How is the surface roughness graded?

The surface roughness is divided into 14 grades, as follows:

Surface roughness 14 =Ra 0.0 12?

Surface roughness 13 =Ra 0.025?

Surface roughness 12 =Ra 0.050?

Surface roughness 1 1 =Ra 0. 1?

Surface roughness 10 =Ra 0.2?

Surface roughness grade 9 =Ra 0.4?

Surface roughness grade 8 =Ra 0.8?

Surface roughness grade 7 =Ra 1.6?

Surface roughness grade 6 =Ra 3.2?

Surface roughness grade 5 =Ra 6.3?

Surface roughness grade 4 =Ra 12.5?

Surface roughness grade 3 =Ra 25?

Surface roughness grade 2 =Ra 50?

Surface roughness 1 =Ra 100.

1, surface roughness refers to the machined surface with small spacing and tiny peak-valley roughness. ?

Tool marks during machining, plastic deformation during cutting separation, friction between the tool and the machined surface, and high-frequency vibration of the process system are all the reasons for the formation of surface roughness, and surface roughness will affect the wear resistance, stability of fit performance, fatigue strength, corrosion resistance and sealing performance of parts.

2, the main reasons for the formation of surface roughness are:

1) tool marks during machining;

2) Plastic deformation during cutting separation;

3) Friction between the tool and the machined surface;

4) High frequency vibration of process system.

Extended data

surface finish

Surface roughness refers to the small spacing and tiny peak-valley unevenness on the machined surface.

Tool marks during machining, plastic deformation during cutting separation, friction between the tool and the machined surface, and high-frequency vibration of the process system are all the reasons for the formation of surface roughness, and surface roughness will affect the wear resistance, fit stability, fatigue strength, corrosion resistance and sealing performance of parts.

In order to study the influence of surface roughness on the performance of parts and measure the surface micro-roughness, from the late 1920s to 1930s, some experts from Germany, the United States and Britain designed and manufactured profilometers, and also produced optical instruments for measuring the surface micro-roughness, such as light cutting microscope and interference microscope, which created conditions for quantitative evaluation of surface roughness. Surface roughness meter

Since 1930s, people began to study the quantitative evaluation parameters of surface roughness. For example, Abbott of the United States proposed to characterize the surface roughness by the curve of the ratio of the depth from the peak of the surface profile to the bearing length.

Schmaltz's monograph on surface roughness was published in 1936, and suggestions were put forward for the standardization of evaluation parameters and values of surface roughness. However, the use and value of roughness evaluation parameters really became a widely accepted standard after the corresponding national standards were issued in 1940s.

At first, the United States issued the national standard ASA B46. 1 in 1940, and after several revisions, it became the current standard ANSI/ASME B46.1-kloc-0/988 "Surface Roughness, Surface Waviness and Surface Texture", which adopted the midline system and took Ra as the main parameter. Then in 1945, the former Soviet Union issued the national standard GOCT2789- 1945 "Surface Smoothness, Surface Microgeometry, Classification and Representation", and then it was revised three times to become GOCT2789- 1973 "Surface Roughness Parameters and Characteristics", which also adopted the midline system and specified the outline. In addition, most of the standards of other industrialized countries were formulated in 1950s, such as DIN4760 and DIN4762 standards on surface roughness evaluation parameters and terms issued by the Federal Republic of Germany 1952 in February.

cause

The main reasons for the formation of surface roughness in surface roughness diagram are:

1) tool marks during machining;

2) Plastic deformation during cutting separation;

3) Friction between the tool and the machined surface;

4) High frequency vibration of process system.

main performance

Surface roughness is mainly manifested in the following aspects:

1) Surface roughness affects the wear resistance of parts. The rougher the surface, the smaller the effective contact area between mating surfaces, the greater the pressure and the faster the wear.

2) Surface roughness affects the stability of matching performance. For clearance fit, the rougher the surface, the easier it is to wear, which makes the clearance gradually increase during working; For interference fit, the actual effective interference decreases and the connection strength decreases, because the micro-peaks flatten out during assembly.

3) Surface roughness affects the fatigue strength of parts. There are large valleys on the surface of rough parts, which are as sensitive to stress concentration as sharp notches and cracks, thus affecting the fatigue strength of parts.

4) Surface roughness affects the corrosion resistance of parts. Rough surface is easy to make corrosive gas or liquid penetrate into the inner metal layer through micro-valleys on the surface, resulting in surface corrosion.

5) Surface roughness affects the tightness of parts. Rough surfaces can't fit tightly, and gas or liquid will leak through the gap between the contact surfaces.