L Journal of Alloys and Compounds 312 (2000) 307–314 www.elsevier.com / locate / jallcom Magnetic properties of an AISI 420 martensitic stainless steel a,b, b b b * S.S.M. Tavares , D. Fruchart , S. Miraglia , D. Laborie a Departamento de Eng. Mecanica / UFF, R. Passo da Patria, 156, CEP 24210-470, Brazil b Laboratoire de Cristallographie, CNRS BP 166, 38042 Grenoble Cedex 9, France Received 28 June 2000; accepted 19 July 2000 Abstract The magnetic properties (coercive force, saturation and residual magnetization, and Curie temperature) of an AISI 420 steel were measured for different heat treatment conditions (quenching and tempering). The results show that the material is magnetically softer in the annealed condition and after oil quenching an increase of coercive force ( H ) and residual induction ( B ) and a decrease of saturation M c r magnetization ( s ) are observed. Tempering in the 300–5008C range promotes a further increase of H and B values. Tempering in the s M c r 500–6508C range promotes an increase of s and a magnetic softening. The magnetization vs. temperature curves of quenched samples s showed a pronounced increase of magnetization before reaching the Curie point. The results are discussed taking the knowledge of the physical metallurgy of the martensitic stainless steels into account.  2000 Elsevier Science B.V. All rights reserved. Keywords: Transition metal alloys; Structural materials; Magnetically ordered materials; Magnetic measurements 1. Introduction heat treatments of MSS [4–10], there is not much available work reporting the magnetic properties of these materials. Martensitic stainless steels (MSS) are extensively used On this subject Ebine and co-workers [11,12] have shown in mechanical constructions as structural material with that the mechanical hardness of a MSS SUS410 can be reasonable corrosion resistance [1]. They are often used in related to its coercive force and other magnetic properties. the quenched-and-tempered (Q and T) condition. The The study of the magnetic properties of MSS are also of quenching heat treatment involves annealing at tempera- interest to the nuclear industry [12,13]. Ara et al. [13] have tures in the 980–11008C range, depending on the chemical determined the magnetic properties of some martensitic composition of the steel, followed by oil or air cooling (SUS 403, SUS 410 J1 and TAF) and ferritic (SUS 405) [2–4]. The tempering treatment may be realized between stainless steels and observed that the MSS showed H c 200 and 7008C. However, in general, the range of 400– values between 5 and 15 Oe, while the ferritic SUS 405 6008C is not recommended since it leads to poor impact steel was rather soft (2–5 Oe). The Curie points ranged properties and poor corrosion resistance due to sensitiza- from 720 to 7508C. tion [2,3]. In the present work the magnetic properties of an AISI An important process that can occur during the temper- 420 MSS sample were measured for different heat treat- ing treatment of MSS is the secondary hardening due to ment conditions. The results are discussed taking into fine carbide and carbonitride precipitation [5–8]. Lim et al. account the physical metallurgy of the steel. [7,8] studied the tempering of an AISI 403 MSS and found the following processes occurring in sequence as the temperature and time of tempering increased: annealing, 2. Materials and methods secondary hardening due to fine precipitates, loss of corrosion resistance due to large Cr C precipitation and An 1/2 inch bar of AISI 420 (UNS 42000) steel 23 6 healing. (composition shown in Table 1) was purchased in the Although many papers have been published on the annealed condition. The annealing treatment consisted of mechanical properties and microstructural changes during heating at 7808C for 1 h, followed by slow furnace cooling to 6508C and air cooling. The material was machined and sliced into discs of 3 mm diameter and 0.5–1 mm *Corresponding author. E-mail address: tavares@polycnrs-gre.fr (S.S.M. Tavares). thickness. The discs were sealed in quartz tubes, soaked at 0925-8388 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0925-8388(00)01149-X