FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD

FOSHAN FEROSTEEL CO., LTD
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09-26

Super September

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05-19

What is the purpose and requirements of bright annealing of stainless steel

Clear work hardening to obtain satisfactory metallographic structure     Bright annealing furnace is mainly used for heat treatment of stainless steel products under protective atmosphere. When the performance requirements are different, the requirements for the metallographic structure after bright annealing are different, and the process of bright heat treatment is also different.     The typical heat treatment process of 300 series austenitic stainless steel is solution treatment. During the temperature rise process, the carbide is dissolved into austenite, heated to 1050 ~ 1150 ℃, properly kept for a short time, so that the carbide is completely dissolved in the austenite, and then quickly cooled to below 350 ℃ to obtain a supersaturated solid solution that is uniform Unidirectional austenite structure. The key to this heat treatment process is rapid cooling, which requires a cooling rate of 55 ° C / s and quickly passes through the reprecipitation temperature range (550-850 ° C) after carbide solid solution. Keep the heat preservation time as short as possible, otherwise the grains will be coarse and affect the surface finish.     The heating temperature of 400 series ferritic stainless steel is relatively low (about 900 ℃), and slow cooling is often used to obtain annealed softening structure. Martensitic stainless steel is annealed, and it can also be quenched and tempered in sections.     It can be seen from the above that 300 series and 400 series stainless steels differ greatly in heat treatment system. To obtain a qualified metallographic structure, the cooling section of the bright annealing furnace requires a lot of room for adjustment. Therefore, modern advanced bright annealing furnaces often use strong convection cooling in their cooling section, with three cooling sections, which can adjust the air volume independently. It is divided into three sections along the width direction of the strip, and the cooling rate in the width direction of the strip is adjusted by the air flow diversion to control the plate shape.     Another key issue in the heat treatment of stainless steel cold-rolled strip is that the entire strip is required to be uniform in width and length. The muffle-type bright annealing furnace adopts a large-sized muffle tube, which uniformly organizes the heating airflow spirally from the outside of the muffle tube, so that the strip steel is heated evenly. In order to ensure the uniformity of the strip along the length, the linear velocity of the strip in the furnace must be kept constant. Therefore, before and after the modern vertical bright heat treatment furnace are equipped with roller tension adjustment device that can be precisely adjusted. It must not only make the speed of the steel strip import and export meet the requirements of the heat treatment speed, and is not affected by the empty or full sleeve of the looper. Claim.     Obtain an oxidation-free shiny surface     Bright annealing is the heat treatment of strip steel under H2 protective atmosphere. To meet the requirements of the BA board, the protective atmosphere in the furnace must be controlled very strictly to avoid oxidation as much as possible. How does oxidation occur under a protective atmosphere of H2     The main alloy components of stainless steel include Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, the oxidation of Fe and Ni is not the main problem. But the oxidation range of Cr, Mn, Si, Ti is just in the heating temperature range. It is the oxidation of these alloy elements that affects the surface brightness of the strip. In particular, the oxidation of chromium will dechromize the surface of the strip steel, which will reduce the corrosion resistance of stainless steel. When Cr content is 17% ~ 18% and Ti content is 0.5%, H2 dew point must be lower than -60 ℃, in order to avoid the oxidation of Cr and Ti in the heating range of 800C ~ 1150 ℃.     At the same time, how to maintain the purity of the protective gas in the furnace also needs attention. In this regard, the muffle cover has good sealing performance, and no pollution of the protective atmosphere such as the material of the electric heating furnace body will occur, providing a purer environmental space. In addition, the strip steel inlet and outlet of the vertical furnace are located at the lowermost part of the furnace, and the furnace pressure is stable, so the risk of air entry is much smaller than that of the horizontal furnace. However, the import and export sealed boxes of the bright annealing furnace, the strip conveying section, the tension adjustment roller and the furnace top guide roller box should ensure that the sealing requirements of parts per million (ppM level) are met, so that oxygen and water vapor cannot enter and protect the gas Can't let out.
05-19

Summary of brightening treatment methods for stainless steel mirror polishing

    When processing products, we generally adopt mechanical polishing, chemical polishing, electrochemical polishing and other methods to achieve the mirror stone gloss according to the complexity of stainless steel products and user requirements. The following describes the advantages and disadvantages of these three methods: Mechanical polishing: good leveling, bright labor intensity, serious pollution, difficult to process complex parts, gloss reduction, higher investment and cost Pieces, medium and small products, and complex pieces cannot be processed. The gloss of the whole product is not consistent, the gloss retention time is not long Chemical polishing: less investment, complex parts can be thrown away, high efficiency, fast speed, insufficient brightness, polishing liquid should be humidified, there is gas overflow, and suitable wind Equipment. For complex products, products with low brightness requirements can be more cost-effective for small batch processing Electrochemical polishing: achieve mirror gloss, long-term maintenance, stable process, less pollution, low cost, good anti-pollution. The one-time investment is large, the complicated parts need to be installed with tooling, auxiliary electrodes, mass production needs to cool down the dirt blocking products, and it is required to maintain the mirror light and bright products for a long time. The process is stable and easy to operate, Can be widely used Stainless steel coloring not only gives various colors of stainless steel products, increases the variety of products, but also improves the wear resistance and wear resistance of products. Stainless steel coloring methods are as follows: 1 ion deposition oxide or oxide. 2 High temperature oxidation method. 3 chemical oxidation method. Electrochemical oxidation method. 4 gas phase cracking method. A brief overview of the various methods is as follows: 1 Ion deposition oxide or oxide method is to place the stainless steel workpiece in a vacuum coating machine for vacuum evaporation plating: For example: titanium-plated watch case and watch band. Generally golden. This method is suitable for mass production. Because of the large investment and high cost, small batch products are not cost-effective. 2 High temperature oxidation method is to immerse the workpiece in a specific molten salt to maintain a certain process range, so that the workpiece forms a certain thickness of the oxide film, and shows a variety of different colors. 3 The chemical method is to form the color of the film through chemical oxidation in a specific solution. Generally, "the method can be used more, but to ensure that a batch of products have the same color, it must be controlled by reference telegram. 4 Electrochemical method is to form the color of the film by electrochemical oxidation in a specific solution, which is used in this business. 5 gas-phase cracking method is more complicated and less used in industry. For industrial products, mechanical polishing, chemical polishing, electrochemical polishing and other methods can be used to achieve the mirror stone gloss according to the complexity of stainless steel products and user requirements. The following describes the advantages and disadvantages of these three methods: Mechanical polishing: good leveling, bright labor intensity, serious pollution, difficult to process complex parts, gloss reduction, higher investment and cost Pieces, medium and small products, and complex pieces cannot be processed. The gloss of the whole product is not consistent, the gloss retention time is not long Chemical polishing: less investment, complex parts can be thrown away, high efficiency, fast speed, insufficient brightness, polishing liquid should be humidified, there is gas overflow, and suitable wind Equipment. For complex products, products with low brightness requirements can be more cost-effective for small batch processing Electrochemical polishing: achieve mirror gloss, long-term maintenance, stable process, less pollution, low cost, good anti-pollution. The one-time investment is large, the complicated parts need to be installed with tooling, auxiliary electrodes, mass production needs to cool down the dirt blocking products, and it is required to maintain the mirror light and bright products for a long time. The process is stable and easy to operate, Can be widely used Stainless steel coloring not only gives various colors of stainless steel products, increases the variety of products, but also improves the wear resistance and wear resistance of products. Stainless steel coloring methods are as follows: 1 ion deposition oxide or oxide. 2 High temperature oxidation method. 3 chemical oxidation method. Electrochemical oxidation method. 4 gas phase cracking method. A brief overview of the various methods is as follows: 1 Ion deposition oxide or oxide method is to place the stainless steel workpiece in a vacuum coating machine for vacuum
05-19

Stainless Steel Surface Treatment Technology

For all stainless steel and stainless steel, pickling and passivation is carried out to remove all kinds of oil stains, rust, oxide scale, welding spots and other dirt. After treatment, the surface becomes uniform silver white, which greatly improves the corrosion resistance of stainless steel and is suitable for various types of stainless steel parts , Plates and equipment. Features: Simple operation, easy to use, economical and practical. At the same time, high-efficiency corrosion inhibitors and fog inhibitors are added to prevent metal over-corrosion and hydrogen embrittlement, and to suppress the generation of acid mist. Especially suitable for small and complex workpieces, not suitable for the application of paste, better than similar products on the market. Usage: Depending on the stainless steel material and the scale of the scale, it can be diluted with water or diluted with water at a ratio of 1: 1 ~ 4; ferrite, martensite and austenitic stainless steel with low nickel content (such as 420, 430, 200, 201, 202, 300, 301, etc.) after dilution, austenitic stainless steel with high nickel content (such as 304, 321, 316, 316L, etc.) is soaked in the original solution; generally at room temperature or heated to 50 ~ 60 degrees After use, soak for 3-20 minutes or more (the specific time and temperature are determined by the user according to their own trial situation), until the surface dirt is completely removed, and it becomes uniformly silver-white and forms a uniform and dense passivation film. , Rinse with clean water.
05-19

Three steps of stainless steel etching

    The types of stainless steel are different, and the etching process is also different, but the general process is as follows: stainless steel erosion → degreasing → water washing → etching → water washing → dryness → screen printing → thousand dryness → water immersion 2 ~ 3min → etching pattern Text → Washing → Deinking → Washing → Pickling → Washing → Electrolytic Polishing → Washing → Dyeing or Electroplating → Washing → Hot Water Washing → Dryness → Soft Cloth Throw (Gloss) Light → Spray Clear Paint → Dryness → Inspection → Waste Packaging.     1. Disposal before etching     The processes before the stainless steel etching are pre-treatment. It is a key process to ensure that the screen printing ink has good adhesion to the stainless steel surface. Therefore, it is necessary to completely remove the oil stains and oxide films on the metal etching surface. Degreasing should be based on the oil pollution status of the work piece to make a plan, it is best to carry out electrical degreasing on the silk screen to ensure the effect of degreasing. In addition to the oxide film, the best etching solution should be selected according to the type of stainless steel and the thickness of the film to ensure that the appearance is clean. It should be dry before screen printing. If there is moisture, it will also affect the adhesion of the ink, and it will affect the effect of subsequent pattern etching and even aliasing, which will affect the decorative effect.     2. Screen printing     Screen printing should be based on the needs of printing manufacturing standard pattern screen printing screen. In the pattern decoration process, the silk screen is mainly used for maintenance, and the number of times when applying the photoresist is more, in order to make a thick screen template, so as to make the covering performance good, and the clarity of the etched pattern is high. Under the action of light, the screen film's adhesive film produces a photochemical reaction, so that the light is partially cross-linked into a water-insoluble adhesive film, but the unexposed light is partially dissolved by water to reveal the screen space, so that the silk film The screen is etched with a leaky pattern that matches the black and white positive sun pattern.       Fix the screen printing screen with pattern on the screen printing machine, use alkali-soluble acid-resistant ink to print the required pattern on the metal plate, and then stop etching after it is dry.     3. Disposal after etching     After etching, the screen printing ink must be removed. Ordinary acid-resistant ink is easily soluble in alkali. Immerse the etched board in a sodium hydroxide solution of 40-60g / L at a temperature of 50-80 ° C and immerse it for a few minutes to remove the ink. After the removal, if you request high brightness, you can stop polishing and then stop dyeing. In order to avoid discoloration and increase wear resistance and corrosion resistance after dyeing, you can spray transparent varnish. Some metals themselves have good corrosion resistance and are not stained, or they can be painted without transparent paint, depending on practical needs.
05-19

Stainless Steel Pickling Principle

    The corrosion resistance of stainless steel mainly depends on the surface passivation film. If the film is incomplete or defective, stainless steel will still be corroded. In engineering, pickling and passivation treatment is usually carried out to make the corrosion resistance of stainless steel play a greater role.     The corrosion resistance of stainless steel is mainly due to the surface covered with a very thin (about 1nm) dense passivation film. This layer of 1n corrosion medium isolation is the basic barrier for stainless steel protection. The passivation of stainless steel has dynamic characteristics. It should not be considered that the corrosion has completely stopped, but that it forms a diffusion barrier, which greatly reduces the anode reaction rate. Usually in the presence of reducing agents (such as chloride ions) tend to damage the membrane, and in the presence of oxidizing agents (such as air) can maintain or repair the membrane.     A stainless steel workpiece placed in the air will form an oxide film, but the protection of this film is not perfect. Generally, thorough cleaning is required, including alkaline cleaning and pickling, and then passivation with an oxidizing agent can ensure the integrity and stability of the passivation film. One of the purposes of pickling is to create favorable conditions for passivation treatment and ensure the formation of a high-quality passivation film. Because the surface of the stainless steel surface is corroded by an average of 10 μm by acid washing, the chemical activity of the acid solution makes the dissolution rate of the defective part higher than that of other parts on the surface, so the acid washing can make the entire surface tend to be evenly balanced. The hidden dangers that easily cause corrosion are eliminated.     But more importantly, through acid pickling and passivation, the iron and iron oxides are preferentially dissolved than the chromium and chromium oxides, and the chromium-depleted layer is removed, resulting in chromium enrichment on the surface of stainless steel. This chromium-rich passivation film The potential can reach + 1.0V (SCE), which is close to the potential of precious metals, which improves the stability of corrosion resistance. Different passivation treatments will also affect the composition and structure of the film, thereby affecting the rust. For example, through electrochemical modification, the passivation film can have a multilayer structure, forming CrO3 or Cr2O3 in the barrier layer, or forming a glassy state The oxide film allows stainless steel to exert maximum corrosion resistance.
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