Method for eliminating crack-shaped morphology on surface of carbon steel hot-rolled pickling plate strip
By adjusting the cold rolling pressure rate and process speed in the cold continuous rolling section of the carbon steel hot-rolled acid continuous rolling mill group, the problem of crack morphology of the surface of the carbon steel hot-rolled pickling plate strip is solved, and a more uniform hydrochloric acid pickling effect is achieved, which improves the surface quality and reduces production costs.
Patent Information
- Application Number
- CN202510418607.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-03
- Publication Date
- 2025-05-13
AI Technical Summary
The surface of existing carbon steel hot-rolled pickled plate strips has cracked micromorphology, resulting in surface quality problems such as uneven coating, leakage plating, and local internal oxidation, which affects the stability of production quality.
The cold rolling pressure ratio of the first stand of the cold rolling section of the acid continuous rolling mill group is adjusted to 6 to 10%, and pretreatment is performed when the steel coil is first launched, and the pickling section is empty, and the steel coil is then coiled. Then, the acid continuous rolling machine is launched again, and the scale breaker press pressure rate and the hydrochloric acid pickling section process speed are adjusted to ensure that the hydrochloric acid liquid is in contact with the strip substrate evenly.
Through uniform and high-density crack defects, hydrochloric acid pickling is ensured to contact the strip steel substrate evenly, solving the problem of surface crack morphology, improving surface quality, and avoiding equipment transformation and high-cost material consumption.
Smart Images
Figure CN119972835A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of carbon steel surface treatment, in particular to a method for eliminating the crack-like morphology on the surface of a hot-rolled pickled carbon steel strip. Background Art
[0002] Carbon steel hot-rolled strips are usually removed from hot-rolled scale by continuous hydrochloric acid pickling in the pickling mill. However, since the pickling time of the continuous pickling mill is short and the hydrochloric acid solution must come into contact with the strip steel matrix before an efficient pickling reaction occurs, mechanical descaling equipment must be installed before the continuous hydrochloric acid pickling process to make the scale have a large number of crack defects, so as to open up the contact channel between the acid solution and the matrix.
[0003] At present, the continuous hydrochloric acid pickling section of the acid continuous rolling mill is usually only equipped with a scale breaker as a mechanical descaling method. The elongation of the strip steel is low. Although it can increase the hot-rolled oxide scale crack defects, the crack density is insufficient and the distribution is uneven. During hydrochloric acid pickling, the acid liquid will preferentially corrode the substrate locally in the oxide scale cracks. After the oxide scale is removed, the local corrosion position will remain in the form of transverse cracks. This pickled plate with a large number of transverse crack-like micromorphology is used as a cold rolling and hot dip plating base material, which will cause surface quality problems such as uneven coating, missed plating, and local internal oxidation, which seriously affects the production quality stability of high-quality and high-grade carbon steel plates and strips.
[0004] To solve the problem of crack-like micromorphology of carbon steel pickled strip, the following measures are currently disclosed: first, a shot blasting device is installed after the scale breaker to remove most of the hot rolling scale to improve the uniformity of hydrochloric acid pickling; second, a pickling tank for other pickling processes such as electrolytic pickling is added, electrolytic pickling is used and high-concentration corrosion inhibitor is added to the hydrochloric acid solution to improve the uniformity of pickling. However, these disclosed methods all require large-scale equipment modification of the existing pickling continuous rolling mill and increase the consumption of high-cost materials (such as corrosion inhibitors). Summary of the invention
[0005] In response to the above technical problems, the present invention provides a method for eliminating the crack-like morphology on the surface of carbon steel hot-rolled pickled strip, which is used to solve the problem that solving the crack-like microscopic morphology of carbon steel pickled strip requires large-scale equipment modification of the existing acid continuous rolling unit, which is time-consuming and labor-intensive, and increases high-cost material consumption.
[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for eliminating crack-like morphology on the surface of a hot-rolled pickled carbon steel strip comprises the following steps: S1: When the steel coil is put into the pickling mill for the first time, the pickling section of the pickling mill is completely empty, the cold rolling reduction rate of the first stand of the cold rolling section is adjusted to 6-10%, and the remaining stands of the cold rolling section are empty, and then the steel coil is coiled; S2: After the pretreatment in step S1, the steel coil is put back on the acid continuous rolling unit for normal hydrochloric acid pickling and cold continuous rolling production.
[0007] Furthermore, in step S1, the rolling speed of the cold rolling section is 100-500 m / min.
[0008] Furthermore, in step S2, when the steel coil passes through the acid continuous rolling unit for the second time, the reduction rate of the scale breaker is 0.3%-3.0%, the process speed of the hydrochloric acid pickling section is 95-180m / min, the hydrochloric acid concentration is 180-220g / L, the metal ion is 25-35g / L, the acid solution temperature is 75℃-85℃, the process speed of the cold continuous rolling section is 95-180m / min, the first to fourth frames are put into cold rolling, and the total reduction rate of cold rolling is 45%-70%.
[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention utilizes the advantages of large pressing capacity, large tension and high rolling stability of the first frame of the cold rolling section of the acid continuous rolling mill to act as a mechanical descaling device. The large plasticity difference between the oxide scale and the steel matrix is utilized, and a large pressing rate is used to make the hot rolled oxide scale have uniform and high-density crack defects, thereby laying the foundation for the hydrochloric acid pickling to uniformly contact the strip steel matrix during the second pass to produce a uniform corrosion morphology; and the equipment and process methods used are all basic equipment and conventional processes of the acid continuous rolling mill, without any equipment modification and consumption of additional materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 The microscopic morphology of the surface SEM secondary electron image of 65Mn hot-rolled black coil produced by the acid continuous rolling unit when the present invention is not used; Figure 2 The surface SEM secondary electron image microscopic morphology of 65Mn hot-rolled black coil produced by the present invention through the acid continuous rolling unit; Figure 3 This is a surface macroscopic photograph of a 65Mn hot-rolled black coil produced by the present invention through an acid continuous rolling unit; Figure 4 The microscopic morphology of the surface SEM secondary electron image of the HF1500 hot-rolled black coil after being produced by the acid continuous rolling unit when the present invention is not used; Figure 5 The surface SEM secondary electron image microscopic morphology of HF1500 hot-rolled black coil produced by the present invention after being produced by the acid continuous rolling unit; Figure 6 The microscopic morphology of the surface SEM secondary electron image of 50W470 hot-rolled black coil produced by the acid continuous rolling unit when the present invention is not used; Figure 7This is the surface SEM secondary electron image microscopic morphology of 50W470 hot-rolled black coil produced by the acid continuous rolling unit when the present invention is not used. DETAILED DESCRIPTION
[0011] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.
[0012] Embodiment 1, The steel coil is 65Mn hot-rolled annealed steel coil, and the specific chemical composition (mass percentage) is C: 0.65%; Si: 0.25%; Mn: 1.0%; P: 0.0281%; S: 0.0049%; Al: 0.0184%, Cr: 0.0429%. The steel coil thickness is 3.2mm and the width is 1250mm.
[0013] A method for eliminating crack-like morphology on the surface of a hot-rolled pickled carbon steel strip comprises the following steps: S1: When the 65Mn hot-rolled annealed steel coil is put into the pickling mill for the first time, the pickling section of the pickling mill is completely empty, the cold rolling reduction rate of the first stand of the cold rolling section is adjusted to 6%, the rolling speed is 100m / min, and the remaining stands of the cold rolling section are empty, and then the steel coil is coiled; S2: After the pretreatment in step S1, the steel coil is put back on the acid continuous rolling unit, the reduction rate of the scale breaker is 0.4%, the process speed of the hydrochloric acid pickling section is 95m / min, the hydrochloric acid concentration is 180g / L, the metal ion is 25g / L, the acid solution temperature is 75°C, the process speed of the cold continuous rolling section is 95m / min, the first to fourth stands are put into cold continuous rolling, and the total reduction rate of cold rolling is 45%.
[0014] Figure 1 The surface SEM secondary electron image microscopic morphology of 65Mn hot-rolled black coil after being produced by the acid continuous rolling unit when the present invention is not used. Figure 2 This is the surface SEM secondary electron image microscopic morphology of 65Mn hot-rolled black coil after being produced by the acid continuous rolling unit when using the present invention; by comparison, it can be seen that after the implementation of this patented technology, the surface crack morphology of 65Mn after acid continuous rolling disappears.
[0015] Embodiment 2, The steel coil is a hot-rolled annealed steel coil of hot-formed steel HF1500, with the specific chemical composition (mass percentage) of C: 0.21%; Si: 0.26%; Mn: 1.24%; P: 0.0120%; S: 0.0046%; Al: 0.0313%; Cr: 0.0429%; Ti: 0.0326%; Cr: 0.2422; B: 0.0029%. The thickness of the steel coil is 3.4mm and the width is 1220mm.
[0016] A method for eliminating crack-like morphology on the surface of a hot-rolled pickled carbon steel strip comprises the following steps: S1: When the HF1500 hot-rolled annealed steel coil is put into the pickling mill for the first time, the pickling section of the pickling mill is completely empty, the cold rolling reduction rate of the first stand of the cold rolling section is adjusted to 8%, the rolling speed is 200m / min, and the remaining stands of the cold rolling section are empty, and then the steel coil is coiled; S2: After the pretreatment in step S1, the steel coil is put back on the acid continuous rolling unit, the reduction rate of the scale breaker is 2.0%, the process speed of the hydrochloric acid pickling section is 140m / min, the hydrochloric acid concentration is 200g / L, the metal ion is 30g / L, the acid solution temperature is 80°C, the process speed of the cold continuous rolling section is 140m / min, the first to fourth stands are put into cold continuous rolling, and the total reduction rate of cold rolling is 55%.
[0017] Figure 4 This is the surface SEM secondary electron image microscopic morphology of HF1500 hot-rolled black coil after being produced by the acid continuous rolling unit when the present invention is not used. Figure 5 This is the surface SEM secondary electron image microscopic morphology of HF1500 hot-rolled black coil after being produced by the acid continuous rolling unit when using the present invention. By comparison, it can be seen that after the implementation of this patented technology, the surface crack morphology of HF1500 after acid continuous rolling disappears.
[0018] Embodiment 3, The steel coil is a hot-formed steel 50W470 hot-rolled annealed steel coil, with the specific chemical composition (mass percentage) of C: 0.0038%; Si: 1.779%; Mn: 0.846%; P: 0.0035%; S: 0.6188%; Al: 0.0313%. The thickness of the steel coil is 3.0mm and the width is 1250mm.
[0019] A method for eliminating crack-like morphology on the surface of a hot-rolled pickled carbon steel strip comprises the following steps: S1: When the 50W470 hot-rolled annealed steel coil is put into the pickling mill for the first time, the pickling section of the pickling mill is completely empty, the cold rolling reduction rate of the first stand of the cold rolling section is adjusted to 10%, the rolling speed is 500m / min, and the remaining stands of the cold rolling section are empty, and then the steel coil is coiled; S2: After the pretreatment in step S1, the steel coil is put back on the acid continuous rolling unit, the reduction rate of the scale breaker is 3.0%, the process speed of the hydrochloric acid pickling section is 180m / min, the hydrochloric acid concentration is 220g / L, the metal ion is 35g / L, the acid solution temperature is 85°C, the process speed of the cold continuous rolling section is 180m / min, the first to fourth stands are put into cold continuous rolling, and the total reduction rate of cold rolling is 70%.
[0020] Figure 6 The surface SEM secondary electron image microscopic morphology of 50W470 hot-rolled black coil after being produced by the acid continuous rolling unit when the present invention is not used. Figure 7 This is the surface SEM secondary electron image microscopic morphology of 50W4700 hot-rolled black coil after being produced by the acid continuous rolling unit when using the present invention; by comparison, it can be seen that after the implementation of this patented technology, the crack-like morphology on the surface of 50W470 after acid continuous rolling disappears.
[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for eliminating the crack-like morphology on the surface of a hot-rolled pickled carbon steel strip, characterized in that: The following steps are involved: S1: When the steel coil is put into the pickling mill for the first time, the pickling section of the pickling mill is completely empty, the cold rolling reduction rate of the first stand of the cold rolling section is adjusted to 6-10%, and the remaining stands of the cold rolling section are empty, and then the steel coil is coiled; S2: After the pretreatment in step S1, the steel coil is put back on the acid continuous rolling unit for normal hydrochloric acid pickling and cold continuous rolling production.
2. A method for eliminating crack-like morphology on the surface of hot-rolled pickled carbon steel strip according to claim 1, characterized in that: The rolling speed of the cold rolling section in step S1 is 100-500 m / min.
3. The method for eliminating the crack-like morphology on the surface of hot-rolled pickled carbon steel strip according to claim 1, characterized in that: In step S2, when the steel coil passes through the acid continuous rolling unit for the second time, the reduction rate of the scale breaker is 0.3%-3.0%, the process speed of the hydrochloric acid pickling section is 95-180m / min, the hydrochloric acid concentration is 180-220g / L, the metal ion is 25-35g / L, the acid solution temperature is 75℃-85℃, the process speed of the cold continuous rolling section is 95-180m / min, the first to fourth stands are put into cold rolling, and the total reduction rate of cold rolling is 45%-70%.