H13 steel is the most widely used of the hot work mold steel in the world. It has great heat intensity properties, hardness and wear resistance. The toughness and anti-fatigue performance are good. It is widely used to make all kinds of hammer dies, hot-extrusion dies and etc. Hot die steel needs to sustain huge impulse load, friction and high-temperature oxidation. But something always happens during work time. Such as the crack, dent, abrasion, formation of cracking and etc. The chemical composition chart of H13 die steel as below.
|ASTM A681-08 Alloy Tool Steel||0.32-0.45||0.20-0.60||≤0.030||≤0.030||0.80-1.25||4.75-5.50||0.80-1.20||1.10-1.75|
|EN ISO 4957:1999 Tool Steel||0.35-0.42||0.25-0.50||-||-||0.80-1.20||4.80-5.50||0.85-1.15||1.20-1.50|
|JIS G4404: 2006 Alloy Tool Steel||0.35-0.42||0.25-0.50||≤0.030||≤0.020||0.80-1.20||4.80-5.50||0.80-1.15||1.00-1.50|
|ISO 4957: 1999 Tool Steel||0.35-0.42||0.25-0.50||-||-||0.80-1.20||4.80-5.50||0.85-1.15||1.20-1.50|
Its carbon content can make sure the high hardness, toughness and other properties. Adding the elements Cr, Mn, Si, Mn, which can make the hardenability get better to change the nature and shape of the oxide in the time of steel become solidification. That move can avoid the formation of low melting point Fes on the grain boundary. Instead, existence as Mns with certain plasticity. Then it will clean out the bad influence of sulfur to make the hot workability of H13 mold steel. Adding the elements of Mo, V to make it harden secondary. And it can enhance temper resistance.
It is a complicated question. But we can analysis it on four ways of material, design, manufacture and use.
H13 steel belongs to the type of graphitic alloy steel. There is so many nonmetallic inclusion in it. And has the defects of the center be loosen and etc. That will make the strength, toughness and etc get down. And the quality of H13 steel has two levels for common and high-quality. High quality H13 steel is made from high technology and material. It has better toughness and thermal fatigue property. However, the common one needs the processing of forging. Which will destroy the big non-metallic inclusion and make the carbide get small.
The design of mold depends on the shapes and specification of products to make sure the size of the die. That was good for the strength of die. Furthermore, too small radius of rounded corner, ill-suited groove position and etc will make the die gets big pressure during the heat treatment. That is easy to cause crackle. So must make the taper angle, hole and etc at the right position in the mold.
Raise the purity of H13 steel. Decrease the content of sulfur which is the most efficient way to increase the working life of H13 steel mold. The sulfur content is at the range of 0.005-0.008% of high-quality H13 steel. According to the analysis of chemical composition and quality of material can get the result of if it is eligibility. That will help us to make the right decision on the technology of heat treatment and forging.
Test Method: Sampled the H13 steel stuff to analyze its chemical composition and if it complies to the requirements. And take the sample at the steel center. Then grinding, polishing, etching with 4% nitric acid alcohol solution, examining the microstructure on an optical microscope, and assessing the grade of carbide segregation and the grade of inclusion according to relevant national technical standards.
The manufacture of H13 steel die must do a good job at design, the material chosen, forging, annealing, heat treatment and etc to make sure the quality at a high level. Every step is important and has a big influence on the mold product.
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