Why choose vacuum heat treatment

Vacuum heat treatment, a comprehensive technology combining vacuum technology and heat treatment, involves performing all or part of the heat treatment process under vacuum. Vacuum heat treatment can perform nearly all heat treatment processes, including quenching, annealing, tempering, and carburizing. Quenching can be performed using gas quenching, oil quenching, nitrate quenching, and water quenching. Compared to conventional heat treatment, vacuum heat treatment offers the following advantages.

Advantages of Vacuum Heat Treatment

1. Vacuum heat treatment provides excellent protection for the workpiece’s interior and surface

Vacuum heat treatment prevents oxidation, decarburization, and carbon accumulation. Oxidation causes the metal surface to lose its metallic luster, increase surface roughness, and reduce precision. Furthermore, scale on the steel surface is often the cause of quenching soft spots and quenching cracks. Oxidation reduces the strength of steel parts and degrades other mechanical properties.
Typically, oxidation and decarburization occur simultaneously. Oxidation in the decarburized layer reduces the carbon content, significantly reducing the steel’s quenching hardness, wear resistance, and fatigue properties. Decarburization of high-speed steel can also reduce red hardness.
Since vacuum heat treatment heats the metal in a certain vacuum, the workpiece is shielded from oxygen, preventing oxidation and decarburization. This results in a bright surface and excellent heat treatment quality. Furthermore, under vacuum conditions, reduction reactions and carbon accumulation are prevented.

2. Vacuum heat treatment improves overall mechanical properties

Vacuum heat treatment degasses and promotes surface purification. A vacuum significantly degasses liquid metals and effectively removes dissolved gases from solid metals. The most harmful gas in metals is hydrogen. Vacuum heating can quickly reduce hydrogen levels in metals and alloys to a minimum, eliminating hydrogen embrittlement. This improves the material’s plasticity, toughness, and fatigue strength, enhancing the overall mechanical properties of the workpiece. When heating metals and alloys in a vacuum, if the vacuum level falls below the decomposition pressure of the corresponding oxide, the oxide will decompose, and the resulting free oxygen will be immediately expelled from the vacuum chamber, further improving the metal’s surface quality and even activating the surface, thus purifying it.

3. Minimal deformation of workpieces during vacuum heat treatment

Generally speaking, the workpiece being treated is heated by thermal radiation within the furnace, resulting in a small temperature difference between inside and outside, and low thermal stress. This results in minimal deformation of parts treated in vacuum heat treatment. Furthermore, heating and quenching are performed automatically under vacuum, eliminating the need to transport the hot workpiece through air. (Although salt bath treatment and atmosphere treatment involve heating in an oxygen-free environment, quenching is still completed in air or a quenching medium containing oxygen molecules, reducing artifactual processing distortion.) For example, a Cr12MoV thread rolling wheel undergoes both vacuum heat treatment and salt bath treatment. Vacuum heat treatment results in 70% less deformation than salt bath treatment, resulting in a higher product yield.

4. Vacuum heat treatment reduces the volatility of gold in the workpiece

Vacuum heat treatment allows heating and vacuum quenching in a controlled atmosphere, thereby reducing the volatility of gold in the workpiece and ensuring heat treatment quality.

5. Other Advantages of Vacuum Heat Treatment

Vacuum heat treatment furnaces offer high thermal efficiency, rapid heating and cooling, and excellent stability and repeatability. They provide a favorable working environment, safe operation, and zero pollution or environmental hazards.

Vacuum Heat Treatment Furnace