CN100476032C - A chemical passivation method for improving the corrosion resistance of continuous annealed IF steel cold-rolled sheets - Google Patents

Abstract

The chemical inactivation process for raising the anticorrosion of continuously annealed IF cold rolled steel plate is completed in a cold rolled plate continuously annealing production line. The present invention features that inactivating solution containing corrosion inhibitor in 1-5 wt% concentration and pH 8-12 is filled into the quenching tank the annealed cold plate passes through. The inactivating solution contains amine benzoate 20-30 wt%, sodium benzoate 20-30 wt%, urotropine 30-40 wt%, monoethanol amine 10-20 wt%, and water as solvent for the rest. The inactivating solution inside the quenching tank is maintained at 50-70 deg.c, and the annealed cold plate passes through the quenching tank in the speed of 200 m/min. The present invention can raise the anticorrosion performance of continuously annealed IF cold rolled steel plate easily and effectively.

Description

A chemical passivation method for improving the corrosion resistance of continuous annealed IF steel cold-rolled sheets

technical field

The invention relates to an antirust technology for cold-rolled steel plates produced by continuous annealing, and an on-line chemical passivation method for steel plates.

Background technique

Because there is no protection of coating or coating on the surface of cold-rolled sheet, it is easy to rust under high temperature and high humidity climate conditions, especially the continuous annealed IF steel cold-rolled sheet, due to the high temperature and low speed annealing process, a small amount of Mn, Si, etc. Easily oxidizable elements form granular oxides and iron oxide films on the surface to form corrosion micro-batteries, which accelerates the corrosion rate of IF steel cold-rolled plates. During the storage, transportation and user use of IF steel cold-rolled sheets, when the atmospheric humidity exceeds 65%, the surface is prone to rust, which directly affects the normal use of the material and increases the user's processing costs. Therefore, how to suppress, remove or cover the Mn and Si enriched layers on the surface of the cold-rolled sheet has become a key technology to improve the corrosion resistance of the cold-rolled sheet of continuous annealed IF steel.

At present, the method of oiling the cold-rolled sheet of continuous annealed ^IF steel before coiling after annealing is usually used to prevent rust ^. effect, but has the following limitations: First, the anti-rust time is short: oiling for anti-rust protection can only be effective within tens of hours, and because the anti-rust oil on the surface of the cold-rolled plate is unevenly distributed, especially after long-distance After transportation and the user opens the package, it is difficult to play an effective anti-rust effect. The second is the pollution problem: the oil-coated cold-rolled sheet must be degreased and cleaned before use, which increases the cost of use and brings pollution problems.

Japan's Kawasaki Iron and Steel Institute of Technology (CAMP-ISIJ 82-S449) studied the bismuth treatment technology before annealing of cold-rolled sheets, and suppressed the enrichment of Mn and Si during the annealing process of IF steel by forming a bismuth film, thereby improving its corrosion resistance. However, this method has two disadvantages: one is that bismuth salt is a turbid solution, and it is easy to crystallize at the bottom after preparation, so it is difficult to use in practice. The second is that the existing continuous annealing facilities for cold-rolled sheets must be transformed, that is, a chemical treatment process section is added before annealing.

Cockerill, Belgium found that the "HOWAQ" continuous annealing process can eliminate the Mn and Si enriched layers formed in the annealing process section of the IF steel cold-rolled sheet, thereby significantly improving its corrosion resistance. The process is to take a series of chemical treatments such as water cooling, pickling and rinsing after annealing. In addition, "Nippon Steel" also added flash nickel treatment after continuous annealing and pickling. Japanese patent JP 56112420A also proposes the technology of carrying out neutralization treatment after pickling earlier. But these methods have the following two limitations:

1. The technology of pickling and post-treatment is relatively complicated and the cost is high.

2. The process section of pickling and post-treatment is very long, and the existing continuous annealing production line usually does not have enough space for transformation.

All of the above all show that suppressing or removing the Mn and Si enriched layers on the surface of cold-rolled sheet is a high-cost technology, and the existing continuous annealing production line must be relatively large modified.

Contents of the invention

The purpose of the present invention is to provide a chemical passivation method for improving the corrosion resistance of continuous annealed IF steel cold-rolled sheets, without the need to modify the continuous annealing production line, and improve the corrosion resistance of cold-rolled sheets without pollution and at low cost.

A chemical passivation method for improving the corrosion resistance of continuous annealed IF steel cold-rolled sheets, using the continuous annealed cold-rolled sheet production line facilities, is characterized in that the quenching tank that the annealed IF steel cold-rolled sheets pass through contains corrosion inhibitors Passivation solution, concentration 1-5%, pH 8-12, the corrosion inhibitor in the passivation solution is: 20--30% of ammonium benzoate, 20--30% of sodium benzoate, urotox Product 30-40%, monoethanolamine 10-20%, solvent is water; keep the temperature of the passivation solution in the quenching tank at 50-70°C, and the normally annealed IF steel cold-rolled plate passes through the quenching process at 200m/min after coming out of the annealing furnace. sink.

The chemical passivation method of the present invention can change the water in the quenching tank into a passivation liquid on the existing continuous annealing production line without any modification to the equipment, so that the surface of the cold-rolled sheet coming out of the annealing furnace will undergo a chemical reaction and Passivation is directly realized; then the passivated cold-rolled sheet passes through the extrusion and drying process sections of the original production line, and the chemical protection layer is formed after the surface is completely dried.

The chemical passivation method of the present invention has the following characteristics:

1. The chemical passivation is directly completed on the existing continuous annealing production line, and there is no need to modify the production line.

2. The chemical passivation solution is easy to prepare, the cost is very low, and the actual use is simple and convenient.

3. After chemical passivation, the corrosion resistance of the cold-rolled sheet is obviously improved.

4. The passivation film on the surface of the cold-rolled sheet does not change the original surface state of the substrate.

5. The passivation film on the surface of the cold-rolled sheet does not affect the subsequent phosphating process of the user.

Feasibility and prospect of popularization and application of the invention are expected: at present, there are about 16 continuous annealing production lines in China, with an output of about 6.4 million tons, and more are under construction or proposed. and real problems directly faced by end users. The invention can directly improve the corrosion resistance of the cold-rolled sheet produced by continuous annealing, has the characteristics of simplicity and effectiveness, and does not need any modification to the existing production line, does not affect the use of the user's subsequent process, and can be used in domestic continuous annealing lines gain wide application.

Description of drawings

Accompanying drawing 1 is that this method implements schematic diagram in the production after 1550 continuous annealing cold-rolled plates come out of the furnace;

Accompanying drawing 2.1 is the comparison of the microscopic morphology of the cold-rolled plate without passivation and the phosphating film of the cold-rolled plate after chemical passivation in Figure 2.2;

Detailed ways

A kind of implementation step of the chemical passivation method that improves the corrosion resistance of continuous annealed IF steel cold-rolled sheet is illustrated in conjunction with accompanying drawing 1:

Step 1: Select corrosion inhibitor raw materials, by component weight percentage:

Ammonium benzoate 20--30%, sodium benzoate 20--30%, urotropine 30-40%, monoethanolamine 10-20%;

Step 2: Add the above-mentioned corrosion inhibitor into the quenching tank after the continuous annealing production line, dissolve with the water in the tank, and become a passivation solution with a concentration of 1 to 5% after dissolution. In this example, add 1550 at a concentration of 2%. Continuously annealing the cold-rolled sheet in the quenching water bath after it comes out of the furnace.

Step 3: Use a small amount of sodium carbonate or triethanolamine to adjust the pH of the passivation solution to a range of 8-12, or 9-10.

Step 4: Heat the passivation solution in the quenching tank to 50-70°C, and keep the temperature of the passivation solution in the quenching tank within this range during the operation. The passivation solution in this example is heated to 60°C.

Step 5: When the normal annealed IF steel cold-rolled plate comes out of the annealing furnace, the temperature is about 120°C, and it passes through the quenching tank of the 60°C passivation solution at a speed of 200 meters per minute. The chemical passivation of the cold-rolled plate takes two seconds Finished within, to passivate the surface of the steel plate.

Step 6: Then the chemically passivated cold-rolled sheet goes through the 5.4-meter drying process and 7.3-meter drying tunnel (100° C.) on the original production line, and forms a chemical protection layer after its surface is completely dried.

Step 7: Finally, the chemically passivated cold-rolled sheet is smoothed, oiled, and coiled on the original production line to become a finished coil.

The performance inspection of the IF steel cold-rolled plate processed by this method:

1. Moisture and heat resistance

After the chemical passivation of the IF steel cold-rolled sheet, the heat and humidity resistance performance is at 49° C. and RH > 95%, and the heat and humidity resistance time is > 48 hours.

The cold-rolled sheet after chemical passivation and the cold-rolled sheet without passivation were subjected to damp heat test. The cold-rolled sheet without passivation would appear red rust within 12 hours, while the cold-rolled sheet after chemical passivation could reach 48 hours. No red rust, significantly improved the moisture and heat resistance of the original IF steel cold-rolled sheet.

2. Phosphatability

The surface morphology was observed by scanning electron microscope. Compared with the unpassivated cold-rolled sheet, there was no significant difference in the morphology of the phosphating film.

The chemically passivated cold-rolled sheet and the non-passivated cold-rolled sheet were subjected to degreasing, surface adjustment, and phosphating treatment in simulated user process, and then the surface morphology was observed with a scanning electron microscope, compared with the SEM photos in Figure 2.1 and Figure 2.2 It can be seen that there is no significant difference in the morphology of the phosphating film compared with the unpassivated cold-rolled sheet. It is proved that chemical passivation has no effect on the phosphating crystallization of cold-rolled sheet. Even if the environmental conditions change greatly, the chemically passivated IF steel cold-rolled plate can keep the product from rusting for a long period of time during storage, transportation and user use, and there will be no change on the surface, and it will not affect the surface. Exterior. During the subsequent use of the cold-rolled sheet, its surface film can be removed with surface cleaning, without affecting the subsequent use of the product.

In the process of effect inspection, the test of the influence of leveling on the passivation film was also carried out: the cold-rolled plate after chemical passivation was leveled at a reduction rate of 1%, compared with the unleveled chemically passivated cold-rolled plate, it was wet-heated Test, two kinds of cold-rolled plates have no rust after 48 hours damp heat test. It is proved that the leveling has no effect on the corrosion resistance of the passivation film on the surface of the cold-rolled sheet.

Claims (2)

1, the corrosion proof chemical passivation method of a kind of raising annealing IF steel cold-reduced sheet, utilize the cold-reduced sheet production line facility of continuous annealing, be the passivating solution that contains inhibiter in the hardening groove of the cold-reduced sheet process after it is characterized in that annealing, concentration 1～5%, pH 8～12, inhibiter by the solute weight percent in the passivating solution is: phenylformic acid amine 20--30%, Sodium Benzoate 20--30%, urotropine 30-40%, monoethanolamine 10-20%, and solvent is a water; 50～70 ℃ of passivating solution temperature in the maintenance hardening groove, the IF steel cold-reduced sheet of normarzing annealing passes through the hardening groove with 200m/min after coming out from annealing furnace.

2, the corrosion proof chemical passivation method of a kind of raising annealing IF steel cold-reduced sheet according to claim 1 is characterized in that the performance evaluation index of the annealed IF steel cold-reduced sheet handled with this method can reach:

(1) at 49 ℃, RH＞95% time, hot time＞48 of moisture-proof hour;

(2) phosphatization: the processing of chemical passivation method to IF steel cold-reduced sheet phosphatization crystallization do not have influence.

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