Keywords: material, treatment, test, heat, Heat Treatment, Hardenability, 42CrMo, quench, structural steel,

Mold Material and Heat Treatment

Course Code: 01620

　　1. fill-in questions (8 items in total, 1 point for each blank, 15 points in total)

　　　1. There are________,________,________.

　　　2. Factors that affect graphitization are: ________ and________.

　　　3.42CrMo is a quenched and tempered structural steel, in which the mass fraction of carbon is about______and the mass fraction of chromium is about________.

　　　4. Hardenability refers to the ability of steel to form ________ when quenched.

　　　5. In a face-centered cubic lattice, the number of atoms actually occupied by the unit cell is________.

　　　6. The basic reason for alloy solid solution strengthening is________.

　　　7. Generally, solid metals are polycrystalline, in which grain boundaries have four properties.

　　　8. The lattice type of Fe3C is________.

　　2. True or False (15 items in total, 2 points for each item, 30 points in total)

　　nbsp;　 to judge the following questions, type & ldquo;& radic;& rdquo; in the brackets after the questions, type & ldquo;& times;& rdquo; in the wrong;.

　　　1. Martensite is an interstitial solid solution of carbon in & alpha;-Fe. (　　　　　)

　　　　2. Annealing is usually used to improve the machinability of mild steel.(　　　　　)

　& nbsp. (　　　　　)

　　　　　4.45 When a steel is heated to 760°C in equilibrium, the mass fraction of carbon in austenite is higher than the steel itself. (　　　　　　)

　　　　5. Malleable cast iron has a steel matrix and can be forged. (　　　　　　)

　　　　6. The equilibrium microstructure of T12 steel at room temperature is composed of proeutectoid ferrite and pearlite. (　　　　　)

　　　　7. The temperature at which the liquid metal crystallizes is higher than the theoretical crystallization temperature. (　　　　　)

　　& nbsp. (　　　　　)

　　& nbsp. (　　　　　)

　　　　10. The hardness of martensite is very high, so we can obtain 100% martensite by quenching. (　　　　　)

　　　　11. When steel is quenched, only rapid cooling can achieve the purpose. (　　　　　　)

　　　　12. T12 steel after quenching has higher hardness than 40Cr steel, indicating good hardenability. (　　　　　　)

　　　　13. Generally, air cooling after the forging of ordinary carbon steel is stopped is equivalent to normalizing. (      )

    14.The hardness of T12 steel in the annealed state is higher than that of 20 steel in the quenched state. (　　　　　)

　　　　　　If the 15.20 steel is not fully quenched (T

　　　　Explanation of 3. terms (4 items in total, 3 points for each item, 12 points in total)

　　　1. Critical deformation degree

　　　2. Work hardening

　　　3. Deterioration

　　　4.Pearlite

　　4. select appropriate materials and determine their use status: (1 point for each space, 16 points in total)

　　　　40Cr, W18Cr4V, 60Si2Mn, HT200, Q235A, GCr15, 3Cr2W8V, T12

　 5, total 27 points)

　　　1.To estimate the steel grade of annealed hypoeutectoid steel, it is known that the area ratio of preeutectoid F to P is

　　　　1:4 (excluding Fe3C Ⅲ). (4 points)

　　　2. Point out the difference between tempered martensite and martensite. (4 points)

　　　3. why can hypoeutectoid steel obtain higher strength and hardness than annealing after normalizing?(3 points)

　　　4.45 steel parts, the processing route is:

　　　& nbr; annealing & rarr; Rough machining & rarr; Quenching & rarr; Mechanical finishing & rarr; High-frequency induction heating Surface quenching and low-temperature tempering & rarr; Grinding, try to explain the role of forging and heat treatment processes. (5 points)

　　　5. draw the iron-carbon alloy phase diagram (part of steel) divided by microstructure, calculate the relative microstructure of annealed 60 steel at room temperature, and compare the strength, plasticity and hardness with 45 steel. (11 points)

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