Why does steel pipe get rust?

 Our daily production and life are inseparable from steel materials, but the amount of steel lost in the world due to corrosion is enormous. Therefore, how to protect steel from corrosion is of great significance.

What is the principle of steel corrosion? We can explore according to the small experiment shown in the figure below: add a small amount of calcium chloride in the first tube (calcium chloride can absorb the water vapor in the air, dry it), put a nail, plug it tightly Test tube mouth. A nail was placed in the second test tube, and the molten iron was immersed in distilled water which was boiled and rapidly cooled, and then the vegetable oil was poured to form an oil layer on the water surface. Place a nail in the third tube and add a small amount of distilled water to immerse a part of the nail in water. Three tubes were observed and recorded for a week. From the experimental results, we can find that the nails in the first and second tubes are not rusted, but the nails in the third tube are rusted, and reddish brown rust appears on the surface of the nail. It can be seen that iron rust requires the participation of water and oxygen.

The corrosion process of steel products is a complex chemical reaction process. The rust is usually reddish brown, and different forms of rust are formed under different conditions. The rust is mainly composed of iron oxide hydrate (Fe2O3·nH2O) and iron hydroxide [Fe(OH)3]. The rust structure on the steel surface is loose, and it cannot prevent the internal iron from coming into contact with oxygen, water vapor, etc., and eventually the iron is completely rusted.

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Which one of hydrochloric acid and sulfuric acid has strong rust removal ability?

 We placed the rusted nails in an equal volume, hydrochloric acid and sulfuric acid with equal hydrogen ion concentration. Finally, we found that the rust removal effect of hydrochloric acid is better. It can also be demonstrated by experiments that when other conditions are the same, the reaction rate of dilute sulfuric acid and metal oxide is slower than that of hydrochloric acid.

Then, from the aspects of production, transportation and safe use, which one is more dominant in hydrochloric acid and sulfuric acid? The industrial preparation of hydrochloric acid is to obtain hydrogen and chlorine gas by electrolyzing saturated brine. The two gases react to form hydrogen chloride gas. After water absorption, hydrochloric acid is formed. Hydrogen chloride gas can not be dissolved in water without limitation. Therefore, the concentrated mass fraction of concentrated hydrochloric acid is the most. At around 37%. Sulfuric acid is obtained by calcining pyrite at a high temperature to produce sulfur dioxide. Sulfur dioxide reacts with oxygen to form sulfur trioxide. Sulfur trioxide is absorbed into concentrated sulfuric acid to form pyrosulfuric acid, and pyrosulfuric acid is added to sulfuric acid. Therefore, hydrochloric acid is superior to sulfuric acid in terms of raw materials, preparation processes, and environmental impact. Concentrated hydrochloric acid needs to be sealed and stored in glass bottles or plastic drums. For transportation, special steel tankers with rubber inside are required. Concentrated sulphuric acid has a mass fraction of up to 98%. It can be stored and transported in steel or aluminum containers. In this respect, sulfuric acid is stronger than hydrochloric acid.

Hydrochloric acid with a large solute mass fraction is volatile, and the hydrogen chloride gas volatilized has strong irritating and corrosive effects on the human body, while hydrochloric acid with a low solute mass fraction is relatively stable. Concentrated sulfuric acid needs to be diluted before use. Dilution will generate a lot of heat, which is easy to cause burns, and concentrated sulfuric acid is much more corrosive than concentrated hydrochloric acid. It can be seen that the use of hydrochloric acid is safer.

According to the above information, it is obvious that the rust removal effect of hydrochloric acid is better, the cost is lower, and the use is safer.

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Research progress on VOCs emission reduction in sintering process of iron and steel industry

 Volatile organic compounds (VOCs) generally refer to organic acids with high vapor pressure and volatilization at normal temperature and pressure, including aliphatic and aromatic various alkanes, alkenes, and oxygenated hydrocarbons. And halogenated hydrocarbons, such as benzene, toluene, dichloromethane, formaldehyde and ethyl acetate.

There are many types of VOCs, but it is impossible to include all volatile organic compounds during monitoring and supervision. Therefore, some indicators are sometimes used to characterize VOCs such as TVOC, NMVOC and hydrocarbons. VOCs generally have strong irritancy and toxicity, some have teratogenic, carcinogenic and mutagenic effects, and quite a few are flammable and explosive. Some VOCs are factors that cause photochemical smog; halogenated hydrocarbon VOCs can destroy the ozone layer. It causes a greenhouse effect; VOCs are also an important precursor of ozone and PM2.5, and ash weather is closely related to the environmental concentration of ozone and PM2.5. Therefore, studying the production of VOCs and reducing the emission of VOCs is of great significance to human and biological health, ecological environment, and ozone reduction, PM2.5 and smog.

At present, the industry generally believes that the coking process in the steel production process produces VOCs; the sintering process is also one of the sources of VOCs due to the use of fuel. This paper investigates the current status, standards and technologies of VOCs emission in the sintering process of steel industry at home and abroad, and provides references for reducing VOCs emissions in the steel industry sintering process.

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What are the advantages of the sub-lance device?

 What are the advantages of the sub-lance device?

(1) There are many functions. The external probe type structure can be equipped with probes with different functions to achieve different functions of the probe to achieve different detection purposes;

(2) The gun body adopts a water-cooled structure, so it has a long service life;

(3) There are many measures taken by the organization for security purposes, so the operation is safe and reliable;

(4) The measuring speed is fast and the precision is high. After the operation is proficient, the two-way hit rate of carbon content and temperature can reach more than 90%.

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What are the differences between sinter and pellets?

 What are the differences between sinter and pellets?

Sintering and pellets are all methods of powder ore agglomeration, but their production process and the basic principle of solid sectioning are quite different. The effect of smelting on the blast furnace also has its own characteristics. The difference between sinter and pellets is mainly reflected in the following aspects:

1) different requirements for raw material particle size;

2) different mechanisms for solid jointing;

3) different shapes of finished ore;

4) different production processes.

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Why is it required to reduce the amount of slag in the ladle?

 1) Since iron oxide is contained in the slag, a part of the iron alloy is added to the iron oxide in the slag to burn, and if the amount of slag in the ladle is less, the burning loss of the iron alloy is less, that is, the alloy is saved.

2) Reduce the phosphorus return during the tapping process and the phosphorus return during the secondary refining.

3) Reduce the erosion of ladle bricks and improve the life of ladle.

4) Reduce the spillage of slag in the steel during the tapping process and during secondary refining to avoid accidents.

5) It is good for the quality of steel.

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Ten Ways to Remove Burrs from Steel Pipes

 Burrs are ubiquitous in the metalworking process. No matter how advanced and sophisticated equipment you use, it will be born with the product. It is mainly due to the plastic deformation of the material and an excess iron filings generated on the edge of the processed material, especially for materials with good ductility or toughness, which are particularly prone to burrs.

The types of burrs mainly include flash burrs, sharp corner burrs, splashes, etc., a protruding excess metal residue that does not meet the product design requirements. For this problem, so far there is no effective method to eliminate it in the production process, so in order to ensure the design requirements of the product, engineers have to work hard on the later removal. So far, for different steel pipe products, There are already many different methods and equipment for deburring.

The seamless pipe manufacturer (PMC) has sorted out the 10 most common deburring methods for you:

1) Manual deburring

This is also a method commonly used by general enterprises, using files, sandpaper, grinding heads, etc. as auxiliary tools. The file has manual file and pneumatic stagger.

Comment: The labor cost is more expensive, the efficiency is not very high, and it is difficult to remove complex cross holes. The technical requirements for workers are not very high, and it is suitable for products with small burrs and simple product structure.

2) Die deburring

Deburring is carried out by using a production die and a punch.

Comment: It requires a certain amount of die (rough die + fine die) production fee, and may also need to make a shaping die. It is suitable for products with simpler parting surfaces, and the efficiency and deburring effect are better than those of manual work.

3) Grinding and deburring

This type of deburring includes vibration, sandblasting, rollers, etc., and is currently used by many companies.

Comment: There is a problem that the removal is not very clean, and subsequent manual processing of residual burrs may be required or other methods of deburring may be required. Suitable for small products in larger batches.

4) Freeze deburring

Use cooling to quickly embrittle the burrs, and then spray projectiles to remove the burrs.

Brief comment: The price of the equipment is about 200,000 or 300,000; it is suitable for products with small burr wall thickness and small products.

5) Hot blast deburring

Also called thermal deburring, explosion deburring. By introducing some flammable gas into an equipment furnace, and then through the action of some media and conditions, the gas is instantly exploded, and the energy generated by the explosion is used to dissolve and remove the burr.

Brief comment: The equipment is expensive (millions of price), high technical requirements for operation, low efficiency, side effects (rusting, deformation); it is mainly used in some high-precision parts and components, such as automotive and aerospace precision parts.

6) Deburring of engraving machine

Brief comment: The price of the equipment is not very expensive (tens of thousands), it is suitable for simple space structure, and the required deburring position is simple and regular.

7) Chemical deburring

Using the principle of electrochemical reaction, the parts made of metal materials can be automatically and selectively deburred.

Brief comment: It is suitable for internal burrs that are difficult to remove, and suitable for small burrs (thickness less than 7 wires) of products such as pump bodies and valve bodies.

8) Electrolytic deburring

An electrolytic machining method that uses electrolysis to remove burrs from metal parts.

Brief comment: The electrolyte is corrosive to a certain extent, and the vicinity of the burr of the parts is also subjected to electrolysis, the surface will lose its original luster, and even affect the dimensional accuracy. The workpiece should be cleaned and rust-proof after deburring. Electrolytic deburring is suitable for removing burrs in hidden parts of intersecting holes or parts with complex shapes. The production efficiency is high, and the deburring time is generally only a few seconds to tens of seconds. It is suitable for deburring gears, connecting rods, valve bodies and crankshaft oil passages, etc., as well as rounding of sharp corners.

9) High pressure water jet deburring

Using water as a medium, it can use its instantaneous impact force to remove the burrs and flashes generated after processing, and at the same time, it can achieve the purpose of cleaning.

Brief comment: The equipment is expensive, mainly used in the heart of the car and the hydraulic control system of the construction machinery.

10) Ultrasonic deburring

Ultrasonic produces instant high pressure to remove burrs.

Comment: It is mainly aimed at some microscopic burrs. Generally, if the burrs need to be observed with a microscope, you can try to remove them with ultrasonic waves.

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