A method for manufacturing a hot-processed quenched and tempered petroleum storage tank steel

Abstract

The application belongs to the field of thick plate production, and particularly relates to a manufacturing method of heat treatment and tempering petroleum storage tank steel, which collects equipment parameters of a thick plate unit, and improves a flow production process of thick plates from thick plate two cutting to thick plate shape integration into a warehouse. The manufacturing method of heat treatment and tempering petroleum storage tank steel can effectively improve a yield ratio of a steel plate, control a steel plate with a thickness greater than or equal to 21 mm, and make the actual yield ratio of the steel plate not greater than 0.91; control a steel plate with a thickness less than 21 mm, and make the actual yield ratio of the steel plate not greater than 0.93, effectively improve quality control of the steel plate, and reduce production cost.

Description

Technical Field

[0001] This invention belongs to the field of thick plate production, and in particular relates to a method for manufacturing heat-treated and tempered oil storage tank steel. Background Technology

[0002] Oil storage tank steel plates are an important component of thick plate products. In recent years, with the rapid development of the oil market, the demand for oil storage tank steel has increased significantly. Major steel mills in China have successively increased their production of oil storage tank steel. The production process of this steel is complex, the performance requirements are high, and the market requires oil storage tank steel with a low yield strength ratio, which greatly increases the difficulty of producing this steel. In the production process, this steel mainly involves two indicators: 12MnNiVR and 12MnNiVR-SR. The steel tapping marks involve two types: JT6P34P6 (≤20mm) and JT6P39P6 (>20mm), with a thickness range of 14~39mm.

[0003] The production process of heat-treated and tempered oil storage tank steel:

[0004] Secondary cutting of thick plates: mainly involves cutting steelmaking billets into sections according to instructions;

[0005] Thick plate heating: mainly for heating the slabs charged into the furnace. The slab exit temperature is set at 1150 (±20)℃, and the furnace time is controlled by cold and hot charging.

[0006] Thick plate rolling: mainly involves rolling the incoming slab into the required specifications and dimensions according to the process design requirements, and obtaining the required rolling temperature;

[0007] Thick plate shearing: Cutting steel plates into the required dimensions according to instructions;

[0008] Shot blasting of thick plates: Removing iron oxide scale from the surface of steel plates before heat treatment;

[0009] Thick plate heat treatment: The steel plate is quenched and tempered according to the process instructions;

[0010] Thick plate straightening: The steel plate is straightened according to its actual shape after heat treatment;

[0011] Thick plate printing: Printing steel plate information on the surface and sides of the steel plate according to instructions;

[0012] Thick plate assembly and warehousing: After confirming the appearance, size, and shape of the steel plate and ensuring it meets the technical requirements, the plate is assembled and put into storage.

[0013] (1) Due to the influence of carbon content and carbon equivalent in different heat treatments, the strength of steel plates fluctuates to a certain extent, resulting in the yield strength ratio of steel plates failing to meet technical requirements.

[0014] (2) Due to the influence of rolling specifications and roll positions, heat-treated and tempered oil storage tank steel is prone to batch thickness reduction at the edges;

[0015] (3) Thin-gauge (14, 18mm) oil storage tank steel is prone to head and tail plate warping after quenching, which affects the delivery cycle of the steel plate.

[0016] The purpose of this invention is to provide a method for manufacturing heat-treated and tempered oil storage tank steel. This method can effectively improve the yield strength ratio of steel plates, control the yield strength ratio of steel plates with a thickness ≥21mm to be no greater than 0.91, and control the yield strength ratio of steel plates with a thickness <21mm to be no greater than 0.93. At the same time, it effectively improves the quality control of steel plates and reduces production costs. Summary of the Invention

[0017] To achieve the above objectives, the present invention adopts the following technical solution:

[0018] Thick plate second cutting: The slab is hot-sent and hot-charged as a whole. The hot-sent long slab is cut into short slabs according to the set instructions, and deburring is performed online to ensure that the slab size and surface quality are normal and meet the furnace charging requirements.

[0019] Thick plate heating: The furnace exit temperature is controlled at 1150 (-20, +20)℃. The furnace time of the slab is controlled according to different furnace charging temperatures. The specific furnace time can be calculated as t = 0.05T + 205, where t represents the furnace time and T represents the furnace charging temperature.

[0020] Thick plate rolling: For thicknesses of 14–27 mm, the initial rolling temperature is controlled at 940 (-20, +10)℃, the final rolling temperature is controlled at 850 (-20, +10)℃, and the rolling point thickness is controlled at 3T; for thicknesses of 36–39 mm, the initial rolling temperature is controlled at 900 (-20, +10)℃, the final rolling temperature is controlled at 850 (-20, +10)℃, and the rolling point thickness is controlled at 2T. During the rolling process, the production plan is optimized to avoid thinning of the steel plate at the edges.

[0021] Thick plate shearing: Shearing the ends and edges of steel plates according to the contract dimensions.

[0022] Thick plate heat treatment: The heat treatment process is controlled according to the holding temperature and holding time. The quenching process is a holding temperature of 910℃ and a holding time of 10min. The tempering process is a holding temperature of 620~670℃ and a holding time of 20~30min.

[0023] (1) Heat treatment furnace setting table:

[0024]

[0025] (2) Quenching setting table (Zones 1-12 represent the water flow rate of each zone in the high-pressure section of the quenching machine):

[0026]

[0027]

[0028] Thick plate straightening: The steel plate is straightened according to its shape after exiting the furnace to ensure that the shape meets the requirements.

[0029] Thick plate printing: Printing key information such as plate number, size, and grade on the surface and sides of steel plates.

[0030] Thick plate assembly and warehousing: The three-dimensional dimensions, appearance, and shape of the steel plate are reconfirmed, and the plate is assembled and put into storage after meeting the standards.

[0031] Compared with existing technologies:

[0032] (1) The quenching and tempering process is adjusted according to the carbon content and carbon equivalent of the steel plate, and a trial production mechanism is adopted to stabilize the performance and yield strength ratio of the steel plate.

[0033] (2) During the rolling process, the planned number of steel plates of the same specification is strictly controlled, which reduces the risk of low minimum thickness in batches.

[0034] (3) Thin-gauge (14, 18mm) oil storage tank steel reduces the flow rate of upper and lower surface water by 5% to 10%, increases the speed by 2 to 3%, and significantly improves the plate shape.

[0035] Further optimization of heat treatment:

[0036] The heat treatment tempering process was optimized based on the carbon content and carbon equivalent of the steel plate. For steel plates from furnaces with high carbon equivalent, the holding temperature was increased in increments of 5°C and the holding time was increased in increments of 5 minutes. The process was gradually optimized based on the performance of the steel plate.

[0037]

[0038] Rolling process further optimized:

[0039] To prevent thinning of the steel plate at the edges during the rolling process, production planning is controlled:

[0040] (1) For batches of more than 100 pieces of steel of the same width (width difference ±50mm), ensure that the thinner pieces are rolled first, and then the thicker pieces are rolled.

[0041] (2) For rolling target thickness ≤ 22mm and rolling target width ≥ 2500mm, batch rolling should begin before the new rolls are installed about 250 pieces.

[0042] (3) Maximum number of rolled blocks in the same roll batch with the same width (target rolling width ≥ 2500 mm, width difference ± 50 mm):

[0043] Rolling thickness range Number of rolled blocks of the same width in a batch T<19mm 160 19mm≤T<26mm 180 T≥26mm 220

[0044] (4) During the production process, the thickness of the steel plate edge is measured once per hour to verify the deviation between the thickness measured by the thickness gauge and the actual thickness.

[0045] Quenching has been further optimized:

[0046] Based on the shape of the steel plate after quenching, the water flow rate and quenching speed of the quenching machine are adjusted. The specific adjustment parameters are shown in the table below (zones 1-12 represent the water flow rate of each zone in the high-pressure section of the quenching machine):

[0047] Detailed Implementation

[0048] Example 1:

[0049] On June 24th, eight heats of 12MnNiVR(-SR) were tapped, with the 14mm grade concentrated in heats 21474867, 21474868, 21474870, 21474873, and 21474874. The tapping designation was JT6P34P6. The carbon composition was 0.0769–0.0798%, and the LR carbon equivalent was 0.36757–0.35998. Given the previous batch production situation, heats 21474867 and 21474868... The carbon equivalent is relatively high, and the heat treatment process uses 670℃ for 30 minutes. Furnaces 21474870 and 21474873 have compositions similar to the first batch, and the temperature target is based on the first batch process. To prevent the batch from exceeding the upper limit for low yield strength ratio, the holding time is increased by 5 minutes, using 665℃+30 minutes and 660℃+30 minutes respectively. The composition of furnace 21474874 is lower than that of the first batch, and the original process of 660℃+25 minutes is used. The details are shown in the table below.

[0050]

[0051] Example 2:

[0052] The implementation steps are as follows:

[0053] On October 12th, a total of 138 heat-treated 12MnNiVR plates of the same specification were rolled in a large batch using the same rolls. The rolled dimensions were 15.36mm*2529mm*39000mm (contract dimensions were 15.00mm*2440mm*12600mm, with Class C tolerance). The production plan was arranged according to the principle of thinner plates first and thicker plates later. The rolling plan was scheduled to start with the batch rolling of 235 plates from the new rolls. During the production process, the operators strictly monitored the thickness and measured the actual thickness of the plates every hour. The rolling thickness of the steel plates was adjusted based on the actual thickness of the plates. After the completion of this batch of steel plates, all plates were assembled and put into storage without any deviation from the contract.

[0054] The above embodiments are only for illustrating the technical concept and features of the present invention. Through the above technology, the problem of unsuitable yield strength ratio of heat-treated and tempered oil storage tank steel is effectively improved, ensuring the stability of steel plate performance. At the same time, it has a positive significance for improving the quality of steel plates. Moreover, the technology has a wide range of applications and can effectively improve the pass rate of steel plate quality. It is fully worthy of promotion and use.

Claims

1. A method for manufacturing heat-treated and tempered oil storage tank steel, comprising: thick plate double cutting, thick plate heating, thick plate rolling, thick plate shearing, thick plate shot blasting, thick plate heat treatment, thick plate straightening, thick plate inkjet printing, and thick plate assembly and warehousing, characterized in that: Thick plate double cutting: The slab is hot-sent and hot-charged as a whole. The hot-sent long slab is cut into short slabs according to the set instructions, and deburring is performed online to ensure that the slab size and surface quality are normal and meet the furnace charging requirements. Thick plate heating: The furnace exit temperature is controlled at 1130℃~1170℃. The furnace time of the slab is controlled according to different furnace charging temperatures. The specific furnace time is calculated as t=0.05T+205, where t represents the furnace time in minutes and T represents the furnace charging temperature in degrees Celsius. Thick plate rolling: For thicknesses of 14~27mm, the initial rolling temperature is controlled at 920℃~950℃, the final rolling temperature at 830℃~860℃, and the rolling point thickness is controlled at 3T, where T represents the target thickness of the rolled steel plate; for thicknesses of 36~39mm, the initial rolling temperature is controlled at 880℃~910℃, the final rolling temperature at 830℃~860℃, and the rolling point thickness is controlled at 2T, where T represents the target thickness of the rolled steel plate; to avoid thinning of the steel plate at the edges during the rolling process, the production plan is controlled, specifically as follows: (1) When the batch of steel plates of the same width with a width difference within ±50mm is greater than 100 pieces, the thinner ones are rolled first, and then the thicker ones are rolled. (2) Steel plates with a rolling target thickness ≤ 22 mm and a rolling target width ≥ 2500 mm shall be rolled in batches before the 250th batch of new rolls are installed; (3) For steel plates of the same width with a rolling target width ≥ 2500 mm and a width difference within ± 50 mm, the maximum number of rolling blocks in the same roll batch shall be controlled as follows: no more than 160 blocks when the rolling thickness T < 19 mm, no more than 180 blocks when 19 mm ≤ T < 26 mm, and no more than 220 blocks when T ≥ 26 mm. (4) During the production process, the thickness of the steel plate edge is measured once per hour to verify the deviation between the thickness measured by the thickness gauge and the actual thickness; Thick plate shearing: Shearing the ends and edges of steel plates according to the contract dimensions; Shot blasting of thick plates: Removing iron oxide scale from the surface of steel plates before heat treatment; Thick plate heat treatment: The heat treatment process is controlled by holding temperature + holding time. The quenching process is a holding temperature of 910℃ and a holding time of 10min; the tempering process is a holding temperature of 620~670℃ and a holding time of 20~30min. The quenching and tempering processes are adjusted according to the carbon content and carbon equivalent of the steel plate, and a trial production mechanism is adopted to stabilize the steel plate properties and yield strength ratio. For steel plates from furnaces with high carbon equivalent, the holding temperature is increased in increments of 5℃ and the holding time is increased in increments of 5min, and the process is gradually optimized according to the steel plate properties. Thick plate straightening: The steel plate is straightened according to its shape after exiting the furnace to ensure that the shape meets the requirements; Thick plate printing: Printing the steel plate number, size, and grade information on the surface and sides of the steel plate; Thick plate assembly and warehousing: The three-dimensional dimensions, appearance, and shape of the steel plate are confirmed, and the assembly and warehousing are carried out after meeting the standards.

2. The method for manufacturing heat-treated and tempered petroleum storage tank steel according to claim 1, characterized in that: For thin-gauge oil storage tank steel with a thickness of 14mm or 18mm, the plate shape can be improved by reducing the flow rate of water in the upper and lower surfaces of the quenching machine by 5% to 10% and increasing the speed of the roller conveyor of the quenching machine by 2% to 3%.

3. The method for manufacturing heat-treated and tempered petroleum storage tank steel according to claim 1, characterized in that: The water flow rate and quenching speed of the quenching machine are adjusted according to the shape of the steel plate after quenching.

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