Six Major Characteristics of Metal-cutting Machine Parts Heat Treatment

Metal-cutting machine is this kind of machine that can process metal blank into parts by means of cutting. Traditionally, we call it machine tools. Machine tools industry in our country have different production capacity and size. Generally speaking, the mass production is for medium and small machine tools and a single or small batch production for large and heavy duty machine tools. The workpiece conditions of general machine tool, such as load, impact and lubrication condition, are better than that of cars, tractors and heavy machinery.

Parts are the support of machine tool, which have high requirements for precision retaining ability. The characteristics of machine tool parts heat treatment can be roughly summed up in the following aspects:

A. Selection of steel

Generally, it uses the alloy (carbon) structural steel, alloy steel and a few parts, such as steel plated guide rail, hardened lead screw, low alloy tool steel, bearing steel, etc.

B. Local hardening and surface hardening parts

There are many machine parts that only requires local and surface with high wear resistance, and in addition to a few local hardening parts using salt bath furnace, most of the parts use the local and surface quenching method (e.g., induction heating, laser heating and ultrasonic frequency heating, etc.) for hardening.

C. The use of batch type furnace

Most of the parts use salt bath furnace without oxidation heating. Vacuum furnace may drip kerosene in the gas carburizing furnace for protection atmosphere.

D. Precision parts with high dimension stability

Usually, it often is arranged one or more stabilizing treatment in the process, such as the stress relieving, low temperature aging treatment and cold treatment, etc., to minimize the residual internal stress, so as to guarantee high dimensional stability.

E. Most of steel parts must go through heat treatment in advance.

The steel castings, forgings and rolled stock, etc., must go through annealing, normalizing, tempering treatment and other prior heat treatment, to improve its strength, eliminate tissue defects and improve process performance. And it also makes good organization preparation for the final heat treatment at the same time, and reduces heat treatment distortion.

F. The chemical heat treatment at low temperature

The design of the machine tool parts is mostly considered from rigidity, and has lower requirements for heat treatment and great wear-resistant stability. Therefore, the nitriding, nitrocarburizing and other low temperature chemical heat treatment process, obtain wide applications.