What methods can be used to test the purity and carbide uniformity of H13 steel?

The purity and carbide uniformity testing of H13 steel mainly relies on methods such as chemical composition analysis, metallographic testing, and non-destructive testing. These methods can effectively evaluate the internal structure, inclusion content, and carbide distribution of materials, ensuring that they meet the requirements of high-performance mold steel.

Purity testing method for H13 steel

Chemical composition analysis
Accurately measure the content of key elements such as C, Cr, Mo, V, etc. through handheld spectrometers or laboratory equipment to determine whether they meet the standard requirements. Low sulfur (S ≤ 0.005%~0.008%) and low phosphorus are important indicators of high-purity H13 steel.

Non metallic inclusion rating
Samples were taken from the center of H13 steel, polished and observed under an optical microscope, and the inclusion grade was evaluated according to the NADCA 207-90 standard. High quality H13 steel should have a lower level of inclusions.

Gas content detection
Take steel chips or steel rod samples to detect nitrogen (N) and oxygen (O) content, and combine SEM+EDS to perform statistical analysis on inclusions larger than 1 μ m in size to evaluate metallurgical cleanliness.

Verification of the Effect of Electroslag Remelting
Comparison of microstructure differences between electric furnace steel and electric slag steel: Electric slag remelting can significantly improve purity, reduce band segregation and liquid carbide precipitation, and improve microstructure uniformity.

Method for testing the uniformity of carbides in H13 steel

Evaluation of non-uniformity of eutectic carbides
According to the national standard "Evaluation Method for Heterogeneity of Eutectic Carbides in H13 Steel", the distribution morphology of carbides (such as network, strip, layer) is observed in the longitudinal section of the corroded sample in the annealed state, and classified according to the standard rating chart.

Metallographic structure analysis
Observe the grain size, carbide precipitation state, and distribution to identify the presence of carbide segregation zones, large non-metallic inclusions, or eutectic carbide aggregation phenomena. High quality H13 steel should have uniform structure and slight segregation.

Forging Process Impact Assessment
H13 steel is subjected to the "modified forging" process (multiple upsetting and cross forging) to crush coarse carbides and improve their distribution uniformity. A total forging ratio greater than 4 can effectively improve uniformity.

Comparative testing before and after heat treatment
After isothermal spheroidization annealing, H13 steel is checked for dispersed distribution of carbides to avoid grain boundary segregation, thereby improving plasticity and toughness.