热门搜索:

  • /?50
  • 下载费用:30 金币 ?

热处理 heat treat 101.pdf

关?键?词:
热处理 HEAT TREAT 101
资源描述:
Heat Treating 101 Chris Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing Heat Treat 101 Heat Treating Ferrous Non-Ferrous Cast Iron Steel Aluminum Cast Wrought Plain Carbon Alloy What is Heat Treating? ? Heat Treatment is the controlled application of time and temperature to produce a predictable change in the internal structure of a material What is Heat Treating? ?Heat treating is a highly manipulative manufacturing process – Heat treating can alter the (mechanical, physical, metallurgical) properties of material and thus influence the end of that product Purpose of Heat Treatment: – Increase hardness – Soften or remove stresses – Increase fatigue resistance (service life) – Increase toughness – Increase wear resistance – Improve machinability – Homogenize the microstructure – Develop desired properties – Alter properties of economical grades of steel Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing Why Iron? ?Iron has the ability to combine with many other elements. These elements are capable of changing the properties of iron ?Adding carbon, and sometimes manganese produce STEEL – Steel is not only stronger than iron, but the properties of steel can be dramatically changed by heat treating. Classes of Steel Carbon Steels Alloy Steels Stainless Steels Tool Steels 10 Material Designation / Types of Steel ? 10XX Plain carbon steels ? 11XX Plain carbon (Resulfurized for machinability) ? 12XX Contains P & S for improved machinability ? 15XX Mn (1.0-2.0%) ? 40XX Mo (0.20-0.30%) ? 41XX Cr (0.40-1.2%), Mo (0.08-0.25%) ? 43XX Ni (1.65-2.0%), Cr (0.40-0.90), Mo (0.20-0.30) ? 51XX Cr (0.70 – 1.2%) ? 61XX Cr (0.70-1.10%), V (0.10) ? 86XX Ni (0.30-0.70%), Cr (0.4-0.85%), Mo (0.08-0.25) ? 92XX Si (1.8-2.20%) ? 12L14 Contains Lead for improved machinability ? 10B21 Contains Boron for increased hardenability 11 Carbon vs. Alloy Steels ?Carbon Steels – The percent of carbon defines the maximum obtainable hardness of the steel. For example, a 1080 steel (0.8% C) can achieve a higher hardness than a 1030 steel (0.3% C) ?Alloy Steel – The percent of alloying elements (Cr, Mo, Ni, etc.) define the hardenability of the steel. For example, a 4140 alloy steel can achieve a greater depth of hardening than a 1040 carbon steel. Why Iron? Property Condition Yield Strength (MPa) Tensile Strength (MPa) Elongation (%) Pure Iron Untreated 200 310 26 Steel Untreated 379 689 12 Steel Heat treat & slow cool 428 773 10 Steel HT & fast quenching (water) 1380 1380 1 13 This presentation will focus on heat treating hypoeutectoid medium carbon steels. (C = 0.18%-0.77%) 14 Ferrite 1010 Steel 0.08-0.13 % C Not enough carbon to effectively harden 15 Pearlite 1035 Steel 0.31-0.38 % C Hardenable 16 Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Why does Hardening Steel Work – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing ?What are the generic steel hardening principles? ?What happens to steel when it is heat treated? Lattice Structures ?FCC – Face Centered Cubic ?BCC – Body Centered Cubic ?BCT – Body Centered Tetragonal ?Steel is unique in that it transforms between crystal lattice systems during heat treatment. 19 What happens to steel when it is heat treated? ?As the alloy is cooled rapidly, the carbon atoms cannot escape from the iron lattice. This results in distortion of the lattice which manifests itself in the form of hardness and/or strength. If cooling is fast enough, a new phase known as martensite forms. *Heat Treament of Steel (1987), Course 3, Page 11-7 Quench Austenite (FCC) Martensite (BCT) Example Austenite (FCC) Pearlite (BCC) Martensite (BCT) 22 TTT Diagram 23 24 TTT vs. Bar Diameter 25 Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Why does Hardening Steel Work – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing Steel Heat Treating Processes 1. Martensite Formation (Austenize, Quench & Temper) 2. Annealing (& Stress Relief) 3. Surface Hardening 1. Martensite Formation ?Austenize – Heating up the steel to red hot (Upper Transformation Temp – A 3 ) ?Quench – Rapid cooling in a quenchant such as oil, water, brine solution, or polymer. ?Temper – Reheating after quenching to improve toughness. This consequently lowers strength and increase ductility. Tempering 50B40 2. Annealing ?A heat treatment process that involves heating, holding, and slow cooling. It is used to soften metals and change the microstructure by relieving induced cold work and internal stresses. ?The process results in lower strength with greater ductility and improved toughness. 3. Surface Hardening ?Case Hardening – Carburizing – Carbonitriding – Nitriding ? Gas & Liquid – Nitrocarburizing (FNC) ? Gaseous & Fluidized Bed – Less Common Methods –Boronizing, Chromizing ?Selective Surface Hardening – Induction Hardening – Less Common Methods – Flame Hardening, Laser Beam (LB), Electron Beam (EB) Induction Hardening (Ball Stud) Figure 1: Scanning Induction Hardening Indexing Figure 2: Single-Shot Induction Hardening Quench Quench Movement Rotating Rotating Induction Coils Induction Coils Induction Hardening Induction Type Pro Con Scanning Simple Coil Design More Variability in Heat Treat Pattern Multiple Coils Wired in Series to Reduce Cycle Time Parts Hand Loaded into Machine Immediate Quenching Single-Shot Less Variability in Heat Treat Pattern More Complicated Coil Design Parts Auto-fed Via Indexing Tables More Machines Needed to Decrease Cycle Time Delay in Quenching While Indexing Part to Quench Station Induction Hardening Websites ?http://www.ameritherm.com/video_hardenin g.html ?http://www.ajaxtocco.com/default.asp?ID=61 Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing Heat Treating Defects ? Decarb ? Quench Cracks ? Grain Boundary Oxides ? Incomplete Transformation ? Low Hardness ? High Hardness ? Spalling – Case Hardening ? Incorrect Grains Size ? Retained Austenite – Surface Carbon Too High ? Low Carbon Atmosphere, Leaky Furnace, Long Cooling Times ? Quench Rate Too Severe, Delayed Tempering, Part Geometry ? Air (Oxygen) in the Furnace, Leaky Furnace ? Thermal Mass of Load Exceeds Quench Capacity, Contaminated or Wrong Quenchant ? Improper Tempering, Delayed or Improper Quenching, Malfunctioning Quench Tank Agitation ? Improper Tempering - Too Low Time or Temp, or Overloaded Furnace ? Improper Case Hardening, Too Much Carbon in Atmosphere ? Too High or Too Low Austenitizing Temp ? Too Much Carbon in Steel Embrittlement - Hydrogen ? Hydrogen diffuses into the surface of hardened steel via one of the following common practices: 1. Electroplating 2. Acid cleaning 3. Phosphating ? The steel must be baked within a certain timeframe to relieve/release the hydrogen. ? Steels above 39 HRC cannot be subjected to hydrogen infusing processes. 37 Decarburization 38 Quench Cracks 39 Seams ?Although not caused by heat treating, laps that are rolled into the bar during forming operations. These defects are characterized by the presence of oxides and/or other surface contaminants on either side of the defect. They can serve as quench crack initiation sites. 40 Grain Boundary Oxides Incomplete Transformation Proper Martensitic Microstructure Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing Heat Treating Furnaces Presentation Outline ?What is Heat Treating ?How is heat treating performed – Heat Treatable Steel Alloys – Types of Heat Treatment – Heat Treating Defects – Heat Treating Equipment ?How to call-out a heat treatment on a drawing How to Specify a Heat Treatment ? Don’t do it! ? Contact Materials Eng ?Depending on the type of heat treat process ?Several items should be called-out on the drawing – Surface hardness – Hardness depth (case depth) – Core hardness Surface Hardness ?The hardness should be specified in the manner that it is intended to be checked – Brinell hardness gives the most accurate readings but requires a large checking area, through-hardened or a thick case – Rockwell Rc or Rb … – Superficial 15N or 15T… – Micro Hardness Knoop or Vickers… Case Hardness Checking ?Depth needs to be called out – Total case depth – Effective case depth Core Hardness ?Some parts require through-hardening for applications that require strength. – Ex. Fasteners ?Some parts require soft core for applications that require ductility/toughness. – Ex. Ball studs, Sector shafts Heat Treating Requirements ?Control of Heat Treating Processes and Auxiliary Equipment ?AIAG CQI-9 –Heat Treat System Guideline ? Embrittlement Avoidance (Direct) Questions Result in (Evasive) Answers
? 汽车智库所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

关于本文
本文标题:热处理 heat treat 101.pdf
链接地址:http://www.autoekb.com/p-9439.html
关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服客服 - 联系我们

copyright@ 2008-2018 mywenku网站版权所有
经营许可证编号:京ICP备12026657号-3?

收起
展开