Normalization process of steel

Classification of steel

Before Normalization process of steel, a few words about the classification of steel are in order. Steel is a material of a certain shape, size and properties made from ingots, billets or steel by pressure machining. Steel is mostly processed by means of pressure processing, which causes plastic deformation of the processed steel (billets, ingots, etc.). According to the steel processing temperature can be divided into two kinds of cold processing and hot processing; according to the different shapes of the section, steel can be divided into four categories: profiles, plates, tubes and metal products. The normalisation process of steel

Use classification

1. Structural steel

(1) Structural steel for construction and engineering is referred to as construction steel, which refers to the steel used in buildings, bridges, ships, boilers or other engineering to make metal structural parts. Such as carbon structural steel, low-alloy steel, steel reinforcing steel, etc.

(2) Structural steel for machinery manufacturing refers to the steel used to manufacture structural parts on machinery and equipment. These steels are basically high-quality steel or advanced quality steel, mainly high-quality carbon structural steel, alloy structural steel, easy to cut structural steel, spring steel, rolling bearing steel, etc.

2. Tool steel

Generally used in the manufacture of various tools, such as carbon tool steel, alloy tool steel, high-speed tool steel, etc.. According to the use can be divided into cutting tool steel, mold steel, gauge steel.

3. Special steel

Steel with special properties, such as stainless acid-resistant steel, heat-resistant steel without skin, high resistance alloy, wear-resistant steel, magnetic steel, etc.

4. Professional steel

This refers to the steel for professional use in various industrial sectors, such as automotive steel, agricultural machinery steel, aviation steel, chemical machinery steel, boiler steel, electrical steel, welding rod steel, etc.

he maening of Normalization process of steel

The normalisation process of steel is a heat treatment process in which the steel is heated to 30 to 50°C above Ac3 (or Acm), held for an appropriate amount of time and then cooled in still air. The steel parts heated to Ac3 above 100 ~ 150 ℃ normalized is called high-temperature normalization.

The purpose of the Normalization process of steel

For low carbon steel castings, forgings, the main purpose of normalizing is to refine the organization. Compared with annealing, after normalizing the pearlite layer is fine, ferrite grains are also relatively small, and therefore higher strength and hardness.
Low carbon steel due to annealing hardness is too low, cutting and processing the phenomenon of sticky knife, cutting performance is poor, through the annealing to improve hardness, can improve cutting performance, certain parts of carbon structural steel can be used instead of tempering, simplify the heat treatment process.
Over-eutectoid steel normalized heating knife Acm or more, so that the original was a network of carburized body all dissolved into the austenite, and then cooled at a faster rate to inhibit the precipitation of carburized body in the austenite grain boundaries, so as to eliminate the network carbide, improve the organization of over-eutectoid steel.
Welded parts require weld strength parts with normalising to improve the weld organization and ensure weld strength.
In the heat treatment process reworked parts must be normalized, requiring mechanical performance indicators of structural parts must be normalized after tempering to meet the mechanical performance requirements. Medium and high alloy steel and large forgings must be normalized with high temperature tempering to eliminate the internal stress generated during normalization.
Some alloy steels produce partial martensite transformation during forging, forming a hard tissue. In order to eliminate this bad organization to take normalizing, than the normal normalizing temperature of about 20 ℃ heating insulation for normalizing.

Defects of the Normalization process of steel

The normalising process is relatively simple and facilitates the use of forging waste heat normalisation, which saves energy and shortens the production cycle.
Normalizing process and improper operation also produces organizational defects, similar to annealing, the remedy is basically the same.
The “four fires” with the different heating temperatures and cooling methods, and the evolution of different heat treatment processes. In order to obtain a certain strength and toughness, the quenching and high-temperature tempering process combined, known as tempering. After quenching certain alloys to form a supersaturated solid solution, they are kept at room temperature or a slightly higher appropriate temperature for a longer period of time to improve the hardness, strength or electrical magnetism of the alloy. Such a heat treatment process is known as ageing treatment. The pressure processing deformation and heat treatment effectively and closely combined to carry out, so that the workpiece to obtain a good strength, toughness with the method known as deformation heat treatment; in the negative pressure atmosphere or vacuum heat treatment is called vacuum heat treatment, it can not only make the workpiece does not oxidation, not decarburisation, to maintain the surface of the workpiece after treatment, improve the performance of the workpiece, but also through the infiltration agent for chemical heat treatment.

Shandong Baowu Steel Group.

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