Journal of Northeastern University Natural Science ›› 2017, Vol. 38 ›› Issue (3): 350-355.DOI: 10.12068/j.issn.1005-3026.2017.03.010

• Materials & Metallurgy • Previous Articles     Next Articles

Brittle Fracture Mechanism and Impact Energy Scattering of Quenched and Tempered 07MnNiMoDR Steel

SHI Kun1, HOU Hong2, LI Jin-fu1, ZHANG Han-qian1, 3   

  1. 1. School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; 2. School of Metallurgy, Northeastern University, Shenyang 110819, China; 3. Baosteel Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai201900, China.
  • Received:2015-10-21 Revised:2015-10-21 Online:2017-03-15 Published:2017-03-24
  • Contact: ZHANG Han-qian
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Abstract: The impact energy of quenched and tempered (Q&T) 07MnNiMoDR steel was measured. The brittle fracture micro-mechanism in the ductile-brittle transition temperature (DBTT) region was studied. The results showed that the brittle fracture behavior is controlled by bainitic packets size. A critical packet size exists. When a micro-crack formed in the bainitic packet with a size exceeding the critical size propagates into adjacent packets under normal stress, brittle cleavage fracture occurs. The discrete distribution of the coarse bainitic packets leads to the scatter of brittle fracture load, which results in the impact energy scattering. It is suggested that homogenizing the distribution of fine bainitic packet sizes is an effective method of improving the impact energy and reducing its scattering in the DBTT region.

Key words: bainitic packet, impact energy, cleavage fracture, fracture mechanism, scattering

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