How To Polish Stainless Steel

#1 The Polishing Types Of Stainless Steel

There are currently seven commonly used stainless steel polishing methods:

• Mechanical Polishing
• Chemical Polishing
• Electropolishing
• Ultrasonic Polishing
• Fluid Polishing
• Magnetic Grinding And Polishing
• Chemical Mechanical Polishing

1.Mechanical Polishing

Mechanical polishing is a polishing method that removes the polished convex part by cutting and plastic deformation of the material surface to obtain a smooth surface. Generally, oil stone strips, wool wheels, sandpaper, etc. are used, and manual operations are mainly used. Special parts such as the surface of a rotating body can be polished. Using auxiliary tools such as turntables, ultra-fine grinding and polishing methods can be used for high surface quality requirements. Ultra-fine polishing uses a special abrasive tool, which is pressed against the surface of the workpiece to be processed in a polishing liquid containing abrasives for high-speed rotation. The surface roughness of Ra0.008μm can be achieved by using this technology, which is the highest among various polishing methods. Optical lens molds often use this method.

2.Chemical Polishing

Chemical polishing is to make the microscopic convex part of the surface of the material dissolve preferentially compared with the concave part in the chemical medium, so as to obtain a smooth surface. The main advantage of this method is that it does not require complex equipment, can polish workpieces with complex shapes, and can polish many workpieces at the same time, with high efficiency. The core problem of chemical polishing is the preparation of polishing fluid. The surface roughness obtained by chemical polishing is generally several 10 μm.

3.Electrolyticpolishing

The basic principle of electrolytic polishing is the same as that of chemical polishing, that is, to make the surface smooth by selectively dissolving the tiny protrusions on the surface of the material. Compared with chemical polishing, it can eliminate the influence of cathode reaction, and the effect is better. The electrochemical polishing process is divided into two steps: (1) Macro leveling The dissolved product diffuses into the electrolyte, and the geometric roughness of the material surface decreases, Ra>1μm. (2) Twilight smoothing Anodized, surface brightness improved, Ra<1μm.

4.Ultrasonic Polishing

The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, and the abrasive is ground and polished on the surface of the workpiece by means of ultrasonic oscillation. Ultrasonic machining has a small macroscopic force and will not cause deformation of the workpiece, but it is difficult to manufacture and install tooling. Ultrasonic machining can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution, so that the dissolved products on the surface of the workpiece are separated, and the corrosion or electrolyte near the surface is uniform; the cavitation effect of ultrasonic waves in the liquid can also inhibit the corrosion process and facilitate surface brightening.

5.Fluid Polishing

Fluid polishing relies on the high-speed flowing liquid and the abrasive particles carried to scour the surface of the workpiece to achieve the purpose of polishing. Commonly used methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding, etc. Hydrodynamic grinding is driven by hydraulic pressure, so that the liquid medium carrying abrasive particles flows back and forth across the surface of the workpiece at high speed. The medium is mainly made of a special compound (polymer-like substance) with good flowability under relatively low pressure and mixed with abrasives. The abrasives can be silicon carbide powder.

6.Magnetic Grinding And Polishing

Magnetic grinding and polishing is to use magnetic abrasives to form abrasive brushes under the action of a magnetic field to grind the workpiece. This method has high processing efficiency, good quality, easy control of processing conditions, and good working conditions. With suitable abrasives, the surface roughness can reach Ra0.1μm.

7.Chemical Mechanical Polishing

Chemical mechanical polishing technology combines the advantages of chemical polishing and mechanical polishing. It is the most commonly used polishing method at present. Even the mobile phone case, card removal needle, and buttons are polished with Jinxin flat surface grinding machine. While ensuring the material removal efficiency, a more perfect surface can be obtained, and the flatness obtained is 1-2 orders of magnitude higher than that of the two kinds of grinding alone, and the surface roughness from the nanometer to the atomic level can be achieved. Moreover, the polished mirror surface has high brightness, no faults, and good planarity. Generally, Jinxin plane grinder can be used to achieve fast and good results.

#2 The Process Of Polishing Stainless Steel

1.Preprocessing

A: Remove burrs and weld scars; use a portable grinder, and the grinding discs have fiberglass matrix resin type and sandpaper type.
B : Remove oil stains, dust, dirt, fingerprints; use alkali or acid washing or organic solution washing, sandblasting, rolling and other methods.

2.Polishing Treatment:

A : Use a buffing wheel for polishing;The polishing wheel is the kind made of laminated cloth pieces, which are rubbed under high-speed rotation (20~35M/S, that is, when using a Φ300 cloth wheel, the speed is 2000r/min). Apply polishing paste (white, yellow, green, and red), and the green one is suitable for polishing stainless steel, which can produce a mirror effect].

B : Sandblasting:It can make the surface more delicate and beautiful.

• Dry sand blasting treatment; stainless steel below 1 mm thickness is suitable for quartz sand (grain size is 0.5~0.2/mm), the air pressure is 10 industrial atmospheres, that is, 0.5~0.1mpa, and the compressed air is water-free and oil-free.
• Wet sand blasting treatment: Mix quartz sand and water to make mortar, add some sodium nitrite in an appropriate amount, and the others are the same as above.
• After the above is completed, the workpiece is cleaned and dried.

3.Surface Treatment Range:

The surface of stainless steel can be sent to a special factory for processing; it can be electroplated with chrome/copper/zinc/tin/cadmium/titanium/nitriding/nitrocarburizing/electrolytic tinting/blackening/color/corrosion processing/engraving pattern/relief Finishing processing, etc.

#3 About Polishing Stainless Steel

The variety of surface processing of stainless steel broadens its application fields. Different surface processing makes the surface of stainless steel different, making it unique in application. Surface finishing of stainless steel is important for many reasons in architectural applications.

1.The Basic Types Of Surface Processing

There are roughly five types of surface processing that can be used for stainless steel, and they can be combined to transform more final products.

The five types are:

• Rolled Surface Processing
• mechanical surface processing
• chemical surface processing
• Textured surface processing and color surface processing

There are also specialized finishes, but whichever one is specified, the following steps should be followed:

1. Agree with the manufacturer on the required surface processing. It is best to prepare a sample as the standard for future mass production.
2. When used in a large area (such as composite boards, it must be ensured that the base coils or coils used are of the same batch.)
3. The production process should be considered when selecting the surface processing. For example, in order to remove the welding beads, it may be necessary to grind the weld seam and restore the original surface processing. Checkered plates are difficult or even impossible to meet this requirement.
4. For some surface processing, grinding or polishing lines are directional, which is called unidirectional. If the texture is vertical instead of horizontal, the dirt will not easily adhere to it, and it will be easy to clean.

2.Rolling Surface Processing

There are three basic rolling surface finishes for plates and strips, which are represented by the production process of plates and strips.

• No.1: After hot rolling, annealing, pickling and descaling. The surface of the treated steel plate is a dull surface, somewhat rough.
• No.2D: Better surface finish than N0.1, but also dull surface. After cold rolling, annealing, descaling, and finally light rolling with rough surface rollers.
• No.2B: This is the most commonly used in architectural applications. Except for the last light cold rolling with polishing rolls after annealing and descaling, the other processes are the same as 2D. The surface is slightly shiny and can be polished.
• No.2B Bright Annealed: This is a reflective finish that is polished roll rolled and final annealed in a controlled atmosphere. Bright annealing still maintains its reflective surface and does not produce scale. Since no oxidation reaction occurs during the bright annealing process, no pickling and passivation treatment is required.

3.Polishing Surface Processing

• No.3: represented by 3A and 3B. 3A: The surface is uniformly ground, and the abrasive grain size is 80-100. 3B: The rough surface is polished, and the surface has uniform straight lines. It is usually polished once on the 2A or 2B board with an abrasive belt with a particle size of 180-200.
• No.4: Unidirectional surface finish, not very reflective, this finish is probably the most versatile in architectural applications. The process steps are first to polish with coarse abrasives, and finally to grind with abrasives with a particle size of 180.
• No.6: It is a further improvement on No.4. It uses Tampico polishing brush to polish the surface of No.4 in abrasive and oil medium. This surface finish is not included in “British Standard 1449”, but can be found in the American Standard.
• No.7: It is called bright polishing, which is to polish the surface that has been ground very finely but still has wear marks. Usually 2A or 2B boards are used, with fiber or cloth polishing wheels and corresponding polishing pastes.
• No.8: Mirror polished surface with high reflectivity, usually called mirror surface processing, because the reflected image is very clear. Continuous polishing of stainless steel with fine abrasives followed by very fine polishing pastes. In architectural applications, it should be noted that if this surface is used in a place with a large flow of people or where people often touch it, it will leave fingerprints. Of course, fingerprints can be wiped off, but sometimes it affects the appearance.

4.Surface Roughness

The classification of rolled surface finish and polished surface finish is to describe the degree that can be achieved. Another effective way of expressing it is to measure the surface roughness. The standard method of measurement is called CLA (Center Line Average), where the gage is moved across the surface of the steel plate, recording the magnitude of the peaks and valleys. The lower the number of CLA, the smoother the surface. The end results of the different grades can be seen from the surface finishes and CLA numbers in the table below.

5.Mechanical Polishing

A note of caution: We should remember that grinding with sandpaper or belts in grinding operations is essentially a buff cutting operation, leaving very fine lines on the surface of the steel plate. We have had trouble with alumina as an abrasive, partly because of pressure issues. Any grinding parts of the equipment, such as abrasive belts and grinding wheels, must not be used for other non-stainless steel materials before use. Because this will contaminate the stainless steel surface.

6.Electropolishing

This is a metal removal process in which stainless steel acts as the anode in the electrolyte and the metal is removed from the surface when energized. The process is often used on components whose shapes are difficult to polish using traditional methods. The process is often used on the surface of cold-rolled steel sheets because the surface is smoother than that of hot-rolled steel sheets. However, electropolishing will make the surface impurities more obvious, especially titanium and niobium stabilized materials will cause differences in the weld zone due to granular impurities.

Small weld scars and sharp edges can be removed by this process. The process focuses on protruding parts of the surface, preferentially dissolving them. The electropolishing process is to immerse stainless steel in a heated liquid, and the ratio of the liquid involves many proprietary technologies and patented technologies. Electropolishing works well for austenitic stainless steels.

7.Textured Surface Processing

There are many types of patterns that can be used in stainless steel. The advantages of adding a pattern or textured surface to the steel plate are as follows:

• Reduce “oil can-ning”, a term used to describe shiny material surfaces that are optically uneven. For example: for large-area decorative panels, it is difficult to make the surface completely straight even after stretching or tension straightening, so there will be shrinkage of metal roofing materials.
• The mesh pattern can reduce the glare emitted in the sun.
• If the checkered plate has slight scratches and small area indentations, it is not obvious.
• Increase the strength of the steel plate.
• Provide architects with a choice. Patented patterns include cloth (used for the Ed Building in London), mosaic, pearl and leather. Moiré and linear patterns are also available. The textured surface is particularly suitable for interior decoration such as: elevator panels, counters, wall panels and entrances. When applying externally, it should be considered that the stainless steel can be cleaned by rainwater and manual washing, so as to avoid dead corners where dirt and airborne impurities are easy to accumulate, so as not to cause corrosion and affect the appearance.

8.Rough Surface Processing

Rough surface processing is one of the most commonly used surface processing. It is polished or polished with a nylon abrasive belt or brush on the surface of a polished or bright annealed steel plate.

#4 Stainless Steel Polishing Precautions

1.Brightness Grade Of Stainless Steel After Polishing

Grinding with sandpaper or belts in grinding operations is essentially a buff cutting operation, leaving very fine lines on the surface of the steel plate. Trouble has been encountered with alumina as an abrasive, partly due to pressure problems. Any grinding parts of the equipment, such as abrasive belts and grinding wheels, must not be used for other non-stainless steel materials before use. Because this will contaminate the stainless steel surface. In order to ensure the consistency of the surface finish, the new grinding wheel or abrasive belt should be tried on the scrap of the same composition first, so that the same sample can be compared.

Visually, the brightness of the surface of the polished part is divided into 5 grades:

• Level 1: There is a white oxide film on the surface, without brightness;
• Level 2: Slightly bright, the outline cannot be seen clearly;
• Level 3: The brightness is good, and the outline can be seen;
• Level 4: The surface is bright, and the outline can be seen more clearly (equivalent to the surface quality of electrochemical polishing);
• Level 5: Bright as a mirror.

2.The Basic Procedure Of Mechanical Polishing

In order to obtain a high-quality polishing effect,

The most important thing is to have high-quality oil stones, sandpaper and diamond grinders.

3.Grinding Paste And Other Polishing Tools And Accessories.

The choice of polishing procedure depends on the surface condition after pre-processing, such as machining, EDM, grinding and so on. The general process of mechanical polishing is as follows:

(1) Coarse Throwing

After milling, EDM, grinding and other processes, the surface can be polished by a rotary surface polishing machine or an ultrasonic grinding machine with a rotation speed of 35 000-40 000 rpm. The commonly used method is to remove the white electric spark layer by using a wheel with a diameter of Φ 3mm and WA # 400. Then manual whetstone grinding, strip whetstone plus kerosene as lubricant or coolant. The general order of use is #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000. Many moldmakers choose to start with #400 to save time.

(2) Semi-Fine Polishing

Semi-fine polishing mainly uses sandpaper and kerosene. The numbers of sandpaper are: #400 ~ #600~ #800 ~ #1000 ~ #1200 ~ #1500. In fact, #1500 sandpaper is only suitable for hardened mold steel (above 52HRC), not for pre-hardened steel, because it may cause surface burns of pre-hardened steel parts.

(3) Fine Polishing

Fine polishing mainly uses diamond abrasive paste. If the polishing cloth wheel is mixed with diamond grinding powder or grinding paste for grinding, the usual grinding sequence is 9 μm (#1800) ~ 6 μm (#3000) ~ 3 μm (#8000). 9 µm Diamond Paste and Cloth Wheels can be used to remove hair marks from #1200 and #1500 sandpaper. Then polish with sticky felt and diamond abrasive paste, the order is 1 μm (#14000) ~ 1/2 μm (#60000) ~ 1/4 μm (#100000). The polishing process whose accuracy is required to be above 1 μm (including 1 μm) can be carried out in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is required. Dust, smoke, dandruff and drool can all ruin a highly polished finish after hours of work.

4.Common Problems And Preventive Measures

Stainless steel has excellent characteristics such as unique strength, high wear resistance, superior anti-corrosion performance and not easy to rust. Therefore, it is widely used in chemical industry, food machinery, electromechanical industry, environmental protection industry, household appliance industry and home decoration, fine decoration industry, giving people a gorgeous and noble feeling.

The application and development prospects of stainless steel will become wider and wider, but its application development largely determines the development level of stainless steel surface treatment technology.

1. Common stainless steel surface treatment methods

Commonly used stainless steel surface treatment techniques have the following treatment methods:

• White treatment of the natural color of the surface;
• Surface mirror bright treatment;
• Surface coloring treatment.

2.The stainless steel surface treatment methods are as follows:

• Chemical oxidation coloring method;
• Electrochemical oxidation coloring method;
• Lon deposition oxide coloring method;
• High temperature oxidation coloring method;
• Vapor-phase pyrolysis coloring method.

3.There are problems in the process of stainless steel surface treatment

• 3.1 Weld seam defects: Weld seam defects are serious, and manual mechanical grinding is used to make up for them. The resulting grinding marks will cause uneven surfaces and affect the appearance.
• 3.2 Surface inconsistency: Only pickling and passivating the weld seam also causes uneven surface and affects the appearance.
• 3.3 Scratches are difficult to remove: the overall pickling passivation can not remove all kinds of scratches generated during processing, and can not remove carbon steel, spatter and other impurities adhered to the surface of stainless steel due to scratches and welding spatter. Causes chemical corrosion or electrochemical corrosion to rust in the presence of corrosive media.
• 3.4 Uneven grinding and polishing passivation: pickling and passivation treatment after manual grinding and polishing, it is difficult to achieve a uniform treatment effect for large-area workpieces, and it is impossible to obtain an ideal uniform surface. And the cost of working hours and the cost of auxiliary materials are also higher.
• 3.5 Pickling ability is limited: pickling passivation paste is not a panacea, and it is difficult to remove the black oxide scale produced by plasma cutting and flame cutting.
• 3.6 The scratches caused by human factors are relatively serious: in the process of hoisting, transportation and structural processing, the scratches caused by human factors such as bumping, dragging and hammering are relatively serious, which makes the surface treatment more difficult, and is also the cause of rust after treatment. main reason.
• 3.7 Equipment factors: During the bending and bending process of profiles and plates, scratches and creases are also the main reasons for rust after treatment.
• 3.8 Other factors: In the process of procurement and storage of stainless steel raw materials, bumps and scratches caused by hoisting and transportation are also relatively serious, which is also one of the reasons for corrosion.

4.Stainless steel surface treatment should take preventive measures

1. Storage, hoisting and transportation

• A.Storage of stainless steel parts: There should be special storage racks, and the storage racks should be wooden or painted carbon steel brackets or cushioned with rubber pads to isolate them from other metal materials such as carbon steel. When storing, the storage location should be convenient for hoisting, relatively isolated from other material storage areas, and protective measures should be taken to avoid contamination of stainless steel by dust, oil, and rust.
• B.Hoisting of stainless steel parts: When hoisting, special lifting tools should be used, such as lifting belts, special chucks, etc. It is strictly forbidden to use steel wire ropes to avoid scratching the surface; and when lifting and placing, scratches caused by impact bumps should be avoided.
• C.Transportation of stainless steel parts: When transporting, use transportation tools (such as trolleys, battery cars, etc.), and should be clean and have isolation protection measures to prevent dust, oil, and rust from contaminating stainless steel. Dragging is strictly prohibited to avoid bumps and scratches.

2.Stainless steel surface treatment

• A.Cleaning and grinding: If there is any damage, it should be polished, especially the scratches and splashes caused by contact with carbon steel parts, and the damage caused by cutting slag must be carefully and thoroughly cleaned and polished.
• B.Mechanical polishing: use appropriate polishing tools for polishing, requiring uniform treatment, and avoiding over-polishing and re-scratching.
• C.Oil removal and dust removal: before pickling and passivation of stainless steel parts, oil, scale, dust and other sundries must be removed according to the process.
• D.Water blasting treatment: According to different treatment requirements, different micro glass beads and different process parameters should be selected, and overspray should be avoided.
• E.Pickling passivation: The pickling passivation of stainless steel parts must be passivated strictly according to the process requirements.
• F.Cleaning and drying: After pickling and passivation, neutralization, rinsing and drying should be carried out in strict accordance with the process to completely remove the residual acid.
• G.Protection: After the surface treatment of stainless steel parts is completed, protection should be done to avoid secondary pollution from personnel touching and oil, dust and other sundries.
• H.Avoid reprocessing: After the surface treatment of stainless steel parts, reprocessing of the parts or products should be avoided.

The current treatment methods for stainless steel surfaces:

• Surface natural color whitening treatment;
• Surface mirror bright treatment;
• Surface coloring treatment.

During the processing of stainless steel, black oxide skin is produced after coiling, edge binding, welding or warm surface fire treatment on the part of the handler. This kind of hard gray-black oxide skin is mainly composed of NICR2O4 and NIF EO4. In the past, hydrofluoric acid and nitric acid were generally used for strong corrosion removal. But this method costs a lot, pollutes the environment, and is harmful to the human body. The corrosion is large and gradually eliminated.
At present, there are two kinds of treatment methods for this oxide skin:

• Use shot (shot) sand method.
• Using chemical method.

#1. Use one bell of non-polluting pickling passivation paste and normal temperature non-toxic cleaning solution with inorganic additives for immersion. So as to achieve the purpose of whitening the natural color of stainless steel. Basically, it looks like a glance of color. This method is more suitable for large and complex products, and it is worth popularizing and applying.

#2. Stainless steel surface mirror bright treatment method: According to the complexity of stainless steel products and user requirements, methods such as mechanical polishing, chemical polishing, and electrochemical polishing can be used to achieve mirror stone luster.

#3. Stainless steel coloring not only endows stainless steel products with various colors, increases the variety of designs and colors of products, but also improves the wear resistance and wear resistance of products.

Stainless steel coloring methods are as follows:

• Lon deposition of oxides or oxides;
• High temperature oxidation method;
• Chemical oxidation method. Electrochemical oxidation method;
• Gas phase cracking method.

#5 Grinding And Polishing For Different Stainless Steels

Stainless steel has become a widely used engineering material due to its excellent corrosion resistance, good mechanical properties, processing properties and good welding performance. At the same time, through different polishing processing methods, the surfaces of various stainless steel plates, pipes, rods, and profiled materials can have different levels of surface finish, which greatly improves the appearance of stainless steel and achieves aesthetic effects. Attractive, to people with the enjoyment of beauty. It is widely used in daily production and life.

1. Stainless Steel Slab (Finished Steel Plate)

The polishing of stainless steel slabs can be polished in a variety of ways such as abrasive sand, abrasive belt and yarn reinforcement abrasive materials. According to different purposes, different or combined polishing methods can be selected.

• After polishing and finishing the cold-rolled stainless steel plain plate with the abrasive material with a particle size of 100~120 specified in GB2477, the surface of the stainless steel is a semi-polished surface. The surface roughness Ra value is 0.4~1.5μm. It is suitable for building materials, kitchen utensils and occasions that require further finishing after manufacture.
• After polishing and finishing the cold-rolled stainless steel plain plate with an abrasive belt with a particle size of 150-180 specified in GB2477, the surface of the stainless steel is a finely polished surface with a brighter surface, and the surface roughness Ra value is 0.2-1.5 μm . This kind of finely polished surface is not easy to leave fingerprints on it, and is also suitable for making stainless steel doors. This surface has a mirror-like reflection effect and has the special property of reflecting various light sources. Due to the use of abrasive belt polishing, no matter what the shape of the light source is, it will be a bright straight line after reflection. Regardless of the position of the stainless steel plate and the angle of incidence, this bright straight line is always perpendicular to the polishing direction. Depending on the direction in which the steel plate is installed, it may appear as a horizontal bright line or a vertical bright line on the building. If the bright line is horizontal, it means that the polished texture of the steel plate surface is vertical. In this way of use, the surface of the steel plate is not easy to accumulate dust, and it is also easy to wash, which is very important for the maintenance of high-rise buildings.
• The surface obtained by polishing and finishing the cold-rolled stainless steel plain plate with the abrasive belt with a grain size of No. 240 specified in GB2477 is equivalent to the No. 240 surface of the Japanese standard. Suitable for kitchen utensils.
• Polish and finish the cold-rolled stainless steel plain plate after polishing with the abrasive belt No. 150~180 with the abrasive material W63 with a particle size specified in GB2477. The surface of the stainless steel has a good metallic luster, soft surface and reflective properties. Weak and non-reflective image, it is very suitable for making building curtain walls and building edge trim, and is also widely used as kitchen utensils.
• Polish the stainless steel plate with W50 grinding material specified in GB2477, which has a quasi-mirror surface with high reflectivity. Equivalent to a US standard surface obtained by fine polishing with a No. 600 rotary buffing wheel. Stainless steel plate polishing equipment uses yarn-reinforced abrasive materials on the equipment to carry out floating dry grinding or/and wet grinding and polishing on stainless steel plates. Since operators do not understand abrasive tools, the ideal polishing effect is often not achieved.

2. Small Stainless Steel Plate

After decomposing the finished stainless steel plate, many small stainless steel plates of different specifications and sizes will be obtained. These small stainless steel plates are the most heavily used stainless steel workpieces in production. Due to the different situations of each manufacturer or polishing “workshop”, they will use different methods to polish.

• “Cloth wheel sticky sand” polishing “Cloth wheel sticky sand” polishing is the polishing of abrasive materials bonded with a cloth wheel. In the past it was the most common method of polishing stainless steel. Polishing paste is applied to the rotating cloth wheel of a motor-driven single-head or double-head polishing machine (evolved from a grinder), and the operator holds a stainless steel workpiece for polishing. The labor intensity is high, the working environment is poor, and the workshop workers are highly polluted and often need to wear masks to operate. Stainless steel polishing is mainly made of hard, sharp, and highly removable green wax made of chromium oxide and binder. Green wax is a kind of polishing wax. Polishing wax (paste) is a solid form of polishing materials, mainly composed of abrasives, organic pastes and additives. Among them, the type, crystal form, particle size of abrasives, and the type and proportion of organic pastes are all important factors affecting the polishing quality. .
• Sandpaper polishing Put the stainless steel workpiece on a table or other platform, replace the coarse and fine sandpaper, and use manpower to polish. This polishing method is closely related to the skill of the operator. Operators with high skills can throw better. However, due to the low polishing speed, it is impossible to achieve the same level of surface roughness as the machine operation.
• Angle grinder polishing The operator holds the angle grinder and installs No. 120 or/and No. 220 PVA small grinding discs (angle grinding discs) on the angle grinder to polish the workpiece. Before polishing, it is sometimes necessary to install ordinary resin angle grinding discs for rough grinding. After the PVA small abrasive disc is polished, it is sometimes re-polished with a felt wheel to achieve a brighter surface.
• Pneumatic grinder polishing Install grinding and polishing wheels on the pneumatic grinder in the production workshop to polish stainless steel plates with an area of less than 1 square meter. (Note: The limited linear speed of the grinding and polishing wheel should match the pneumatic grinder, otherwise a safety accident will occur.)
• Grinding machine polishing On the surface grinding machine, install the PVA grinding wheel, select the appropriate workpiece speed, radial feed, and grinding wheel speed, and polish the stainless steel workpiece to obtain a high-gloss surface quality.
• Floating grinding head polishing On a self-made floating grinding head, a cloth wheel made of expensive materials is used to polish a stainless steel plate with an area of about 1 square meter. A foggy mirror effect can be obtained. There are some other methods, such as vibration polishing.