304 stainless steel grade: 0Cr18Ni9 (0Cr19Ni9) 06Cr19Ni9 S30408
Chemical composition: C: ≤0.08, Si: ≤1.0 Mn: ≤2.0, Cr: 18.0～20.0, Ni: 8.0～10.5, S: ≤0.03, P: ≤0.035 N≤0.1.
304L is more corrosion resistant and 304L contains less carbon.
304 is widely used, with good corrosion resistance, heat resistance, low temperature strength and mechanical properties; good hot workability such as stamping and bending, and no heat treatment hardening phenomenon (non-magnetic, service temperature -196°C~800°C).
304L has excellent resistance to grain boundary corrosion after welding or stress relief; it can also maintain good corrosion resistance without heat treatment, and the service temperature is -196°C-800°C.
According to the production method, it can be divided into two types: hot rolling and cold rolling, and can be divided into 5 types according to the structural characteristics of steel types: austenitic type, austenite-ferritic type, ferritic type, martensitic type, and precipitation hardening type. It is required to be able to withstand the corrosion of various acids such as oxalic acid, sulfuric acid-ferric sulfate, nitric acid, nitric acid-hydrofluoric acid, sulfuric acid-copper sulfate, phosphoric acid, formic acid, acetic acid, etc. It is widely used in chemical industry, food, medicine, papermaking, petroleum, atomic energy, etc. Industry, as well as construction, kitchen utensils, tableware, vehicles, various parts of household appliances.
The stainless steel plate has a smooth surface, high plasticity, toughness and mechanical strength, and is resistant to corrosion by acids, alkaline gases, solutions and other media. It is an alloy steel that is not easy to rust, but it is not absolutely rust-free.
Stainless steel plate According to the production method, it can be divided into two types: hot rolling and cold rolling, including thin cold plate with a thickness of 0.02-4 mm and medium and thick plate with a thickness of 4.5-100 mm.
In order to ensure that the mechanical properties such as yield strength, tensile strength, elongation and hardness of various stainless steel plates meet the requirements, the steel plates must undergo heat treatment such as annealing, solution treatment, and aging treatment before delivery. 05.10 126.96.36.199 special symbols
The corrosion resistance of stainless steel mainly depends on its alloy composition (chromium, nickel, titanium, silicon, aluminum, etc.) and internal structure, and the main role is chromium. Chromium has high chemical stability and can form a passivation film on the steel surface to isolate the metal from the outside world, protect the steel plate from oxidation, and increase the corrosion resistance of the steel plate. After the passivation film is destroyed, the corrosion resistance decreases.
National standard nature：
Tensile strength (Mpa) 520
Yield strength (Mpa) 205-210
Elongation (%) 40%
Hardness HB187 HRB90 HV200
The density of 304 stainless steel is 7.93 g/cm3. Austenitic stainless steel generally uses this value. 304 chromium content (%) 17.00-19.00, nickel content (%) 8.00-10.00, 304 is equivalent to my country’s 0Cr19Ni9 (0Cr18Ni9) stainless steel
304 stainless steel is a versatile stainless steel material, and its anti-rust performance is stronger than that of 200 series stainless steel materials. High temperature resistance is also better.
304 stainless steel has excellent stainless corrosion resistance and better resistance to intergranular corrosion.
For oxidizing acids, it is concluded in experiments that 304 stainless steel has strong corrosion resistance in nitric acid below the boiling temperature with a concentration of ≤65%. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids.
304 stainless steel plate has beautiful surface and diversified use possibilities
Good corrosion resistance, better corrosion resistance than ordinary steel
High strength, so the possibility of thin plate use is great
Resistant to high temperature oxidation and high strength, thus resistant to fire
Normal temperature processing, that is, easy plastic processing
Simple and easy maintenance because no surface treatment is required
clean, high finish
Good welding performance
1，Dry grinding brushed
The most common ones on the market are long wire and short wire. After processing such a surface, 304 stainless steel plate shows a good decorative effect, which can meet the requirements of general decorative materials. Generally speaking, 304 series stainless steel can form a good effect after one scrub. Due to the low cost, simple operation, low processing cost and wide application of this kind of processing equipment, it has become a necessary equipment for processing centers. Therefore, most machining centers can provide long-wire and short-wire frosted plates, of which 304 steel accounts for more than 80%.
2, oil mill drawing
The 304 family stainless steel shows a perfect decorative effect after oil grinding, and is widely used in decorative panels such as elevators and home appliances. Cold-rolled 304 series stainless steel can generally achieve good results after one frosting pass. There are still some processing centers on the market that can provide oily frosting for hot-rolled stainless steel, and its effect is comparable to that of cold-rolled oil grinding. Oily drawing can also be divided into long filament and short filament. Filament is generally used for elevator decoration, and there are two kinds of textures for various small household appliances and kitchen utensils.
Difference from 316
The two most commonly used stainless steels 304 and 316 (or corresponding to German/European standard 1.4308, 1.4408), the main difference in chemical composition between 316 and 304 is that 316 contains Mo, and it is generally recognized that 316 has better corrosion resistance. It is more corrosion resistant than 304 in high temperature environment. Therefore, in high temperature environments, engineers generally choose parts made of 316 materials. But the so-called nothing is absolute, in the concentrated sulfuric acid environment, do not use 316 no matter how high the temperature is! Otherwise, this matter may become a big deal. Anyone who studies mechanics has learned threads, and remember that in order to prevent the threads from being seized at high temperatures, a dark solid lubricant needs to be applied: molybdenum disulfide (MoS2), from which 2 points are drawn The conclusion is not:  Mo is indeed a high temperature resistant substance (do you know what crucible is used to melt gold? Molybdenum crucible!). : Molybdenum easily reacts with high-valent sulfur ions to form sulfide. So there is no one kind of stainless steel that is super invincible and corrosion-resistant. In the final analysis, stainless steel is a piece of steel with more impurities (but these impurities are more corrosion-resistant than steel^^), and steel can react with other substances.
Surface Quality Inspection：
The surface quality of 304 stainless steel is mainly determined by the pickling process after heat treatment. If the surface oxide skin formed by the previous heat treatment process is thick or the structure is uneven, pickling cannot improve the surface finish and uniformity. Therefore, full attention should be paid to the heating of heat treatment or the surface cleaning before heat treatment.
If the surface oxide thickness of the stainless steel plate is not uniform, the surface roughness of the base metal under the thick place and the thin place is also different. Different, so the surface of the steel plate is uneven. Therefore, it is necessary to uniformly form oxide scales during heat treatment and heating. To meet this requirement, attention must be paid to the following issues:
If oil is attached to the surface of the workpiece when the stainless steel plate is heated, the thickness and composition of the oxide scale at the oil-attached part will be different from the thickness and composition of the oxide scale at other parts, and carburization will occur. The carburized part of the base metal under the oxide skin will be severely attacked by acid. The oil droplets sprayed out by the heavy oil burner during the initial combustion will also have a great impact if they are attached to the workpiece. It can also have an effect when the operator’s fingerprints are attached to the workpiece. Therefore, the operator should not directly touch the stainless steel parts with his hands, and do not allow the workpiece to be stained with new oil. Clean gloves must be worn.
If there is lubricating oil attached to the surface of the workpiece during cold processing, it must be fully degreased in trichlorethylene degreasing agent and caustic soda solution, then cleaned with warm water, and then heat treated.
If there are impurities on the surface of the stainless steel plate, especially when organic matter or ash is attached to the workpiece, heating will of course affect the scale.
Differences in the atmosphere in the stainless steel plate furnace The atmosphere in the furnace is different in each part, and the formation of oxide skin will also change, which is also the reason for the unevenness after pickling. Therefore, when heating, the atmosphere in each part of the furnace must be the same. To this end, the circulation of the atmosphere must also be considered.
In addition, if the bricks, asbestos, etc. that make up the platform used to heat the workpiece contain water, the water will evaporate when heated, and the atmosphere of the part directly in contact with water vapor will be different from that of other parts. just different. Therefore, objects that are in direct contact with the heated workpiece must be fully dried before use. However, if it is placed at room temperature after drying, moisture will still condense on the surface of the workpiece under high humidity conditions. So, it is best to dry it before use.
If the part of the stainless steel plate to be treated has residual scale before heat treatment, there will be differences in the thickness and composition of the scale between the part with residual scale and the part without scale after heating, resulting in uneven surface after pickling , so not only should we pay attention to the final heat treatment, but we should also pay full attention to the intermediate heat treatment and pickling.
There is a difference in the oxide scale produced on the stainless steel surface that is in direct contact with the gas or oil flame and the place that is not in contact. Therefore, it is necessary to keep the treatment piece from directly contacting the flame mouth during heating.
Effect of different surface finish of stainless steel plate
If the surface finish is different, even if it is heated at the same time, the oxide scales on the rough and fine parts of the surface will be different. For example, in the place where the local defect has been cleaned and the place where it has not been cleaned, the situation of forming oxide skin is different, so the surface of the workpiece after pickling is uneven.
The overall heat transfer coefficient of a metal depends on other factors besides the thermal conductivity of the metal. In most cases, the heat dissipation coefficient of the film, the scale and the surface condition of the metal. Stainless steel keeps the surface clean, so it transfers heat better than other metals with higher thermal conductivity. Liaocheng Suntory Stainless Steel provides 8. Technical standards for stainless steel plates High-strength stainless steel plates with excellent corrosion resistance, bending performance, toughness of welded parts, and stamping performance of welded parts and their manufacturing methods. Specifically, C: 0.02% or less, N: 0.02% or less, Cr: 11% or more and less than 17%, appropriate content of Si, Mn, P, S, Al, Ni, and satisfy 12≤Cr Mo 1.5Si≤ 17. The stainless steel plate with 1≤Ni 30(C N) 0.5(Mn Cu)≤4, Cr 0.5(Ni Cu) 3.3Mo≥16.0, 0.006≤C N≤0.030 is heated to 850～1250°C, and then carried out at 1°C/s Heat treatment for cooling above the cooling rate. In this way, it can become a high-strength stainless steel plate with a structure containing more than 12% martensite by volume, high strength above 730MPa, corrosion resistance and bending performance, and excellent toughness in the welding heat-affected zone. Reusing Mo, B, etc. can significantly improve the stamping performance of the welded part. The flame of oxygen and gas cannot cut stainless steel plate because stainless steel is not easy to be oxidized. 5CM thick stainless steel plate should be processed with special cutting tools, such as: (1) Laser Cutting machine with larger wattage (laser cutting machine) (2) Oil pressure saw machine (3) Grinding disc (4) Human hand saw (5 )Wire Cutting machine (wire cutting machine). (6) High-pressure water jet cutting (professional water jet cutting: Shanghai Xinwei) (7) Plasma arc cutting
Post time: Mar-10-2023