Mar 27,2026
Golden Phase Organization and Performance Regulation of Mold Steel
Golden Phase Organization and Performance Regulation of Mold Steel
Metallographic structure, Heat treatment, Microstructure, Tool steel, Property control
The macroscopic performance of cast steel—hardness, toughness, abrasion resistance, and corrosion resistance—is ultimately determined by its microscopic phase organization. The internal phase organization of a piece of steel undergoes a series of changes from the time it leaves the steel factory, to the time the mold is completed, and to the time it becomes obsolete. Understanding the relationship between these tissues and performance, and mastering methods to regulate the tissues through thermal processing, are core technologies for the application of cast materials.
The basic gold-phase composition phase of cast steel. Common cast steel tissues include ferroid bodies, perolid bodies, Bayesian bodies, Ma‘s bodies, residual Ochsian bodies, and various carbonides. Ferroid bodies are solid solvents of carbon in α-Fe, soft and resilient; perolid bodies are layered mixtures of ferroid bodies and carbon permeating bodies, with moderate strength and hardness; Bayesian bodies are products of the transformation of overcooled Ochsian bodies in the medium temperature zone, with higher strength and resilience; Ma‘s bodies are oversaturated solid solvents of carbon in α-Fe and are the main strengthened phase obtained after tempering, with extremely high hardness but more brittle; residual Ochsian bodies are Ochsian bodies that failed to transform after tempering, soft and unstable; carbonides are compounds formed by alloy elements and carbon, such as Cr7C3, Mo2C, VC, etc., which have extremely high hardness and are the main contributors to abrasion resistance.
Tissues and processing performance in the defrosted state. Molded steel is usually in the defrosted state when it comes out of the factory, organized into globular carbonides (globalized defrosted tissue) uniformly distributed on the iron body substrate. This tissue has lower hardness (approximately HB200-250), making it easier for cutting processing and cold plastic deformation (such as cold compression). The size and distribution of the globularized carbonides have an important effect on subsequent tempering performance: small, diffuse-distributed carbonides are easier to dissolve when heated by tempering, have higher degree of metalization of the Ma body after tempering, and are more resilient; large, concentrated carbonides lead to decreased performance.
The evolution of tissues during the tempering and re-firing processes. Tempering is heating steel to the temperature of Austrian corporealization, allowing carbonides to dissolve, carbon and alloy elements to be uniformized, and then rapidly cooling, allowing Austrian bodies to transform into Mars bodies. After tempering, the tissues are Mars bodies + residual Austrian bodies + unsolved carbonides. The form of Mars bodies changes with carbon content: low-carbon Mars bodies are strip-like, with higher toughness; high-carbon Mars bodies are sheet-like (needle-like), with high hardness but high fragility. Re-firing is heating tempered steel below the critical temperature, allowing unstable Mars bodies and residual Austrian bodies to decompose, isolate carbonides, eliminate internal stress, and adjust hardness and toughness. The tissues after re-firing are called re-firing Mars bodies or re-firing Thor bodies, depending on the temperature of re-firing. Low-temperature refire (150–250°C) obtained refire horse cell, maintaining high hardness; high-temperature refire (500–650°C) obtained refire cord cell, enhancing toughness and plasticity.
Secondary hardening phenomenon and high-performance cast steel. Cast steel containing strong carbonide-forming elements (such as Cr, Mo, W, V) will break down small diffused alloy carbonides when returned to fire at high temperatures, resulting in hardness not only not decreasing, but increasing instead. This is called “secondary hardening.” Using the secondary hardening effect, cast steel can maintain high hardness (red hardness) at high temperatures of 500–600 °C, which is a core characteristic of hot cast steel and high-speed steel.
Influence of gold-phase tissues on failure patterns. Mold failure is often associated with tissue abnormalities. Rough carbonides or carbonide biolysis are the source of fatigue fracture germination; excessive residual oxide undergoes macroscopic phase change during service, leading to size changes and stress fracture; insufficient feedback leads to excessive internal stress, leading to early fracture; crystalline thickening leads to decreased toughness, prone to brittle fracture. Therefore, examining the tissues of mold steel through gold-phase microscopy is an important means for failure analysis.
Fine tissue regulation technology in modern cast steel. The emergence of powder metallurgy technology has achieved unprecedented levels of tissue homogeneity and carbonide refinement in cast steel. The carbonide size of powder high-speed steel, such as the ASP series, can be controlled at 2-5 μm, is uniformly distributed, isotropic, and combines high hardness, high toughness, and excellent abrasive performance. Technologies such as electro-slag remelting (ESR) and vacuum arc remelting (VAR) further improve the purity of steel materials and reduce non-metallic impurities.
In short, the performance code of the cast steel is buried deep within its microscopic phase tissue. From material selection to thermal processing, every step is writing the “gene” of the tissue. Only by deeply understanding the relationship between tissue-performance-processing can the most suitable steel be chosen for each set of cast and its potential be maximized through sophisticated thermal processing processes.
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