Stainless steel processing technology, stainless steel heat treatment process

Summary. Pro, heat treatment process of stainless steel.

1. Normalizing of stainless steel pipes.

Normalizing is the heating of steel to a critical temperature. This is a heat treatment method that converts all the steel into homogeneous austenite and then cools it naturally in air. It can eliminate the reticulated cementite of the eutectic steel, and the crystal lattice can be refined for the normalization of sub-eutectic steel, and the comprehensive mechanical properties can be improved, and it is more economical to normalize instead of annealing process for parts with low requirements.

2. Quenching of stainless steel pipes.

Quenching is a heat treatment method in which the steel is heated above the critical temperature, kept warm for a period of time, and then quickly put into the quenching agent to reduce its temperature abruptly, and it is rapidly cooled at a speed greater than the critical cooling rate, and the unbalanced structure dominated by martensite is obtained. Quenching can increase the strength and hardness of the steel, but reduce its plasticity. The quenching agents commonly used in quenching are:

Water, oil, alkaline water and salt solutions, etc.

3. Tempering of stainless steel pipes.

Reheating the quenched steel to a certain temperature and then cooling it in a certain way is called tempering. Its purpose is to eliminate the internal stresses caused by quenching and reduce hardness and brittleness in order to achieve the desired mechanical properties. Tempering is divided into three categories: high-temperature tempering, medium-temperature tempering and low-temperature tempering.

Tempering is mostly used in conjunction with quenching and normalizing.

Heat treatment process for stainless steel.

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Pro, the heat treatment process of stainless steel 1, the normalizing of stainless steel pipe is to heat the steel to a critical temperature. This is a heat treatment method that converts all the steel into homogeneous austenite and then cools it naturally in air. It can eliminate the reticulated cementite of the eutectic steel, refine the crystal lattice for the normalizing of the sub-eutectic steel, improve the comprehensive mechanical properties, and it is more economical to normalize instead of annealing process for the parts that do not require high cavity requirements.

2. The quenching and quenching of stainless steel pipes is to heat the steel above the critical temperature, keep it warm for a period of time, and then quickly put it into the quenching agent to reduce its temperature suddenly, and cool it rapidly at a speed greater than the critical cooling rate. Quenching can increase the strength and hardness of the steel, but reduce its plasticity. The quenching agents commonly used in quenching are:

Water, oil, alkaline water and salt solutions, etc. 3. Tempering of stainless steel pipes. Reheating the quenched steel to a certain temperature and then cooling it in a certain way is called tempering.

Its purpose is to eliminate the internal stresses caused by quenching and reduce hardness and brittleness in order to achieve the desired mechanical properties. Tempering is divided into three categories: high-temperature tempering, medium-temperature tempering and low-temperature tempering. Tempering is mostly used in conjunction with quenching and normalizing.

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With the properties of stainless steel, stainless steel is sheared, bent, bent, welded and other mechanical processing.

The corrosion resistance of stainless steel decreases with the increase of carbon content, therefore, the carbon content of most stainless steels is low, the maximum is not exceeded, and the WC (carbon content) of some steels is even lower than that of e.g. 00Cr12).

The main alloying element in stainless steel is CR (chromium), and it is only when the CR content reaches a certain value that the steel is corrosion-resistant. Therefore, stainless steel generally has a cr (chromium) content of at least. Stainless steel also contains elements such as Ni, Ti, Mn, N, Nb, Mo, Si, and Cu.

1. Calendering and annealing.

This is a metal heat treatment process in which the workpiece is heated to a predetermined temperature, held for a certain period of time, and then slowly cooled. The purpose of annealing is to:

1) Improve or eliminate various structural defects and residual stresses caused by steel in the process of casting, forging, rolling and welding, and prevent deformation and cracking of the workpiece.

2) Softening of chemical parts for machining.

3) Refine the grain and improve the structure to improve the mechanical properties of the workpiece.

4) Prepare the organization for the final heat treatment and tube making.

2. Slitting. The slitting of stainless steel coil is to cut the stainless steel coil into the corresponding width, so as to carry out further deep processing and pipe making, the process of slitting needs to pay attention to the scratch of the slitting knife to the coil, the width and error of slitting, in addition to the slitting is related to the pipe making process, the slitting cloak and burr are very important for the pipe making process.

3. Welding. The most important process of stainless steel pipe, non-state leakage rapid rust steel mainly adopts argon arc welding and plasma welding, argon arc welding shielding gas is pure argon, mainly welding stainless steel pipes below 3mm, plasma welding has a strong penetrating force, mainly welding 5-8mm stainless steel pipe sails.

4. Weld bead grinding.

In the process of stainless steel pipe welding, it is necessary to carry out the corresponding polishing and water cooling treatment on the weld bead of the outer surface, after the water cooling of the weld bead is carried out first, the weld bead is directly polished with a water mill to a flat level, and 3-5 groups of water mills are added to the thickness of the stainless steel pipe to grind and trim the weld bead.

5. Plastic surgery. The process of stainless steel welded pipe is called extrusion production, all square pipes and rectangular pipes are originally made of round pipes, through the production of round pipes with the same circumference and then extruded into corresponding square pipes and rectangular pipes, and finally shaped and straightened with molds.

6. Cutting. The process of making and cutting stainless steel pipes is relatively rough, most of them are cut with grinding wheels, and a cloak will be produced after cutting, which needs to be further trimmed; In addition, one is band saw cutting, the accuracy is relatively good, and there is also a cloak heat treatment for special purpose pipes, which need to be brightly heat treated to make the duct reach a higher level.

7. Polishing. The usual product pipe and decorative pipe have several processes for surface treatment, polishing, divided into 400, and sand drawing is divided into round sand and straight sand, there are 180, which are suitable for the needs of customers at different levels.

8. Inspection. Inspection, mainly check whether the outer diameter and thickness of the pipe are up to standard, whether the surface treatment is up to standard, and whether the welding process is up to standard.

9. Packaging. For the packaging of rusty steel pipes, the most common is to use plastic bags for packaging, for strict surface requirements, you can choose sponge packaging, bubble bag packaging, woven bag packaging and other packaging processes.

10. Warehousing.

There are many specifications of stainless steel pipes, and stainless steel pipes are generally put on the shelves, which not only makes it easier to distinguish the specifications of Sohuai, but also reduces the land area.

Smelting is classified as pyrometallurgy, wet extraction, or electrochemical deposition

Pyrometallurgy: also known as dry metallurgy, the ore and the necessary additives are heated to high temperature in a furnace, melted into a liquid, and the required chemical reaction is generated to separate the crude metal, and then the crude metal is refined.

Wet metallurgy: Hydrometallurgy is a metallurgical process that uses aqueous solutions of acids, alkalis, and salts to chemically extract the required metal components from ores, and then uses various methods such as electrolysis of water solutions to prepare metals.

Chemical reaction: a metallurgical process that uses a certain solvent to extract and separate metals from raw materials with the help of chemical reactions (including oxidation, reduction, neutralization, hydrolysis and complexation).

1. Stainless steel crude steel smelting process.

At present, the smelting process of stainless steel in the world is mainly divided into one-step, two-step and three-step methods, as well as new integrated production methods. One-step smelting is: molten iron + AOD (argon oxygen refining furnace); The two-step method is:

EAF (Electric Arc Furnace) + AOD (Argon Oxygen Refinery). The three-step method is: EAF (Electric Arc Furnace) + AOD (Argon Oxygen Refining Furnace) + VOD (Vacuum Refining Furnace).

In addition to several traditional production processes, the current integrated production process, that is, the production process from molten iron directly to stainless steel, has also been adopted by many enterprises, and the production process is: RKEF (rotary kiln electric furnace) + AOD (argon oxygen refining furnace).

Second, stainless steel hot rolling process.

The stainless steel hot rolling process uses slabs (mainly continuous casting billets) as raw materials, which are heated by roughing mills and finishing mills to make strip steel. The hot steel strip from the last rolling mill is cooled to a set temperature by laminar flow, and is rolled into a steel coil by the coiler, and the cooled steel coil has an oxide scale on the outside, which is black, commonly known as "stainless steel black coil". After annealing and pickling, the oxidized surface is removed, that is, "stainless steel white coil", and most of the hot-rolled products circulating in the stainless steel market are stainless steel white coils.

The specific stainless steel hot rolling production process is as follows:

3. Stainless steel cold rolling process.

After the hot rolling of stainless steel, some of the hot rolled stainless steel products are directly used downstream, and some of the hot rolled products need to be processed into cold rolling before being used.

Stainless steel cold rolling, mostly using hot-rolled stainless steel hot-rolled products with a thickness of thickness, after calendering processing by cold-rolling equipment, produced into stainless steel cold-rolled products. At present, there are two main production processes of stainless steel cold rolling: stainless steel single-stand cold rolling and stainless steel multi-stand cold rolling.

The specific production process is shown in the following figure:

After the stainless steel has been cold-rolled, it needs to go through an annealing and pickling unit. The annealing of stainless steel after cold rolling is to achieve the purpose of softening by eliminating work hardening through the process of recrystallization; The purpose of pickling is to remove the oxide layer formed on the surface of the steel strip during the annealing process, and the second is to passivate the surface of the stainless steel to improve the corrosion resistance of the steel plate.