What are the Internal Defects of Bearing Steel Mmaterials?

The main internal defects of bearing steel materials include non-metallic inclusions, foreign metal inclusions, hairline, shrinkage, bubbles, white spots and micro porosity. The resulting hazards are as follows:

1. If there are non-metallic inclusions in the bearing steel, will seriously affect the continuity of the bearing steel, greatly reducing the bearing performance, life and reliability.

2. Hairline is a kind of bearing steel material surface or the lower layer of the epidermis appears to be a small crack-like defects. Along the rolling direction is intermittent distribution, some alone a, some several. If there is a serious hairline defects in the bearing parts, in the actual use of the bearing process is easy to produce fatigue spalling and reduce the service life of the bearing. Therefore, the working surface and secondary surface of the bearing is not allowed to have serious hairline defects, if the bearing parts are found to have serious hairline defects during magnetic particle inspection, they can not continue to use.

3. Ingot in the process of condensation after casting, due to volume contraction and the formation of tubular, flared or scattered holes in the upper center of the ingot, known as shrinkage. Before opening the ingot, all the shrinkage holes on the top and bottom of the ingot should be removed. If the shrinkage is not cut out, it will lead to the formation of shrinkage (tube) residue when rolling along the rolling direction.

If there is a shrinkage residual defects in the bearing parts, easy to produce quenching cracks in the heat treatment quenching, or steel ball in the surface strengthening broken. Shrinkage residues lead to bearing parts of the impact resistance (crushing load of the steel ball) and contact fatigue life is greatly reduced.

4. Due to the presence of air bubbles is equivalent to reduce the effective cross-section of the part, and produce a large gap effect (gap sensitivity), thus greatly reducing the strength of the steel.

5. White point is the performance of bearing steel and bearing mechanical properties, service life of the most harmful kind of defects. Therefore, in the current national standards for bearing steel materials expressly provide that this defect is absolutely not allowed to exist, once found in the ingot or steel white spot defects exist, do not allow re-sampling for retesting, must be scrapped.

6. Microporosity, also known as microscopic cracks. If there are microscopic porosity in the bearing steel, will greatly reduce the intergranular bonding, not only seriously affect the mechanical properties of bearing parts, quenching in the heat treatment is prone to quenching cracks, and in the use of the bearing process is easy to cause stress concentration at the microscopic porosity defects, making it a source of fatigue cracks, reducing the service life and reliability of the bearing.

Contact us for more details:

E-mail: emily@gainhui.com

Tel: +86-029-88692376

Mob/WhatsApp: +86-18710850036