Alloy structural steel is widely used in many industrial fields, but hydrogen embrittlement problems pose a serious threat to its performance and reliability.
First of all, the generation of hydrogen embrittlement susceptibility of alloy structural steel is closely related to the source of hydrogen. In the smelting, processing and use environment of steel, hydrogen may enter the steel through various ways. For example, during the smelting process, moist raw materials or moisture in the atmosphere may decompose to produce hydrogen and dissolve into the molten steel; during processing, if pickling, electroplating and other processes are not handled properly, hydrogen may also penetrate into the steel. Even under normal use conditions, hydrogen-containing media such as certain chemical environments or humid atmosphere may cause hydrogen to enter alloy structural steel.
Secondly, the microstructure of alloy structural steel has a significant impact on hydrogen embrittlement susceptibility. Different alloy compositions and heat treatment processes will form different microstructures. For example, martensite structures tend to have higher susceptibility to hydrogen embrittlement than ferrite and pearlite structures. This is because the high strength and high dislocation density of martensite provide more trap sites for hydrogen, and hydrogen atoms easily gather in these sites, causing local stress concentration, thereby reducing the toughness and ductility of the material and increasing hydrogen embrittlement fractures. risk.
Furthermore, hydrogen embrittlement is extremely harmful to the mechanical properties of alloy structural steel. The presence of hydrogen in steel will reduce the fracture toughness of the material, making the steel likely to undergo brittle fracture when it is subjected to stress below its yield strength. This kind of fracture usually manifests as intergranular fracture or quasi-cleavage fracture, and unique characteristics of hydrogen embrittlement can be observed on the fracture surface, such as white spots, hydrogen-induced cracks, etc. Moreover, the occurrence of hydrogen embrittlement is often delayed, and the material suddenly breaks after it has endured stress for a period of time, which brings great hidden dangers to the safety of engineering structures.
In order to prevent hydrogen embrittlement of alloy structural steel, vacuum degassing and other technologies can be used during the smelting process to minimize the hydrogen content in the molten steel. During the processing, the pickling and electroplating process parameters are strictly controlled, such as controlling the pickling time, temperature and acid concentration, as well as the baking temperature and time after electroplating, to promote the hydrogen that has penetrated into the steel to escape as soon as possible. For materials that have experienced hydrogen embrittlement, the hydrogen in the steel can be diffused and eliminated through appropriate heat treatment, such as high-temperature tempering.
In terms of material design, optimizing alloy composition and microstructure is also an important measure. Adding appropriate amounts of alloying elements such as nickel and molybdenum can reduce the hydrogen embrittlement susceptibility of steel. At the same time, an appropriate heat treatment process is used to obtain a uniform, stable and low hydrogen embrittlement susceptibility microstructure, such as the tempered sorbite structure obtained by quenching and tempering treatment.
During use, try to avoid exposing alloy structural steel to hydrogen-containing environments, or perform surface protection treatments, such as coating protection, to prevent the intrusion of hydrogen. Regularly inspect alloy structural steel parts in use, such as using non-destructive testing methods to monitor the occurrence and development of hydrogen-induced cracks, promptly discover potential hydrogen embrittlement risks and take corresponding measures.
Understanding the hydrogen embrittlement susceptibility of alloy structural steel and taking effective preventive measures are extremely important to ensure the safety and reliability of alloy structural steel in engineering applications.
