He Causes Of Hydrogen Embrittlement Of Steel And The Main Measures Of Dehydroembrittlement Treatment

Definition of hydrogen embrittlement

 

Hydrogen embrittlement is the polymerization of hydrogen in steel into hydrogen molecules, resulting in stress concentration, exceeding the strength limit of steel, forming small cracks inside the steel, also known as white point. Hydrogen embrittlement mainly occurs in the high strength low alloy steel, stainless steel and elastic parts, the main cause of hydrogen embrittlement is the surface treatment, such as electroplating, nitriding parts produced during the processing of hydrogen into metal internal lattice order confusion, distortion, cause internal stress increase, make the metal or coated produces brittleness, causing parts of fracture or coating fall off. The occurrence of hydrogen embrittlement in the process needs to meet two conditions: the metal has a high hydrogen content; There is some external force acting.

 

The range of hydrogen embrittlement

 

Not all metals produce hydrogen embrittlement in the process of surface treatment. According to research data and practice, hydrogen embrittlement mainly occurs in the following materials after surface treatment.

 

(1) Heat-treated carbon steel and alloy steel parts with tensile strength of 981N/mm2 (or hardness of 38HRC) or above.

 

(2) Spring steel (including harp wire, oil tempering wire, high carbon steel wire) with a hardness of more than 370HV.

 

(3) Martensite stainless steel products with heat treatment at tensile strength of 1236N/mm2 or above 36HRC.

 

Now in the processing, can lead to hydrogen embrittlement of the main processes are pickling, electroplating, nitriding, electrolysis, the above processes in the treatment of parts surface, hydrogen will be produced and infiltrated into the parts, resulting in hydrogen embrittlement.

 

Measures and prevention of hydrogen embrittlement

 

To remove hydrogen embrittlement generated by hydrogen adsorption of parts, drying treatment is generally selected. Drying treatment is generally divided into:

 

(1) General drying treatment, drying temperature of about 200℃.

 

(2) Low temperature drying treatment, drying temperature below 180℃.

 

The drying method is as follows:

 

First, the drying process is best carried out immediately after the hydrogen adsorption process, the maximum time is not more than 4h.

 

Second, the drying time and temperature shall be carried out according to the requirements in the attached table. In principle, the treatment must be completed once. After the treatment begins, it cannot be interrupted.

 

Third, the coating after stripping again electroplating situation, or plating after the implementation of other coating, embrittlement process more than two times, from the initial process to the implementation of the final process after the drying processing time in 4h, can only implement the drying process after the final process, the other can be omitted.