CN1044624C - Internal blowing process of hot-dip galvanized pipe - Google Patents

Abstract

The present invention discloses an improved inner-blowing technique for a hot galvanized tube. The present invention is characterized in that heated compressed air is used as an inner-blowing medium, and the compressed air which is offered by an air compressor is heated with the adoption of a drying brick bed, namely that the compressed air out of the compressor goes through tubes buried in the drying brick bed for heating, and then the compressed air is blown to the inner surface of the hot galvanized tube. The improved inner-blowing technique can enhance the quality of the galvanized layer of the tube, and the thickness of the galvanized layer tends to be uniform; zinc is saved so production cost is reduced, and meanwhile, the investment cost is reduced and energy is saved.

Description

Internal blowing process of hot-dip galvanized pipe

The invention relates to a production process of a hot-dip galvanized steel pipe, especially its internal blowing process.

The existing hot-dip galvanized steel pipe production process is basically as follows: 1. Derusting means immersing the steel pipe to be galvanized in a certain concentration of acid solution for a period of time to remove the rust on the inner and outer surfaces of the steel pipe; 2. Cleaning, that is, cleaning the acid solution on the steel pipe with clean water; 3. Dip the liquid, that is, soak the cleaned steel pipe in zinc chloride solvent for a certain period of time, let the solvent adhere to the pipe wall by reacting with iron; 4. Drying to remove the water molecules on the surface of the steel pipe dipped in the liquid medicine; 5. 6. Galvanizing means that the steel pipe treated by the aforementioned process is placed in a zinc solution at a certain temperature for a certain period of time, and zinc is plated on the inner and outer surfaces of the steel pipe; 6. Blowing outside, that is, using compressed air with a pressure of 3-5 kg/ ^cm2 to blow off the residual zinc liquid and floating objects on the outer surface of the steel pipe; 7. Internal blowing, use 5-8 kg/ ^cm2 pressure of water vapor to blow off the residual zinc liquid and floating objects on the inner surface of the pipe; 8, cooling, put the galvanized steel pipe in the cooling water tank to cool to normal temperature.

In the above process flow, external blowing and internal blowing are two key processes that directly affect the quality of the inner and outer surfaces of the pipe. Among them, the compressed air used for external blowing is provided by the compressor. Because the pipe has just come out of the zinc liquid, the temperature does not drop much. After the compressed air heated by the compressor is blown off, the surface quality basically meets the requirements. But sometimes the quality of the external blowing is affected due to the low temperature of the compressed air.

Since the internal blowing is carried out with heated water vapor, it has many disadvantages as follows: a set of boiler equipment and supporting facilities is required, which increases the investment cost; due to the requirements of environmental safety, the boiler room must be far away from the production workshop, causing pipeline Prolonging and consuming heat energy; during production, the internal blowing of the pipe requires the steam pressure to be kept at 6-8 kg/cm ² , so the boiler must be fired continuously for 24 hours to maintain the pressure. Don’t dare to decompress, for fear that the pressure will not go up during production; the coal consumption is large, resulting in great energy loss; because the steam contains a certain amount of water, sometimes it can not only remove the sundries, but will leave zinc liquid in the pipe when it comes into contact with it Finally, the solidification of the zinc liquid is accelerated, the roughness of the inner surface of the pipe is increased, the zinc layer is thickened, the zinc consumption is increased, and the cost is increased; It is easy to cause cracking after liquid, resulting in missing plating, so that the product cannot be put into use.

The purpose of the present invention is to provide an internal blowing process for hot-dip galvanized pipes to improve the quality of the pipe coating, make its thickness uniform, save zinc consumption, and reduce production costs; at the same time, it also reduces investment costs and saves energy.

The technical solution of the present invention is: an internal blowing process of hot-dip galvanized pipe, which is characterized in that the compressed air provided by the compressor is heated through the pipeline buried in the drying kang, and then the heated compressed air is blown to the For the inner surface of the hot-dip galvanized pipe, the heating temperature of the compressed air is 230--280°C, and the pressure is 6--8 kg/ ^cm2 .

In the above-mentioned internal blowing process of the present invention, since compressed air is used instead of traditional water vapor as the internal blowing medium, the moisture content in the medium is greatly reduced. The thickness of zinc is easy to blow evenly, which improves the quality and yield of internal blowing, and also saves zinc consumption; replacing steam boilers with compressors and drying kangs saves more than 70% of equipment investment and labor. It is convenient for production management.

The present invention will be described in further detail below through the accompanying drawings and examples.

Figure 1 is a plan view of an exemplary embodiment of the present invention.

As shown in Figure 1, the embodiment of the present invention, the external air blowing source is provided by ^3M3 heating air compressor 5, and the pressure is 3--5 kg/cm ² ; the internal blowing air source is provided by ^6M3 heating air compressor 6 Provide; the pressure is 6--8 kg/ ^cm2 ; the temperature of the compressed air output by the two air compressors is 150--180 ℃.

Drying kang 1 is a closed device made of refractory bricks with an air intake flue and an exhaust chimney. The heat source used is introduced by the hot gas and flame of the zinc heating furnace 2 through the flue 17; The compressed air passes through the S-shaped pipes 8 and 7 and is further heated to 230--280°C in the drying kang 1, and then the compressed air is blown to the Blow the hot-dip galvanized pipe on the roller way 16 in the interior, blow out the compressed air outside and blow out the air duct 11 and the outer blowing ring 13 and blow to the hot-dip galvanized pipe on the roller way 15 outside.

When implementing the present invention, the internal blowing control steam valve preferably adopts a quick-opening stop valve. Compared with the traditional general ball valve, the quick-opening globe valve is adopted, and the air can form a greater explosive force inside the pipe during internal blowing, and instantly blow out the residue and sundries in the pipe. The compressed air pipeline through the kang drying kang is preferably arranged in an S shape to improve the heating effect. It is advisable to ensure that the compressed air can be heated to 230--280°C for the size of the kang and the length of the heating pipe. In the above-mentioned embodiment of the present invention, the pipeline of the air compressor that is blown outside is changed from the original non-heating to heating, and the pipeline is also passed through the drying kang, so that the temperature of the pipe that is blown outside first will not drop too much and cause damage. Affect the completion of internal blowing in the next process.

Process 4 minutes--4 inch hot-dip galvanized pipes according to the scheme of the above-mentioned embodiment, and the average daily output can reach 50 tons.

Claims (4)

1. An internal blowing process of hot-dip galvanized pipe, which is characterized in that the compressed air provided by the compressor passes through the pipeline buried in the drying kang for heating, and then the heated compressed air is blown to the hot-dip galvanized pipe. For the inner surface, the heating temperature of the compressed air is 230-280° C., and the pressure is 6-8 kg/cm ² . 2. The internal blowing process of hot-dip galvanized pipe according to claim 1, characterized in that the internal blowing steam control valve adopts a quick-opening stop valve. 3. The internal blowing process of hot-dip galvanized pipe according to claim 1, characterized in that the compressed air pipeline passing through the drying kang adopts an S-shaped layout. 4. The internal blowing process of hot-dip galvanized pipe according to claim 1, characterized in that the heat source used for the drying kang is introduced by the hot gas and flame of the zinc heating furnace through the flue.

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