Application of stainless steel in range hood

(According to the manufacturing method, it can be divided into hot rolling and cold rolling. The thickness of the thin plate is generally 0.5-4 mm, and the thickness of the thick plate is generally

At 4.5-35mm, it has higher toughness, plasticity and mechanical strength, resistance to acid and alkali gases, solutions and other

Corrosion of gas. The corrosion resistance of stainless steel mainly depends on its alloy composition and internal structure.

The main role is chromium. Chromium has high chemical stability and can form a passivation film on the surface of steel.

Protect the steel plate from oxidation and enhance the corrosion resistance of the steel plate. After the passivation film is destroyed, the corrosion resistance will be reduced.

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Types of stainless steel commonly used in range hoods

A. 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 others

Kind of stainless steel.

Crl7, Cr17Mo2Ti, Cr25, Cr25Mo3Ti, Cr28, etc. belong to this category. Ferritic stainless steel is resistant to corrosion due to its high chromium content

Corrosion performance and oxidation resistance are relatively good, but the mechanical performance and process performance are poor. It is mostly used for acid-resistant structures with little stress and as an antioxidant

Chemical steel use. This kind of steel can resist the corrosion of the atmosphere, nitric acid, and salt solution, and has good high-temperature oxidation resistance and low thermal expansion coefficient.

It can be 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.

B. Austenitic stainless steel:

Containing more than 18% chromium, 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. Oh

The commonly used grades of 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, and weldability

And corrosion resistance, good corrosion resistance in oxidizing and reducing media, used to make acid-resistant equipment, such as corrosion-resistant containers and equipment linings,

Conveying pipelines, nitric acid-resistant equipment parts, etc. Austenitic stainless steel generally adopts solution treatment, that is, heating the steel to 1050～1150℃,

Then water-cooled to obtain a single-phase austenite structure.

304—namely 18/8 stainless steel. The GB grade is 06Cr19Ni10.

200-Series-Chromium-Manganese-Nickel Austenitic Stainless Steel (202 201)

Forming method:

1. Cold forming

Cold bending is widely used in the production of stainless steel sheet and strip steel components. The punch is basically an open single-acting, mechanical or hydraulic drive, with a long and narrow worktable. This machine can only produce linear parts, but skilled tool designers can also use this machine to produce parts with complex shapes. The length of the parts produced by the cold bending press depends on the original type and thickness of the stainless steel, the power of the machine, and the size of the tools that can be installed.

Some large punch presses, such as the standard 900-ton cold-formed punch press with a length of 11 meters, can produce cold-formed austenitic stainless steel parts with a length of 9m and a thickness of 8.0mm. In order to minimize the abrasion of stainless steel, the tools of the cold bending press are usually made of hot work die steel with a chromium content of 12%, and plastic film can also be used as a further protective measure.

It is quite economical to use the general mold of a cold-formed press to produce small batches of general-purpose parts, but if a special mold is used to produce parts with special shape requirements, large batches are required to reduce mold processing costs to meet its economy.

2. Roll forming

The roll forming method is to roll stainless steel into products with complex shapes using a set of continuous racks, which is suitable for the production of plates and special-shaped wires. The sequence of the rolls is designed according to the principle of gradually deforming the product. The rolling mill adopts automatic control, and the roll profile of each stand can be rolled gradually and continuously until the desired final product shape is obtained.

If the shape of the component is complex, up to thirty-six racks can be used, but for simple-shaped components, three or four racks are sufficient. Rolls are often made of cold work die steel, and their hardness is generally HRC62

Above, at the same time, in order to ensure the smoothness of the workpiece surface after rolling, the requirements for the smoothness of the roll surface are also very high. The use of roll forming technology to produce large quantities of long parts is the most economical. For a conventional plate rolling mill, the width of the strip that can be processed is 2.5 mm to 1500 mm, and the thickness is 0.25 mm to 3.5 mm; for a conventional wire rolling mill, the width of the wire that can be processed is 1 mm to 30 mm, and the thickness is 0.25 mm to 3.5 mm. It is 0.5 mm～10mm.

The shapes of the parts processed by the roll forming method are diverse, from simple planes to complex, closed cross-sections.

Generally speaking, due to the high cost of cutting tools, mold processing, and equipment, it is economical to adopt a roll forming process when the monthly output of stainless steel plates is more than 30,000 meters, and the monthly output of stainless steel wire rods must reach more than 1,000T. Regardless of the rolling production of plates or wires, the surface of the raw materials must be guaranteed to be smooth and clean, and the surface of the mold must be checked regularly to prevent surface contamination and scratches.

The equipment also needs to withstand the cold work hardening of stainless steel and have a high rebound margin. Ability.

3. Stamping and forming

This technology uses punches and molds to produce the required product shapes. Domestic stainless steel stamping and forming production is common in stainless steel kitchenware manufacturers. Stainless steel pots and basins need to be deep drawn and the handles of kitchenware also need to be stamped, bent, and flattened. The punch can be mechanically driven or hydraulically driven, but it is best to use hydraulic transmission when deep drawing because the hydraulic punch can provide full load pressure over the full length of the stroke.

Most of the traditional techniques can be used for stamping and forming of stainless steel, but because the force required for stamping stainless steel is more than 60% greater than the force required for stamping mild steel, the frame of the punch press should be able to withstand such a large impact force. Moreover, it is also critical to solving the problem of scratches, especially the scratches on the surface of the workpiece caused by the high friction and high temperature when stamping stainless steel.

Commonly used soaps or emulsions are not effective. Special stamping lubricants or lubricants containing UHV additives should be used. However, because such UHV additives will corrode the surface of stainless steel, the workpiece should be removed after stamping and forming. Oil stains on the surface. Due to the high processing cost of stamping dies, stamping technology is only used in mass production.

4. Rubber gasket molding

The use of rubber gasket molding technology can greatly reduce the cost of mold processing and can be used to produce small batches of products. The molding machine used in this technology is made of low-cost materials, such as hardwood or reinforced epoxy resin as the male mold, and rubber pads to make the female mold. The rubber can be a solid rubber block or a layered rubber block, the depth of which is about 30% higher than the molding mechanism.

When the molding machine is closed, the rubber block squeezes the stainless steel blank into shape. When the molding machine is lifted, the rubber pad recovers, and the rubber pad can be used repeatedly. The process characteristics of molding with rubber gaskets determine that it cannot be used to produce products with complex shapes, and the maximum depth of the parts produced is also limited. This process is usually used to produce small batches of stainless steel parts with a thickness of less than 1.5mm.

5. Folding forming

As a simple bending machine, the folding machine can be manual or motorized. The simplest method is to use a model with a bending radius to firmly fix the steel plate on the machine tool table, and place the protruding part of the material on another table, which can rotate along the center of the bending radius. When the movable workbench rises, it bends the stainless steel to the required angle.

Obviously, when bending, the stainless steel slides on the workbench. Therefore, in order to prevent the stainless steel from being scratched, the surface of the workbench must be smooth. In the actual processing process,

Plastic film is usually used to protect the surface of stainless steel. The upper beam piece is usually wedge-shaped to form a gap so that it can be folded into a quadrilateral box or groove with a blank of an appropriate shape. Folding machines have been used to produce large-size and simple stainless steel sheet products, but these products are currently more produced by cold-formed punching machines.

6. Cylinder molding

The bending method is usually used to produce the cylinders or cylinder sections made of thin plates for various purposes. The traditional plate rolling machine has a pair of adjustable rollers, which can be adjusted according to the thickness of the steel plate. The third roller, the bending roller, controls the diameter of the forming cylinder. There is also a variant of this machine, which also uses three rollers, and the roller configuration is in the shape of a pagoda. The bottom roller is a driving roller, and the top roller is rotated by the friction between the top roller and the workpiece.

The diameter of the bottom roll is often half of the diameter of the top roll. The minimum diameter of the cylinder produced by the above two equipment is the diameter of the top roller plus 50mm.

The maximum diameter of the cylinder produced depends on the size of the incoming material, the rigidity of the machine and the molded part, and external support is required under special circumstances. To support the cylinder.

Application of stainless steel in range hood