You wanna know why the hardness of files and rasps produced by Pai Lu can be higher than 60HRC? Because we pay attention to two very important parts of all our file and rasps.
First part, the surface, if you have learned about the whole manufacturing process of files and rasps, you will know that,during quenching, there will be carbon emission, which will lead to lack of hardness of the surface. So a very important step will be took in our third working shop--to remove(polish) the surface which is lack of carbon. In this way, we keep the surface of our files and rasps as hard as the rest part .
Second part, tang part, it is the most fragile part of the file and rasps, so we have to do special heat treatment to this part to make it strong and hard. So now you know our secret!
- Pulling force: 30 kg or 50kg or requested
- Keep the handle as straight as the file and rasps themselves
About How Can The Life Expectancy Of Steel Files and Rasps Can Reach a High Level of 500,000 Times?(1)Failure analysis of steel files and rasps:
The failure mode of the high-quality steel files and rasps made of the same material is worn-out; the poor quality steel files and rasps is often early broken and chipped. Failure analysis shows that the results are only because of differences in organizational structure, ie, the morphology of the carbides and the morphology of the matrix.(2) Heat treatment process analysis
Since T12A steel is hypereutectoid steel, it is brittle. Conventional heat treatment is generally aimed at obtaining fine carbides,improving their toughness and obtaining a toughening effect.
a) Pre-heat treatment: The two-stage isothermal spheroidizing annealing process shown in Figure 5-1 is used to change the original tissue state of thesteel file and rasps. First heated to a temperature slightly higher than Accm (820 ° C) 840 ~ 850 ° C, with proper heat preservation, only a small number of carbides remain in the structure, and the austenite structure is not uniform. Then, entering the first-stage spheroidizing annealing, the high-concentration carbon segregation zone and the undissolved carbide of the uneven austenite in the microstructure become the core of the growth of the large-grain carbide. At the same time, the carbon concentration in the surrounding tissue is reduced, and the preparation is ready for getting low carbon martensite structure after quenching. Upon entering the second-stage spheroidizing annealing, that is, isothermal below Ac1, the carbide further diffuses, precipitates, and gathers, spheroidizes, further enlarges the large-particle carbide, and regenerates many dispersed small-particle carbides. Thus, a certain amount of large particle carbides and a large amount of pearlite lay a good foundation for the final heat treatment. b) Final heat treatment: a heat treatment process using rapid heating and short-time heat preservation. Since the actual teeth heating temperature is low, the heating time is short, the carbide size is uneven, and the dissolution rate is different, the austenite structure is very uneven and a certain amount of carbide are obtained, besides the microstructure after quenching is good. c) Processing results: The organization is a certain number of low carbon martensite + more hidden needle martensite + angular passivation and uneven-size carbide; fracture morphology is a large number of shallow dimples and tears edges; The life expectancy of steel files and rasps can reach a high level of 500,000 times.