Galvanizing method for profile steel workpiece
The steel galvanizing method using pickling, alkaline washing, and high-temperature heating solves the problems of high investment and high zinc consumption in existing technologies, improves galvanizing efficiency and quality, and ensures coating uniformity and substrate cleanliness.
Patent Information
- Application Number
- CN202411130017.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-16
- Publication Date
- 2026-03-03
AI Technical Summary
Existing steel galvanizing methods suffer from problems such as high investment, high zinc consumption, excessive zinc fumes, difficulty in controlling coating thickness, and incomplete substrate treatment.
The process involves pickling, washing with water, alkali washing, drying, and then heating to 450-500℃ for hot-dip galvanizing under a protective atmosphere. The process is followed by blowing and passivation treatments, avoiding the use of additives.
It reduces the generation of zinc fumes and zinc ash, improves galvanizing efficiency and coating thickness uniformity, and enhances the cleanliness and corrosion resistance of the substrate.
Smart Images
Figure CN121592977A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a galvanizing method for steel profiles, belonging to the field of hot-dip galvanizing technology. Background Technology
[0002] Currently, the galvanizing methods for channel steel, angle steel, square and rectangular tubes, and rebar are based on additive-based batch dip-plating or blow-plating, which have the following problems:
[0003] (1) Due to the characteristics of the additive method (the additive is heat-resistant to 140-180℃), it is impossible to heat to the temperature of zinc liquid (440-450℃), requiring a large capacity of zinc pot and high initial investment.
[0004] (2) Batch dip plating or blow plating: Due to the use of additives, zinc chloride will decompose, causing a large amount of zinc fumes to be generated in the zinc pot, which need to be collected and treated; due to the generation of zinc fumes and zinc ash, the overall zinc consumption is high.
[0005] (3) Batch plating or blow plating results in weak continuity of zinc plating, and it is difficult to control the surface quality and coating thickness, which wastes zinc resources.
[0006] (4) Batch plating or blow plating only uses pickling + water washing + fluxing process. The substrate is not clean enough, and there are missed plating cases, which wastes zinc resources. Summary of the Invention
[0007] In view of the problems existing in the prior art, the present invention provides a galvanizing method for steel workpieces, which improves the efficiency and quality of galvanizing.
[0008] To achieve the above objectives, the present invention provides a galvanizing method for steel workpieces, comprising the following steps:
[0009] 1) Pretreatment: The steel workpiece is subjected to pickling, water washing, alkali washing, and water washing in sequence;
[0010] 2) Drying the steel workpieces;
[0011] 3) Heating reduction: Preheat the dried steel workpiece to 450-500℃;
[0012] 4) Hot-dip galvanizing: Maintain the temperature of the steel workpiece at 450-500℃ and galvanize the surface of the steel workpiece.
[0013] 5) Blow-dry the steel workpiece;
[0014] 6) Cooling down;
[0015] 7) Passivation of structural steel workpieces.
[0016] In some embodiments, the steel workpiece is any one of angle steel, channel steel, I-beam, round tube, and square tube.
[0017] In some embodiments, the pickling in step 1) involves immersing the steel workpiece in a hydrochloric acid solution with a mass fraction of 8%-20%, aerating it, and then rinsing the surface of the steel workpiece with water after pickling.
[0018] In some embodiments, the alkaline washing involves immersing the steel workpiece in an alkaline solution with a pH of 10-14, aerating it, and then rinsing the surface of the steel workpiece with water after the alkaline washing is completed.
[0019] In some embodiments, the pickling time in step 1) is 20-40 min; the alkaline solution time in step 2) is 0.5-1 min.
[0020] In some embodiments, radiant heating is used in step 2), with a heating temperature of 70°C.
[0021] In some embodiments, natural gas is used for open flame heating in step 3), the temperature of the heating furnace is 500-550°C, nitrogen is used to seal the furnace inlet, and a mixed gas consisting of 95% nitrogen and 5% hydrogen is introduced into the heating furnace.
[0022] In some embodiments, a protective atmosphere is used in steps 2), 3), and 4).
[0023] In some embodiments, after the galvanizing of the medium-sized steel workpiece in step 5) is completed, it is blown along its length.
[0024] In some embodiments, the steel workpiece is subjected to immersion water cooling in step 6); and the steel workpiece is subjected to passivation by pass-through or immersion in step 7).
[0025] Compared with the prior art, the galvanizing method for steel workpieces of the present invention has the following beneficial effects:
[0026] 1. The method of pickling and protective hydrogen reduction is adopted to ensure the cleanliness of the substrate, improve the surface quality, and reduce the occurrence of incomplete plating.
[0027] 2. No additives are required, and the amount of zinc fume generated is significantly reduced (over 80%), while the amount of zinc ash generated is reduced (over 70%).
[0028] 3. No additives are needed. The steel workpiece can be preheated to 450-500℃, slightly higher than the temperature of the zinc liquid. The capacity of the zinc pot can be reduced significantly (by more than 85%), and the galvanizing capacity can be greatly increased.
[0029] 4. It can ensure the uniformity of the zinc coating thickness of the workpiece, and can be zinc-aluminum-magnesium coated, thus improving the corrosion resistance of the product. Attached Figure Description
[0030] Figure 1 This is a flowchart of the present invention. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.
[0032] Example 1
[0033] like Figure 1 As shown, a method for galvanizing a steel profile workpiece, wherein the steel profile workpiece is a Q195 material 4# angle steel, includes the following steps:
[0034] 1) Pretreatment at room temperature:
[0035] First, the steel workpiece is pickled to remove surface oxide scale and loose rust. Specifically, the steel workpiece is immersed in an 8% hydrochloric acid solution and aerated for 20 minutes. After pickling, the acid solution on the surface of the steel workpiece is rinsed with water.
[0036] Then, the steel workpiece is alkaline washed to remove the acid from the surface of the workpiece, ensuring the subsequent heating and reduction process. Specifically, the steel workpiece is soaked in an alkaline solution with pH 10 and overflowed or soaked with aeration and agitation for 0.5 minutes. After the washing is completed, the alkaline solution on the surface of the steel workpiece is washed with water. The washing method is soaking and overflowing or soaking with aeration and agitation for 0.5 minutes.
[0037] 2) Drying steel workpieces to ensure surface dryness and reduce oxygen content in the heating reduction section:
[0038] Specifically, radiant heating is used, and the heat source is the exhaust gas from the combustion of natural gas in the furnace through a heating reduction process, so as to make secondary use of the heat source. The heating temperature is 70℃.
[0039] 3) Heating reduction: This method preheats the workpiece to 450°C; hydrogen reduction at high temperature further removes any potential rust from the workpiece surface, resulting in a clean substrate suitable for galvanizing.
[0040] Specifically, natural gas is used for open flame heating, the furnace temperature is 500℃, the furnace inlet is sealed with nitrogen, a mixed gas consisting of 95% nitrogen and 5% hydrogen is introduced into the furnace, and two thermocouples are installed in the furnace for temperature control.
[0041] 4) Hot-dip galvanizing: Zinc liquid (by mass fraction, including 92% zinc, 6% aluminum, and 2% magnesium) is used to maintain the temperature of the steel workpiece at 450℃, and zinc is galvanized on the surface of the steel workpiece; the steel workpiece is put into the pot using a "sealed" structure, and a nitrogen nozzle is installed at the sealed inlet; the sealed inlet is connected to the heating reduction chamber and the drying chamber to ensure that the entire process is under atmospheric protection;
[0042] 5) Blowing and wiping the steel workpiece is used to remove the molten zinc from the surface of the galvanized workpiece to ensure that the zinc layer thickness is within a certain range, such as 8-30 micrometers; specifically, the workpiece is wiping along its length after galvanizing is completed and the workpiece is removed from the zinc pot.
[0043] 6) Immersion water cooling is used to cool the workpiece for 0.5 minutes at a temperature of 50°C.
[0044] 7) Passivation of steel workpieces is used to further improve corrosion resistance (pure zinc layer is prone to white rust when damp). Passivation is carried out by pass-through or immersion for 10 seconds.
[0045] Example 2
[0046] like Figure 1 As shown, a method for galvanizing a steel section workpiece, wherein the steel section workpiece is an 8# channel steel of Q235 material, includes the following steps:
[0047] 1) Pretreatment at room temperature:
[0048] First, the steel workpiece is pickled to remove surface oxide scale and loose rust. Specifically, the steel workpiece is immersed in a 10% hydrochloric acid solution and aerated for 30 minutes. After pickling, the acid solution on the surface of the steel workpiece is rinsed with water.
[0049] Then, the steel workpiece is alkaline washed to remove the acid from the surface of the workpiece, ensuring the subsequent heating and reduction process. Specifically, the steel workpiece is soaked in an alkaline solution with pH 12 and overflowed or soaked with aeration and agitation for 1 minute. After the washing is completed, the alkaline solution on the surface of the steel workpiece is rinsed with water. The rinsing method is soaking and overflowing or soaking with aeration and agitation for 1 minute.
[0050] 2) Drying steel workpieces to ensure surface dryness and reduce oxygen content in the heating reduction section:
[0051] Specifically, radiant heating is used, and the heat source is the exhaust gas from the combustion of natural gas in the furnace through a heating reduction process, so as to make secondary use of the heat source. The heating temperature is 70℃.
[0052] 3) Heating reduction: This method preheats the workpiece to 480℃; hydrogen reduction at high temperature further removes any potential rust from the workpiece surface, resulting in a clean substrate suitable for galvanizing.
[0053] Specifically, natural gas is used for open flame heating, the furnace temperature is 510℃, the furnace inlet is sealed with nitrogen, a mixed gas consisting of 95% nitrogen and 5% hydrogen is introduced into the furnace, and two thermocouples are installed in the furnace for temperature control.
[0054] 4) Hot-dip galvanizing: Using zinc liquid (by mass fraction, including 92% zinc, 6% aluminum, and 2% magnesium) or other zinc liquid components, the temperature of the steel workpiece is maintained at 480℃, and zinc is galvanized on the surface of the steel workpiece; the steel workpiece is introduced into the pot using a "sealed" structure, and a nitrogen nozzle is installed at the sealed inlet; the sealed inlet is connected to the heating reduction chamber and the drying chamber to ensure that the entire process is under atmospheric protection;
[0055] 5) Blowing and wiping the steel workpiece is used to remove the molten zinc from the surface of the galvanized workpiece to ensure that the zinc layer thickness is within a certain range, such as 8-30 micrometers; specifically, the workpiece is wiping along its length after galvanizing is completed and the workpiece is removed from the zinc pot.
[0056] 6) Immersion water cooling is used to cool the workpiece for 0.5 minutes at a temperature of 60°C.
[0057] 7) Passivation of steel workpieces is used to further improve corrosion resistance (pure zinc layer is prone to white rust when damp). Passivation is carried out by pass-through or immersion for 20 seconds.
[0058] Example 3
[0059] like Figure 1 As shown, a method for galvanizing a steel section workpiece, wherein the steel section workpiece is a square tube made of Q345 material, includes the following steps:
[0060] 1) Pretreatment at room temperature:
[0061] First, the steel workpiece is pickled to remove surface oxide scale and loose rust. Specifically, the steel workpiece is immersed in a 20% hydrochloric acid solution and aerated for 40 minutes. After pickling, the acid solution on the surface of the steel workpiece is rinsed with water.
[0062] Then, the steel workpiece is alkaline washed to remove the acid from the surface of the workpiece, ensuring the subsequent heating and reduction process. Specifically, the steel workpiece is soaked in an alkaline solution with pH 14 and overflowed or soaked with aeration and agitation for 1 minute. After the washing is completed, the alkaline solution on the surface of the steel workpiece is rinsed with water. The rinsing method is soaking and overflowing or soaking with aeration and agitation for 1 minute.
[0063] 2) Drying steel workpieces to ensure surface dryness and reduce oxygen content in the heating reduction section:
[0064] Specifically, radiant heating is used, and the heat source is the exhaust gas from the combustion of natural gas in the furnace through a heating reduction process, so as to make secondary use of the heat source. The heating temperature is 70℃.
[0065] 3) Heating reduction: used to preheat the workpiece to 500℃; through high-temperature hydrogen reduction, possible rust on the workpiece surface is further removed, resulting in a clean substrate suitable for galvanizing.
[0066] Specifically, natural gas is used for open flame heating, the furnace temperature is 530°C, the furnace inlet is sealed with nitrogen, a mixed gas consisting of 95% nitrogen and 5% hydrogen is introduced into the furnace, and two thermocouples are installed in the furnace for temperature control.
[0067] 4) Hot-dip galvanizing: Using zinc liquid (by mass fraction, including 96.5% zinc, 2% aluminum, and 1.5% magnesium) or other zinc liquid components, the temperature of the steel workpiece is maintained at 500℃, and zinc is galvanized on the surface of the steel workpiece; the steel workpiece is introduced into the pot using a "sealed" structure, with a nitrogen nozzle at the sealed inlet; the sealed inlet is connected to the heating reduction chamber and the drying chamber to ensure that the entire process is under atmospheric protection;
[0068] 5) Blowing and wiping the steel workpiece is used to remove the molten zinc from the surface of the galvanized workpiece to ensure that the zinc layer thickness is within a certain range, such as 8-30 micrometers; specifically, the workpiece is wiping along its length after galvanizing is completed and the workpiece is removed from the zinc pot.
[0069] 6) Immersion water cooling is used to cool the workpiece for 1 minute at a temperature of 75°C.
[0070] 7) Passivation of steel workpieces is used to further improve corrosion resistance (pure zinc layer is prone to white rust when damp). Passivation is carried out by pass-through or immersion for 40 seconds.
[0071] The galvanizing method for steel workpieces of the present invention does not require fluxing or coating processes, but employs a heating reduction method. The heating process is pre-positioned: pickling – heating the workpiece (500°C) – introducing a mixture of hydrogen and helium (to prevent oxidation). Without coating, no zinc ash or zinc dross is produced. Simultaneously, the workpiece temperature is higher than the galvanizing bath (440-450°C), eliminating the need for further heating, thus saving energy and improving efficiency.
[0072] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features found in other embodiments but not others, combinations of features from different embodiments are also within the scope of protection of this invention and form different embodiments. For example, in the embodiments described above, those skilled in the art can use them in combination based on known technical solutions and the technical problems to be solved by this application.
Claims
1. A method for galvanizing steel workpieces, characterized in that, Includes the following steps: 1) Pretreatment: The steel workpiece is subjected to pickling, water washing, alkali washing, and water washing in sequence; 2) Drying the steel workpieces; 3) Heating reduction: Preheat the dried steel workpiece to 450-500℃; 4) Hot-dip galvanizing: Maintain the temperature of the steel workpiece at 450-500℃ and galvanize the surface of the steel workpiece. 5) Blow-dry the steel workpiece; 6) Cooling down; 7) Passivation of structural steel workpieces.
2. The galvanizing method for a steel workpiece according to claim 1, characterized in that, The steel workpiece can be any one of angle steel, channel steel, I-beam, round tube, or square tube.
3. The galvanizing method for a steel workpiece according to claim 1, characterized in that, The pickling in step 1) involves immersing the steel workpiece in a hydrochloric acid solution with a mass fraction of 8%-20% and aerating it. After pickling, the surface of the steel workpiece is rinsed with water to remove the acid solution.
4. The galvanizing method for a steel workpiece according to claim 3, characterized in that, The alkaline washing process involves immersing the steel workpiece in an alkaline solution with a pH of 10-14, aerating it, and then rinsing the surface of the steel workpiece with water after the alkaline washing is completed.
5. The galvanizing method for a steel workpiece according to claim 4, characterized in that, The pickling time in step 1) is 20-40 min; the alkaline solution time in step 2) is 0.5-1 min.
6. The galvanizing method for a steel workpiece according to claim 1, characterized in that, In step 2), radiant heating is used, and the heating temperature is 70°C.
7. The galvanizing method for a steel workpiece according to claim 1, characterized in that, In step 3), natural gas is used for open flame heating, the temperature of the heating furnace is 500-550℃, nitrogen is used to seal the furnace inlet, and a mixed gas consisting of 95% nitrogen and 5% hydrogen is introduced into the heating furnace.
8. The galvanizing method for a steel workpiece according to claim 1, characterized in that, A protective atmosphere is used in steps 2), 3), and 4).
9. The galvanizing method for a steel workpiece according to claim 1, characterized in that, After the galvanizing of the medium-sized steel workpiece is completed in step 5), it is blown along its length.
10. A method for galvanizing a steel workpiece according to claim 1, characterized in that, In step 6), the steel workpiece is cooled by immersion water; in step 7), the steel workpiece is passivated by pass-through or immersion.