Treating fluid for controlling surface quality of pickled high-strength steel, preparation method and surface treatment process

Abstract

The invention provides a treating fluid for controlling the surface quality of pickled high-strength steel, a preparation method and a surface treatment process, and the surface treating fluid comprises the following components in percentage by mass: 1.5-6% of weak acid, 0.5-2% of a corrosion inhibitor, 0.02-1% of a surfactant and the balance of water.

Description

Technical Field

[0001] The invention relates to a metal material surface treatment process, and in particular to a treatment liquid for surface quality control of pickled high-strength steel, a preparation method and a surface treatment process. The surface treatment liquid is used for surface treatment of high-strength steel pickled by high-pressure spraying. The treated pickled high-strength steel has good surface quality and can also improve phosphating performance and production efficiency, thus belonging to an efficient, green and environmentally friendly production process. Background Art

[0002] Pickled high-strength steel has the advantages of high strength, light weight and good processing performance. It is widely used in high-quality automotive parts and new energy vehicles. It has broad market prospects and shows a compound growth trend.

[0003] In order to improve the strength, the content of silicon and manganese elements will be increased in the component design of high-strength steel. Silicon and manganese elements can play a role in solid solution strengthening, while improving the hardenability of steel, which can effectively improve the strength of high-strength pickled steel. However, the oxygen partial pressure of silicon and manganese elements is higher than that of iron elements, and they tend to precipitate preferentially on the surface of steel. On the one hand, silicon and manganese oxides increase the adhesion between the matrix and the oxide scale, and on the other hand, they are difficult to dissolve in the pickling solution, resulting in increased difficulty in pickling. After pickling, there are problems such as residual oxides and indentation, uneven surface color, easy rust, and poor phosphating in the pre-painting process.

[0004] In the prior art, the directions for improving the surface pickling quality of pickled high-strength steel mainly include: increasing the acid concentration, extending the pickling time, controlling the concentration and temperature of the pickling solution, adding polishing process, electrolytic pickling, etc. For example, the Chinese patent document with the publication number CN115647070A mentioned that in the comprehensive quality control method for producing a thin-gauge ultra-high-strength steel plate, three-stage continuous hydrochloric acid pickling is adopted, and the acid temperature is controlled in the high temperature section of 70-80°C. At the same time, the pickling rate is controlled at 30-50m / min, and the pickling rate should not be too fast to ensure the surface quality. In the pickling process of a stainless steel plate strip provided by the Chinese patent document with the application number 201210174749.9, a mixed acid composite pickling method is used to improve the pickling efficiency. In the US patent document with publication number US10597741B2, the quality and efficiency of pickling of high-strength steel plates are guaranteed by adding an electrolytic pickling section in a sulfuric acid solution before conventional chemical pickling; the European patent document with publication number EP1307609B1 mentions that the use of continuous electrolytic pickling and descaling process for carbon steel and stainless steel can increase the pickling efficiency by 20%.

[0005] Although increasing the acid concentration and temperature and extending the pickling time can solve the problems of difficult pickling and incomplete pickling of high-strength steel to a certain extent, these technologies also increase the pickling cost and bring about problems such as over-pickling and rust on the steel plate surface. Adding polishing and electrolytic pickling processes requires large-scale transformation of the production line, which requires large initial investment and has certain negative impacts on the environment. Summary of the invention

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

[0007] The technical problem to be solved can be implemented through the following technical solutions.

[0008] A treatment liquid for controlling the surface quality of pickled high-strength steel and a preparation method thereof, wherein:

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

[0010] (2) Preparation of a weak acid solution: The weak acid is a mixture of phosphoric acid, tartaric acid and oxalic acid, with phosphoric acid: tartaric acid: oxalic acid = 1: 0.05-0.25: 0.01-0.20 (mass ratio). 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°C and normal pressure for 2 h to prepare a 1.5-6 wt.% 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° C. and normal pressure for 2 h. The addition ratio here is based on the ratio of the weak acid solution.

[0012] (4) Surfactant addition: 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 ratio here is based on the ratio of the weak acid solution with the addition of the corrosion inhibitor.

[0013] Another technical problem to be solved by the present invention is to provide a surface treatment process based on the surface quality control of pickled high-strength steel. The present invention adds a high-pressure surface treatment process between the traditional chemical pickling section and the pure water cleaning section. Specifically, the high-pressure surface treatment technology is performed after conventional chemical pickling, and the high-strength steel hot-rolled coil is pickled and dephosphorized. The surface of the pickled high-strength steel is chemically and mechanically treated by spraying a high-pressure surface treatment liquid. The following steps are included:

[0014] (1) Preparation of hot rolled coils

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

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

[0017] The acid solution is mainly hydrochloric acid, wherein the concentration of hydrochloric acid is 50-250 g / L, Fe 2+ The concentration range is 10~50g / L.

[0018] (3) Surface high-pressure spray treatment: The high-strength steel hot-rolled coil after chemical pickling and dephosphorization is subjected to high-pressure spray treatment. The high-pressure treatment section has three nozzles, and the distance between two nozzles is 0.5-1m. The first nozzle sprays high-pressure water on the surface of the slab after chemical pickling, and the spraying pressure is 2-5MPa. The second and third nozzles spray surface treatment liquid on the slab, and the solution temperature is 30-60°C, the spraying pressure is 50-100MPa, and the spraying speed of the solution is 150-600m / s. The pressure (MP) is matched with the production line speed (m / min), and the ratio of the two is 1: (1.3-2.5), preferably 1:2. The surface roughness of the steel plate after spraying is not higher than 1.5μm.

[0019] Furthermore, the nozzle is a fan-shaped nozzle, and the distance between the nozzles is 15 to 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 three-stage water washing tank.

[0021] (5) Coiling: The pickled steel plate is dried by hot air and then coiled to obtain a pickled high-strength steel coil.

[0022] Furthermore, the chemical composition mass percentage of the continuous casting slab of the pickled high-strength steel is: 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%, and the rest is Fe.

[0023] After the pickled high-strength steel is treated by the above-mentioned surface treatment process, there is no oxide scale remaining on the surface, which solves the problem of small black spots on the surface; at the same time, a corrosion inhibition layer is formed on the surface of the pickled high-strength steel to solve surface quality problems such as yellowing and rust. This process is green and environmentally friendly, has strong process adaptability, can effectively improve the pickling efficiency of high-strength steel and improve the surface quality. It is a green and environmentally friendly steel production process. That is, the treated pickled high-strength steel has good surface quality such as no yellowing, no small black spots, and low roughness, and can also improve the phosphating performance of the coating process. The application of this process can improve production efficiency and is an efficient, green and environmentally friendly steel production process.

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

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention adopts the pickling process of "hydrochloric acid chemical pickling + high-pressure solution surface treatment + pure water cleaning" for pickling high-strength steel hot-rolled coils, changes the traditional pickling process, and can effectively shorten the chemical pickling period and reduce the impact of acid on the environment through the effective guarantee of high-pressure solution surface treatment.

[0027] 2. The surface treatment liquid of the present invention can quickly remove the red iron scale and small black spots remaining on the surface of the pickled plate. The weak acid system of the treatment liquid will micro-corrode the oxide scale remaining on the surface, and at the same time, the mechanical stripping effect of high-pressure spraying is used to quickly remove the small black spot defects on the surface of the pickled plate.

[0028] 3. The high-pressure surface treatment liquid of the present invention is used to inhibit the corrosion of the pickled plate surface. The sodium silicate, triethanolamine and benzotriazole in the high-pressure surface treatment liquid can be adsorbed on the surface of the steel plate substrate to quickly form a nano-scale corrosion inhibition layer, which can effectively prevent the surface of the steel plate from yellowing (slight corrosion) during the subsequent water washing process. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and more forms may be made without departing from the scope of the present invention and the claims, but the present invention is not limited in any form.

[0030] Example 1

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

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

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

[0034] (3) Surfactant addition: 0.02 wt.% sodium lauryl sulfate and 0.04 wt.% butanediol were added to the above mixed solution, and stirred 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 liquid of this embodiment is used for the surface treatment and control of the pickling section of pickling high-strength steel, and the process steps include hot-rolled coil material preparation, chemical pickling, high-pressure spraying of surface treatment liquid, pure water cleaning, and purging and coiling. Among them:

[0036] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0037] The continuous casting slab of high-strength steel is heated to 1260°C and kept at this temperature for 40 minutes, then rough rolled and finish rolled, air cooled to 750°C, and coiled.

[0038] (2) The hot rolled coil cooled to room temperature is subjected to chemical pickling for phosphorus removal, the acid solution temperature is 60°C, and the strip speed is 170 m / min. The hydrochloric acid concentration is 120 g / L, Fe 2+ Concentration range: 25g / L.

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

[0040] (4) After the surface treatment, the high-strength steel hot-rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid-washed high-strength steel coil.

[0041] Example 2

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

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

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

[0045] (3) Surfactant addition: Add 0.10 wt.% sodium dodecyl sulfate and 0.06 wt.% butanediol to the above mixed solution, and stir at 60 rpm for 1 to 2 hours at 50°C and 0.3 MPa to form a surface treatment solution.

[0046] The surface treatment liquid of this embodiment is used for the surface treatment and control of the pickling section of pickling high-strength steel, and the process steps include hot-rolled coil material preparation, chemical pickling, high-pressure spraying of surface treatment liquid, pure water cleaning, and purging and coiling. Among them:

[0047] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0048] The continuous casting slab of high-strength steel is heated to 1250°C and kept at this temperature for 45 minutes, and then rough rolled and finish rolled, air cooled to 750°C, and coiled.

[0049] (2) The hot rolled coil cooled to room temperature is chemically pickled for phosphorus removal. The temperature for phosphoric acid removal is 65°C and the strip speed is 170 m / min. The concentration of hydrochloric acid is 120 g / L, Fe 2+ The concentration range is: 20g / L.

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

[0051] (4) After the surface high pressure treatment, the high strength steel hot rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid washed high strength steel coil.

[0052] Example 3

[0053] The preparation method of the high-pressure spray surface treatment liquid for pickling high-strength steel surface quality control provided in this embodiment is as follows:

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

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

[0056] (3) Surfactant addition: 0.15 wt.% sodium dodecyl sulfate and 0.5 wt.% butanediol were added to the above mixed solution, and stirred 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 liquid of this embodiment is used for the surface treatment and control of the pickling section of pickling high-strength steel, and the process steps include hot-rolled coil material preparation, chemical pickling, high-pressure treatment liquid spraying treatment, pure water cleaning, and purging and coiling. Among them:

[0058] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0059] The continuous casting slab of high-strength steel is heated to 1250°C and kept at this temperature for 50 minutes, then rough rolled and finish rolled, air cooled to 780°C, and coiled.

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

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

[0062] (4) After the surface high pressure treatment, the high strength steel hot rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid washed high strength steel coil.

[0063] Example 4

[0064] The preparation method of the pickled high-strength steel high-pressure spray surface treatment liquid provided in this embodiment is as follows:

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

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

[0067] (3) Surfactant addition: 0.1 wt.% sodium dodecyl sulfate and 0.04 wt.% butanediol were added to the above mixed solution, and stirred 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 liquid of this embodiment is used for the surface treatment and control of the pickling section of pickling high-strength steel, and the process steps include hot-rolled coil material preparation, chemical pickling, high-pressure spraying of surface treatment liquid, pure water cleaning, and purging and coiling. Among them:

[0069] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0070] The continuous casting slab of high-strength steel is heated to 1250°C and kept at this temperature for 50 minutes, then rough rolled and finish rolled, air cooled to 780°C, and coiled.

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

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

[0073] (4) After the surface high pressure treatment, the high strength steel hot rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid washed high strength steel coil.

[0074] Example 5

[0075] The preparation method of the pickled high-strength steel high-pressure spray surface treatment liquid provided in this embodiment is as follows:

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

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

[0078] (3) Surfactant addition: 0.1 wt.% sodium dodecyl sulfate and 0.04 wt.% butanediol were added to the above mixed solution, and stirred 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 liquid of this embodiment is used for surface treatment and control of the pickling section of pickling high-strength steel. The process steps include hot-rolled coil material preparation, chemical pickling, high-pressure spraying of surface treatment liquid, pure water cleaning, and purging and coiling.

[0080] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0081] The continuous casting slab of high-strength steel is heated to 1250°C and kept at this temperature for 50 minutes, then rough rolled and finish rolled, air cooled to 780°C, and coiled.

[0082] (2) The hot rolled coil cooled to room temperature is subjected to chemical pickling for phosphorus removal, the acid solution temperature is 60°C, and the strip speed is 170 m / min. The hydrochloric acid concentration is 120 g / L, Fe 2+ Concentration range: 25g / L.

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

[0084] (4) After the surface high pressure treatment, the high strength steel hot rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid washed 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 as follows:

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

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

[0089] (3) Surfactant addition: 0.1 wt.% sodium dodecyl sulfate and 0.06 wt.% butanediol were added to the above mixed solution, and stirred 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 liquid of this embodiment is used for the surface treatment and control of the pickling section of pickling high-strength steel, and the process steps include hot-rolled coil material preparation, chemical pickling, high-pressure spraying of surface treatment liquid, pure water cleaning, and purging and coiling. Among them:

[0091] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0092] The continuous casting slab of high-strength steel is heated to 1260°C and kept at this temperature for 40 minutes, then rough rolled and finish rolled, air cooled to 750°C, and coiled.

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

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

[0095] (4) After the surface high pressure treatment, the high strength steel hot rolled coil is cleaned with pure water using a continuous three-stage water washing tank, and then coiled after hot air blowing and drying to obtain an acid washed high strength steel coil.

[0096] Comparative Example:

[0097] The high-strength steel continuous casting slab of this embodiment is subjected to chemical dephosphorization, and the process steps include hot-rolled coil material preparation, chemical pickling, pure water cleaning, and purging and coiling. Among them:

[0098] (1) The chemical composition percentage by mass of the high-strength steel continuous casting slab in this embodiment is: 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%, and the rest is Fe.

[0099] The continuous casting slab of high-strength steel is heated to 1260°C and kept at this temperature for 40 minutes, then rough rolled and finish rolled, air cooled to 750°C, and coiled.

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

[0101] (6) After chemical pickling and phosphorus removal, the high-strength steel hot-rolled coil is cleaned with pure water using a continuous 6-stage water washing tank, and then coiled after hot air blowing and drying to obtain a pickled high-strength steel coil.

[0102] The surface treated substrates of Examples 1 to 6 and Comparative Examples were evaluated by the following method:

[0103] (1) Yellowing degree of the surface

[0104] After the pickled high-strength steel sample has been surface treated, the surface is observed to assess the degree of yellowing;

[0105] The evaluation criteria are as follows:

[0106] ◎: No yellowing, rust area 0%

[0107] ○: Light spots on the edge, yellowing area <5%

[0108] Δ: Rust stains appear in the wider edge area, and the stain area is less than 20%

[0109] ×: Severe yellow spots on the board surface, with the spot area > 50%

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

[0111] After the pickled high-strength steel sample has been subjected to high-clean surface treatment, the surface is observed to evaluate the number of surface black spots;

[0112] The evaluation criteria are as follows:

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

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

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

[0116] ×: Severe rust on the board surface, the number of black spots > 100 / m 2

[0117] (3) Surface roughness

[0118] After the pickled high-strength steel sample has been subjected to high-clean surface treatment, the surface roughness test is performed;

[0119] (4) Phosphating performance

[0120] After the pickled high-strength steel samples were subjected to high-clean surface treatment, the samples were subjected to phosphating performance treatment to evaluate the phosphating crystal size and phosphating film weight.

[0121] ◎: Phosphate coverage of the entire board surface is 100%

[0122] ○: Phosphate coverage of the entire board surface >95%

[0123] Δ: Phosphate coverage of the entire board surface is less than 90%, but ≥ 80%

[0124] ×: Phosphate coverage of the entire board surface <80%

[0125] The performance parameters of the hot-rolled high-strength steel surfaces in Examples 1 to 6 and the comparative example after pickling and high-pressure spraying surface treatment were sampled and tested as shown in Table 1 below.

[0126] Table 1:

[0127] Yellowing surface Surface black spots 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] From the data in Table 1, it can be seen that the process parameters of the hot rolled coil feed and the high pressure spray section in Examples 1 to 3 are basically the same, and the main changes are the concentration of the surface treatment liquid, and more importantly, the concentration of the weak acid and the corrosion inhibitor. Compared with the comparative example, at the lower limit (Example 1) and upper limit (Example 3) of the concentration range and the optimal range (Example 2), the surface yellowing, the number of surface black spots, the roughness and the phosphating performance are all in a good state. The phosphating performance in Example 1 fluctuates slightly, but can still be maintained in a qualified state.

[0129] In Examples 4 and 5, the concentrations of the hot rolled coil material and the surface treatment solution are kept basically the same on the basis of Example 1, and the spraying pressure, flow rate and temperature of the solution in the surface treatment section are mainly changed. When these parameters change within the lower limit (Example 1) and upper limit (Example 5) of the process range and the optimal range (Example 4), the surface yellowing, the number of surface black spots, the roughness and the phosphating performance are all in a good state, and the roughness is basically maintained in a relatively stable state.

[0130] Example 6 changes the strip speed and acid concentration in the chemical pickling section on the basis of Example 2. The strip speed is increased by 35% and the acid concentration is reduced by 20%. The surface yellowing, the number of surface black spots, the roughness and the phosphating performance are all in good condition.

[0131] Based on Examples 1-6 and the comparative example, the high-pressure surface treatment process for pickled high-strength steel of the present invention is highly efficient and environmentally friendly. The process can efficiently treat the surface of the pickled high-strength steel plate, 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 user-end use.

[0132] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A treatment liquid for controlling the surface quality of pickled high-strength steel, characterized in that: In terms of mass percentage, the surface 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.

2. The treatment liquid for controlling the surface quality of pickled high-strength steel according to claim 1, characterized in that: The weak acid is a mixture of phosphoric acid, tartaric acid and oxalic acid, and the mixing mass ratio is phosphoric acid: tartaric acid: oxalic acid = 1: 0.05-0.25: 0.01-0.

20.

3. The treatment liquid for controlling the surface quality of pickled high-strength steel according to claim 2, characterized in that: During mixing, 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°C and normal pressure to prepare a 1.5-6wt.% weak acid solution.

4. The treatment liquid for controlling the surface quality of pickled high-strength steel according to claim 1, characterized in that: The corrosion inhibitor is a mixture of 0.1-0.5 wt. % sodium silicate, 0.2-0.5 wt. % triethanolamine and 0.5-2 wt. % benzotriazole relative to the mass ratio of the weak acid.

5. The treatment liquid for controlling the surface quality of pickled high-strength steel according to claim 1, characterized in that: The surfactant is a mixture of 0.01-0.2 wt. % sodium dodecyl sulfate and 0.02-0.8 wt. % butanediol relative to the mass ratio of the weak acid solution to which the corrosion inhibitor is added.

6. A method for preparing the treatment solution according to any one of claims 1 to 5, characterized in that: The steps include: (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, 1.5-4wt.% phosphoric acid, 0.075-1wt.% tartaric acid and 0.015-0.8wt.% oxalic acid are added into water, and stirred at 35-50°C and normal pressure to prepare a 1.5-6wt.% weak acid solution; (2) Corrosion inhibitor addition: Based on a weak acid solution, 0.1-0.5 wt.% sodium silicate, 0.2-0.5 wt.% triethanolamine and 0.5-2% benzotriazole are added as corrosion inhibitors to the weak acid solution, and stirred at 35-50° C. and normal pressure; (3) Surfactant addition: Based on the weak acid solution with corrosion inhibitor added, 0.01-0.2wt.% sodium dodecyl sulfate and 0.02-0.8wt.% butanediol are added, and stirred for 1-2 hours at a temperature of 35-50°C and a pressure of 0.3-0.5MPa to form a surface treatment solution.

7. A surface treatment process based on pickling high-strength steel surface quality control, characterized in that: The method comprises the step of performing surface high-pressure spraying treatment between the chemical pickling and phosphorus removal sections and the pure water cleaning sections.

8. The surface treatment process according to claim 7, characterized in that: During the chemical pickling and dephosphorization, the temperature of the dephosphorization is 50-80° C., and the strip speed is 150-250 m / min.

9. The surface treatment process according to claim 7, characterized in that: Three nozzles are used for the surface high-pressure spraying treatment, and the distance between each nozzle is 0.5-1m; the first nozzle sprays room temperature high-pressure water onto the surface of the slab after chemical pickling, and the spraying pressure is 2-5MPa; the second and third nozzles spray the surface treatment liquid onto the slab, the solution temperature is 30-60°C, the spraying speed of the solution is 150-600m / s, the spraying pressure of the high-pressure solution is 50-100MP, the pressure (MP) is matched with the production line speed (m / min), and the ratio of the two is 1:1.3-1:2.

5. The surface roughness of the steel plate after spraying is not higher than 1.5μm.

10. The surface treatment process according to claim 9, characterized in that: The nozzle is a fan-shaped nozzle, and the nozzle spacing of a single-channel nozzle is 15 to 30 mm.