Efficient production method for low-alloy structural steel extra-thick plate

Abstract

The invention discloses a high-efficiency production method for a low-alloy structural steel extra-thick plate, which comprises the following steps of: reducing the contents of V and Ni, and adopting a high-temperature and high-pressure non-controlled rolling mode as a rolling mode, and the extra-thick plate comprises the following components in percentage by mass: 0.15-0.17% of C, 1.45-1.55% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.1-0.2% of Ni, 0.03-0.04% of Nb, 0.04-0.05% of V and 0.005-0.02% of Ti. The method has the advantages that the alloy cost is effectively reduced, the production efficiency is improved, and the mechanical property and the internal quality of the extra-thick plate are improved, so that the flaw detection qualification rate of the extra-thick plate is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel production, and particularly relates to a high-efficiency production method for low-alloy structural steel super-thick plates. BACKGROUND

[0002] In order to meet the performance requirements, a certain amount of alloy is usually added in the super-thick plate, which undoubtedly increases the production cost. In order to reduce the cost, with the continuous expansion of the market demand for the low-alloy structural steel super-thick plate products with a specification greater than 150mm-250mm, the continuous casting technology of the billet is continuously updated, and the continuous casting billet has broken through the specification of 460mm. When the super-thick continuous casting billet is used to develop the super-thick plate, because the rolling reduction of the conventional control rolling method is small and the holding time of the intermediate billet is long, the output steel plate cannot meet the expected requirements in the production efficiency, the internal quality and the mechanical performance, and therefore, the high-temperature large-reduction non-controlled rolling method is needed to develop the super-thick plate structure steel. SUMMARY

[0003] The application aims to solve the problems of the low-alloy structural steel super-thick plate, such as low production efficiency, poor quality and unable to meet the performance requirements, and provides a high-efficiency production method for the low-alloy structural steel super-thick plate, which can effectively reduce the alloy cost, improve the production efficiency, improve the mechanical performance and the internal quality of the super-thick plate, and thus improve the flaw detection qualification rate of the super-thick plate.

[0004] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: A high-efficiency production method for low-alloy structural steel super-thick plates, which comprises reducing the contents of V and Ni, and adopting a high-temperature large-reduction non-controlled rolling method, and the composition and the mass percentage of the super-thick plate are as follows: C: 0.15-0.17, Mn: 1.45-1.55, P≤0.012, S≤0.003, Ni: 0.1-0.2, Nb: 0.03-0.04, V: 0.04-0.05, Ti: 0.005-0.02.

[0005] Further, in the heating process of the billet, 30-50 DEG C is added to the austenite tapping temperature, so that the rolling can obtain a larger reduction.

[0006] Further, in the rolling process of the super-thick plate, the controlled rolling is cancelled, the maximum reduction of the rough rolling is used by using a higher tapping temperature, and the rolling passes are reduced.

[0007] Further, the tapping temperature is set to 1200-1260 DEG C.

[0008] Further, after the rough rolling is completed, spraying is added to accelerate the cooling temperature of the steel plate.

[0009] In the technical scheme of the present application, the alloy cost is reduced by about 30 yuan / ton through component redesign; meanwhile, for single block blank production, 2-4 rolling passes can be reduced, the rolling time is reduced by about 30 s, the machine time output is increased by about 1.5 tons / hour, and the internal quality of the 150-250 mm thick plate is greatly improved, and the flaw detection qualified rate is increased by about 2-5%. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is the original rolling pass distribution and the uncontrolled rolling large reduction rolling pass distribution diagram of the present application; Figure 2 is the parameter table of the conventional controlled rolling in the present embodiment; Figure 3 is the parameter table of the high temperature large reduction uncontrolled rolling in the present embodiment; Figure 4 is the steel plate performance comparison table of the conventional controlled rolling and the high temperature large reduction uncontrolled rolling in the present embodiment; Figure 5 is the metallographic structure diagram of the thick plate produced by the method of the present application. DETAILED DESCRIPTION EMBODIMENT

[0011] In order to make the present application clearer and more understandable, the present application is further described below in combination with the drawings, and the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0012] Referring to Figure 1 , in the original rolling pass distribution, the heating stage, the rough rolling stage, the controlled rolling stage and the finishing rolling stage are included, wherein the conventional two-stage rolling is adopted in the heating stage, and the low temperature heating is generally selected; in the controlled rolling stage, the single block blank is controlled to be at a temperature for more than 40 s. In the uncontrolled rolling large reduction rolling pass distribution of the present application, the high temperature heating blank is set, and the maximum reduction rate is set in the whole rolling stage.

[0013] In the present embodiment, taking the steel grade S355J2+N, 200*2500 mm specification order as an example, the component design includes C: 0.15-0.17, Mn: 1.45-1.55, P≤0.012, S≤0.003, Ni: 0.1-0.2, Nb: 0.03-0.04, V: 0.04-0.05, Ti: 0.005-0.02.

[0014] The conventional controlled rolling adopts the furnace discharge temperature of 1150±20℃; the high temperature large reduction uncontrolled rolling adopts 1200±20℃.

[0015] Referring to Figure 2, the conventional controlled rolling needs to use 13 passes to complete the rolling, and the intermediate blank needs to be kept warm for 45s.

[0016] Referring to Figure 3 In the embodiment, the high-temperature large reduction non-controlled rolling mode is adopted, the heating temperature is increased, the rolling passes are reduced by 4 passes, the large blank rolling time is reduced by about 30s on average, and one pass is about 5-10s.

[0017] Referring to Figure 4 Meanwhile, according to the performance test results of the steel plates, the mechanical properties of the two modes can meet the standard requirements, but the strength of the high-temperature large reduction non-controlled rolling mode is relatively higher, the waiting time is cancelled and the rolling time is shortened, and the flaw detection qualified standard is higher, so the high-temperature large reduction non-controlled rolling mode is adopted for the low-alloy special thick plate, which meets the actual demand and increases the economic benefits. Figure 5 The metallographic diagram of the low-alloy structural steel special thick plate produced by the method of the present application.

[0018] The present application re-designs the production mode of the low-alloy structural steel special thick plate, designs the low-alloy composition, cancels the intermediate blank waiting time by using the high-temperature large reduction instead of the intermediate blank controlled rolling mode, improves the rolling efficiency and the internal quality of the steel plate, increases the mechanical properties of the steel plate, reduces the alloy cost by 30 yuan / ton, increases the machine time output by about 1.5 tons / hour, improves the thick plate flaw detection qualified rate by about 2-5%, and generates direct economic benefits of 4-6 million yuan / year.

[0019] In addition to the above embodiments, the present application can have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A highly efficient production method for extra-thick low-alloy structural steel plates, characterized in that: Including reduced V and Ni content, and using a high-temperature, high-pressure uncontrolled rolling method, the composition and mass percentage of its extra-thick plate are as follows: C: 0.15~0.17, Mn: 1.45~1.55, P≤0.012, S≤0.003, Ni: 0.1~0.2, Nb: 0.03~0.04, V: 0.04~0.05, Ti: 0.005~0.

02.

2. The efficient production method for extra-thick low-alloy structural steel plates according to claim 1, characterized in that: In the aforementioned extra-thick plate billet heating process, the temperature of the austenitic steel tapping is increased by 30-50°C to enable the rolling process to achieve a greater reduction.

3. The efficient production method for extra-thick low-alloy structural steel plates according to claim 1 or 2, characterized in that: The rolling process for the extra-thick plate eliminates controlled rolling, utilizes a higher furnace exit temperature and the maximum reduction in rough rolling, and reduces the number of rolling passes.

4. The efficient production method for extra-thick low-alloy structural steel plates according to claim 3, characterized in that: The furnace exit temperature is set to 1200~1260℃.

5. The efficient production method for extra-thick low-alloy structural steel plates according to claim 1 or 2, characterized in that: After rough rolling, spraying is added to accelerate the cooling temperature of the steel plate.

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