金属材料的加工工艺性能（Processing properties of metal materials）

1、金属材料的加工工艺性能（Processing properties of metal materials）Processing properties of metal materialsThe information collection to add this information to print: anonymous source: unknown-Blanking (blank) - heat treatment - rough processing - heat treatment (quenching and tempering) - finishing (surface tre

2、atment) (heat treatment) blank manufacturing methods, casting, welding, forming. This chapter deals with casting, forging, welding, heat treatment and machinability. The casting properties of 14.1. metal materials usually refer to fluidity, shrinkage, casting stress, segregation, suction tendency an

3、d crack sensitivity. The alloy is commonly used in casting, and the alloy grain is small. Influence factors of 14.1.1. on alloy fluidity factors: alloy chemical composition, casting temperature and mold filling conditions. Alloy chemical composition: carbon content: pure iron liquidity is good, the

4、greater the carbon content, the worse the liquidity. About 2% of the fluidity is the worst, and eutectic cast iron has the best fluidity in cast iron. The fluidity of the alloy can be reduced by forming elements with high melting point inclusions in the alloy composition. The iron in the melting poi

5、nt of MnS is 1620, is not conducive to flow. P can form Fe-Fe3P-Fe3C and the melting point is 950, which is favorable to flow. The 14.1.2. casting shrinkage shrinkage and shrinkage of 14.1.2.1. cast iron with carbon content increasing, graphite is conducive to eliminate this kind of phenomenon crack

6、 14.1.2.2. casting cold crack and hot cracking, the increase of P and S alloy strength, the cracking tendency increases. Forging properties of 14.2. metal materials: plasticity and deformation resistance 14.2.1. the forging of high alloy tool steel is aimed at breaking the coarse eutectic carbides i

7、n steel. Slow cooling after forging (furnace cooling) to prevent cracks. 14.2.2. stainless steel forged stainless steel because of its special organization, pay attention to the process of forging and heat treatment on intergranular corrosion of 475 DEG C brittleness: high Cr steel containing Cr was

8、 more than 15% in the temperature range of 400-525 long time to pause or slow cooling, Cr atomic ordering, phase and the parent lattice distortion caused by crystal figure large internal stress caused by large the. Martensitic stainless steel: slow cooling to about 600 degrees of air cooling, so as

9、to avoid martensitic transformation. Ferritic and austenitic stainless steels: rapid cooling (air cooling) in intergranular corrosion and brittleness temperature range of 475. High temperature deformation resistance and lower plasticity of 14.2.3. superalloy forging alloy at high temperature are obs

10、erved. The mould is firm and the power is large. It is sensitive to forging temperature and air cooled after forging. 14.2.4. nonferrous metal forging aluminum: forging temperature narrow. Magnesium: forging temperature is narrow, heat transfer is fast, easy to cool, mold needs preheating. Copper: t

11、he forging temperature is narrow, the mold needs preheating, forging should be protected, avoid oxidation. Titanium: deformation resistance, chemical properties of active, pay attention to protection. The performance of electric arc welding of metal materials 14.3., electroslag welding, friction wel

12、ding, brazing, welding and brazing explosion: non ferrous metal filled in contact with molten solder such as brass and the like (the melting point is lower than that of the base metal to the weld metal melting point). 14.3.1. carbon steel and alloy steel welding low carbon steel, low alloy steel wel

13、dability. For medium and high carbon steel and alloy steel, pre weld preheating and post weld heat treatment are adopted. Improve the microstructure and eliminate the welding stress. Austenitic stainless steel welded with 14.3.2. stainless steel: intergranular corrosion.Martensitic stainless steel:

14、martensite microstructure was obtained in the weld zone under air cooling condition, preheating before welding (200-400), heat treatment after welding, heating to 730-790 degrees, then slowly cooling to 540 DEG C, air cooling. Ferritic stainless steel: pre weld preheating, post welding heat treatmen

15、t (730-840 C) 14.3.3. non-ferrous metal welding copper: poor welding performance, brazing. Aluminum: argon arc welding, high surface requirements of weldment. Titanium: automatic welding, high surface requirements. The machinability of 14.4. metal materials is called machinability of materials.Influ

16、encing factors: machinability is related to the chemical composition, hardness, toughness, thermal conductivity, metallographic structure and working hardening ability of metal materials. The effect of 14.4.1. chemical composition on the strength and hardness of steel reduced by carbon content: S, A

17、l, alloying elements that increase the strength and hardness of steel: graphitization: free graphite improves machinability. The influence of 14.4.2. structure and heat treatment process is different, the mechanical properties are different, and the processability is different. Pearlite, bainite, ma

18、rtensite, decrease in processability. The advantage of measuring machinability of materials is commonly measured by relative machinability Kr index. Table 14.2 machinability classification, machinability grade name and type, relative processability, Kr representative material1 easy cutting non-ferro

19、us metal material general 3 5-5-5 copper alloy, 9-4 alloy, aluminum magnesium alloy2 easy cutting material easy to cut steel 2.5 3 15Cr annealing Sigma b=380 450MPa,Automatic machine steel b=400 500MPa,Normalization of Steel 30 b=450 to 560MPa,3 easy cutting steel 1.6 2.54 ordinary materials general

20、 steel and cast iron1 1.645 steel, gray iron2Cr13 quenched and tempered Sigma b=850MPa,35 steel Sigma b=900MPa,5 slightly difficult to cut materials 0.65 16 difficult to cut material difficult to cut material 0.5 0.65 45Cr quenched and tempered Sigma b=1050MPa,65Mn quenched and tempered Sigma b=950

21、1000MPa,50CrV quenched and tempered 1Cr18Ni9Ti some titanium alloys,Some titanium alloys, cast nickel base superalloys,7 hard cutting materials 0.15 0.58 difficult to cut material less than 0.15 different grades of weaving, different hardness of different cutting operations (such as car, milling, pl

22、aning, boring, pulling, etc.) machinability is different. Such as tempered medium carbon steel, turning better, drilling medium, pull, dial poor processing. 14.4.3. heat treatment process performance of machine tool spindle in the selection of machine tool spindle material and heat treatment process

23、, we must consider the following points: (1) the size of the force. Different types of machine tools, there is a big difference between working conditions, such as high speed machine tools and precision machine tool spindle working conditions and heavy machine tool spindle to be compared, both in be

24、nding and torsion fatigue characteristics are large differences. (2) bearing type. If the shaft is working on the sliding bearing, the shaft neck needs high wear resistance. (3) the shape of the spindle and its possible defects in heat treatment. The spindle with complex shape is easy to be deformed

25、 or even cracked during heat treatment, so the material selection should be paid attention to. Spindle is one of the main parts in the machine tool, and its quality directly affects the accuracy and life of the machine tool. Therefore, the steel must be selected according to the working conditions a

26、nd performance requirements of the spindle, and the reasonable cold and hot processing technology should be worked out. 1. Working conditions and performance requirements of machine tool spindle. The main work are as follows: (1) under alternating bending stress and torsional stress, sometimes subje

27、cted to impact loading; (2) main spindle taper bore and tapered outer circle often have friction with chuck and thimble; (3) there is often a splined portion collision or relative sliding. The technical conditions: (1) the overall hardness after quenching and tempering should be HB200 230, the micro

28、structure is tempered sorbite; (2) inner and the outer conical surface hardness is HRC45 50, 3 5mm in the surface microstructure of tempered troostite and a small amount of martensite; (3) the spline part hardness is HRC48 53, the microstructure. 2, choose steel C515 lathe belongs to medium speed, m

29、edium load, in the rolling bearing machine tool, so choose 45 steel. 3, the spindle process blanking - forging - normalizing: rough machining (cylindrical remaining 4 5mm) - and - semi finishing outside the circle (the remaining 2.5 3.5mm), central hole drilling, precision turning round (the remaini

30、ng 0.6 0.7mm, cone stay more than 0.6 0.7mm),Keyway milling: local quenching (cone and cone) - car fixed knife groove, coarse grinding cylindrical (the remaining 0.4 0.5mm), spline spline hobbing, quenching and grinding. 4, heat treatment process normalizing treatment is in order to obtain the appro

31、priate hardness (HB170 230), in order to machine processing, improve forging organization, for quenching and tempering preparation. The quenching and tempering treatment is for the comprehensive mechanical performance and fatigue strength of the spindle, the hardness is HB200 - 230 after quenching a

32、nd tempering, and the structure is tempered bainite. In the taper hole and the outer conical part of the local salt bath quenching and tempering after get the required hardness, wear resistance and to ensure the accuracy of assembly. 5, heat treatment process quenching and tempering, due to the diff

33、erent parts of the spindle diameter, should pay attention to deformation problems. After quenching and tempering, the deformation can be corrected by straightening, but the additional stress during straightening is unfavorable to the dimensional stability of the spindle after finishing. In order to

34、reduce the deformation, attention should be paid to the operation method of quenching. Pre cooling quenching and cooling time in water can be used to reduce deformation. The spline part is quenched in high frequency to reduce deformation and meet the requirement of hardness. The part of an inner con

35、e hole and the outer cone surface quenched by 260 300 DEG C tempering, spline part subject to 240 to 250 DEG C tempering, to eliminate quenching stress and achieve the required hardness.Ductile iron instead of 45 steel, hardness HRC52 58 low, small deformation.The fifteenth chapter for boiler and pr

36、essure vessel steels commonly used in 15.1. boiler and pressure vessel of steel performance according to the working conditions are divided into two categories: one, to the steel plate and steel pipe manufacturing at room temperature and medium temperature pressure components has the characteristics

37、 of high strength at room temperature: 1Usually, the yield limit s and the strength limit B are taken as the design basis, which requires a good toughness of the sigma S and the sigma BThe material should have enough toughness to prevent brittle fracture, and the toughness should not be neglected wh

38、ile considering the strength,(1) the toughness of materials is usually expressed in terms of the impact toughness value, alpha K.Requirements for impact toughness of pressure vessel steelThe impact toughness value is K (N. M/cm2) 20-40 C=60=35(2) aging toughness aging should be considered, that is,

39、when the steel is deformed by cold working, the impact toughness changes with time at room temperature or higher temperature. Generally, the impact toughness decreases significantly at 200-300. Generally speaking, the rate of decline is not more than 50%. Because the vessel crack and crack fracture

40、process includes two stages in the formation of diffusion defect, the corresponding two kinds of method to prevent fracture (1) with enough toughness of steel to prevent cracks, requirements as shown in the above table (2) with higher toughness materials, in order to produce crack can prevent the cr

41、ack propagation. (notch sensitivity temperature than the nil ductility transition temperature of NPT high values, such as the design of the components stress yielding stress s half, to 17 DEG C 3 lower in the manufacturing process of holes and welding will produce local stress concentration, materia

42、l with notch sensitivity, low to prevent crack 4 good machining performance and welding performance of the welding thermal cycle, will (1) plastic reduce the toughness of the material, the heat affected zone (2) produce a variety of defects in the weld inside (1), (2) will produce crack should be ta

43、ken into account in material selection when (1) in carbon materials the equivalent value (to ensure the material has good weldability) (2) the appropriate welding material and welding process (3) has a good plasticity material (carbon steel and carbon manganese steel s alloy steel of not less than 1

44、6%, not less than 14% s) (4) the macrostructure of good (5) steel lamination, non-metallic inclusions, porosity, porosity and other defects to reduce as much as possible (to prevent cracks) two, with high temperature and high pressure pipe manufacturing element 1 has sufficient creep strength, creep

45、 rupture strength and plasticity usually lasting strength as the basis of design,To ensure the safe operation of 2 long-term high temperature has good organizational stability under no organization change 3 has good high temperature oxidation resistance requirement of oxidation corrosion rate of mat

46、erials under high temperature conditions is less than 4 0.1mm/a has good processing technology for cold working in creep conditions (cold bending and welding of boiler and 15.2.) pressure vessel steel, a classification of the working temperature is below 500 DEG C steel structure steel, carbon steel

47、 and low alloy 1 ferrite pearlite steel yield strength s is 300-450MPa 16Mn 15MnV, adding alloying elements 15MnVN, solid solution strengthening, strengthening the role of the 2 crystallization of low carbon bainite steel yield strength s 500-700Mpa 14CrMnMoVB retard austenite decomposition, obtaine

48、d bainite, martensite and increase the strength of 3 high carbon steel 600Mpa 18MnMoNb and 14MnMoNbB normalized and tempered yield strength, good toughness, two working temperature higher than 500 DEG C steel low alloy heat resistant steel and austenitic stainless steel 1 low alloy pearlitic heat re

49、sistant steel 15CrMo and 12Cr1MoV, crystal strengthening, precipitation strengthening characteristics of 2 low alloy bainite heat resistant steel 12Cr2MoWVTiB and 12Cr3MoVSiTiB. The number and amount of alloy, high temperature strength and oxidation resistance of 3 austenitic stainless steel 18-8 ty

50、pe chromium nickel austenitic stainless steel: 1Cr18Ni9Ti and 0Cr18Ni9Ti, high temperature strength, oxidation resistance, and has the effect of main components of high toughness and good processing property of 15.3. carbon steel, carbon steel, the effect on performance of carbon 1 the increase of c

51、arbon, increase the strength of plastic reduction, weldability poor, aging sensitivity reduces the effect of Mn 2 DNA (FeO) desulfurization, influence of cold brittleness effect to improve thermal processing performance of 3 silicon deoxidation effect of 4 sulfur phosphorus 5 hot 6 oxygen to reduce

52、the influence of strength and plasticity of 7 nitrogen high strength and hardness, reduce the classification of chemical composition, the effect of hydrogen embrittlement two carbon steel plastic: high (containing 8 hydrogen the amount of carbon is 0.65%), (carbon 0.25-0.65%), low carbon steel (carb

53、on content less than 0.25%) uses: ordinary carbon steel, quality carbon structural steel and carbon steel 1 ordinary carbon steel structure: a steel supply according to the mechanical properties (A), steel plate, angle steel and other 2 high quality carbon structural steel according to the mechanica

54、l properties and chemical composition of the supply of low carbon steel plate, container, screw and nut carbon: axis gear, high carbon steel wire rope: spring, 3 (T) high carbon tool steel The hardness and wear resistance, cutting tools, measuring tools, mold manufacturing, three common carbon steel

55、 boiler and pressure vessel pressure components mainly used for low carbon steel, plastic, toughness, processing and good solderability (1) high quality carbon steel No. 10 and No. 20 seamless steel No. 20 steel carbon content more than 10 steel twice, high strength, yield limit and ultimate strengt

56、h of sigma sigma S B high 20%, aging sensitivity is low, the use of Steel No. 20 (2) A3g A3R 15g 20g special steel, impact toughness, metal surface and internal defects of 15.4. less common low alloy structural steel low alloy steel is based on carbon steel. Adding a small amount of Si, Mn, Cu, Ti,

57、V, Nb, P and other alloy elements, its carbon content is low, less than 0.2%. Most of the tissues are still F P. Because of the addition of small amount of alloying elements, the strength of the steel can be greatly improved, and the corrosion resistance and low temperature performance of the steel

58、can be improved. Low alloy steels can be rolled into various steels, such as plates, tubes, bars and profiles. It is widely used in the manufacture of ocean going ships, long span bridges, high pressure boilers, large containers, cars, mining machinery and agricultural machinery, etc. 16MnR is used in large chemical container, and 1/3 can be r