Final examination paper of engineering materials

《 Foundation of engineering materials and forming technology 》

One 、 Right and wrong ( Please mark after the correct question “√”, Mark the wrong question “×”, Each question 1 branch , common 10 branch )

1． Because single crystals are anisotropic , Therefore, the performance of practical metal materials in all directions is also different . ( × )

2． The basic phases of the alloy include solid solution 、 Metal compounds and mechanical mixtures of these two fall into three categories . ( × )

3．Fe3CⅠ And Fe3Cll Its morphology and crystal structure are different .( × )

4． Quenching plus high temperature tempering treatment is called quenching and tempering treatment . Tempered martensite structure is obtained after treatment , It has comprehensive mechanics

Good features .(× )

5． Fiber reinforced composites , The smaller the fiber diameter , The more obvious the enhancement effect . ( √ )

6． There are crystalline phases in ceramic materials 、 Solid solution phase and gas phase coexist . ( √ )

7． Casting production is especially suitable for manufacturing parts with large or complex forces . ( × )

8． Cast iron can change the matrix structure and graphite morphology after heat treatment . ( × )

9． Manual arc welding 、 Automatic submerged arc welding 、 Argon arc welding and gas shielded welding belong to fusion welding .( √ )

10． Bainite is the product of medium temperature transformation of undercooled austenite , In the process of transformation , Carbon atoms can diffuse over short distances ,

Iron atoms cannot diffuse . (√ )

Two 、 Indefinite multiple choice questions （ Every little question 1 branch , common 26 branch ）

1、 Glass transition temperature of plastic products ( b ) For good , Glass transition temperature of rubber products ( ) For good

1) low , high 2) high , low 3) high , high 4) low , low

2、 The following thermosetting plastics are ( c )

1)PA 2)PP 3) Epoxy 4)PVC

3、 With the increase of cold plastic deformation , Metallic material （ b ）

1） Strong hardness decreases , Plastic toughness is improved 2） The strength and hardness are improved , Plastic toughness decreases 3） The strength, hardness and plastic toughness decreased 4） The strength, hardness and plastic toughness are improved 5） There is no change in strength, hardness and plastic toughness

4、 In the following cast alloys , The best casting process performance is ：（ a ）

1） Grey cast iron 2） cast steel 3） Cast copper alloy 4 ） Cast aluminum alloy

5、 The casting of high melting point difficult to cut alloy precision castings with complex shapes should adopt ( b )

1) Metal mold casting 2) Investment casting 3) Die casting 4） Low pressure casting

6、 The main function of riser during casting is ( b )

1) Increase the local cooling rate 2) Compensate for liquid metal , Exhaust and slag collection

3) Improve liquidity 4） Realize sequential solidification

7、 Powder pressing is suitable for ：（ ade ）

1） Mass production 2） Single piece small batch production 3） Large piece production

4） Refractory 、 Extremely hard 、 Production of ceramic parts 5） Production of porous components

8、 In the following products or products , Which are usually formed by solid-state connection to obtain blanks or finished products ：（ ade ）

1） Liquefied gas cylinders 2） Crankshaft of engine 3） Oil bearing 4） Steel tables and chairs 5） Glass fish tank

9、 Cast iron is difficult to weld because （ abc ）

1、 The joint is easy to form hard and brittle Fe3C 2、 Low tensile strength 、 Poor plasticity

3、 Easy to produce pores 、 Slag inclusion 4、 The weld is easy to precipitate graphite

10． Cast into shape （ ac d ）.

1、 There are many processes , Casting quality is not stable 2、 Good mechanical properties of castings

3、 Prone to organizational defects 4、 The material, shape and size of castings are almost unlimited

11． Injection molding is suitable for （ abd ）

1、 Mass production 2、 The shape is complicated 、 Production of precision parts

3、 Production with metal inserts 4、 Thermoplastics 、 Production of rubber parts

12. Extrusion can produce （ abc ）

1、 Profiles 2 Wire wrapping 3、 Agricultural film 4、 TV casing

13. The following statement is correct （ abc ）

1、 Rubber can be injected 、 Molded 、 Squeeze out 、 Rolling and other forming methods to produce products 2、 Vulcanization of rubber refers to crosslinking and curing

3、 Rubber before vulcanization is called raw rubber 4、 Natural rubber does not need vulcanization

14. The general principle of formulating the material forming technology scheme is ：abc

1、 The material selected for the part should be suitable for the forming technology

2、 The realistic possibility and economy of the selected materials and forming technology of the parts

3、 Safety of material forming technology 4、 Material performance

15． Quenched + After low temperature tempering, it may be “ High carbon tempered martensite + Carbides + A small amount of retained austenite ” The structural steel is ( abcd )

1、T9 2、Cr12MoV 3、9SiCr 4、W18Cr4V

16． Pearlite structure in steel is ( acd )

1、 Eutectoid products 2、 Eutectic products 3、 Biphasic organization 4、 Mechanical mixture

17、 The following materials suitable for high temperature and heat resistant parts are ( ad )

1、 ceramics 2、 Fiberglass 3、40Cr 4、12CrMoV

18、 The spindle of the machine tool can be controlled by ： 1、45# steel , Temper + Surface hardening + Low temperature tempering ;

2、40Cr, Temper + Surface hardening + Low temperature tempering ;

3、20CrMnTi, Carburizing + quench + Low temperature tempering ;

4、38CrMoAl, Temper + Nitriding .

In the above materials and strengthening processes ：

1） The lowest cost is a , The most resistant to impact and heavy load is c , The one with high accuracy and minimum deformation is d .

2） The highest hardenability is a , The lowest is c , The most heat-resistant and corrosion-resistant is d .

3） The axis part may be low carbon martensite , The surface layer of high carbon martensite is c ; The surface of the 、 The same composition of the heart is ab .

3、 ... and 、 Completion （ common 20 branch ）

The grades of the following engineering materials are known , Please fill out the forms in order .（ Each grid 1 branch , common 20 branch ）

material	species	General composition	Strengthen the way	Performance features	Application, for example,
Q235
ZL102
W18Cr4V
RuT300

Four 、 Short answer （ common 16 branch ）

1． According to the iron carbon phase diagram , Analyze the causes of the following phenomena ：（9 branch ）

(1) The carbon content is 1.0% The specific carbon content of steel is 0.5% High hardness of steel ;

(2) At room temperature , Carbonaceous 0.8% The strength ratio of steel containing carbon 1.2% Steel height ;

(3) stay 1l00℃ when , The carbon content is 0.4% Of steel can be forged , The carbon content is 4.0% White iron cannot be forged .

1． answer ： Cause analysis ：

（1） From the analysis of iron carbon phase diagram , Carbon steel in equilibrium is made of F and Fe3C Two phase composition .F Good plasticity , and Fe3C Hard and crisp . When the carbon content in steel is low ,Fe3C Distributed in layers F in , With the increase of carbon content ,Fe3C The more the number of , The greater the resistance to dislocation movement , Its strength 、 The higher the hardness , plasticity 、 The lower the toughness .（3 branch ）

（2） When the carbon content of steel exceeds 0．9％ when , Reticular distribution along the grain boundary Fe3CⅡ, With the increase of carbon content , The more they are , The thicker the network, the more complete , The weaker the binding force between grains , therefore , The strength of steel decreases with the increase of carbon content . （3 branch ）

(3) contain 0．4％C The steel of is hypoeutectoid steel , Heat to 1100℃ when , It has been completely converted to single-phase A organization , plasticity

good , Small deformation resistance , It has good forging performance ; But contains 4．0％C White cast iron , Due to the high carbon content , Heat to

1100℃ when , There are a lot of Ld（A+Fe3C） and Fe3CⅡ, Poor forging performance , Therefore, it cannot be forged .（3 branch ）

2． Please select the appropriate blank production method or process for the following parts ：（7 branch ）

(1) Car fuel tank ;(2) Mass produced gearbox ;(3) Single piece steel frame ;(4) The shape is simple 、 Steel shaft with large bearing capacity ;(5) Engine piston ;(6) hull ;(7) Crankshaft on automobile engine .

5、 ... and 、 Comprehensive analysis questions （ common 28 branch ）

1、 Current use 38CrMoAl The processing route of the spindle for manufacturing high-precision grinding machine is as follows ： To lay down → forging →（ ）→ Rough machining →（ ）→ finish machining →（ ）→ Rough grind →（ ）→ Fine grinding .

Try to answer the following questions ： （13 branch ）

1） Heat treatment process ： Temper , Nitriding , Stress relief , Annealing is filled in the brackets above ;（4 branch ）

2） What is the main purpose of the heat treatment process before rough machining ？（2 branch ）

3） Before rough grinding 、 What role does the post heat treatment process play ？（3 branch ）

4） In use , What is the sectional organization of the shaft ？ How the performance ？（4 branch ）

2． According to the state of the material at the time of forming , The forming principles of forming technology mainly fall into several categories ？ What are their characteristics and

What is the scope of application ？（15 branch ）

Casting —— Liquid solidification forming , The material is metal material, especially brittle material （ Such as cast iron , Cast aluminum alloy, etc ） The blank production of all kinds of parts, especially the parts with complex inner cavity ;（3 branch ）

forging （ Pressure machining ）——— Solid plastic deformation , The material is mainly the production of rough or semi-finished products or parts with no inner cavity or simple inner cavity of ductile metal materials ;（3 branch ）

welding —— Solid state connection forming , It is mainly the connection of various components made of ductile metal materials ;（3 branch ）

Powder pressing （ Powder metallurgy ）—— Granular forming , Production of various parts or semi-finished products with granular raw materials ;（3 branch ）

Polymer materials （ polymer ） Take shape —— Viscous flow （ Colloid ） Solidify and form , Production of all kinds of plastic or rubber products .（3 branch ）

《 Foundation of engineering materials and forming technology 》 Refer to the answers and scoring criteria

（ One ） Right and wrong

1．×;2．×;3．×;4．×;5．√;6．√;7．×;8．×;9．√;10．√.

( Two ) Indefinite multiple choice questions

1-2）; 2-3); 3-2); 4-1); 5-2); 6-2); 7-1),4),5); 8-1),4),5); 9-1,2,3; ;10-1,3,4; 11-1,2,4; 12-1,2,3;13-1,2,3;14-1,2,3;15-1,2,3,4;16-1,3,4;17-1,4;18-1）1;3;4;18-2）1;3;4;18-3）3;1/2;

( 3、 ... and ) Completion （ common 20 branch ）

1． answer

material	species	General composition	Strengthen the way	Performance features	Application, for example,
Q235	Carbon structural steel	C%≤0.22%; Total alloy ＜5%		The intensity is average , Good plasticity ; Easy to shape and weld	Metal structure 、 The steel plate 、 reinforced 、 Section steel 、 Stub shaft 、 mandrel 、 Nut 、 Weldments, etc
ZL102	Casting Silicon alloy	Si：8—25%, Yu Wei Al	Metamorphic treatment	The mechanical properties are not as good as deformed aluminum Alloy , But the casting performance is good	Parts with complex shapes , Like a plane 、 Instrument parts , Pump housing
W18Cr4V	High speed steel	High carbon ;W18%;Cr4%V＜1.5%	forging , quench + Temper ; Diffusion enhancement	High wear resistance 、 High heat hardness	High speed cutting or cutting tools with complex shapes
RuT300	Vermicular graphite cast iron	High carbon , High silicon , Low sulfur , Low phosphorus C=3.2%	Inoculation treatment , Vermiculation treatment	High compressive strength , It is good to bear the thermal cycle load , Good castability	cylinder head 、 Cylinder liner 、 Glass mold and other parts

Four 、 Short answer （ common 16 branch ）

1． answer ： Cause analysis ：（1） From the analysis of iron carbon phase diagram , Carbon steel in equilibrium is made of F and Fe3C Two phase composition .F Good plasticity , and Fe3C Hard and crisp . When the carbon content in steel is low ,Fe3C Distributed in layers F in , With the increase of carbon content ,Fe3C The more the number of , The greater the resistance to dislocation movement , Its strength 、 The higher the hardness , plasticity 、 The lower the toughness .（3 branch ）（2） When the carbon content of steel exceeds 0．9％ when , Reticular distribution along the grain boundary Fe3CⅡ, With the increase of carbon content , The more they are , The thicker the network, the more complete , The weaker the binding force between grains , therefore , The strength of steel decreases with the increase of carbon content .（3 branch ）

(3) contain 0．4％C The steel of is hypoeutectoid steel , Heat to 1100℃ when , It has been completely converted to single-phase A organization , plasticity

good , Small deformation resistance , It has good forging performance ; But contains 4．0％C White cast iron , Due to the high carbon content , Heat to

1100℃ when , There are a lot of Ld（A+Fe3C） and Fe3CⅡ, Poor forging performance , Therefore, it cannot be forged .（3 branch ）

2． answer ：(1) Cold stamping — Stamping parts ;(2) Sand casting — casting ;(3) Arc welding — Weldments ;(4) forging — forging ;(5) Casting — casting ;(6) Arc welding — Weldments ;(7) Casting — casting .

( 5、 ... and ) Comprehensive analysis questions

1． answer ：

1） Anneal , Temper , Stress relief , Nitriding .（4 branch ）

2） Annealing before rough machining is to stabilize the internal structure of the workpiece , Eliminate the internal stress of forging , Prepare for subsequent heat treatment and surface strengthening .（2 branch ）

3） Stress relief annealing of workpiece before rough grinding , To eliminate the internal stress generated in the machining process , Prevent workpiece size change and deformation ; Nitriding after rough grinding is to form a nitride layer on the surface of the workpiece , To significantly improve its surface hardness and wear resistance , Improve fatigue strength and corrosion resistance .（3 branch ）

4） The surface is nitride layer （ Such as AlN, CrN, MoN etc. ）, Hardness is 950~1100HV, Good wear resistance and corrosion resistance ;

The heart is tempered sorbite ; It has high strength and enough toughness .（4 branch ）

2． answer ：

Casting —— Liquid solidification forming , The material is metal material, especially brittle material （ Such as cast iron , Cast aluminum alloy, etc ） The blank production of all kinds of parts, especially the parts with complex inner cavity ;（3 branch ）

forging （ Pressure machining ）——— Solid plastic deformation , The material is mainly the production of rough or semi-finished products or parts with no inner cavity or simple inner cavity of ductile metal materials ;（3 branch ）

welding —— Solid state connection forming , It is mainly the connection of various components made of ductile metal materials ;（3 branch ）

Powder pressing （ Powder metallurgy ）—— Granular forming , Production of various parts or semi-finished products with granular raw materials ;（3 branch ）

Polymer materials （ polymer ） Take shape —— Viscous flow （ Colloid ） Solidify and form , Production of all kinds of plastic or rubber products .（3 branch ）