430 stainless steel
430 stainless steel is a general-purpose steel with good corrosion resistance. It has better thermal conductivity than austenite, a smaller thermal expansion coefficient than austenite, heat fatigue resistance, addition of stabilizing element titanium, and good mechanical properties of the weld. 430 stainless steel is used for building decoration, fuel burner parts, household appliances, and home appliance parts.
430F is a steel grade with free-cutting performance added to 430 steel. It is mainly used for automatic lathes, bolts and nuts. 430LX adds Ti or Nb to 430 steel, reduces C content, improves processing performance and welding performance, and is mainly used for hot water tanks, hot water supply systems, sanitary appliances, household durable appliances, bicycle flywheels, etc. Because of its chromium content, it is also called 18/0 or 18-0. Compared with 18/8 and 18/10, it contains slightly less chromium, and the hardness is correspondingly lower.
430 stainless steel is a general-purpose steel with good corrosion resistance. It has better thermal conductivity than austenite, a smaller thermal expansion coefficient than austenite, heat fatigue resistance, addition of stabilizing element titanium, and good mechanical properties of the weld. 430 stainless steel is used for building decoration, fuel burner parts, household appliances, and home appliance parts.
430F is a steel grade with free-cutting performance added to 430 steel. It is mainly used for automatic lathes, bolts and nuts.
430LX adds Ti or Nb to 430 steel, reduces C content, improves processing performance and welding performance, and is mainly used for hot water tanks, hot water supply systems, sanitary appliances, household durable appliances, bicycle flywheels, etc. Because of its chromium content, it is also called 18/0 or 18-0. Compared with 18/8 and 18/10, it contains slightly less chromium, and the hardness is correspondingly lower.
chemical composition
Carbon (C): ≤0.12%
Silicon (Si): ≤0.75%
Manganese (Mn): ≤1.00%
Phosphorus (P): ≤0.040%
Sulfur (S): ≤0.030%
Nickel (Ni): ≤0.60% (may contain)
Chromium (Cr): 16.00~18.00%
Mechanical properties
Density: 7.75g/cm³
Melting point: 1427℃
Expansion coefficient: mm/℃(at 20-100℃)
Young’s modulus: kN/mm²
Rigid modulus: kN/mm²
Application standard: n/a (UNS)
Product specifications
| Product name | Specification/mm | Material |
| Cold round | Ф5.5-30 | 430 stainless steel |
| Cold drawn light circle | Ф3.0-100 | 430 stainless steel |
| Hot rolled plate | 5-100 | 430 stainless steel |
| Hot rolled round steel | Ф100-200 | 430 stainless steel |
| Hot rolled round steel | Ф20-100 | 430 stainless steel |
| Hot rolled steel sheet | 1-100 | 430 stainless steel |
| Hot rolled round steel | Ф200-400 | 430 stainless steel |
| Hot rolled steel sheet | 4-180 | 430 stainless steel |
Classification and process
Surface grade
430 stainless steel has the following states, the state is different, and the dirt resistance and corrosion resistance are also different.
NO.1, 1D, 2D, 2B, No. 4, HL, BA, Mirror, and various other surface treatment states.
Feature processing technology
1D—The surface has discontinuous granular shape, also called matte surface. Processing technology: hot rolling + annealing shot peening pickling + cold rolling + annealing pickling.
2D—Slightly shiny silver-white. Processing technology: hot rolling + annealing shot peening pickling + cold rolling + annealing pickling.
2B—Silver white and better gloss and flatness than 2D surface. Processing technology: hot rolling + annealing shot peening pickling + cold rolling + annealing pickling + tempering rolling.
BA—The surface has excellent gloss and high reflectivity, just like the surface of a mirror. Processing technology: hot rolling + annealing shot peening pickling + cold rolling + annealing pickling + surface polishing + tempering rolling.
No.3—has good gloss and rough surface. Processing technology: 100~120 abrasive materials (JIS R6002) for 2D or 2B products are polished and tempered and rolled.
No.4—has good gloss and fine lines on the surface. Processing technology: polishing and tempering rolling of 150~180 abrasive materials (JIS R6002) for 2D or 2B products.
HL—Silver gray with hairline stripes. Processing technology: 2D or 2B products are polished with an abrasive material of appropriate granularity to make the surface continuously abrasive.
MIRRO—in a mirror surface state. Processing technology: Grind and polish 2D or 2B products with an abrasive material of appropriate grain size to a mirror surface effect.
Material characteristics
430 stainless steel has the ability to resist oxidation to corrosion, but has a tendency to intergranular corrosion.
430 stainless steel wire is widely used in the axis.
Because it is safe and non-toxic, it is widely used in food tableware.
Stainless steel knowledge
Stainless steel refers to steel that is resistant to weak corrosive media such as air, steam, and water, and chemically corrosive media such as acids, alkalis, and salts. It is also called stainless acid-resistant steel. In practical applications, steel that is resistant to corrosion by weak corrosive media is often called stainless steel, and steel that is resistant to chemical media is called acid-resistant steel. Due to the difference in chemical composition between the two, the former is not necessarily resistant to corrosion by chemical media, while the latter is generally non-corrosive. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel.
Stainless steel type
Stainless steel is often divided into martensitic steel, ferritic steel, austenitic steel, etc. according to the state of organization. In addition, it can be divided into chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel according to the composition.
1. Ferritic stainless steel:
Containing 12% to 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its resistance to chloride stress corrosion is better than other types of stainless steel.
Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28, etc. belong to this category. Because of its high chromium content, ferritic stainless steel has good corrosion resistance and oxidation resistance, but its mechanical properties and process properties are poor. It is mostly used for acid-resistant structures with little stress and as anti-oxidation steel. This type of steel can resist corrosion from the atmosphere, nitric acid and salt solutions, and has the characteristics of good high-temperature oxidation resistance and low thermal expansion coefficient. It is used in nitric acid and food factory equipment, and can also be used to make parts that work at high temperatures, such as gas turbine parts, etc. .
2. Austenitic stainless steel:
The chromium content is more than 18%, and it also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistant to corrosion by various media. Commonly used grades of austenitic stainless steel are 1Cr18Ni9, 0Cr19Ni9 and so on. The wC of 0Cr19Ni9 steel is less than 0.08%, and the steel number is marked as “0”. This type of steel contains a large amount of Ni and Cr, making the steel austenitic at room temperature. This type of steel has good plasticity, toughness, weldability and corrosion resistance. It has good corrosion resistance in oxidizing and reducing media. It is used to make acid-resistant equipment, such as corrosion-resistant containers and equipment linings, pipelines, and Nitric acid equipment parts, etc. Austenitic stainless steel generally adopts solution treatment, that is, the steel is heated to 1050~1150℃, and then water-cooled to obtain a single-phase austenite structure.
3. Austenitic-ferritic duplex stainless steel:
It has the advantages of austenitic and ferritic stainless steel, and has superplasticity.
Austenitic and ferritic structures each account for about half of stainless steel. In the case of low C content, the Cr content is 18% to 28%, and the Ni content is 3% to 10%. Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, and N. This type of steel has the characteristics of austenitic and ferritic stainless steel. Compared with ferrite, it has higher plasticity and toughness, no room temperature brittleness, and significantly improved intergranular corrosion resistance and welding performance, while still maintaining iron The 475℃ brittleness, high thermal conductivity, and superplasticity of element stainless steel. Compared with austenitic stainless steel, it has high strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel-saving stainless steel.
4. Martensitic stainless steel:
High strength, but poor plasticity and weldability.
The commonly used grades of martensitic stainless steel are 1Cr13, 3Cr13, etc. Because of the higher carbon content, it has higher strength, hardness and wear resistance, but the corrosion resistance is slightly worse. It is used for higher mechanical properties and corrosion resistance. Some general parts are required, such as springs, steam turbine blades, hydraulic valves, etc. This type of steel is used after quenching and tempering.
Stainless steel adjustment calculation formula
Stainless steel bar weight = diameter mm * diameter mm * 0.00623 = kg/m
Stainless steel hexagonal bar weight = opposite side mm × opposite side mm × 0.0069 = kg/m
Stainless steel block/plate weight=length m*width m*height mm*7.93 (201 202 301 302 304 304L 305 310 321) = total weight (kg)
Length m*width m*height mm*7.98 (309S 310S 316 316L 347) = total weight (kg)
Length m*width m*height mm*7.75 (405 410 420) = total weight (kg)
Length m*width m*height mm*7.70 (409 430 434) = total weight (kg)
Stainless steel square bar/flat steel weight=side width (thickness) mm*side width mm*0.00793=kg/m
Stainless steel pipe weight = (outer diameter mm-wall thickness mm) * wall thickness mm * 0.02491 = kg/m
Stainless steel angle steel weight = side length mm* side length mm*7.8*0.000198=kg/m
Stainless steel rectangular tube weight=(length mm+width mm)*2/1000*thickness mm*7.93=kg/m
Stainless steel square tube weight = (side length mm*4/3.14-thickness mm)*thickness mm*0.02491=kg/m
Common types
Austenite
301, 302, 303, 303se, 304, 304L, 304N1, 304N2, 304LN, 305, 309S, 310S, 316, 316L, 316N, 316J1, 316J1L, 317, 317L, 317J1, 321, 347, XM7, XM15J1
Ferrite
405, 430, 430F, 434, 447J1, 403
Martensite
410, 410L, 405, 416, 410J1, 420J1, 420J2, 420F, 431, 440A, 440B, 440C, 440F, 630, 631, 632
There is also a kind of stainless steel, 201, 202, 203, 204, which has low chromium content and high manganese content. (High chromium can increase corrosion resistance, and high manganese can make the material non-magnetic). This type of stainless steel has poor corrosion resistance and is generally used in dry environments. For decoration.
Stainless steel effect
Stainless steel will not produce corrosion, pitting, rust or wear. Stainless steel is also one of the strongest materials among the metal materials used in construction. Because stainless steel has good corrosion resistance, it can make structural components permanently maintain the integrity of the engineering design. Chromium-containing stainless steel also integrates mechanical strength and high extensibility, and is easy to process and manufacture parts, which can meet the needs of architects and structural designers.
Typical use of stainless steel
Most of the requirements for use are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to be selected, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be adopted.
However, other applications are increasingly seeking structural integrity or impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner’s construction cost may be more important than the aesthetics, and the surface may not be very clean.
The effect of using 304 stainless steel in a dry indoor environment is quite good. However, if you want to maintain its appearance outdoors in the countryside and cities, you need to wash it frequently. In heavily polluted industrial areas and coastal areas, the surface will be very dirty and even rusty. However, to obtain the aesthetic effect in the outdoor environment, nickel-containing stainless steel is required.
Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs and other construction purposes. However, 316 stainless steel is best used in severely corrosive industries or marine atmospheres.
Stainless steel sliding door
People have fully realized the advantages of using stainless steel in structural applications. There are several design criteria that include 304 and 316 stainless steel. Because “duplex” stainless steel 2205 has integrated good atmospheric corrosion resistance with high tensile strength and elastic limit strength, this steel is also included in the European standards.
Product shape
In fact, stainless steel is manufactured in full-standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of thin plates and strip steel, and medium and heavy plates are also used to produce special products, such as the production of hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded pipes or seamless steel pipes and other forms of products, including profiles, bars, wires and castings.
Surface condition of stainless steel
As will be discussed later, in order to meet the aesthetic requirements of architects, many different commercial surface finishes have been developed. For example, the surface can be highly reflective or matte; it can be smooth, polished or embossed; it can be colored, colored, electroplated, or patterned on the surface of stainless steel, or it can be drawn. To meet the various requirements of designers for appearance.
It is easy to maintain the surface condition. Only occasional rinsing can remove dust. Due to its good corrosion resistance, it is also possible to easily remove graffiti contamination or other similar surface contamination on the surface.
The following methods are often used in engineering to prevent intergranular corrosion:
(1) Reduce the amount of carbon in the steel so that the carbon content in the steel is lower than the saturated solubility in the austenite in the equilibrium state, which fundamentally solves the problem of the precipitation of chromium carbides (Cr23C6) on the grain boundaries . Generally, the amount of combined carbon in steel can be reduced to less than 0.03% to meet the requirements of intergranular corrosion resistance.
(2) Adding elements such as Ti and Nb that can form stable carbides (TiC or NbC) to avoid precipitation of Cr23C6 on the grain boundaries can prevent intergranular corrosion of austenitic stainless steel.
(3) By adjusting the ratio of austenite-forming elements to ferrite-forming elements in the steel, it has a dual-phase structure of austenite + ferrite, in which ferrite accounts for 5% to 12%. This two-phase structure is not easy to produce intergranular corrosion.
(4) The use of appropriate heat treatment process can prevent intergranular corrosion and obtain the best corrosion resistance.
Stress corrosion of austenitic stainless steel
Stress corrosion of austenitic stainless steel
The cracking caused by the combined action of stress (mainly tensile stress) and corrosion is called stress corrosion cracking, or SCC (Stress Crack Corrosion) for short. Austenitic stainless steel is prone to stress corrosion in corrosive media containing chloride ions. When the Ni content reaches 8%-10%, the stress corrosion tendency of austenitic stainless steel is the largest. Continue to increase the Ni content to 45-50% and the stress corrosion tendency gradually decreases until it disappears.
The most important way to prevent stress corrosion of austenitic stainless steel is to add Si2~4% and control the N content below 0.04% from the smelting. In addition, the content of impurities such as P, Sb, Bi, and As should be minimized. In addition, A-F dual-phase steel can be used, which is not sensitive to stress corrosion in Cl- and OH- media. When the initial microcracks meet the ferrite phase, they will not continue to grow, and the ferrite content should be about 6%.
Deformation strengthening of austenitic stainless steel
Single-phase austenitic stainless steel has good cold deformation properties and can be cold drawn into very thin steel wires and cold rolled into very thin steel strips or steel tubes. After a large amount of deformation, the strength of the steel is greatly improved, especially when rolling in the sub-zero temperature zone, the effect is more significant. The tensile strength can reach more than 2000 MPa. This is because in addition to the cold work hardening effect, deformation induced M transformation is also superimposed.
Austenitic stainless steel can be used to make stainless springs, clock springs, steel wire ropes in aerospace structures, etc. after being deformed and strengthened. If welding is required after deformation, spot welding can only be used, and deformation will increase the stress corrosion tendency. And because of the partial γ->M transition, ferromagnetism is produced, which should be considered when using it (such as in instrument parts).
The recrystallization temperature changes with the amount of deformation. When the amount of deformation is 60%, the recrystallization temperature drops to 650℃. The recrystallization and annealing temperature of cold deformed austenitic stainless steel is 850~1050℃. At 850℃, it needs to be held for 3h, 1050℃ It can be burned at once, and then cooled with water.
Heat treatment of austenitic stainless steel
Commonly used heat treatment processes for austenitic stainless steel include: solution treatment, stabilization treatment and stress relief treatment.
(1) Solution treatment. The steel is heated to 1050~1150℃ and then water quenched. The main purpose is to dissolve the carbide in austenite and keep this state to room temperature, so that the corrosion resistance of the steel will be greatly improved. As mentioned above, in order to prevent intergranular corrosion, solid solution treatment is usually used to dissolve Cr23C6 in austenite, and then rapidly cool. Air cooling can be used for thin-walled parts, and water cooling is generally used.
(2) Stabilization treatment. It is usually carried out after solution treatment, which is usually used for 18-8 steel containing Ti and Nb. After solidification treatment, heat the steel to 850~880℃ and then cool it in air. At this time, the carbides of Cr are completely dissolved and the titanium is removed. The carbide is not completely dissolved, and it is found out during the cooling process that it is impossible for the carbon to form chromium carbides, thus effectively eliminating the intergranular corrosion.
(3) Stress relief treatment. Stress relief treatment is a heat treatment process that eliminates the residual stress of steel after cold working or welding. Generally, it is heated to 300~350℃ and tempered. For steels that do not contain stabilizing elements Ti and Nb, the heating temperature should not exceed 450°C to avoid precipitation of chromium carbides and cause intergranular corrosion. For ultra-low carbon and cold-worked parts and welded parts of stainless steel containing Ti and Nb, heating at 500~950℃, and then slow cooling, to eliminate stress (elimination of welding stress takes the upper limit temperature), which can reduce the tendency of intergranular corrosion and improve the steel The stress corrosion resistance.
Austenitic-ferritic duplex stainless steel
On the basis of austenitic stainless steel, appropriately increase the Cr content and reduce the Ni content, and cooperate with the remelting treatment to obtain a dual-phase structure with austenite and ferrite (containing 40~60% δ-ferrite ) Stainless steel, typical steel grades are 0Cr21Ni5Ti, 1Cr21Ni5Ti, OCr21Ni6Mo2Ti, etc. Duplex stainless steel has good weldability, does not require heat treatment after welding, and its tendency to intergranular corrosion and stress corrosion is also small. However, due to the high Cr content, σ phase is easily formed, so care should be taken when using it.
Ferritic stainless steel
Its internal microstructure is ferrite, and the mass fraction of chromium is in the range of 11.5%~32.0%. With the increase of chromium content, its acid resistance also improves. After adding molybdenum (Mo), the acid corrosion resistance and stress corrosion resistance can be improved. The national standard grades of this type of stainless steel are 00Cr12, 1Cr17, 00Cr17Mo, 00Cr30Mo2, etc.
Martensitic stainless steel
Its microstructure is martensite. The mass fraction of chromium in this type of steel is 11.5%~18.0%, but the mass fraction of carbon can reach up to 0.6%. The increase in carbon content improves the strength and hardness of steel. A small amount of nickel added to this type of steel can promote the formation of martensite and at the same time improve its corrosion resistance. This type of steel has poor weldability. The steel plates listed in the national standard grades include 1Cr13, 2 Cr13, 3 Cr13, 1 Cr17Ni2 and so on.
Austenitic stainless steel
Its microstructure is austenite. It is formed by adding appropriate nickel (the mass fraction of nickel is 8% to 25%) in high chromium stainless steel, and it is a stainless steel with austenitic structure. The austenitic stainless steel is based on the Cr18Ni19 iron-based alloy. On this basis, with different uses, it has developed into the chromium-nickel austenitic stainless steel series shown in Figure 1-2.
Austenitic stainless steel generally belongs to corrosion-resistant steel and is the most widely used type of steel. Among them, 18-8 stainless steel is the most representative. It has good mechanical properties and is convenient for machining, stamping and welding. It has excellent corrosion resistance and good heat resistance in oxidizing environment. But it is particularly sensitive to the medium containing chloride ions (CL-) in the solution and is prone to stress corrosion. 18-8 type stainless steel is divided into three grades according to the carbon content in its chemical composition: general carbon content (Wc≤0.15%) low carbon grade
(Wc≤0.08%) and ultra-low carbon grade (Wc≤0.03%). For example, the three steel plates 1Cr18Ni9Ti, 0Cr18Ni9, 00Cr17Ni14M02 in my country’s national standards belong to the above three grades. Many countries in the world feel the shortage of nickel reserves. In order to save nickel, as early as the 1940s and 1950s, the world began to use manganese and nitrogen to replace part of the nickel in 18-8 stainless steel. The steel plates developed and listed in the national standards include 1Cr17Mn6Ni5N and 0Cr19Ni9N.
Austenitic-ferritic stainless steel
Its microstructure is austenite plus ferrite. Stainless steel with a ferrite volume fraction of less than 10% is a steel type developed on the basis of austenitic steel.
Precipitation hardening stainless steel
According to its structure, it can be divided into three categories: precipitation hardening semi-austenitic stainless steel, precipitation hardening martensitic stainless steel and precipitation hardening austenitic stainless steel. Included in my country’s national standard steel plate grades are 0Cr17Ni7A, 0Cr17Ni4Cu4Nb and 0Cr15Ni7M02Al, which are precipitation hardening semi-austenitic stainless steels. The structure of the steel is characterized by austenite plus ferrite with a volume fraction of 5% to 20% in the solid solution or annealed state. This kind of steel undergoes a series of heat treatment or mechanical deformation treatment, the austenite is transformed into martensite, and then through aging precipitation hardening to achieve the required high strength. This kind of steel has good formability and good weldability, and can be used as an ultra-high-strength material in the nuclear industry, aviation and aerospace industries.
Stainless steel future outlook
As stainless steel has many ideal properties required by building materials, it can be said to be unique among metals, and its development continues. In order to make stainless steel perform better in traditional applications, the existing types have been improved, and in order to meet the strict requirements of advanced construction applications, new stainless steels are being developed. Due to continuous improvement in production efficiency and continuous improvement in quality, stainless steel has become one of the most cost-effective materials chosen by architects. Stainless steel combines performance, appearance and use characteristics, so stainless steel will still be one of the best building materials in the world.
410 stainless steel
410 stainless steel is a stainless steel grade produced in accordance with the American ASTM standard, which is equivalent to my country’s 1Cr13 stainless steel, S41000 (American AISI, ASTM). It contains 0.15% carbon and 13% chromium.
410 stainless steel:
Has good corrosion resistance, machinability, general purpose blades, valves.
410 stainless steel heat treatment:
Solution treatment (℃) 800-900 slow cooling or 750 fast cooling.
410 stainless steel chemical composition:
C≤0.15, Si≤1.00, Mn≤1.00, P≤0.035, S≤0.030, Cr=11.50~13.50.
Marking method
The American Iron and Steel Institute uses three digits to indicate various standard grades of forgeable stainless steel. in:
①Austenitic chromium-nickel-manganese type is 200 series, such as 201,202;
②Austenitic chromium-nickel type is 300 series, such as 301, 302, 304, 304L, 316, 316L, etc.;
③Ferritic and martensitic stainless steels are 400 series, such as 405, 410, 443, etc.;
④The heat-resistant chromium alloy steel is 500 series,
⑤Martensite precipitation hardening stainless steel is 600 series.
Features
1) High strength;
2) Excellent machinability
3) Hardening occurs after heat treatment;
4) Magnetic;
5) Not suitable for harsh corrosive environment.
3. Scope of application
General blades, mechanical parts, class 1 tableware (spoon, fork, knife, etc.).
Chemical parameters
Reference standard: JIS G 4305-2005
| chemical composition | C | Si | Mn | P | S | Cr |
| standard | 0.15 | 1 | 1 | 0.04 | 0.03 | 11.5~13.5 |
| generally | 0.045 | 0.45 | 0.5 | 0.02 | 0.001 | 13. 0 |
Physical parameter
| Density (g/cm) | Magnetism | Specific heat 25℃(J/kg.℃) | Thermal conductivity 100℃(W/m.℃) | Thermal expansion rate 20~100℃(10/℃) |
| 7.7 | have | 460 | 24.9 | 9.9 |
Mechanical parameters
Reference standard: JIS G 4305-2005
| distinguish | Mechanical properties | Remark | |||
| Ys (Mpa) | Ts (Mpa) | El (%) | Hv | ||
| standard | ≥ 205 | ≥ 440 | ≥ 20 | ≤ 210 | NO.2B/1.2t |
| generally | 260 | 470 | 30 | 145 | |
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