郓城县武安镇地貌:Stainless Steel

A: 【concept 】
       Stainless Steel (Stainless Steel) refers to the resistance of air, steam, water and other corrosive medium and weak acid, alkali, salt and other chemical attack by corrosive media, steel, also known as acid-resistant stainless steel.
Practical applications, often the weak corrosion resistance as stainless steel, corrosion medium, and the chemical resistance of steel known as acid corrosion of steel.As the two differences in the chemical composition, the former
Corrosion resistant chemical media are not, while the latter are generally of a stainless steel.The corrosion resistance of stainless steel depends on the alloying elements contained.
Second, 【Introduction】
All metals and the reaction of oxygen in the atmosphere, in the surface oxide film.Unfortunately, the iron oxide formed on carbon steel continue to oxidation, corrosion is not
Off to expand, and ultimately the formation of holes.Can use paint or oxidation-resistant metals (eg, zinc, nickel and chromium) plating to protect the steel surface, but, as people know
Out, this protection is only a film.If the protective layer is damaged, the steel began to rust the following
       Chromium is to corrosion resistance of stainless steel to obtain the basic elements, when the chromium content in steel up to 12%, the chromium and corrosive media, the role of oxygen in the steel surface to form a thin
The oxide film (passive film from), can prevent further corrosion of steel substrate.In addition to chromium, the commonly used alloying elements nickel, molybdenum, titanium, niobium, copper, nitrogen, so as to meet
Use of Stainless Steel and performance requirements.
III: 【Category】(stainless steel is usually classified according to matrix)
 1, ferritic stainless steel.12% Chromium 30%.Its corrosion resistance, toughness and weldability with the increase of chromium content increased resistance to chloride stress corrosion better than other types of stainless steel.
 2, austenitic stainless steel.More than 18% chromium, 8% also contains a small amount of nickel and molybdenum, titanium, nitrogen and other elements.Comprehensive performance, and can be resistant to a variety of media corrosion.
 3, austenitic - ferritic duplex stainless steel.Both austenitic and ferritic stainless steel, the merits, and has superplasticity.
 4, martensitic stainless steel.High strength, but poor ductility and weldability. 
IV 【History 】
       Graduated from the University of Sheffield, the famous British scientist Henry Blair metallurgical interest (Harry Brearley) in the early 20th century invented the stainless steel.
The invention and use of stainless steel, dates back to World War I period.British scientists share Lileierli cloth military arsenal by the British government commissioned a study of weapons
Improvement work.At that time, soldiers can easily use the rifle bore wear, mine Hurley would like to invent a scratch-resistant alloy steel.Brearly invented stainless steel in 1916 to take
May begin mass production of the British patent and, thus, from the garbage in the accidental discovery of stainless steel will swept the world, Henry Blair Lee is also known as the "Father of stainless steel."
Fifth, 【For use】
Stainless steel will not produce corrosion, pitting, corrosion or wear.Stainless steel or metal materials used in construction materials in one of the highest intensity.Because stainless steel has good resistance to
Corrosive, so it can permanently maintain the structural components of the integrity of engineering design.Chromium stainless steel with high mechanical strength and also set extension in one, easy-to-part machining system
Made to meet the architects and structural designers need.
Four groups 【stainless steel grades】
Precipitation hardening stainless steel.Has good formability and good weldability, high strength materials can be used as the nuclear industry, aviation and aerospace industry applications.
Components can be divided by:
      Cr system (400 series), Cr-Ni system (300 series), Cr-Mn-Ni (200 series) and precipitation hardening line (600 series).
200 - chromium - nickel - manganese austenitic stainless steel
300 Series - chromium - nickel austenitic stainless steel
  301 - scalability, for molding products.It can also be rapidly hardened by mechanical processing.Welding is good.Abrasion resistance and fatigue strength than 304 stainless steel.
302 - 304 with corrosion resistance, due to relatively high carbon intensity and therefore better.
303 - by adding a small amount of sulfur and phosphorus to more than 304 cutting.
304 - or 18 / 8 stainless steel.GB grades for 0Cr18Ni9.
309 - 304 better than the heat resistance.
316 - Following the 304, the second most widely used of steel, mainly for the food industry, pharmaceutical industry and surgical equipment to be added Mo
                 The special structure of an anti-corrosion.Better than the 304 because of its resistance to chloride corrosion and thus as "marine steel" to use.SS316 is usually
                 For fuel recovery.18/10 grade stainless steel is usually in line with the application level.Model 321 - Apart from reducing the added titanium material
                 Other than the risk of weld corrosion properties are similar to 304.
400 Series - Ferritic and martensitic stainless steel
  408 - good heat resistance, low corrosion resistance, 11% Cr, 8% of Ni.
409 - the cheapest model (England), commonly used as automobile exhaust pipe, is a ferritic stainless steel (chrome steel).
410 - martensite (high strength chrome steel), good wear resistance, corrosion resistance is poor.
416 - sulfur added to improve the processing properties of the material.
420 - "Cutting Class" martensitic steel, similar to Brandt's first high-chromium stainless steel this.Also used for surgical tools, can do very light.
430 - ferritic stainless steel, decorative, such as for car accessories.Good shape, but heat resistance and corrosion resistance worse.
440 - high strength cutting tool steel, carbon slightly higher, after appropriate heat treatment to obtain a higher yield strength and hardness up to 58HRC, are among the most hard stainless steel
                 List.The most common application example is the "razor blades."There are three common models: 440A, 440B, 440C, in addition to 440F (and easy processing.)
500 Series - heat-resistant chromium alloy steel.
600 Series - martensitic precipitation hardening stainless steel.
       630 - The most commonly used precipitation hardening stainless steel models, often called 17-4; 17% Cr, 4% Ni.
 
V. 【corrosion resistance】
All metals and the reaction of oxygen in the atmosphere, in the surface oxide film.Unfortunately, the iron oxide formed on carbon steel continue to oxidation, corrosion
Expanding, and ultimately the formation of holes.Can use paint or oxidation-resistant metals (eg, zinc, nickel and chromium) plating to ensure the steel surface, but, as people
Know, this protection is only a film.If the protective layer is damaged, the following steel began to rust.Stainless steel corrosion resistance depends on the chromium, but because chromium is
One of the components of steel, so the protection methods vary.
Add in the chrome above reached 11.7%, atmospheric corrosion resistant steel increased significantly, but the chromium content higher, although still improve corrosion resistance, but not obvious.
The reason is steel with a chromium alloy processing, the type of change in the surface oxide into the metal is similar to pure chromium oxide formed on the surface.This tight adhesion of chromium-rich
Protection of the surface oxide to prevent further oxidation.This very thin oxide layer, through which you can see the surface of the natural sheen of steel, the stainless steel has a unique surface.Moreover,
If the damage to the surface, the exposed steel surface and atmospheric response to self-repair, re-formation of this oxide "passive film" and continue to play a protective role.
Therefore, all the stainless steel elements have a common characteristic, namely, chromium content of 10.5% or more.
 
VI 【Type】
"Stainless steel" is not just a simple means of a stainless steel, but said that more than one hundred kinds of industrial stainless steel, stainless steel, each developed in their specific fields of application with
Good performance.The key to success is to understand the purpose first, and then determine the correct steel.Further details of the stainless steel can be found compiled by the NiDI
"Stainless Steel Guide" floppy disk.
Fortunately, building construction and steel-related applications are usually only six.They contain 17 to 22% chromium, a better steel also contains nickel.Adding Mo can be further changed
Good atmospheric corrosion, in particular resistance to atmospheric corrosion with chloride.
 
VII 【advantages - atmospheric corrosion resistance】
Experience has shown that atmospheric corrosion from region to region.For illustration purposes, proposed to be divided into four regions, namely: rural, urban, industrial area and coastal areas.
Country: is essentially pollution-free area.Low population density area, only non-polluting industries.
City: for the typical residential, commercial and light industrial areas, there is light pollution in the area, such as traffic pollution.
Industrial Area: The area of air pollution caused by heavy industry.Contamination may be due to the formation of fuel gases such as sulfur and nitrogen oxides, or chemical or processing
              Factory release of other gases.Particles suspended in air travel, such as iron and steel dust generated in the production process or the deposition of iron oxide corrosion will also increase.
 
Coastal areas: usually refers to less than a mile from the beach area.However, deep ocean-atmosphere can be spread to the inland, especially on the island, the prevailing winds come from
                       Ocean, and bad weather.For example, the British climate is the case, so the entire country belongs to the coastal area.If the wind mixed with the ocean mist,
                       Particular concentration due to evaporation caused by salt deposition, coupled with less rain, less often by rainfall, coastal areas is even more unfavorable conditions.If there is work
                       Industry pollution, then the greater the corrosion.
United States, Britain, France, Italy, Sweden and Australia carried out the research work has identified these areas for a variety of stainless steel resistant to atmospheric corrosion.For
Content published in the NiIDI "architect Fact Sheet," a brief description in the book of the table can help designers to select cost-effective for a variety of regional best stainless steel.
Making choices, it is important to determine whether there are factors that affect the use of the local environment of the scene.For example, stainless steel chimney with the bottom of the plant, used in air-conditioning exhaust block
Board or scrap field near the vicinity of non-general conditions will exist.
VIII. 【Magnetic】
       In real life, most people think that stainless steel is not magnetic, and using magnets to identify stainless steel, this approach is very scientific.First, zinc alloy, copper alloy
Gold generally be the appearance of imitation stainless steel color, there is no magnetic, easily mistaken for a stainless steel; and even our 304 most frequently used species in Canada through the cold
After work, there will be varying degrees of magnetism.It is not just by a magnet to determine the authenticity of stainless steel.
 
       So how did the magnetic properties of stainless steel come from?According to the research material physics, the magnetic metal structure from the electron spin, electron spin is quantum mechanical
Performance, either "up" can also be "down."In ferromagnetic metals, electronics will automatically rotate according to the same direction, while the anti-ferromagnetic metal material, a
These electronic mode in accordance with the rules, and the adjacent electrons in the opposite direction or anti-parallel spin, but for the electronic triangular lattice, because each triangle
The two electronic spin must be in the same direction, so the spin structure does not exist.In general, austenitic stainless steel (with a 304 as the representative) is non-magnetic, but
May also be with the weak magnetic and ferrite (mainly 430,409 L, 439, and 445NF) and martensite (in 410 as the representative) are generally magnetized.Stainless steel in
There are some steel surface (such as 304, etc.) are classified as "non-magnetic stainless steel" refers to a value below its magnetic indicators only, that is, generally stainless steel are more or less
A certain magnetism.In addition, the above-mentioned austenitic non-magnetic or weakly magnetic that, while the ferrite and martensite are magnetic, the composition segregation smelting or improper heat treatment,
304 austenitic stainless steel will cause a small amount of martensite or ferrite, so that there will be 304 stainless steel in weak magnetic.In addition, 304 stainless steel after cold working,
Organizational structure will be transformed to martensite, the greater the cold deformation, martensitic transformation of the more stronger the magnetic will.Want to completely eliminate magnetic 304 stainless steel, can be high
Solution treatment temperature to stabilize austenite, thereby eliminating the magnetic.Therefore, the magnetic material is whether the rules of molecular arrangement and electronic spin with the sexual decisions, we believe
The physical properties of the material, and corrosion resistance of the material is determined by the material's chemical composition, and chemical properties of the material, nothing to do with whether the material is magnetic.
IX. 【Rusting】
       In layman's terms, is not easily rust stainless steel, in fact, part of the stainless steel, stainless steel of both, but also acid resistance (corrosion resistance).Stainless steel and stainless steel
Corrosion resistance is due to the chromium-rich oxide film on the surface (passive film) is formed.Tests showed that steel in the atmosphere, water and other weak medium and nitric oxide in the medium, its corrosion resistance
With the water content of chromium in steel increases.When the stainless steel surface of brown rust (points), people great surprise: that "Stainless steel is not rust, and rust on
Is not stainless steel, the steel may be a problem. "In fact, this is a one-sided stainless steel misconceptions. Stainless steel under certain conditions will rust.
The size of the corrosion resistance of steel itself, with its chemical composition, plus each state, the use of conditions and the type of change in environmental media.Therefore, not any kind of stainless steel,
Capability in any environment corrosion, do not rust.
       Stainless steel causes rusty
       More common in daily life are summarized as follows:
  (1) stainless steel storage product with other metal elements containing dust or metal particles heterogeneous attachment, in the humid air, fixtures and stainless steel between the condensate will
           The two together into a micro-cell, causing the electrochemical reaction, the destruction of protective film, known that the electrochemical corrosion.
  (2) stainless steel surface adhesion of organic juice (such as vegetables, soup, sputum, etc.), in the case of water of oxygen to form organic acids, organic acids long is the corrosion on the metal surface.
  (3) stainless steel surface adhesion containing acid, alkali, salts (such as a wall decoration alkaline, lime water splash), causing localized corrosion.
  (4), where air pollution (such as rich in sulfides, carbon dioxide, nitrogen oxide in the atmosphere), the case of condensation water to form sulfuric acid, nitric acid, acetic acid solution point, causing chemical corrosion.
 
【Above excerpt from the "Baidu Encyclopedia"】

                【Translation by Google】