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Nickel base alloy has excellent corrosion resistance, and has high corrosion resistance in many substances and even strong corrosive substances. Nickel base alloys have excellent physical and technological properties, but they are generally not used casually because of their high price. However, due to the development trend of high main parameters (temperature, working pressure, material concentration) in the whole process of chemical plants, there are more and more places with strong corrosivity, and the corrosion standards are becoming more and more strict. Therefore, the common machinery and equipment are not only required to be resistant to overall corrosion but also more and more resistant to pitting, stress corrosion, gap corrosion, etc. When selecting raw materials, we should not only consider the one-time project investment cost but also consider the maintenance, depreciation, shutdown loss, and other costs and their safety factors. Therefore, we pay more attention to the stability of the long-term operation of machinery and equipment. This element promotes the use of nickel-based alloys with high corrosion resistance.

At present, most of the nickel base alloys commonly used in the processing and manufacturing industry adopt the models of international standards. Therefore, the following is dominated by the American nickel base wrought aluminum alloy, and a brief and detailed introduction to pure nickel is given.

Pure nickel has good corrosion resistance in hot concentrated alkaline solution, does not cause alkali ductile stress corrosion cracking, and has good corrosion resistance to water, seawater, high- temperature dry fluoride, but is not corroded by oxidizing acid, aqueous solution with reducing agent and most of its molten metal materials. It can corrode and become brittle in gas with high-temperature sulfur content. With the increase of nickel content in stainless steel and nickel base alloy, the corrosion resistance in dilute hydrochloric acid, sulfuric acid, and ammonium sulfate is significantly enhanced, and the stress corrosion resistance in sodium hydroxide solution is also significantly enhanced. The corrosion resistance in caustic soda solution is basically positive correlation with nickel content.

For a pure nickel, the market generally includes NICKEL200 and NICKEL201

NICKEL200 COMPOSITION:

Carbon C ≤ 0.15

Silicon Si ≤ 0.35

Manganese Mn ≤ 0.35

Sulfur S ≤ 0.01

Nickel Ni+Cobalt Co greater than or equal to 99

Copper Cu ≤ 0.25

Fe ≤ 0.4

NICKEL200 is mainly used to solve the problem of oxidizing halogen system vapor, alkali solution, non-reducing acid salt, organic acid, and other machinery, equipment, and components. In the application, the temperature should be less than 315 ℃ in the natural environment. NICKEL200 corrosion resistance: corrosion is relatively slow in the air, and HCl has excellent corrosion resistance in various sulfuric acids in the sea. However, it should be used cautiously in HIC acid with high water flow. It is not easy to use in H3PO4 and HNO3. It has very good corrosion resistance in H2SO4, which is only used to block gas, in HF without water at high temperature, in chlorine and HCl at high temperature, and in chlorine and fluorine.

There are many materials for faucets, such as stainless steel and copper. Is the faucet material all copper or copper alloy better? Let me take you all to find out.

The faucet is better to choose all copper material. The all-copper material can kill 99% of the bacteria in tap water. Even if the tap water bursts and causes foreign objects to enter, there is no need to worry about a bacterial infection; good metal-cutting performance reduces production costs, making it a must-have copper faucet for every household.

The main material of kitchen faucets currently used in China is brass HPb59, which contains trace amounts of lead. At present, the national faucet safety certification rules stipulate that the inspection should be carried out in accordance with the regulations, and the amount of lead precipitation should be less than or equal to 11 micrograms. At present, the lead-washing technology of big brands can inhibit the precipitation of most heavy metals.

The price of copper alloy faucets is much lower than that of full copper faucets, and this faucet is easier to produce on a large scale. The biggest disadvantage of alloy faucets is that they have no toughness and are prone to cracks after long-term use, and their service life is short.

Many people believe that stainless steel will not rust. In fact, everything has a life span. Stainless steel is also a kind of metal, which will be oxidized and corroded in nature, causing rust; The only difference is that the material or protection degree is different, which can delay the probability and time of rusting to the greatest extent. However, in many cases, stainless steel will also be “rusted”. Here are the main culprits of stainless steel rust:

1、 Presence of chloride ions in the service environment

Chloride ions mainly exist in purified liquids and gases. The use of stainless steel in the presence of chloride ions will accelerate its corrosion, even exceeding that of ordinary low-carbon steel. Therefore, there are requirements for the use environment of stainless steel, and it needs to be wiped frequently to remove dust and keep it clean and dry.

2、 Without solution treatment

Solution treatment: refers to the heat treatment process that heats the alloy to the high-temperature single-phase area and maintains the constant temperature, so that the surplus phase can be fully dissolved in the solid solution and then rapidly cooled to obtain the supersaturated solid solution. Its purpose is to fully dissolve various phases in the alloy, strengthen solid solution, improve toughness and corrosion resistance, eliminate stress, and soften, so as to continue processing or molding. If the alloy elements are not dissolved in the matrix material, the alloy content in the matrix structure is low and the corrosion resistance is poor.

3、 Natural intergranular corrosion

Under the action of a corrosive medium, a corrosion phenomenon between grains of stainless steel is called intergranular corrosion. When the stainless steel with intergranular corrosion is subjected to stress, it will fracture along the grain boundary and the strength will almost disappear. This is the most dangerous form of stainless steel damage.

Stainless steel will not rust because the content of chromium (Cr) and nickel (Ni) has reached a certain standard. These two alloys are the key to rust prevention in stainless steel. Generally, stainless steel produced by small factories will rust, mainly because of the low nickel content (the cost price of nickel largely reflects the benchmark price of stainless steel); If the nickel content reaches the standard required by various stainless steel, no matter how you cut it, it will not rust.

4、 Mechanical stress corrosion

When stainless steel materials are made into products, they need to go through such processes as stamping, shearing, punching, stretching, grinding, shearing, bending, planing, thermal cutting, or welding. Because of the external stress loading, the machined parts and their edges will be damaged by their own stress to a large extent, which will lead to the intergranular transformation; Therefore, it destroys its corrosion resistance and speeds up the rusting process.

5、 Damage to surface passivation protective layer

Passivation is a method to change the metal surface into a state that is not easy to be oxidized, thus delaying the corrosion rate of the metal. Passivation is due to the interaction between metal and oxidizing substances. During the interaction, a very thin, dense, well-covered, and firmly adsorbed passivation film is formed on the metal surface. Once this “protective film” is damaged by external forces (mainly large scratches), the stainless steel is like a body without resistance, which is easy to react with the outside world to rust and corrosion.

We recognize that, because of its critical role, people are interested in steel and the effect it has on the global economy. We are committed to being open, honest, and transparent in all our communications about our industry, its performance, and the impact we have.

Key facts:

The steel industry publishes data on production, demand, and trade at national and global levels, which is used for analyzing economic performance and making forecasts.
The steel industry presents its sustainability performance with 8 indicators on a global level every year.
The steel industry proactively participates in OECD, IEA, and UN meetings, providing all the information required on key industry topics which have an impact on our society.
The steel industry shares its safety performance and recognizes excellent safety and health programs every year.
The steel industry collects CO2 emissions data, providing benchmarks for the industry to compare and improve on.

A notable feature of titanium plates is their strong corrosion resistance, which is due to their great affinity for oxygen. It can form a dense oxide film on its surface, which can protect titanium from medium corrosion. It has good stability in acidic, alkaline, neutral saline solutions and oxidizing media, and is better than existing stainless steel and other commonly used non-ferrous metals in corrosion resistance.

The quality of titanium plate largely depends on the smelting process of the titanium plate manufacturer, including the chemical composition of titanium, the cleanliness of titanium water (gas, harmful elements, inclusions), and the quality of cast slab (composition segregation, decarburization, and surface conditions), which are the key control points of smelting operation.

In addition, industrial titanium plate also requires sufficient hardenability to ensure uniform microstructure and mechanical properties of the whole spring cross-section. The main reason for fatigue cracks is oxide inclusions in titanium, and the damage of type D inclusions to fatigue life is greater than that of type B inclusions. Therefore, foreign titanium factories and automobile factories put forward higher requirements for oxide inclusions in industrial titanium plates. For example, the Swedish SKF standard requires that the oxygen content in titanium be less than 15 × 10-6, and class D inclusions are lower than class B inclusions. Especially Al2O3 and tin inclusions do great harm to the fatigue life of titanium springs. In order to produce high-quality industrial titanium plates, special smelting methods such as electric furnace electro slag remelting or vacuum arc remelting were usually used in the past.

Because titanium plate has special physical and chemical characteristics, their welding process is very different from other metals. Titanium welding is a TIG welding process that effectively protects the welding area with inert argon. Before using argon, check the factory certificate on the bottle body to verify the purity index of argon, and then check whether the bottle valve leaks or fails.

When welding titanium plates, the following must be ensured:

The metal in the welding area shall not be polluted by the active gas n0h and the harmful impurity element clean above 250 ℃. Argon with purity not less than 99.98% and water content less than 50mg / M32: industrial grade I pure argon.

A coarse crystal structure cannot be formed. The welding process shall be carried out according to the predetermined construction sequence, and no large welding residual stress and residual deformation shall be generated. Therefore, the quality control of the whole process shall be carried out in strict accordance with the procedure quality management standards, so that the factors of human, machine, material, and method are under good control, so as to ensure the quality within a reasonable construction period.