真空油淬火

在许多情况下，油淬火是一种可行的替代高压气体，淬火，特别是齿轮等部件的截面厚度，几何或淬透性，即DI或端淬值表明他们是边缘候选人气淬。许多组件使用油淬火来实现一致和可重复的机械和冶金性能，以及可预测的失真模式。油淬火之所以如此受欢迎，是因为它在广泛的操作条件下具有稳定性。油淬火通过控制淬火过程中的传热来促进钢的硬化，并在淬火过程中增强钢的润湿性，以尽量减少不希望出现的热和相变梯度，从而导致变形和开裂。对许多人来说，石油的选择是对若干因素进行评价的结果，包括：

•经济/成本（初始投资，维修，保养，寿命）
性能（冷却速度/淬火严重度）
•失真最小化（淬火系统）
•可变性（可控冷却率）
•环境问题（回收、浪费处置等）
油淬火真空系统不仅能控制淬火变量的正常设定，而且还可以改变和控制油压力。这种技术可以扩大零件截面和可加工材料的范围。此外，还发现使用真空油淬火可以减少齿轮、轴和滚珠轴承等各种部件的变形。改变压力在淬火油允许在淬火剂的沸点的变化。沸点的位置，即“特征温度”，决定油冷却的各个阶段的位置和长度。较低的压力允许较长的“蒸汽毯”阶段和一个有点长的“蒸汽转移”阶段，由于减少沸点油。变形最小化方法已被用于结合流动特性的改变（例如，一些制造商通过工作量而不是向上推油）和专门的油组合物。混合使用的真空具有低蒸汽压油使他们容易去毒气。整体式真空油淬系统的设计需要考虑除大气油淬火以外的因素。例如，基础油的沸点和蒸汽压以及促进剂添加剂。除淬火油温度、搅拌、清洁度、pH值和粘度外，还必须考虑特性。此外，淬火油的蒸汽压力必须与选定的操作真空度相一致。最后，真空系统不允许在淬火槽中积聚水。在真空炉系统中，真空用于处理工件或清除淬火环境，当系统抽空和油循环时，水分将被除去。循环的油给汽化器表面带来水分，并通过泵送系统从油中除去。

Oil quenching is a viable alternative to high pressure gas quenching in many instances, especially for gears and other components whose cross-sectional thickness, geometry or hardenability, i.e., DI or Jominy values indicate they are marginal candidates for gas quenching. Many components use oil quenching to achieve consistent and repeatable mechanical and metallurgical properties,
as well as predictable distortion patterns. The reason oil quenching is so popular is due to its stability over a broad range of operating conditions. Oil quenching facilitates the hardening of steel by controlling heat transfer during quenching and it enhances wetting of steel during quenching to minimize the formation of undesirable thermal and transformational gradients which may lead to increased distortion and cracking. For many, the choice of oil is the result of an evaluation of a number of factors, including:

• Economics/cost (initial investment, maintenance, upkeep, life)
• Performance (cooling rate/quench severity)
• Minimization of distortion (quench system)
• Variability (controllable cooling rates)
• Environmental concerns (recycling, waste
disposal, etc.)
Oil quench vacuum systems offer not only the ability to control the normal set of quench variables but, in addition, one can vary and control the pressure over the oil. This technique can extend the range of part cross-sections and materials that can be processed.
In addition, the use of vacuum oil quenching has been found to reduce distortion in a wide variety of components such as gears, shafts and ball bearings.
Altering pressure over the quench oil allows for a change in the boiling point of the quenchant.
The position of the boiling point, i.e., “characteristic temperature,” determines where and for how long the various stages of oil cooling take place. The lower pressure allows for longer “vapor blanket” stages and a somewhat long “vapor transfer” stage due to the reduced boiling point of the oil.
Distortion minimization methods have been used in combination with changes to flow characteristics (for example, some manufacturers pull oil down through the workload as opposed to pushing it upward) and oil compositions specially
blended for use in vacuum having low vapor pressure oils so that they are easily de-gassed.
The design of an integral vacuum oil quench system requires considerations beyond those of atmosphere oil quenching. For example, the boiling point and vapor pressure of the base oil—as well as the accelerant additives
characteristics—must be taken into consideration, along with the quench oil temperature, agitation, cleanliness, pH and viscosity. Also, the vapor pressure of the quench oil must be compatible with the selected operating vacuum level.
Finally, vacuum systems do not permit the build-up of water in the quench tanks. In a vacuum furnace system, where vacuum is used to process the work or purge the quench environment, moisture will be removed as the system is evacuated and the oil circulated. The circulated oil brings any moisture to the surface where it is vaporized and removed from the oil by the pumping system.