Understand The Metal Surface Treatment Process in One Article!

1. Surface heat treatment
   
   Surface hardening✦
   
        Surface quenching refers to a heat treatment method that uses rapid heating to austenitize the surface layer and then quench it to strengthen the surface of the part without changing the chemical composition and core structure of the steel.
   
        The main methods of surface heat treatment are flame quenching and induction heating heat treatment. Commonly used heat sources are flames such as oxyacetylene or oxypropane, induced current, laser and electron beam.
   Induction heating
   
         The method of using alternating current to induce huge eddy currents on the surface of the workpiece to rapidly heat the surface of the workpiece.

  Induction heating is divided into:

1. High-frequency induction heating, the frequency is 250-300KHz, and the depth of the hardened layer is 0.5-2mm;

2. Medium frequency induction heating, the frequency is 2500-8000Hz, and the depth of the hardened layer is 2-10mm;

3. Power frequency induction heating, the frequency is 50Hz, and the depth of the hardened layer is 10-15mm.

flame heating

     A method of directly heating the surface of a workpiece using an acetylene flame. The cost is low, but the quality is not easy to control.
 

laser heating

     A method of heating the surface of a workpiece using a high-energy-density laser. High efficiency and good quality.

     Laser surface strengthening can be divided into laser phase transformation strengthening treatment, laser surface alloying treatment and laser cladding treatment.
 

Laser surface strengthening is mainly used for locally strengthened parts, such as blanking dies, crankshafts, cams, camshafts, spline shafts, precision instrument guide rails, high-speed steel tools, gears and internal combustion engine cylinder liners.

Bluing and Phosphating ✦

bluish

     A process in which steel or steel parts are heated to an appropriate temperature in air-water vapor or chemicals to form a blue or black oxide film on the surface. Also called blackening.

     Commonly used in precision instruments, optical instruments, tools, hardness blocks and standard parts in the machinery industry.


Phosphating

     The process in which the workpiece (steel or aluminum, zinc) is immersed in a phosphating solution (some acid phosphate-based solution), and a layer of water-insoluble crystalline phosphate conversion film is deposited on the surface, which is called phosphating .

    Phosphating is widely used in anti-corrosion technology, metal cold deformation processing industry.

2. Chemical surface heat treatment

Chemical Surface Heat Treatment✦

     Chemical heat treatment is a heat treatment process in which the workpiece is placed in a specific medium for heating and heat preservation, so that the active atoms in the medium penetrate into the surface layer of the workpiece, thereby changing the chemical composition and structure of the surface layer of the workpiece, and then changing its performance.



     Chemical heat treatment is also one of the methods to obtain the toughness of the surface, hard and lining. Compared with surface quenching, chemical heat treatment not only changes the surface structure of steel, but also changes its chemical composition. According to the different elements infiltrated, chemical heat treatment can be divided into carburizing, nitriding, multi-infiltration, infiltration of other elements, etc. The chemical heat treatment process includes three basic processes: decomposition, absorption, and diffusion.

     Commonly used chemical heat treatment:

     Carburizing, nitriding (commonly known as nitriding), carbonitriding (commonly known as cyanidation and soft nitriding), etc. Sulfurizing, boronizing, aluminizing, vanadizing, chromizing, etc.



     Bluing and phosphating can be classified as surface treatment, not chemical heat treatment.



Carburizing and Nitriding ✦

3. Surface deformation strengthening

Surface deformation strengthening✦

     Surface deformation strengthening refers to a surface strengthening process that plastically deforms steel parts at room temperature to increase its surface hardness and generate favorable residual compressive stress distribution. The process is simple and the cost is low, and it is an important technological measure to improve the fatigue resistance of steel parts and prolong its service life.



shot peening

     Shot peening is a technique in which a large number of high-speed moving projectiles are sprayed onto the surface of the part, like countless small hammers hammering the metal surface, so that the surface and sub-surface of the part have a certain plastic deformation to achieve strengthening.

     Application: Parts with complex shapes are carried out after grinding, electroplating and other processes.

rolling treatment

     Free-rotating hardened steel rollers are used to roll the machined surface of the steel part to produce plastic deformation, flatten the rough peaks on the surface of the steel part, and form a favorable residual compressive stress, thereby improving the wear resistance of the workpiece and Fatigue resistance.

     Application: parts with relatively simple shapes such as cylindrical surface, conical surface, plane and so on.

Surface swelling (extrusion or extrusion)

      Surface polishing is to extrude a steel ball with a diameter slightly larger than the aperture or a polishing tool of other shapes through the machined inner hole of the workpiece at room temperature to obtain an accurate, smooth and strengthened surface.

Fourth, the surface coating strengthening

Surface cladding reinforcement ✦

     Surface coating strengthening is a surface strengthening process in which one or more layers of other metals or non-metals are coated on the metal surface by physical or chemical methods.



     Purpose: To improve the wear resistance, corrosion resistance, heat resistance or surface decoration of steel parts.



Metal spray technology

     The process of heating metal powder to a molten or semi-molten state, atomizing it with a high-pressure airflow and spraying it on the surface of the workpiece to form a coating is called thermal spraying.


     The use of thermal spraying technology can improve the wear resistance, corrosion resistance, heat resistance and insulation properties of materials.



    It is widely used in almost all fields including aerospace, atomic energy, electronics and other cutting-edge technologies.



metal coating

     Coating one or more layers of metal coating on the surface of the base material can significantly improve its wear resistance, corrosion resistance and heat resistance, or obtain other special properties. There are electroplating, chemical plating, composite plating, infiltration plating, hot dip plating, vacuum evaporation, spray plating, ion plating, sputtering and other methods.

Metal Carbide Coating - Vapor Deposition

     Vapor deposition technology refers to a new type of coating technology that deposits vapor-phase substances containing deposition elements on the surface of materials by physical or chemical methods to form thin films.



     According to the principle of deposition process, vapor deposition technology can be divided into two categories: physical vapor deposition (PVD) and chemical vapor deposition (CVD).



Physical Vapor Deposition (PVD)

     Physical vapor deposition refers to a technology in which a material is vaporized into atoms, molecules or ionized into ions by physical methods under vacuum conditions, and a thin film is deposited on the surface of the material through a gas phase process.



      Physical deposition technology mainly includes three basic methods: vacuum evaporation, sputtering, and ion plating.

     Physical vapor deposition has a wide range of applicable substrate materials and film materials; the process is simple, material-saving, and pollution-free; the obtained film has the advantages of strong adhesion to the film base, uniform film thickness, compactness, and fewer pinholes.



     It is widely used in the fields of machinery, aerospace, electronics, optics and light industry to prepare thin films such as wear-resistant, corrosion-resistant, heat-resistant, conductive, insulating, optical, magnetic, piezoelectric, lubricating, and superconducting.

Chemical Vapor Deposition (CVD)

     Chemical vapor deposition refers to a method in which a mixed gas interacts with the surface of a substrate at a certain temperature to form a metal or compound film on the surface of the substrate.



      Because the chemical vapor deposition film has good wear resistance, corrosion resistance, heat resistance and electrical, optical and other special properties, it has been widely used in machinery manufacturing, aerospace, transportation, coal chemical industry and other industrial fields.

5. Surface cleaning and decoration

picture


Polished ✦

      Polishing is a finishing method for modifying the surface of parts. Generally, only a smooth surface can be obtained, and the original machining accuracy cannot be improved or even maintained. Depending on the pre-processing conditions, the Ra value after polishing can reach 1.6-0.008mm .

mechanical polishing

     Including wheel polishing, barrel polishing and vibratory polishing.
 

chemical polishing

     The metal parts are immersed in a special chemical solution, and the surface of the parts is polished by using the phenomenon that the convex parts of the metal surface dissolve faster than the concave parts.



Electrochemical polishing

      Electrochemical polishing is similar to chemical polishing, the difference is that direct current is also applied, the workpiece is connected to the anode, and the anode is dissolved.



Painting ✦



coating process

      Common coating processes are: brush coating, automatic dip coating, manual spraying (including high-pressure airless spraying), curtain coating, curtain coating, fluidized bed coating, roller coating, electrostatic spraying, etc.