不锈钢相图.docx

1、不锈钢相图AEB-L is a conventionally ingot-cast martensitic stainless steel designed and manufactured by Uddeholm Tooling AB (Sweden). Its nominal chemical composition (in weight percent) is as follows:C = 0.65Cr = 12.8Si = 0.4Mn = 0.65Figure 1 shows the phase diagram of Uddeholm AEB-L stainless steel (in

2、 deg. Celsius) calculated with Thermo-Calc, coupled with TCFE3 thermodynamic database.Figure 1. Phase diagram of Uddeholm AEB-L stainless steel (in deg. Celsius) calculated with Thermo-Calc, coupled with TCFE3 thermodynamic database. Silicon and manganese were excluded from thermodynamic calculation

3、s.The equilibrium values for solidus and liquidus temperatures were calculated to be 1461 C (2661 F) and 1379 C (2515 F), respectively.In the temperature range of 1144-1379 C (2091-2515 F) the microstructure of Uddeholm AEB-L stainless steel consists of just one single phase: austenite. Thus, if AEB

4、-L steel is hardened from an austenitization temperature that is higher than 1144 C (2091F) the resulting martensitic microstructure will contain no primary carbides.Below the temperature of 1144 C (2091 F) the chromium-rich M7C3 primary carbides start to precipitate from the austenitic matrix. At t

5、he austenitization temperature of, say, 1052 C (1925 F) the equilibrium amount of chromium-rich M7C3 primary carbides is 3.3 molar percent (2.6 volume percent). The equilibrium amount of carbon and chromium in the austenitic matrix at 1052 C (1925 F) is 0.44 wt. % and 11.4 wt. %, respectively. (The

6、amount of carbon and chromium in the matrix is a good indicator of the steels hardenability and corrosion resistance, respectively.)The equilibrium value for A1 temperature (eutectoid temperature) was calculated to be 814 C (1497 F). Under equilibrium conditions the austenite in Uddeholm AEB-L stain

7、less steel transforms into ferrite at this temperature.Finally, please see additional information about the Fe-Cr-C ternary phase diagrams.Free Downloads Phase diagram (in deg. Celsius) of Uddeholm AEB-L stainless steel Phase diagram (in deg. Fahrenheit) of Uddeholm AEB-L stainless steelMartensitic

8、stainless steel such as 154CM contains about 4 wt. percent molybdenum (in addition to 1.05 wt. % C and 14.0 wt. % Cr). To determine the effect of 4 wt. % Mo on the Fe-Cr-C ternary system, consider Figures 5 and 6, which show the isothermal sections of Fe-4Mo-Cr-C quaternary phase diagram at 1000C (1

9、832F) and 1100C (2012F), respectively.Figure 5. Isothermal section of Fe-4Mo-Cr-C quaternary phase diagram at 1000C (1832F) calculated with Thermo-Calc coupled with TCFE2000 thermodynamic database.According to Thermo-Calc calculations, the austenitic matrix of Fe-4Mo-14Cr-1.05C alloy at 1000C (1832F

10、) has the following chemical composition (in weight percent):Cr = 8.6 C = 0.33Mo = 2.6 The amount of chromium-rich M23C6 primary carbides in Fe-4Mo-14Cr-1.05C alloy at 1000C (1832F) is calculated to be 16.8 mol. percent. It is worth noting that the addition of 4 wt. % Mo to the Fe-Cr-C system expand

11、s significantly the presence of M23C6 phase at the expense of the M7C3 phase (compare Figure 1 Isothermal Section of Fe-Cr-C Ternary Phase Diagram at 1000C and Figure 3 Isothermal Section of Fe-0.8Mo-Cr-C Quaternary Phase Diagram at 1000C with Figure 5).Figure 6. Isothermal section of Fe-4Mo-Cr-C qu

12、aternary phase diagram at 1100C (2012F) calculated with Thermo-Calc coupled with TCFE2000 thermodynamic database.According to Thermo-Calc calculations, the austenitic matrix of Fe-4Mo-14Cr-1.05C alloy at 1100C (2012F) has the following chemical composition (in weight percent):Cr = 10.6C = 0.58Mo = 3

13、.4 The amount of chromium-rich M23C6 primary carbides in Fe-4Mo-14Cr-1.05C alloy at 1100C (2012F) is calculated to be 11.6 mol. percent.The amount of chromium and molybdenum in the matrix is also an indicator of the secondary-hardening response in general, the higher the amount of chromium and molyb

14、denum in the matrix, the stronger the secondary-hardening response during tempering (especially at higher tempering temperatures.) Part 1: Fe-Cr-C Ternary Phase DiagramsPart 2: Fe-0.8Mo-Cr-C Quaternary Phase DiagramsConsulting ServicesTo cover the costs of running this site, we accept consulting ass

15、ignments to perform customer tailored Thermo-Calc and DICTRA calculations. If we cannot solve your problem, we will help you find at least one organization which has the right human and computational resources to address your specific needs.We offer a money back guaranty for our consulting services

16、if you are not satisfied. Drop us a line; our address is: infocalphad.A high hardness level, a fine array of uniformly distributed primary alloy carbides, and an adequate matrix chromium content are the three most desired properties required to produce a knife with optimum properties. Ideally, a mar

17、tensitic stainless steel grade for knife applications should, therefore, satisfy the following two fundamental requirements:(1) The carbon content of the austenitic matrix has to be around 0.6 wt. pct. or higher in order to achieve the hardness of 63-64 HRC.(2) The chromium content of the austenitic

18、 matrix has to be at least 12 wt. pct. in order to ensure corrosion resistance. (It should be said, however, that a part of matrix chromium can be replaced with molybdenum with little or no negative consequences for corrosion resistance.) Isothermal sections of the Fe-Cr-C ternary phase diagram are

19、a good starting point when it comes to understanding the various trade-offs between the austenitization temperature selected for heat treatment and the resulting chemical composition of the austenitic matrix.The composition plane for the Fe-Cr-C ternary phase diagram at 1000C (1832F) is shown on Fig

20、ure 1. The carbon content is plotted along the horizontal axis and the chromium content along the vertical axis of the composition plane.Figure 1. Isothermal section of Fe-Cr-C ternary phase diagram at 1000C (1832F) calculated with Thermo-Calc coupled with TCFE2000 thermodynamic database.The isother

21、mal section in Figure 1 shows the content of chromium and carbon in the various phases of Fe-Cr-C alloys that can exist at 1000C (1832F). The area labeled (the Greek letter gamma) represents austenite. If the composition of an Fe-Cr-C alloy is plotted on Figure 1 and it falls inside the area, the mi

22、crostructure of that alloy will consist of austenite only, i.e., no carbides will be present at 1000C (1832F).Consider now one of the most basic martensitic stainless steel grades such as AISI 440C (approximately 17 wt. pct. chromium and 1.075 wt. pct. carbon), plotted on the composition plane of Fi

23、gure 1. Its chemical composition falls inside of the region labeled + M7C3. This means that if AISI 440C is heated to 1000C (1832F) its microstructure will consist of austenite and chromium-rich M7C3 primary carbides. Upon quenching the martensite formed from the austenite will contain chromium-rich

24、 M7C3 primary carbides dispersed within it.It is worth noting that on Figure 1 the right-hand boundary of the austenite region is labeled Carbon Saturation Line. This line is important as it tells us the maximum amount of carbon that austenite can dissolve within itself addition of more carbon would

25、 precipitate carbides.The further the alloy composition lies to the right of the saturation line, the larger the volume fraction of chromium-rich M7C3 primary carbides it will contain. The presence of chromium-rich M7C3 primary carbides renders the austenite depleted in both chromium and carbon rela

26、tive to the overall chemical composition of the alloy.Figure 1 can be used to determine the chemical composition of the austenite in an alloy such as AISI 440C. The austenite composition for AISI 440C at 1000C (1832F) is found at the point where the tie line drawn through AISI 440C intersects the ca

27、rbon saturation line. It is worth noting that even though AISI 440C alloy contains 1.075 percent of carbon and 17 percent of chromium overall, the austenite that forms at 1000C (1832F) contains only around 0.3 percent of carbon and 11.7 percent of chromium (see Figure 1). The martensite that forms u

28、pon quenching has the same chemical composition as the austenite. The carbon and chromium contents of the martensite have, in turn, the effect on its hardness and corrosion resistance, respectively. Thus, AISI 440C martensitic stainless steel, when hardened from 1000C (1832F), does not satisfy the t

29、wo requirements stated above (the carbon and chromium content of the matrix of at least 0.6 and 12 percent, respectively).To demonstrate the effect of increasing the austenitization temperature on the volume fraction of primary carbides and the chemical composition of the austenite, consider the cha

30、nge in the position of the carbon saturation line in Figure 2.Figure 2. Isothermal section of Fe-Cr-C ternary phase diagram at 1100C (2012F) calculated with Thermo-Calc coupled with TCFE2000 thermodynamic database.When the austenitization temperature is increased from 1000C (1832F) to 1100C (2012F),

31、 the content of carbon and chromium in the austenitic matrix is increased from 0.3 % C / 11.7 % Cr to 0.5 % C / 13.2 % Cr. The volume fraction of chromium-rich M7C3 primary carbides is smaller at 1100C (2012F) than at 1000C (1832F), as graphically demonstrated by the length of the tie line in Figure

32、s 1 and 2.The Second Edition of Heat Treaters Guide Practice and Procedures for Irons and Steels (published by ASM International in 1995) recommends that AISI 440C be austenitized at 1010C-1065C (1850F-1949F). For maximum corrosion resistance and strength, the Guide recommends the upper end of the austenitization range. Such a recommendation is not surprising. The above given phase diagrams demonstrate th