A treatment liquid for controlling surface quality of an acid-washed high-strength steel, a preparation method and a surface treatment process

Abstract

The application provides a treatment liquid for controlling the surface quality of pickling high-strength steel, a preparation method and a surface treatment process. According to the application, the treatment liquid comprises 1.5-6% of weak acid, 0.5-2% of corrosion inhibitor, 0.02-1% of surfactant and the balance of water.

Description

Technical Field

[0001] This invention relates to surface treatment processes for metal materials, and more particularly to a treatment solution, preparation method, and surface treatment process for surface quality control of pickled high-strength steel. The surface treatment solution is used to treat the surface of high-strength steel by high-pressure spray pickling. The treated pickled high-strength steel has good surface quality and can also improve phosphating performance and increase production efficiency. It belongs to a highly efficient, green, and environmentally friendly production process. Background Technology

[0002] Pickled high-strength steel has advantages such as high strength, light weight and good processing performance. It is widely used in high-quality auto parts and new energy vehicle fields, and has a broad market prospect and shows a compound growth trend.

[0003] To improve strength, high-strength steel incorporates increased silicon and manganese content in its composition design. Silicon and manganese provide solid solution strengthening and improve hardenability, effectively enhancing the strength of high-strength pickled steel. However, silicon and manganese have a higher oxygen partial pressure than iron, leading to preferential precipitation on the steel surface. Silicon and manganese oxides increase the adhesion between the substrate and the oxide scale, and are difficult to dissolve in the pickling solution, increasing the difficulty of pickling. This results in problems such as oxide residue and indentation after pickling, uneven surface color, susceptibility to corrosion, and poor phosphating in pre-coating processes.

[0004] In existing technologies, the main directions for improving the pickling quality of high-strength steel surfaces include: increasing acid concentration, extending pickling time, controlling the concentration and temperature of the pickling solution, and adding polishing processes, electrolytic pickling, etc. For example, Chinese patent document CN115647070A mentions a comprehensive quality control method for producing a thin-gauge ultra-high-strength steel plate, which uses a three-stage continuous hydrochloric acid pickling process, with the acid temperature controlled at a high temperature range of 70-80℃, and the pickling rate controlled at 30-50 m / min. The pickling rate should not be too fast to ensure surface quality. Chinese patent document 201210174749.9 provides a pickling process for stainless steel plates and strips, which uses a mixed acid composite pickling method to improve pickling efficiency. In the US patent document with publication number US10597741B2, an electrolytic pickling stage in sulfuric acid solution is added before conventional chemical pickling to ensure the pickling quality and efficiency of high-strength steel plates; in the European patent document with publication number EP1307609B1, it is mentioned that the pickling efficiency of carbon steel and stainless steel can be increased by 20% by using continuous electrolytic pickling and descaling process.

[0005] While increasing acid concentration and temperature, and extending pickling time can solve the problems of high-strength steel being difficult to pickle and not being pickled thoroughly to some extent, these technologies also increase pickling costs and bring about problems such as over-pickling and corrosion on the steel plate surface. Adding polishing and electrolytic pickling processes requires large-scale modifications to the production line, with large upfront investments, and also has certain negative environmental impacts. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects and deficiencies in the prior art, and to provide a high-pressure treatment liquid for surface quality control of pickled high-strength steel and its preparation method, which can avoid residual oxide scale on steel surface, solve the problem of small black spots on the surface, and form a corrosion-inhibiting treatment layer on the surface of pickled high-strength steel to solve surface quality problems such as yellowing and rust.

[0007] The technical problem it aims to solve can be addressed through the following technical solutions.

[0008] A treatment solution for controlling the surface quality of pickled high-strength steel and its preparation method, wherein,

[0009] (1) The main components of the surface treatment solution include weak acid, corrosion inhibitor and surfactant. The mass percentages of the three are 1.5-6% weak acid, 0.5-2% corrosion inhibitor and 0.02-1% surfactant, with the remainder being water.

[0010] (2) Preparation of weak acid solution: The weak acid is a mixture of phosphoric acid, tartaric acid and oxalic acid, with a mass ratio of phosphoric acid:tartaric acid:oxalic acid = 1:0.05~0.25:0.01~0.20. 1.5~4wt.% phosphoric acid, 0.075~1wt.% tartaric acid and 0.015~0.8wt.% oxalic acid are added to water and stirred at 35~50℃ and normal pressure for 2h to prepare a 1.5~6wt.% weak acid solution.

[0011] (3) Addition of corrosion inhibitor: Add 0.1-0.5 wt.% sodium silicate, 0.2-0.5 wt.% triethanolamine and 0.5-2% benzotriazole as corrosion inhibitors to the above weak acid solution, and stir at 35-50℃ and normal pressure for 2 hours. The proportions added here are based on the proportions of the weak acid solution.

[0012] (4) Addition of surfactant: 0.01–0.2 wt.% sodium dodecyl sulfate and 0.02–0.8 wt.% butanediol. Stir for 1–2 hours at a temperature of 35–50°C and a pressure of 0.3–0.5 MPa to form a surface treatment solution. The proportions here are based on the ratio of a weak acid solution with added corrosion inhibitor.

[0013] Another technical problem this invention aims to solve is to provide a surface treatment process based on the surface quality control of pickled high-strength steel. This invention adds a high-pressure surface treatment process between the traditional chemical pickling stage and the pure water cleaning stage. Specifically, after conventional chemical pickling, a high-pressure surface treatment technology is performed to pickle and descal the hot-rolled high-strength steel coils. The surface of the pickled high-strength steel is then chemically and mechanically treated by high-pressure spraying of a surface treatment solution. The process includes the following steps:

[0014] (1) Preparation of incoming hot-rolled coils

[0015] The high-strength steel continuous casting slab is heated to 1120-1260℃ and held for 30-60 minutes. Then it is rough rolled and finish rolled, air cooled to 730-780℃, and then coiled.

[0016] (2) Chemical pickling to remove phosphorus: The surface oxide scale of the hot-rolled high-strength steel coil is removed by continuous pickling. The temperature of the phosphoric acid pickling is 50-80℃ and the strip speed is 150-250m / min.

[0017] The acid solution is mainly hydrochloric acid, with a concentration of 50–250 g / L, and Fe 2+ The concentration range is 10–50 g / L.

[0018] (3) High-pressure spraying treatment: The high-strength steel hot-rolled coils after chemical pickling and descaling are subjected to high-pressure spraying treatment. The high-pressure treatment section has three nozzles, with a distance of 0.5-1m between two nozzles. The first nozzle sprays high-pressure water onto the surface of the chemically pickled slab at a pressure of 2-5MPa. The second and third nozzles spray a surface treatment liquid onto the slab at a temperature of 30-60℃, a pressure of 50-100MPa, and a spraying speed of 150-600m / s. The pressure (MPa) is matched with the production line speed (m / min) in a ratio of 1:(1.3-2.5), preferably 1:2. The surface roughness of the steel plate after spraying is no higher than 1.5μm.

[0019] Furthermore, the nozzles are fan-shaped, with a nozzle spacing of 15–30 mm.

[0020] (4) Pure water cleaning section: After the surface high pressure spray treatment, the high-strength steel hot-rolled coil is cleaned with pure water using a continuous 3-section water washing tank.

[0021] (5) Coiling: After the pickled plate is dried by hot air, it is coiled to obtain pickled high-strength steel coil.

[0022] Furthermore, the chemical composition of the continuously cast slab of the pickled high-strength steel is as follows (by mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0023] After undergoing the above surface treatment process, pickled high-strength steel exhibits no residual oxide scale, resolving the issue of small black spots on the surface. Simultaneously, a corrosion-inhibiting layer is formed on the surface of the pickled high-strength steel, addressing surface quality problems such as yellowing and rust. This process is environmentally friendly, highly adaptable, and effectively improves the pickling efficiency and surface quality of high-strength steel, making it a green and environmentally friendly steel production process. Specifically, the treated pickled high-strength steel possesses excellent surface quality, including no yellowing, no small black spots, and low roughness, and also improves the phosphating performance in the coating process. The application of this process can increase production efficiency and is considered a highly efficient, green, and environmentally friendly steel production technology.

[0024] This high-pressure surface treatment technology for pickling high-strength steel has the advantages of being green and environmentally friendly, fast and efficient, and improving the surface quality of steel plates. It can solve problems such as the difficulty of pickling oxides and poor surface quality on the surface of pickling high-strength steel, while also ensuring the coating process during user use.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This invention relates to a pickling process for hot-rolled high-strength steel coils, which involves "hydrochloric acid chemical pickling + high-pressure solution surface treatment + pure water rinsing". This process changes the traditional pickling procedure and, through the effective guarantee of high-pressure solution surface treatment, can effectively shorten the chemical pickling time and reduce the environmental impact of acid.

[0027] 2. The surface treatment solution in this invention effectively removes residual red iron scale and small black spots from the surface of pickled plates. The weak acid system of the treatment solution micro-corrodes the residual oxide scale on the surface, while the mechanical peeling effect of high-pressure spraying achieves a rapid removal of small black spot defects on the surface of the pickled plate.

[0028] 3. The high-pressure surface treatment solution of this invention has a corrosion inhibitor effect on the surface of the pickled steel plate. The sodium silicate, triethanolamine and benzotriazole in the high-pressure surface treatment solution can be specifically adsorbed on the surface of the steel plate substrate to quickly form a nano-scale corrosion inhibitor layer, which can effectively prevent the surface of the steel plate from yellowing (slight corrosion) in the subsequent water washing process. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention and to make further modifications without departing from the spirit and scope of the claims, but are not intended to limit the invention in any way.

[0030] Example 1

[0031] This embodiment provides a surface treatment liquid for high-pressure spraying of pickling high-strength steel, and its preparation method is as follows:

[0032] (1) Preparation of weak acid solution: Add 1.5wt.% phosphoric acid, 0.2wt.% tartaric acid and 0.2wt.% oxalic acid to water, and stir for 2h at 35-50℃ under normal pressure to prepare a 1.9wt.% weak acid solution.

[0033] (2) Addition of corrosion inhibitor: Add 0.2 wt.% sodium silicate, 0.23 wt.% triethanolamine and 0.7% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 h at 50°C and normal pressure.

[0034] (3) Addition of surfactant: Add 0.02 wt.% sodium dodecyl sulfate and 0.04 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a high-pressure spray treatment solution.

[0035] The surface treatment solution of this embodiment is used for surface treatment and control in the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure spraying of the surface treatment solution, pure water rinsing, and blowing and coiling. Wherein:

[0036] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0037] The high-strength steel continuous casting slab is heated to 1260℃ and held for 40 minutes, then roughed and finished rolled, air-cooled to 750℃, and then coiled.

[0038] (2) Hot-rolled coils cooled to room temperature are subjected to chemical pickling to remove phosphorus. The acid solution temperature is 60℃, and the strip speed is 170m / min. The hydrochloric acid concentration is 120g / L, Fe 2+ The concentration range is 25 g / L.

[0039] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.5m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at a pressure of 2MPa. The second nozzle sprays surface treatment liquid onto the slab at a temperature of 30℃, a pressure of 55MPa, and a spraying speed of 150m / s. The third nozzle sprays surface treatment liquid onto the slab at a temperature of 50℃, a pressure of 60MPa, and a spraying speed of 200m / s. The strip speed is 120m / min.

[0040] (4) After surface treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank, and then dried by hot air before being rolled up to obtain pickled high-strength steel coil.

[0041] Example 2

[0042] The surface treatment liquid for high-pressure spraying to control the surface quality of pickled high-strength steel provided in this embodiment is prepared by the following method:

[0043] (1) Preparation of weak acid solution: Add 3wt.% phosphoric acid, 0.6wt.% tartaric acid and 0.3wt.% oxalic acid to water, and stir for 2h at 35-50℃ under normal pressure to prepare a 3.9wt.% weak acid solution.

[0044] (2) Addition of corrosion inhibitor: Add 0.25wt.% sodium silicate, 0.30wt.% triethanolamine and 0.85% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 h at 50℃ and normal pressure.

[0045] (3) Addition of surfactant: Add 0.10 wt.% sodium dodecyl sulfate and 0.06 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a surface treatment solution.

[0046] The surface treatment solution of this embodiment is used for surface treatment and control in the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure spraying of the surface treatment solution, pure water rinsing, and blowing and coiling. Wherein:

[0047] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0048] The high-strength steel continuous casting slab is heated to 1250℃ and held for 45 minutes, then roughed and finished rolled, air-cooled to 750℃, and then coiled.

[0049] (2) Hot-rolled coils cooled to room temperature are subjected to chemical pickling to remove phosphoric acid. The phosphoric acid pickling temperature is 65℃, and the strip speed is 170m / min. The concentration of hydrochloric acid is 120g / L, and Fe... 2+ The concentration range is 20 g / L.

[0050] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.5m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at room temperature and a spray pressure of 2.2MPa. The second nozzle sprays surface treatment liquid onto the slab at a solution temperature of 30℃, a spray pressure of 55MPa, and a spray velocity of 160m / s. The third nozzle sprays surface treatment liquid onto the slab at a solution temperature of 50℃, a spray pressure of 60MPa, and a spray velocity of 220m / s. The strip speed is 120m / min.

[0051] (4) After surface high pressure treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0052] Example 3

[0053] The high-pressure spray surface treatment liquid for surface quality control of pickled high-strength steel provided in this embodiment is prepared by the following method:

[0054] (1) Preparation of weak acid solution: Add 4 wt.% phosphoric acid, 0.55 wt.% tartaric acid and 0.45 wt.% oxalic acid to water and stir at 45°C and normal pressure for 2 h to prepare a 6 wt.% weak acid solution.

[0055] (2) Addition of corrosion inhibitor: Add 0.5 wt.% sodium silicate, 0.2 wt.% triethanolamine and 1.8% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 h at 50°C and normal pressure.

[0056] (3) Addition of surfactant: Add 0.15 wt.% sodium dodecyl sulfate and 0.5 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a surface treatment solution.

[0057] The surface treatment solution of this embodiment is used for surface treatment and control in the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure treatment solution spraying, pure water rinsing, and blowing and coiling. Wherein:

[0058] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0059] The high-strength steel continuous casting slab is heated to 1250℃ and held for 50 minutes, then roughed and finished rolled, air-cooled to 780℃, and then coiled.

[0060] (2) The hot-rolled coils cooled to room temperature are subjected to chemical pickling to remove phosphorus at a temperature of 60°C and a strip speed of 170 m / min. The hydrochloric acid concentration is 120 g / L, Fe 2+ The concentration range is 25 g / L.

[0061] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.7m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at a pressure of 2.5MPa. The second nozzle sprays surface treatment liquid onto the slab at a temperature of 30℃, a pressure of 60MPa, and a spraying speed of 150m / s. The third nozzle sprays surface treatment liquid onto the slab at a temperature of 50℃, a pressure of 60MPa, and a spraying speed of 220m / s. The strip speed is 120m / min.

[0062] (4) After surface high pressure treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0063] Example 4

[0064] The high-pressure spray surface treatment solution for pickling high-strength steel provided in this embodiment is prepared by the following method:

[0065] (1) Preparation of weak acid solution: Add 1.5wt.% phosphoric acid, 0.08wt.% tartaric acid and 0.7wt.% oxalic acid to water, and stir for 2h at 35-50℃ and normal pressure to prepare a 2.28wt.% weak acid solution.

[0066] (2) Addition of corrosion inhibitor: Add 0.2 wt.% sodium silicate, 0.23 wt.% triethanolamine and 0.7% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 h at 50°C and normal pressure.

[0067] (3) Addition of surfactant: Add 0.1 wt.% sodium dodecyl sulfate and 0.04 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a high-pressure treatment solution.

[0068] The surface treatment solution of this embodiment is used for surface treatment and control in the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure spraying of the surface treatment solution, pure water rinsing, and blowing and coiling. Wherein:

[0069] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0070] The high-strength steel continuous casting slab is heated to 1250℃ and held for 50 minutes, then roughed and finished rolled, air-cooled to 780℃, and then coiled.

[0071] (2) The hot-rolled coils cooled to room temperature are subjected to chemical pickling to remove phosphorus at a temperature of 60°C and a strip speed of 170 m / min. The hydrochloric acid concentration is 120 g / L, Fe 2+ The concentration range is 25 g / L.

[0072] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.7m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at a pressure of 3.5MPa. The second nozzle sprays surface treatment liquid onto the slab at a temperature of 43℃, a pressure of 70MPa, and a spraying speed of 250m / s. The third nozzle sprays surface treatment liquid onto the slab at a temperature of 45℃, a pressure of 75MPa, and a spraying speed of 320m / s. The strip speed is 150m / min.

[0073] (4) After surface high pressure treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0074] Example 5

[0075] The high-pressure spray surface treatment solution for pickling high-strength steel provided in this embodiment is prepared by the following method:

[0076] (1) Preparation of weak acid solution: Add 1.5wt.% phosphoric acid, 0.9wt.% tartaric acid and 0.02wt.% oxalic acid to water, and stir for 2h at 35-50℃ and normal pressure to prepare a 2.42wt.% weak acid solution.

[0077] (2) Addition of corrosion inhibitor: Add 0.2 wt.% sodium silicate, 0.23 wt.% triethanolamine and 0.7% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 h at 50°C and normal pressure.

[0078] (3) Addition of surfactant: Add 0.1 wt.% sodium dodecyl sulfate and 0.04 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a high-pressure treatment solution.

[0079] The surface treatment solution of this embodiment is used for surface treatment and control of the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure spraying of surface treatment solution, pure water rinsing, and blowing and coiling.

[0080] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0081] The high-strength steel continuous casting slab is heated to 1250℃ and held for 50 minutes, then roughed and finished rolled, air-cooled to 780℃, and then coiled.

[0082] (2) Hot-rolled coils cooled to room temperature are subjected to chemical pickling to remove phosphorus. The acid solution temperature is 60℃, and the strip speed is 170m / min. The hydrochloric acid concentration is 120g / L, Fe 2+ The concentration range is 25 g / L.

[0083] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.7m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at a pressure of 4.6MPa. The second nozzle sprays surface treatment liquid onto the slab at a temperature of 50℃, a pressure of 80MPa, and a spraying speed of 350m / s. The third nozzle sprays surface treatment liquid onto the slab at a temperature of 50℃, a pressure of 85MPa, and a spraying speed of 450m / s. The strip speed is 170m / min.

[0084] (4) After surface high pressure treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0085] Example 6

[0086] The surface treatment liquid for high-pressure spraying of pickled high-strength steel provided in this embodiment is prepared by the following method:

[0087] (1) Preparation of weak acid solution: Add 3.0 wt.% phosphoric acid, 0.6 wt.% tartaric acid and 0.3 wt.% oxalic acid to water and stir at 35°C and normal pressure for 2 hours to prepare a 3.9 wt.% weak acid solution.

[0088] (2) Addition of corrosion inhibitor: Add 0.25wt.% sodium silicate, 0.3wt.% triethanolamine and 0.85% benzotriazole to the above weak acid solution as corrosion inhibitors, and stir at 100 rpm for 2 hours at 50°C and normal pressure.

[0089] (3) Addition of surfactant: Add 0.1 wt.% sodium dodecyl sulfate and 0.06 wt.% butanediol to the above mixture. Stir at 60 rpm for 1 to 2 hours at a temperature of 50°C and a pressure of 0.3 MPa to form a high-pressure treatment solution.

[0090] The surface treatment solution of this embodiment is used for surface treatment and control in the pickling section of pickled high-strength steel. The process steps include hot-rolled coil preparation, chemical pickling, high-pressure spraying of the surface treatment solution, pure water rinsing, and blowing and coiling. Wherein:

[0091] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0092] The high-strength steel continuous casting slab is heated to 1260℃ and held for 40 minutes, then roughed and finished rolled, air-cooled to 750℃, and then coiled.

[0093] (2) The hot-rolled coil, cooled to room temperature, undergoes chemical pickling to remove phosphoric acid. The phosphoric acid removal temperature is 60℃, and the strip speed is 230m / min. The hydrochloric acid concentration is 100g / L, Fe 2+ The concentration is 30 g / L.

[0094] (3) The high-strength steel hot-rolled coil enters the high-pressure spray surface treatment section, with three nozzles at both the top and bottom. The distance between each nozzle is 0.7m, and the distance between each row of nozzles is 20cm. The first nozzle sprays high-pressure water onto the slab surface at a pressure of 3.5MPa. The second nozzle sprays surface treatment liquid onto the slab at a temperature of 43℃, a pressure of 70MPa, and a spraying speed of 250m / s. The third nozzle sprays surface treatment liquid onto the slab at a temperature of 45℃, a pressure of 60MPa, and a spraying speed of 320m / s. The strip speed is 120m / min.

[0095] (4) After surface high pressure treatment, the high-strength steel hot-rolled coil is washed with pure water using a continuous 3-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0096] Comparative example:

[0097] In this embodiment, the high-strength steel continuously cast slab is subjected to chemical descaling. The process steps include hot-rolled coil preparation, chemical pickling, pure water washing, and blowing and coiling. Among these steps:

[0098] (1) The chemical composition of the high-strength steel continuous casting slab in this embodiment is as follows (mass percentage): C: 0.03%, S: 0.006%, P: 0.005%, Mn: 1.55%, Si: 1.1%, Al: 0.02%, Cr: 0.65%, Nb: 0.029%, Ti: 0.073%, with the remainder being Fe.

[0099] The high-strength steel continuous casting slab is heated to 1260℃ and held for 40 minutes, then roughed and finished rolled, air-cooled to 750℃, and then coiled.

[0100] (5) The hot-rolled coil, cooled to room temperature, undergoes chemical pickling to remove phosphoric acid. The phosphoric acid removal temperature is 60℃, and the strip speed is 230m / min. The hydrochloric acid concentration is 100g / L, Fe 2+ The concentration is 30 g / L.

[0101] (6) After chemical pickling and dephosphorization, the hot-rolled high-strength steel coil is washed with pure water using a continuous 6-section water washing tank. After being dried by hot air blowing, it is rolled up to obtain pickled high-strength steel coil.

[0102] The surface-treated substrates of Examples 1-6 and the comparative examples were evaluated using the following method:

[0103] (1) Degree of yellowing of the surface

[0104] After surface treatment, the surface of the pickled high-strength steel sample is observed to assess the degree of yellowing.

[0105] The evaluation criteria are as follows:

[0106] ◎: No yellowing, rust area 0%

[0107] ○: Lighter spots at the edges, yellowing area <5%

[0108] Δ: Rust spots appear in a wider area around the edge, with the spot area less than 20%.

[0109] ×: Severe yellow stains on the board surface, with stain area >50%.

[0110] (2) Number of black spots on the surface

[0111] After the pickled high-strength steel sample undergoes high-cleanliness surface treatment, the surface is observed to assess the number of black spots.

[0112] The evaluation criteria are as follows:

[0113] ◎: No black spots on the entire board surface

[0114] ○: Number of black dots < 10 / m 2

[0115] Δ: Number of black dots < 50 / m 2

[0116] ×: Severe rust stains on the board surface, with more than 100 black spots per m². 2

[0117] (3) Surface roughness

[0118] After the pickled high-strength steel sample underwent high-cleanliness surface treatment, the surface roughness was tested.

[0119] (4) Phosphating performance

[0120] After pickling high-strength steel samples undergo high-cleanliness surface treatment, the samples are subjected to phosphating performance treatment to evaluate the phosphating crystal size and phosphating film weight.

[0121] ◎: 100% phosphate coating coverage across the entire board surface.

[0122] ○: Phosphating coverage of the entire plate surface > 95%

[0123] Δ: Phosphating coverage of the entire board surface <90%, but ≥80%

[0124] ×: Phosphating coverage of the entire plate surface <80%

[0125] The performance parameters of the hot-rolled high-strength steel surfaces in Examples 1-6 and the comparative examples after pickling and high-pressure spraying surface treatment are shown in Table 1 below.

[0126] Table 1:

[0127] Yellowing surface black spots on the surface Roughness, μm Phosphating performance Example 1 ○ ○ 1.5 ○ Example 2 ○ ◎ 1.2 ◎ Example 3 ◎ ◎ 1.3 ◎ Example 4 ◎ ○ 0.9 ○ Example 5 ◎ ◎ 0.9 ◎ Example 6 ○ ○ 0.85 ◎ Comparative Example × × 2.0 Δ

[0128] As can be seen from the data in Table 1, the process parameters of the hot-rolled coil incoming material and the high-pressure spraying section in Examples 1-3 are basically the same. The main change is the concentration of the surface treatment solution, and more importantly, the concentration of the weak acid and corrosion inhibitor. Compared with the comparative example, the surface yellowing, number of black spots, roughness, and phosphating performance are all better within the lower limit (Example 1), upper limit (Example 3), and optimal range (Example 2) of the concentration range. The phosphating performance in Example 1 fluctuates slightly, but can still be maintained at a qualified level.

[0129] Examples 4 and 5 are based on Example 1, maintaining the same concentration of hot-rolled coil material and surface treatment solution, mainly changing the spray pressure, flow rate, and temperature of the surface treatment solution. When these parameters vary within the lower limit (Example 1) and upper limit (Example 5) of the process range, as well as the optimal range (Example 4), the surface yellowing, the number of black spots, roughness, and phosphating performance all show good results, with the roughness remaining relatively stable.

[0130] Example 6 is based on Example 2, but with changes to the strip speed and acid concentration in the chemical pickling section. The strip speed is increased by 35%, and the acid concentration is reduced by 20%. The strip exhibits better performance in terms of surface yellowing, number of black spots, roughness, and phosphating properties.

[0131] Based on Examples 1-6 and the comparative examples, the high-pressure surface treatment process for pickled high-strength steel of the present invention has the characteristics of high efficiency and environmental protection. This process can efficiently treat the surface of pickled high-strength steel plates, so that the pickled high-strength steel has high-quality surface characteristics of no yellowing, no black spots, and low roughness, further ensuring good phosphating performance for end users.

[0132] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A treatment solution for controlling the surface quality of pickled high-strength steel, used for surface treatment between chemical pickling and descaling and pure water rinsing stages, characterized in that, By mass percentage, the treatment solution comprises 1.5–6% weak acid, 0.5–2% corrosion inhibitor, 0.02–1% surfactant, and the balance being water; The weak acid is a mixture of phosphoric acid, tartaric acid, and oxalic acid, with a mixing mass ratio of phosphoric acid:tartaric acid:oxalic acid = 1:0.05~0.25:0.01~0.20; When mixing, add 1.5-4 wt.% phosphoric acid, 0.075-1 wt.% tartaric acid and 0.015-0.8 wt.% oxalic acid to water and stir at 35-50°C and normal pressure to prepare a 1.5-6 wt.% weak acid solution; The corrosion inhibitor, relative to the mass ratio of the weak acid, is a mixture of 0.1–0.5 wt.% sodium silicate, 0.2–0.5 wt.% triethanolamine, and 0.5–2% benzotriazole; The surfactant is a mixture of 0.01 to 0.2 wt.% sodium dodecyl sulfate and 0.02 to 0.8 wt.% butanediol, relative to the mass ratio of the weak acid solution with added corrosion inhibitor.

2. A method for preparing the treatment liquid according to claim 1, characterized in that, Includes the following steps: (1) Preparation of weak acid solution: According to the mass ratio of phosphoric acid: tartaric acid: oxalic acid = 1: 0.05-0.25: 0.01-0.20, 1.5-4 wt.% phosphoric acid, 0.075-1 wt.% tartaric acid and 0.015-0.8 wt.% oxalic acid are added to water and stirred at 35-50℃ and normal pressure to prepare a 1.5-6 wt.% weak acid solution. (2) Addition of corrosion inhibitor: Based on the weak acid solution, 0.1-0.5 wt.% sodium silicate, 0.2-0.5 wt.% triethanolamine and 0.5-2% benzotriazole were added to the above weak acid solution as corrosion inhibitors, and the solution was stirred at 35-50°C and normal pressure. (3) Addition of surfactants: Based on a weak acid solution with added corrosion inhibitor, 0.01–0.2 wt.% sodium dodecyl sulfate and 0.02–0.8 wt.% butanediol are added, and the solution is stirred for 1–2 hours at a temperature of 35–50°C and a pressure of 0.3–0.5 MPa to form a surface treatment solution.

3. A surface treatment process for controlling the surface quality of high-strength steel by using the treatment solution described in claim 1, characterized in that, This includes a step of high-pressure surface spraying treatment between the chemical pickling and phosphorus removal stages and the pure water cleaning stage.

4. The surface treatment process according to claim 3, characterized in that, During the chemical pickling and phosphoric acid removal process, the temperature for phosphoric acid removal is 50–80°C, and the strip speed is 150–250 m / min.

5. The surface treatment process according to claim 3, characterized in that, The surface high-pressure spraying treatment is performed using three nozzles, with a distance of 0.5–1 m between each nozzle. The first nozzle sprays room-temperature high-pressure water onto the chemically pickled slab surface at a pressure of 2–5 MPa. The second and third nozzles spray a surface treatment liquid onto the slab at a temperature of 30–60°C and a spraying speed of 150–600 m / s. The spraying pressure of the high-pressure solution is 50–100 MPa, and the pressure is matched with the production line speed in a ratio of 1:1.3–1:2.

5. After spraying, the surface roughness of the steel plate is no higher than 1.5 μm.

6. The surface treatment process according to claim 5, characterized in that, The nozzle is a fan-shaped nozzle, and the nozzle spacing of a single nozzle is 15-30mm.