Technical inspection of cast iron platforms

Quality inspection:

1. The working surface should not have rust, scratches, bumps and other appearance defects that affect use.

2. The working surface should not have casting defects such as sand holes, pores, cracks, slag inclusions and shrinkage. Various casting surfaces should be cleaned of molding sand, and the surface should be flat and firmly painted. All edges should be blunted. On the flat working surface with an accuracy level lower than "00", sand holes with a diameter of less than 15mm are allowed to be blocked with the same material, and its hardness should be lower than the hardness of the surrounding materials. There should be no more than four blocked parts on the working surface, and the distance between them should not be less than 80mm.

3. On the two opposite sides, threaded holes or cylindrical holes for installing lifting facilities such as handles and lifting rings should be set. When designing the lifting position, it should be considered to minimize the changes caused by lifting.

4. According to user requirements, after threaded holes or grooves are set on the working surface of the plate, these parts should not be protruding above the working surface.

5. It should be made of high-quality fine-grained gray cast iron or alloy cast iron.

6. The hardness of the working surface should be HB 170-220.

7. The working surface should be scraped. For the "3" level flat surface, the planing process can also be used. The surface roughness of the planed working surface should not be greater than 5um according to the arithmetic mean deviation Ra value of the profile.

8. It should be treated for stability and demagnetized.

Flatness: It can be divided into laboratory level (Reference), calibration level (Master), tool room level (Working) Level 3

surface grinding: Platform In the early days, people used three platforms to match each other to produce a true flat surface. A skilled and patient grinder can produce an incredible degree of true flatness without the help of any measuring instrument, but only by matching the three platforms with each other and rotating them 90 degrees many times.

Flatness:

1. AA level: Its flatness (μm) = 1+1.6D2 (D is the diagonal length or diameter of the platform), which is used for high-precision measurement and is often used in laboratories.

2. Grade A: Its flatness is twice the error of Grade AA, and is often used in tool inspection rooms for the inspection of precision measuring tools.

3. Grade B: Its flatness is four times the error of Grade AA, and is often used in tool inspection rooms or on-site for the inspection of measuring tools or marking.

Cast iron flat plate inspection method: Pitch method The

so-called pitch method is an indirect measurement method that uses a bridge plate to divide the measured surface into sections, and the instrument reads the inclination angle or height difference of the measuring line of the two points before and after each section relative to the standard straight coin, and obtains the straightness and flatness error values ​​through data processing.
The pitch method is also called the angle difference method. Its measurement principle is to divide the measured section into several equally spaced blocks, and use a level or autocollimator to measure the inclination angle of each block relative to the measurement reference. According to 1" = 0.005/1000, it is converted into radians and multiplied by the span of the bridge plate, which reflects the height difference between the two supporting points of the bridge plate relative to the measurement reference.

hi = (0.005/1000) Clai (mm)

In the formula, C is the instrument graduation value, (");
L is the span of the bridge plate, mm
Ai is the instrument reading,

and the cumulative sum of the height differences of each block is the height Hi of each measuring point relative to the measurement reference, that is,

Hi = hi.

The pitch method reflects the existence of an imaginary ideal straight line as the measurement reference in the measurement, which improves the measurement accuracy.

Cast iron platform heat treatment process:

Cast iron platform (also known as cast iron plate) and bed casting products as a large casting must be heat treated to improve their own performance and improve the inherent quality of the cast iron plate. Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing technologies, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but rather imparts or improves the performance of the workpiece by changing the internal microstructure of the workpiece or the chemical composition of the workpiece surface. Its characteristic is to improve the intrinsic quality of the workpiece. In

order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often indispensable. Steel is the most widely used material in the machinery industry. The microstructure of steel is complex and can be controlled by heat treatment, so the heat treatment of steel is the main content of metal heat treatment. In addition, the mechanical, physical and chemical properties of aluminum, copper, magnesium, titanium and their alloys can also be changed by heat treatment to obtain different performance. (end)