Mirror finishing of stainless steel products involves polishing and grinding equipment using high-quality oilstones, diamond paste, and sandpaper of varying specifications. A process of rough, medium, and fine grinding is performed to achieve a smooth, glossy surface.

1. Grinding
Grinding stainless steel welded parts aims to remove weld spots, laying the foundation for subsequent finishing, and achieving a surface roughness of R10µm. This process involves multiple steps, including rough, semi-fine, and fine grinding.

First, the workpieces entering the polishing process undergo a thorough visual inspection to ensure there are no defects—such as missing welds, weld penetrations, uneven weld depths, excessive deviation from the joint, localized depressions, and misaligned joints—that cannot be corrected in subsequent processes. Only if these defects are eliminated can the workpiece proceed to the polishing process.

During the rough grinding stage, we use a 600# abrasive belt to perform a reciprocating grinding motion on three sides of the workpiece. The goal is to remove weld spots and dents, initially create a fillet at the weld corner, and ensure that there are no large scratches or dents on the horizontal and vertical surfaces. Next comes semi-finish grinding. In this step, we use an 800# abrasive belt to grind the workpiece on three sides using the same rough grinding method. This step primarily corrects seams and fine-grinds any rough grinding marks, striving for a scratch-free, bright surface.

Finally, fine grinding uses a 1000# abrasive belt to correct fine grain lines introduced by the previous step. The goal is to virtually eliminate the seam between the ground and unground areas, further improving the surface finish to a near-mirror finish.

2. Polishing
After the aforementioned grinding steps, the workpiece surface has reached a roughness of R10um. Next comes polishing. This step aims to further improve the surface finish to a mirror-like finish. During polishing, we use specialized polishing equipment and materials to meticulously polish the workpiece, ensuring a smooth, flawless surface.

The polishing step further polishes the previously polished stainless steel workpiece to a mirror-like finish. This process primarily involves two steps: waxing and buffing. During the waxing process, we use a high-speed motor-driven wool wheel with large blue wax, mimicking the previous polishing method, to mirror-finish the polished workpiece. Please note that this step is intended to polish, not further grind. Care should be taken to ensure that the polishing wax does not come into contact with the workpiece's surface film to avoid damaging it.

Buffing is the final step in the mirror polishing process. We rub the workpiece surface with a clean cotton wheel to remove all traces of the previous process, leaving the surface clean and bright. The goal of this step is to eliminate visible weld marks and polish the waxed and polished areas to a brightness of 8k mirror reflectivity, with no noticeable difference between the polished and unpolished areas, thus achieving a complete mirror finish.

In addition, the standard waxing procedure is to wax the wool wheel before polishing, and then begin polishing after the wool wheel is fully adhered to the blue wax.

The surface anti-corrosion layer of the plastic-coated and galvanized steel pipe is mainly composed of two parts: the inner plastic coating and the outer galvanized layer. These components each have different anti-corrosion properties, but they work together to enhance the corrosion resistance of the steel pipe.

1. Inner Plastic Coating
The inner plastic coating is typically applied using hot extrusion or chemical coating techniques to coat the interior of the steel pipe with thermoplastics such as polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP). The plastic coating's primary function is to isolate the steel pipe from direct contact with the internal media, preventing the penetration of corrosive media such as moisture and oxygen, thereby reducing the generation of corrosion sources.

2. Outer Galvanized Coating
The outer zinc coating is typically applied using a hot-dip galvanizing process, where the steel pipe is immersed in molten zinc to form a uniform zinc layer. This zinc layer offers excellent adhesion and corrosion resistance, shielding the steel pipe substrate from corrosive media in the environment. Zinc also has self-repairing capabilities. When microcracks appear in the coating, zinc will react with oxygen and water in the environment to form a stable zinc oxide protective layer, thereby extending the service life of the steel pipe.

Channel steel is divided into ordinary channel steel and lightweight channel steel. Hot-rolled ordinary channel steel has specifications ranging from 5# to 40#. Hot-rolled variable channel steel, supplied by mutual agreement between the supplier and the buyer, has specifications ranging from 6.5# to 30#. Channel steel is primarily used in building structures, vehicle manufacturing, other industrial structures, and fixed cabinets. Channel steel is often used in conjunction with I-beams.

Channel steel can be divided into four types based on shape: cold-formed equal-leg channels, cold-formed unequal-leg channels, cold-formed inner-flange channels, and cold-formed outer-flange channels. According to steel structure theory, the channel flanges should bear the load, meaning the channel should stand upright, not flat.

Channel Steel Specifications

Channel steel specifications are primarily expressed in terms of height (h), leg width (b), and waist thickness (d). Currently, domestic channel steel specifications range from 5# to 40#, corresponding to heights of 5 to 40cm.
At the same height, lightweight channels have narrower legs, thinner waists, and are lighter than standard channels. Channels ranging from 18 to 40 are considered large, while channels ranging from 5 to 16 are considered medium. Imported channels are marked with the actual dimensions and relevant standards. Import and export orders for channels are generally based on the required specifications after determining the corresponding carbon steel (or low-alloy steel) grade. Aside from the specification number, channels do not have specific composition or performance series.