Analysis of defects in several common vacuum carburized parts for stamping dies

Requirements for stamping dies

1、Spindle for high speed airport. As the stamping die in high speed cutting to go milling speed is very fast, so the speed of the spindle also need to keep up accordingly, generally need to be adjustable in 10,000 to 100,000 per minute, with fast speed up and fast and accurate stop performance. Therefore, the bearing structure form of lathe generally adopts liquid hydrostatic pressure, air hydrostatic pressure and suspension magnetic floating etc.

2、Since high-speed cutting lathes are all controlled by microcomputer programs, they are bound to require a central processor with fast processing of large amount of data and large-capacity storage devices; have fast data transmission capability and network transmission capability; and have error compensation function, including measurement error compensation, quadrant error compensation and thermal error compensation.

3. The drive system requires a large feed speed and acceleration, generally reaching 20-30 metres per minute and 20-40 metres per second squared.

4. The processing of stamping dies is carried out by milling tools, and the hardness and wear resistance of the tools are tested by tens of thousands of revolutions of milling. So for the tool material must be used carbide, polycrystalline diamond, etc.. At the same time the positioning of the tool must require precision, error control within 0.001mm.

Analysis of common defects in the vacuum-carbonated parts of stamping tools.

(1) Low hardness.

The amount of retained austenite is one of the reasons for the low hardness of stamped tools. The amount of retained austenite in the carburized layer is usually due to the high carburizing temperature and therefore the high concentration of carbon on the surface. Another reason for the low hardness of stamping tools is the low carbon concentration on the surface. The reason for the low carbon concentration on the surface is that the carburising temperature is too low, the carburising gas flow is small, the vacuum quenching oil absorbs a lot of air, the vacuum quenching oil is mixed with other oils such as cylinder oil etc.

(2) The depth of the carburizing layer does not meet the technical requirements.

The reason is that the depth of the carburizing layer of the stamping tool is greater than required due to the high carburizing temperature or the long carburizing time. The depth is less than technically required due to low carburizing temperature or short carburizing time.

(3)Uneven carburising layer in the tool itself.

The causes may be: air in the carburising gas; no pulse carburising; too low pressure of the carburising gas; too high and dense charge of the furnace; low purity of the carburising gas, producing more soot, etc.

(4) More soot, which also adheres to the cutting dies.