The purpose of the different requirement for welding performance are different. Kind of tableware generally do not require the performance of welding, even including some pot class enterprise. But the vast majority of products all need raw materials welding performance is good, like the 2 kinds of tableware, thermos flask, steel pipes, water heaters, water dispensers, etc.
The vast majority of stainless steel products for corrosion resistant performance is good, like 1, 2 kinds of tableware, kitchen utensils and appliances, water heaters, water dispensers, etc., some foreign businessmen on corrosion resistance of products also do experiment: in NACL aqueous solution heated to boiling, after a period of time out solution, wash and drying, weight loss, to determine the degree of corrosion (note: When the product is polished, Fe content in the emery cloth or sandpaper will lead to rust spots on the surface of the test.)
Stainless steel products in today’s society are generally polished when the production of this process, only a few products such as water heater, water dispener liner, do not need to be polished. So this requires that the polishing performance of raw materials is very good.
1.Surface defects of raw materials. Such as scratches, pitting, pickling and so on.
2.The problem of raw materials. The hardness is too low, it is not easy to shine when polishing (BQ is not good), and the hardness is too low, it is easy to appear orange peel phenomenon on the surface when deep drawing, thus affecting BQ. BQ with high hardness is relatively good.
3.After deep drawing, small black spots and RIDGING will appear on the surface of the products with great deformation, thus affecting the BQ property.
Smelting and casting
The raw materials that make up stainless steel products are put together and melted in a giant electric furnace. In this step, heat intensely for 8 to 12 hours. After melting, molten steel is cast into the desired semi-finished form. Some of the most common forms or shapes include slabs, billets (rectangles), billets (these can be round or square), bars and tubes.
In the second stage, the semi-finished section steel undergoes a series of molding operations. For example, stainless steel is hot-rolled (heated and passed through huge rollers). The billets and billets mentioned above are converted into bars and wires. A slab, on the other hand, forms a plate, strip, or sheet. It is very common to convert semi-finished steel profiles into bars because it is the most versatile stainless steel profile (it comes in all grades and sizes). You have round, square, octagonal and hexagonal bars, each suitable for different types of applications.
Various stainless steel forms undergo a thorough annealing process in this step. Annealing is another name for heat treatment, in which stainless steel is heated and cooled in a controlled environment. The purpose of this heat treatment is to relieve the pent-up stress in stainless steel and soften the material, making it more suitable for a variety of applications. The person responsible for performing the annealing process must be very careful about the conditions, as even small changes in temperature, pressure, duration or cooling rate can lead to product failure.
In addition to scale
In the annealing process, a certain amount of oxide skin will appear on the surface of stainless steel. A number of different processes can be used to remove this scale, collectively known as descaling. Pickling is one of the common methods for descaling.
Semi-finished, heat-treated and de-skinned stainless steel templates are cut to specific shapes in this step. Mechanical cutting is done with the help of guillotine knives, blanking, stepping and high-speed blades.
Finishing is used to help stainless steel products achieve their signature aesthetic appearance. Finishes are also needed to make stainless steel products smooth and easy to clean, which is the highest requirement in sanitary applications.
Stainless steel fabrication and (re) passivation
Steel is delivered to construction companies and artisans in a variety of forms — from rods to plates and plates.
Matters needing attention in stainless steel machining process:
stainless steel partsThe processing area should be relatively fixed. Protective measures should be taken for the platform in the processing area, such as laying rubber pads. Avoid damaging the surface protective layer of stainless steel when processing stainless steel parts.
Production is often in a dusty site, often with a lot of dust in the air, they continue to fall on the surface of the equipment. They can be removed with water or an alkaline solution. Adhesion grime, however, requires high-pressure water or steam to remove.
Depending on the thickness, the colors can be rainbow, blue, purple to light yellow and brown. Thicker oxides are usually black. It is caused by staying at high temperature or higher altitude for a long time. When these oxide layers exist, the chromium content on the metal surface decreases, resulting in the corrosion resistance of these areas. In this case, not only the hot coke discoloration layer and other oxide layers should be removed, but also the chromium poor metal layer below should be cleaned.
Rust sometimes appears on stainless steel products or equipment before or during production, indicating serious surface pollution. Rust must be removed before the equipment is put into use, and iron test and / or water test shall be carried out on the thoroughly cleaned surface.
Grinding and machining will produce rough surfaces, grooves, overlaps and burrs. Each defect may also damage the metal surface, so that the damaged metal surface cannot be removed by pickling, electropolishing or shot blasting (such as dry sand blasting, glass beads for abrasive). Rough surface may be the root cause of product corrosion and deposition. Before re welding, the weld defects shall be cleaned or the excess weld reinforcement shall be removed, and the rough grinding shall not be used for grinding. In the latter case, fine abrasives should be used again.
When the welder strikes an arc on the metal surface, it will cause surface roughness. The protective film is damaged, leaving a potential corrosion source. The welder shall strike an arc on the weld or the side of the weld. The arc is then fused into the weld.