EFFECTS OF TEMPERING TEMPERATURE ON THE IMPACT TOUGHNESS OF STEEL 42CrMo

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1 48 È 10 Vol.48 No ACTA METALLURGICA SINICA Oct pp ÉË 42CrMo Â Í Ø ÝÕ Ü Å «Æ ( Ì ²Á ß ¾ Ì (Ü )», ß ) ÚÖ Ì 42CrMo ± ³Â, ÙÍº Ó»¼Ü ÆÞ ÓÅ Ë ÞÈÐ. ¼Ï±, 42CrMo ² Ô Ë Ü, ÙÍº É Ü. ¼Ü ÆÕĐ, 12 Ë Õ ; Ü, Ó ¹É» Æ Õ, Ë ³ J; 600 Ü Ó À Ù Ð», Ë Ù³ 104 J; 600 ÕÜ, Ù Ó Ù Ó, Ë Ó. Ó Þ» ÈÐ 42CrMo Ë ÞÄ Á. ÄÏ Ü Æ, 42CrMo, Ë, Ó Đ À Æ TG161 Ô A Ð Æ (2012) EFFECTS OF TEMPERING TEMPERATURE ON THE IMPACT TOUGHNESS OF STEEL 42CrMo CHEN Jundan, MO Wenlin, WANG Pei, LU Shanping Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang Correspondent: LU Shanping, professor, Tel: (024) , shplu@imr.ac.cn Supported by Science and Technology Project of Liaoning Province (No ) Manuscript received , in revised form ABSTRACT 42CrMo heat resistant steel is a kind of structural steel, which is widely used in structural components such as crane weight on wheel, automobile crank shaft, locomotive gear hub and so on, for its good hardening ability, high temperature strength, good creep resistance, and little quenching deformation. However, in industry application, mismatching between the strength and the toughness always occurs for 42CrMo structure components. In order to solve the problem that the strength does not match the toughness in the manufacturing process for the polar crane for the nuclear power station, the effect of tempering temperature on the morphology and distribution of carbides and the impact toughness has been investigated for steel 42CrMo in this study. The experimental results indicated that the microstructure of the quenched steel 42CrMo after tempering was characterized by tempering sorbite. As the tempering temperature increased, the Charpy absorbed energy at 12 initially increased and then decreased. The flake carbides after 500 and 530 tempering are not evenly distributed on the original martensite boundaries, the Charpy absorbed energy are 26 and 44 J, respectively. While the granular carbides are evenly distributed in the microstructure after 600 tempering, the Charpy absorbed energy reaches a maximum value of 104 J. When the tempering temperature is higher than 600, granular carbides coarsened obviously and the Charpy absorbed energy reduced notably. The morphology and distribution of carbides is the key factor that influences the impact toughness of steel 42CrMo. Morphology and structure analysis for the carbide was carried out by TEM together with EDS analysis, the results showed that the carbide after tempering treatment is (Fe, M) 3 C and Fe, Cr, Mo are the main alloy element in the carbide. When the tempering temperature is in the range of , * Đ¹ Ò³ Đ ÙÍ : , Ù ½ : ¾ß : ÌÔ, º, 1987 Ð, Ð DOI: /SP.J

2 10 ËÓÐ : ÛÐ 42CrMo Ê ÝÇ 1187 the uniformly distributed granular carides forms on the matrix and the impact toughness is over 60 J. As the tempering temperature continues increasing, the carbides will coarsen and the impact toughness will decrease. In order to obtain the good strength and toughness matching, for 42CrMo structure, it is recommended that the tempering temperature should be in the range of KEY WORDS tempering temperature, steel 42CrMo, Charpy absorbed energy, carbide, ½² Í ß Ù, Û ß É Ø. ÅË ÈÆ ßÅ Ü, Õ ÛÜ, Ð ³ß Ü, Æ Û ³ Đ Ð ½ ß Ñ Ê. Öß ³ Â ËÛßÅ Ý¹½, ÕÑ Â Û»Ò [1] ; É, Â»Ð ßÅ ÀÖ, «, µä Ú ßÏÛ, Ø«Ûß Ð Â [2,3]. Â, Å ß ß É, É½ Ç Á ßÂ Ç ß¹. Í³ Ò Û Í ³ Í 42CrMo ², ¼ Đ ½, Â Ç ßÄ Á, Ï µ, Â Đ, ÐÇ ß Û µ [4 7], Ê Í Ö Ä Î ÍÐÆ «Þ ¼ ¹Ã Ç [8 14]. È 42CrMo Ç, Õ Õ Û Í ³ Å ÏÜÁ º ¼ß, ÕÁ ¹ Éß Ô, Ì µº. Õ 42CrMo Ö Õ [11 14], Â, Ã Ñ 42CrMo» Û µßé Ç ßÆÍ ÜÅ. 42CrMo Õ Â Í À, Ã [15 22] ² : Ñ ÝĐ Ñ Đ Á ß» µç Ú É, Đ Á Û µß. ß 42CrMo ß Ã Õ Å¼, Å ß Ñ ¹ ß Í µ É, Õ ÝĐ Â» º Û µßé Ñß Ã. À ĐÐß 42CrMo ºÂ Ý Đ Ñ, ÝĐ Ô ±¼ßÉ ß ± ÝĐ Ì ßÉ Ñ, Å Å ß Ñ Ñ Ø. 1 Û Å¼ Í µå ß Û ³, ³ È Æ 1, Åß Ô ± ² 1 Æ. ² 1 Ø Ï GB T CrMo ßÔ ±., Å¼ Í Ô ± GB T CrMo ß ± É. ³ Ã È 70 mm 40 mm 30 mm ß, ÑÐµÀ 3 Ý 3 Ì, Ö h ßÊ Ô Ñ. Ð Ñ Ô: Õ h Ð³, Ð 1 ² Ç Å Fig.1 Dimensional drawing of wheel (a) and level wheel (b) (unit: mm) 1 Î 42CrMo «½Î 42CrMo Õ ² Table 1 Chemical compositions of steel 42CrMo in GBT T and steel 42CrMo in this work (mass fraction, %) Steel 42CrMo C Si Mn S P Cr Ni Cu Mo V Nb Fe GB T <0.01 <0.01 Bal. This work Bal.

1188 48 È Đ ± ÝĐ Ñ, ÝĐ ± 500, 530, 560, 580, 600, 620 650, Ê 3 h, Ç Ñ ÎÞ Æ 2.

3 È Đ ± ÝĐ Ñ, ÝĐ ± 500, 530, 560, 580, 600, , Ê 3 h, Ç Ñ ÎÞ Æ 2. ºÂ Ñ Ôß 42CrMo ÝÅ¼, È À 5 mm ß ± Ý, Í µ ß AG 100KNG Ý ; Ì Å¼ Í Charpy V Ì Å¼, Å¼ 12 ( Å ¼ ±ß «), È 10 mm 10 mm 55 mm ± V Ì, Ì ¼ RKP 450. µ Ê 3 Å¼ Ê. Ý Ì ÆÐÐ, Í Hitachi S 3400N Ò (SEM) Ç ÚÎ», µ (EDS) ±. ºÂ Ñ Ôß Ö ß» ±. ß»É 4%( ± ) ºÄ Ð, Í AXIOVERT 200MAT É ÚÎ (OM) SEM Ç». ± 530, ÝĐÐß Ã, Í Gatan 656 Tenupol 5 ¾±½ ÄÚ (TEM). Í FEI µ ß Tecnai G 2 20 TEM Ç Ô ß ±¼, Â Í EDS Ô ßÔ ± ±. 2 Û Åß Ñ 2.1 ÊÌ 42CrMo Ã ÚÙ ÞÖ 42CrMo h ³ÐßÏ Á σ b 1960 MPa,, Ï, Ì 4 J,», Æ 3 Æ. Æ 4 42CrMo ºÂ ÝĐ 3 h Ðß Ý µ., Õ Ì, ½ÝĐ ß, σ b Ï Á σ s ÔÊ ß Â, ÁÔµßÊ, ÝĐ Õ , Á Ôµ Ð. ÝĐ Å 650, σ b σ s ± ÔµÅ MPa. Ý ½ÝĐ, ÁÖ Ê : 560 ÝĐÐ, Ý ½Đ, 12%, 650 ÝĐÐ, Ý Ú (26%). Temperature, o C Quenching temperature (850 10) o C Tempering temperature o C Time, h 2 42CrMo Ð ÍÝ Fig.2 Heat treatment process curve of steel 42CrMo Æ 5 Ï 42CrMo h ³ Ð ºÂ ÝĐÐÕ 12 ÔßÌ., Õ ÝĐÐ, ½ÝĐ Ì Ú, 500 ÝĐÐÌ 26 J, 600 Ý ĐÐ Ú 104 J; 600 ÝĐ, Ì Ô µ, 650 ÝĐÐÌ µ 44 J; ÝĐÐ, 12 ÔÌ Õ J,. ÛÍ ³ Û µ É : σ b 900 MPa, σ s 650 MPa, 12 ÔßÌ A k ( 12 ) 50 J, 12 ÔßÌ ½ A k ( 12 ) min 35 J. Â, 42CrMo ³ ÐÕ Ì ÝĐµÂ ¹Á Ì ß É. 3 42CrMo ² ÞÍÆº Fig.3 OM (a) and SEM (b) images of quenched steel 42CrMo Tensile strength 20 Yield strength Elongation 600 Fitted line Tempering temperature, o C 4 Ü Æ 42CrMo ÀÆÞÈÐ Fig.4 Effects of tempering temperature on the strength of Strength, MPa steel 42CrMo Elongation, %

$10 CSo} : w}^ 42CrMo 4R ` yo < Charpy absorbed energy, J 120 RTj C 42CrMo Koh ~>zr 42CrMo 6 D' d. J` y Y m l { vv/ in 6 6Æ. ^, DZ 500, 530, 560, 580, 600, 620 d 650 y l, vv/ RZy 4 B, Br<p i{l d%0.j. 500 d 530 y ` 3 h l { / 8(.$

4 10 CSo} : w}^ 42CrMo 4R ` yo < Charpy absorbed energy, J 120 RTj C 42CrMo Koh ~>zr 42CrMo 6 D' d. J` y Y m l { vv/ in 6 6Æ. ^, DZ 500, 530, 560, 580, 600, 620 d 650 y l, vv/ RZy 4 B, Br<p i{l d%0.j. 500 d 530 y ` 3 h l { / 8(.l, <B 6 I 5 $,. Rk % 0 q B E 4, Mf B (N 6a d b); 1y ` 9, <B $!ZZv$ m%0 (N 6c g), y l { <B I m % 0, f B >D. v (N 6e g), b 600 y Ym{, 620 d 650 y Yml <BZv v_ p (N 6f d g). q y, Z d{ C B J Tempering temperature, o C 5S (zp} g x~_æ 5 42CrMo Fig.5 Effect of tempering temperature on the Charpy absorbed energy of steel 42CrMo g 5CY&b -I_Æx~kzuU. 6 42CrMo Fig.6 Microstructures of quenched steel 42CrMo tempered at (e), 620 (f) and 650 (g) for 3 h 1189 (a), 530 (b), 560 (c), 580 (d),

$6 48 P k W, k W {Xrq4 Y F, B E4 < E4, y ` 9f B. B{XrkW. 1y ` { 9, _ )tl, E BD 500 650 y l / RZ y 4 B E'7U kw <B, vrk%0^ < α { B, Y^ <B{ l d%0. J t w! B r. 1 y ` 9 5 $ <B {= d $2, ) {8(.$

5 6 48 P k W, k W {Xrq4 Y F, B E4 < E4, y ` 9f B. B{XrkW. 1y ` { 9, _ )tl, E BD y l / RZ y 4 B E'7U kw <B, vrk%0^ < α { B, Y^ <B{ l d%0. J t w! B r. 1 y ` 9 5 $ <B {= d $2, ) {8( y Y m l, 1 y ` 9 1 FZv$ <B, ry `?Z 600, Zv B y $ Q %, B $ j p, Wh I d W, I $ <B ~_p. [Q, E$ B{y Z J t,bip)r. 1& α { g d ' gz $, AB{ g 2.3 8ej RTO>;VAZs_, 500 ry, _ g ~ p, { F Y^ ~9 42CrMo 6T ){ 06Q %Av, 1y ` { 9 %Av $ =l, α { ~y 5 q 12 p{ Charpy V TC, Z b /d o1a, J [, y `, ) O 7v f B ~9{<, T 0` Z 12. N 7 d 8 %( 1190 g -I_Æx~k 5p ozzs `in (a), 530 (b), 580 (c), 600 (d), 7 42CrMo 12 Fig.7 Low magnification fractographs of steel 42CrMo tempered at (e) and 650 (f) after Charpy impact test at 12

$10 CSo} : w}^ 42CrMo 4R ` yo < g -I_Æx~k 5p 1191 ozzs `UN 42CrMo 6y l T ) { M!J+ < p i { d%0. YvV/ O 7 1 X ^ : 1y ` 9, < piyy {5$ $!ZZv$, Y.Rk%0! v m%0 (N 6). DZ 500 d 530 y l, / < pi 6I5$y %0^f B Er.$ $bdm F (N 8b 6N); bd{wx^ O, T 0 8 42CrMo 12 Fig.$

6 10 CSo} : w}^ 42CrMo 4R ` yo < g -I_Æx~k 5p 1191 ozzs `UN 42CrMo 6y l T ) { M!J+ < p i { d%0. YvV/ O 7 1 X ^ : 1y ` 9, < piyy {5$ $!ZZv$, Y.Rk%0! v m%0 (N 6). DZ 500 d 530 y l, / < pi 6I5$y %0^f B Er. Y^5$< pi w { B9~gl{Nw, C 5$<p i9~a F V b, {y{<pi{ t V b 9 ~ l +&y { < p igu, J [T b, 8, T C% ( Z 26 d 44 J; 500 y l T az 2m a, 530 y lt a^ O 7v s[ T (N 7b), 2m, 500, L G F 2m { T X[ z$ o{ m, o{ myg bdm F (N 8b 6N); bd{wx^ O, T CrMo 12 Fig.8 High magnification fractographs of steel 42CrMo tempered at 500 (a), 530 (b), 580 (c), 600 (d), 620 (e) and 650 (f) after Charpy impact test at 12 (Inset in Fig.8b indicate a band of collection of dimples) >W 42CrMo 6DZ.J` y lq 12 p{j OdVOT a. ^, DZ 500 y l, a r Z # vt, I v {a (N 7a d 8a), D Z 530 y l, s[td KZ tt, #vt t, I%2m a (N 7b d 8b), b?9. 1y ` 9, q 12 pt a rzs[td KZ, Z {b a (N 7c e dn 8c e),? 600 y l abd,llz, %0Rk (N 7d d 8d), b,_. D 650 y l\ia, L a{2m8.,l (N 8f). 6 D' d. J` y Y m l, xv{ / RZ y 4 B, q < p i { d% 0. J, T C W x v 8 H, Y [ ^ O 5, {J A BpQ~ 42CrMo [23]

1192 48 È 9 42CrMo Ü º Þ TEM Å Ó Ù«Fig.9 TEM micrographs of steel 42CrMo quenched and tempered at 530 (a), 600 (b) and 650 (c), and SAD pattern analysis of carbides (d) ¾Ñ ß [24].

7 È 9 42CrMo Ü º Þ TEM Å Ó Ù«Fig.9 TEM micrographs of steel 42CrMo quenched and tempered at 530 (a), 600 (b) and 650 (c), and SAD pattern analysis of carbides (d) ¾Ñ ß [24]. Ð Óß Å ß ÑÕ 650 ÝĐÐßÌ Ö Õ, 530 ÝĐÐß Õ (Æ 8a, b g), Ð 650 ÝĐÐÌ ÆĐ 530 ÝĐÐÌ, ÄÐ Ì ÊÚ 500 ßÅ¼½ ß « ÝĐÐ, 12 Ì Õ J, Ì ; ÚÎ» ÎÏ, ÝĐ Ð» Ô Ý ºÊ ±¼ Ñ±¼ (Æ 6c f), ºÊ ±¼ß Ô ß ÆÛ Â µđ, Ä Ô ½ÝĐ ß Ú, µđ ÆÛ, Ì Â ßÎ ; ÖÎ, ÝĐÐ Ê ß (Æ 7c e), EDS ± ² ³ß Ò MnS, ÎÏ, 580 ÝĐÐ Ä Á ß, ÝĐÐ, ÄÁ Þß,. 600 ÝĐ, C ß Ñ, Ô Å Ð,» ±¼ Ôº Ú, ÕÅ Ð ß Ô ßÊ Ð, ¹ ßÂ ºÂ [25], Ì Â Ô Ø«Ô, 650 ÝĐÐ ÔÜ Ú. Â, Õ Ý Đ, Ô Ñ Ú, Ä±¼ ºÊ Ú Ñ Ô, Ð Ì ¾Ôß Â. ÖÝĐ, Ô ß Ô Ì Ôµß Â. 2.4 ÊÌ ÈÐ TEM ÁÒ Æ 9a c Ï 530, ÝĐÐ Ô ß TEM., ÝĐÐ» Ô Ê (Fe, M) 3 C, ß ½ÝĐ Ú, 600 Ô. EDS ± ½ ², Fe, Cr Mo, Cr Mo, ¹Ú ± ½ Æ 9d. 3 (1) 42CrMo ³Ð», Õ ÝĐ, Ï Á Ï Á ½ÝĐ ÁÖ ÐÔµßÊ, Ôµ ½Ð. 12 Ì ½ÝĐ, ÁÖ ÐÔµßÊ, ÝĐ 600 Ú 104 J. Æ ÛÍ

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