspection, no obvious surface quality defects were found in the finished steel plate obtained in Example 1. The surface quality was good, and all properties of the steel plate after rolling met the standard requirements. However, the finished slab obtained in Example 2 had pitting after air cooling, and its distribution was mostly loose or loose sand. After pickling and sandblasting, this defect appeared in the form of slight surface depressions. There were residual iron oxide particles on the rough pit bottom, which seriously reduced the yield of the finished steel plate.

[0030] In summary, the method provided in the present invention for preventing water ripples from forming on the surface of Q960E steel plate provides reasonable waiting time parameters in the swing waiting process of the intermediate billet, provides reliable cooling water volume and water pressure, and effectively prevents the pitting defects of high-alloy steel plates represented by Q960E, while providing customers with high-quality products and creating considerable benefits for the enterprise.

[0031] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preventing water ripples on the surface of Q960E steel plate. It is characterized in that include: The slab is processed in sequence according to the rough rolling process, the water cooling process, the swing temperature waiting process and the finishing rolling process; Wherein, in the water-penetrating cooling process, the water flow rate is 900-1000 m3 / h, the water pressure is 0.1-0.2 Mpa, and the water cooling speed is 2-3℃ / s; In the swing waiting temperature process, the swing waiting temperature time is 150-210 s, and the swing waiting temperature cooling method is natural air cooling; The chemical composition of the slab is calculated by mass percentage as follows: C: 0.08-0.12%; Si: 0.2-0.4%; Mn: 1.6-1.8%; P<0.015%; S<0.008%; Cr: 0.7-1.0%; Ni: 1.0-1.2%; Cu<0.2%; Mo<0.2%; Ti: 0.01-0.02%; V: 0.05-0.1%; Nb: 0.03-0.04%; B: 0.003-0.005%, and the balance is Fe and unavoidable impurities.

2. A method for preventing water ripples from forming on the surface of a Q960E steel plate according to claim 1, It is characterized in that In the rough rolling process, the inlet temperature is 1020-1050°C, and the outlet temperature is 950-980°C.

3. A method for preventing water ripples from forming on the surface of a Q960E steel plate according to claim 1, It is characterized in that In the rough rolling process, the rough rolling passes are 5 to 7 passes.

4. A method for preventing water ripples from forming on the surface of a Q960E steel plate according to claim 1, It is characterized in that In the finishing rolling process, the inlet temperature is 860-880°C, and the outlet temperature is 800-820°C.

5. A method for preventing water ripples from forming on the surface of a Q960E steel plate according to claim 1, It is characterized in that In the finishing rolling process, the finishing rolling passes are 5 to 6 passes.

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