Surface treatment methods for precision stamped parts

Surface treatment is also very important, but many people often do not pay attention to surface treatment or do not understand some surface treatment methods. The following takes you to understand the possible problems of the surface and the solutions

What is a surface treatment

Surface treatment is the process of artificially forming a surface layer on the surface of the base material with mechanical, physical and chemical properties different from those of the base material.

Why surface treatment of precision stamped parts

After the finished product is processed, some surface treatment is needed for the surface of the precision hardware stamping parts by certain methods, the purpose of which is to improve the quality of the product and to give the precision hardware stamping parts a beautiful and corrosion-resistant surface.

Surface treatment of stamping parts

Surface treatment of precision stamping parts

Spraying process: Stamping parts manufacturers choose the spraying process in the case of manufacturing stamping parts of large objects, according to which spraying process makes stamping parts prevent rust and corrosion, for example, household goods, housings of household appliances, artworks, etc.

Electroplating process: The electroplating process is also a more overall processing process in stamping processing plants, according to the current production process for stamping parts surface plating process to ensure that the goods do not produce mould embroidery rust under long-term application, electroplating process processing is common for precision stamping parts, battery pieces, car parts, decorations these; involves the use of electric current to apply thin metal coating on the main metal surface. Due to its versatility – from micro parts to large products – this method is a widely used surface treatment. It is designed to protect metals from corrosion, improve surface value, and amplify their physical appearance. Metal parts for laboratory and medical equipment, household appliances and automobiles all use this treatment.

surface polishing processing: surface polishing processing is generally more commonly used in household goods, according to the stamping parts to carry out surface burrs. For example, we produce and manufacture a stamping parts shell; the shell is based on the stamping die made of stamping parts, then the stamping die out of the shell edge is very sharp, we need to polish the edge of the sharp part of the polishing into a polished surface according to grinding.

Anodic oxidation: metal or alloy parts as the anode, and then use electrolytic techniques so that the product’s surface forms a layer of the oxide film. This film can not only improve the surface condition of the product so that the surface of the product becomes more beautiful but also can improve the performance of the product, such as can improve the insulation properties of the product, enhancing the wear resistance of the product, improve the hardness of the product, increase the corrosion resistance of the product, and can even better protect the metal surface of the product.

surface quenching: mainly refers to the surface of the product in a relatively short period quickly heated to quenching temperature, and then in a very short period for rapid cooling, within a certain degree to achieve the purpose of quenching, through quenching this processing process, the product surface hardness can be greatly improved, so that the product wear resistance performance to meet the needs of practical applications.

Surface treatment of hardware stamping parts

Electrophoresis: Electrophoresis is electrophoretic paint in the cathode and anode. When the voltage is applied, the charged paint ions move to the cathode and form insoluble materials with an alkaline effect on the cathode surface, which is deposited on the working surface. Features of the electrophoretic surface treatment process: electrophoretic paint film has the advantages of being plump, uniform, flat and smooth, and the hardness, adhesion, corrosion resistance, impact performance and penetration performance of electrophoretic paint film are obviously better than other coating processes.

Blackening: The surface blackening treatment of steel parts, also known as bluing, is based on the principle of rapid oxidation of the surface of steel products to form a dense oxide film protective layer and improve the rust resistance of steel parts. Blackening treatments now commonly used methods are the traditional alkaline heating blackening and the late emergence of two kinds of room temperature blackening.

Zinc and tin plating: Zinc and tin plating is a surface treatment technology that plates a layer of zinc on the surface of the metal, alloy or other materials for aesthetic and rust prevention purposes. The main method used now is hot-dip galvanizing.

Phosphating: Phosphating is a chemical and electrochemical reaction to form a phosphate chemical conversion film process; the phosphate conversion film formed is called phosphate film. The purpose of phosphating is mainly: to protect the base metal, to a certain extent, to prevent corrosion of metals; for priming before painting, to provide adhesion and corrosion resistance of the paint film layer; in the metal cold working process to reduce friction lubrication used.

Baking paint: primer and top coat on the substrate, each time on the paint, are sent to the dust-free constant temperature baking room, baking.

Passivation: The mechanism of passivation can be explained by the film theory; that is, passivation is due to the role of metal and oxidation properties, the role of the metal surface to produce a very thin, dense, good coverage properties, firmly adsorbed on the metal surface of the passivation film. This layer of film into an independent phase exists, usually oxidized metal compounds; it plays a metal and corrosion media completely separated from the role of preventing metal and corrosion media contact so that the metal stops dissolving to form a passivation state to achieve the role of corrosion prevention

The processing method of the uneven surface of precision stamping parts

In the general stamping process, when the punch first presses the blank, elastic warpage and the concave die surface will occur under the convex die. The elastic warpage will be completely removed if the gap is moderate and the shear cracking is carried out in time. When the gap is too large, the blank is severely twisted and stretched at the edges, and shear cracking occurs. Warpage cannot be removed and the blank remains on the stamped part as a concave arc surface. When the film is too small, the workpiece warps to form a concave arc surface because the size of the stamped part falling in the hole of the die is slightly larger than the size of the hole. The method to remove it is to set up a crimping device (such as an elastic unloading plate) and an elastic ejection device on the press die to suppress the elastic warpage. When the gap is small, the concave curved surface of the workpiece can be removed by trimming the punching gap.

The inverted taper of the straight wall section of the die hole or the small contact area between the push plate and the workpiece form the concave curved surface of the workpiece. The removal method is to repair the inverted taper of the cavity wall and replace the top material plate.

When the shape of the punched parts is confused, the workpiece warps unevenly due to the uneven punching force around the workpiece. The precision stamping plant can increase the crimping force.

 When there is oil, gas or debris between the die and the stamping part, the stamping part will also be bent, especially for thin walls and software. The removal method is to pay attention to strengthening the cleaning work, and the exhaust port can be designed when there is air in the die.

Ways to reduce the surface roughness of stamping parts

Selection of raw materials: Many different raw materials are used in stamping. According to the density of raw materials, the choice of tools and machine tools in the processing will directly affect the surface roughness.

Cutting dosage: In terms of cutting feed, choose a good machining process: In stamping production, the machining process is also very important, and an unreasonable process may affect the processing quality and productivity. Many precision stamping parts need finishing after rough machining

 Selection of geometric tool parameters: From the geometric tool parameters, appropriately reduce the auxiliary deflection angle and increase the radius of the tooltip circle. If necessary, the polished edge can be sharpened to make cutting easier and reduce surface roughness

Control machine vibration: reduce the friction and extrusion between the tool and the stamping part, make the tool sharp, add cutting fluid and carry out appropriate heat treatment for some tough stamping materials

Several methods to solve surface scratches of precision stamping parts

Unreasonable planning of die clearance

When planning the die clearance, the size, material, thickness and drawing height of precision stamping parts must be taken into consideration. The little planning of the die clearance can also lead to scratches.

The influence of die surface roughness

For stainless steel products, die surface roughness also greatly impacts the product’s surface quality.

Selection of stamping equipment

Because stamping and drawing parts are a serious deformation process, Z has a good choice of hydraulic presses for processing; the stamping process of mechanical punch is too fast and simple, which makes the surface quality of the products in the process not meet the requirements.

 

Expansion: Other surface treatment

Metal

Chemical plating

In contrast to electroplating, chemical plating is not carried out by an electric current. Instead, it uses a chemical reaction to apply a metallic coating to the target metal (or what we call the “substrate”). It is a smoother, more uniform application than electroplating. It is also more cost-effective throughout the process.

The metal used for this type of surface treatment is nickel. These products supply most parts for aerospace and other industries, such as gun manufacturers. Electroplating is also beneficial for stamped metal parts such as aluminium steel, copper-zinc brass

Chemical coating

This surface treatment is also known as powder coating – in which a smooth protective film is applied to the substrate by compressed air, producing a subsequently melted powder material. It makes stamped metal highly resistant to scratching and cracking, resistant to corrosion, and valuable as a metal colourant.

Chemical coatings are widely used for parts in the automotive industry – making them ideal for customer preference. In addition, the materials used for this surface treatment are aluminium and steel.

Hot-dip galvanizing

This surface treatment is also known as hot dipping. It is applied to steel and iron stampings by dipping them into a molten zinc bath to coat them. With this treatment, metal parts are most likely to have a high degree of corrosion resistance. The hot dip method is popular in industries that manufacture metal parts for consumer appliances and automobiles.

Vacuum Metallization

Vacuum metallization is the process of applying a protective metal barrier to smooth stamped parts. This surface treatment requires the metal to be placed inside a can or container where it is sprayed with a metallic coating. It has a mirror finish suitable for decorative and design purposes, especially in the aerospace and automotive industries. Aluminium is the key metal for this method.

Thermal Spraying

This finish enhances the ability of metal parts to eliminate or minimize scratching, flaking and cracking of metal surfaces by melting and heating the metal coating. It is used as a primer for large structural metal stampings.

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