渗碳凸轮轴热处理工艺设计(2)
正确地选择炉型是炉子设计的关键环节。炉型选择主要是指采用什么类型的炉子能够满足工艺及产量的要求，并能结合企业的具体情况，保证炉型在技术上是先进的，经济上是合理的。本设计采用JHJ-75-6井式回火炉。井式回火炉全称JHJ系列井式回火炉，井式炉是周期式作业炉，适用于杆类，长轴类零件的热处理。
关键词: 凸轮轴；感应淬火；20Cr；感应器3840
The design of Carburizing camshaft heat treatment process
Design Notes：The design need to understand camshaft structure, working conditions and service performance requirements, this design choice is Shanghai Diesel Engine Co.,. This requires each bearing camshaft profiles, cam hardened layer depth ≥ 1.4mm, hardness 58-62HRC. Bending length <0.40mm.
Camshaft material selection 20Cr. 20Cr low hardenability carburizing steel. Unified Numbering: A20202. Standard GB/T 3077-1999 GB/T 17107. 20Cr steel chemical composition. C：0.18～0.24；Si：0.17～0.37；S≤0.035；Mn：0.50～0.80；Ni≤0.030；P≤0.035；Cr≤0.035。
In this design, including the design of the current frequency, specific power, rated power, quench area, sensors, quenching methods and quenching equipment, cooling, tempering equipment and tempering methods.
Current frequency according to
1) The first principle selected of current frequency is penetration heating;
2) The second principle selected of current frequency is higher electrical efficiency of the
sensor;
3) The third principle selected of current frequency is that the current frequency is not too low;
4) The Current frequency also depend on selective noise, shock, power factor, electromagnetic effects.
Design principles through various hardened layer depth of the diameter of the current frequency and the current frequency components between end-selected frequency of 8 kHz of the machine-device.
The selection of specific power requirements depending on the frequency and depth of hardened layer, by virtue of hardened layer depth and material characteristics, select the specific power P0= 1.2kW/cm2.
According to the definition of specific power, it also could Raises an important concept, namely the maximum area. Because camshaft complex shape, so the need for cam profile and bearing block area were calculated maximum quenching. The final result is obtained cam profile: SL = 31.26cm2, bearing block: SL = 51cm2. Meanwhile, parts of the quenching area is less than l00 kW, 8kHz frequency devices simultaneously hardening the maximum area, so use while heating quenching method. Through the rated power of the calculations to determine the use BPSD-160/8000 frequency generator powered, the device's rated power PE = 160 kW.
In this design, the design of inductor is the most complicated, as the inductor designed well, it will be able to meet the technical requirements to ensure product quality.
In this design, the camshaft's cam width and bearing width is larger difference, so it can not share the same inductor, so I would like to design two heights different but the same diameter sensor. Cam height 23mm, bearing height 37mm with a wall thickness of 1.5mm copper induction coil made of induction coil diameter of 67mm. Induction coil diameter is 67mm. The gap of inductor and the workpiece size is 3mm.Spray hole diameter 1.0 ~ 1.20 mm.
Induction heating surface hardening parts need for tempering. Tempering is to reduce the brittleness of parts, Tempering is to reduce the brittleness of parts, improve toughness, to reduce internal stress, to prevent cracking, prevent deformation, improved dimensional stability and to ensure the mechanical properties. Tempering furnace process step is very important, especially in Europe and other countries, most of the induction hardening parts such as crank shaft, axle, steering knuckle camshaft and tempering furnace are measured using tempering furnace. Tempering temperature 180 ℃, holding time of 1.5h.
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