The heart of industry, almost nothing can be manufactured without heat-treating. 我们最近采访了Bob Farrell (Hubbard-Hall的高级副总裁兼技术总监)，并向他询问了一些关于热处理市场的问题, 他在30年的经验中所看到的以及使用这些澳门威尼斯人网上赌场的制造商的前景.
金属为什么要热处理?
Metals are crystalline materials; there are rare cases where they could be amorphous, 但是一般来说, 金属是结晶材料. 通过加热金属, 你可以改变这种金属的晶体结构，得到某些想要的特性，比如硬度. Most people are familiar with the Rockwell Hardness; for instance, you do a transformation crystalline transformation, 然后你试着锁定它, 或者你试着冷却它, so it transforms more to a different phase and lock that phase-in. You could get characteristics such as hardness or toughness; in some cases — although we’re not involved really in salts to do that — you can also infuse materials into the surface of the metal and form what’s called ‘the case.你可以有一个氮的例子, 碳壳, Black oxide is the conversion of a base metal material to an oxide of that base metal material. 最典型的例子就是Fe3O4, 什么是黑色的氧化铁, otherwise known as magnetite; another is a CuO, 或者一氧化铜. 当化学物质与基础物质反应形成基础主要成分的氧化物时，就会发生这种反应. 在不锈钢的情况下, 它不仅形成氧化物, but it also forms sulfides of the base materials that tend to be black as well. 或者是氮化碳. These types of surfaces could give lubricity too, 但是一般来说, 你在做所谓的中性硬化，然后回火，以获得特定的晶体结构，从给定的金属中获得特定的特性.
什么是热处理盐?
Salts are blends of common salts; for instance, what’s called a ‘high heat salt’ is a blend of potassium and sodium chloride. 如果它是一个熔点很高的盐你在更高的温度下工作你也可以在里面放氯化钡, 所以氯化钾钠和氯化钡存在于一种盐中这是一种中性盐它通常也被称为高温盐. You could have what’s called the tempering salt, which typically operates at temperatures below 1000°F but at least 50°F to 100°F above the melting point. Tempering salts are blends of sodium nitrite, sodium nitrate, and 硝酸钾. 有一种盐是卖给铝热处理的那就是硝酸钠和硝酸钾. You have your nitrate salts — which are your tempering salts — and you have your high heat salts, 哪些是你的氯盐. 盐是什么，是干粉末状混合物, 但是你把它加热到熔点, 然后变成液体. It’s a melt just like ice melts, and you have water; it’s the same thing with the salts.
为什么要用热处理盐?
用于热处理金属的方法是盐或熔炉，你可以把零件放在传送带上进入高热熔炉, and it’s just air that’s around that heats the parts. 部分就出来了, 然后你做一个淬火来冷却它们，试图锁定一个结构，或者冷却它们，然后把它们加热到一个通常在300到800华氏度之间的范围, 把金属回火. That can be done on a lot of parts that are fasteners, for instance, small parts. Where salts are really used are where you want very little distortion. As you know, if you heat something and you cool it rapidly, it could distort. 盐，因为它们是相对致密的液体，减少了热处理过程中的变形量. Therefore salts are used on things such as precision gears; lawnmower blades are a huge area where salts are used primarily for distortion purposes. What are salts doing when you look at molten salt? It’s used for two purposes: it’s used to add heat to a part or used to take heat away from a part, 如在淬火中. 如果你还记得热力学的话, 热量从热流向冷, 如果你有热盐, the heat flows into the part to heat it up to a temperature to neutral harden it, 然后它就会被冷却, 而且盐比零件更凉. As it goes in the heat goes from the part back to the salt. 盐吸收热量的程度和速度比空气要大得多如果你用空气淬灭的话, 有些人是用炉子做的吗.
有哪些类型的热处理盐呢?
总结, 有三种基本类型的盐:回火盐是在300°F到900°F范围内工作的盐，这些盐通常用于加热部件，如果部件在该温度范围内发生相变，或者将部件冷却到该温度范围并锁定部件的晶体结构. 你有中性盐，通常在1000°F以上使用，更典型的是在1500°F到1800°F的范围内使用，可能高达2100°F，用于中性硬化. The third salt are the case hardening salts; you don’t see them used as frequently anymore, 但是如果你有一个零件你想要低变形但你想在零件上做碳或氮或碳氮结合的情况，这是一个非常薄的层，你可以使用渗碳或表面硬化盐. There are really three classes of salts that are still out there being used.
所有回火盐都兼容吗?
如果它们是以硝酸盐为基础的盐. The difference between the salts are the ratios; the ratios determine what the melting point is. There’s a salt that has a eutectoid mixture, and it’s a very precise melting point at 275°F. 然后你可以有盐，比如用于铝的盐，它是钾和硝酸钠，在420华氏度融化. All the nitrate based salts contain the three basic nitrogen species, 也就是硝酸钠, 硝酸钾, 亚硝酸钠. 你可以, 在理论上, 同时使用它们, but you’re going to alter the melting point because your ratios are going to change. 它们可以是混合的, but they don’t give you that precise melting point that’s important, 它还能改变热量, 在理论上, 同时使用它们, 但是你会改变熔点因为你的比例也会改变盐的吸收或者传热特性.
What does rectification of the high heat bath do, and how should a person go about adding pellets?
High heat baths react because they react with oxygen and CO2 in the air. 你可以 imagine you have this molten solution of salts; it’s glowing red, it’s reacting with CO2 and oxygen to form carbonates in the bath, 但它也会在溶液中形成氧化物. What happens when you get those is it can interfere with the heat transfer, and it could lead to some difficulties with the metallurgy of the part. What you have to do is you have to rectify to remove those oxides, 这通常是用颗粒来完成的, or as in days past people would bubble methyl chloride gas through a salt to rectify it. 整流器真正要做的是消除那些在那里形成的氧化物并中和碳酸盐. 小球在盐中产生氨, 所以你要慢慢加入颗粒, 当然, 经过任何整改, you may do the rectification when work is not in the bath. You’re evolving ammonia that reacts to neutralize the carbonates and react with the oxides. 确保在通风良好的地方进行，这样就不会有可能形成的气体逃逸到工作环境中.
What’s the best method of desludging a high heat bath and tempering pot?
去除污泥的最佳方法是将其冷却到尽可能接近熔点的温度，在熔点50°F到100°F之间. 你要做的是清除淤泥你在回火盐上看到的更多你从高温浴中出来那是氯化物浴，盐的熔点达到1000华氏度或更高, and you go into a tempering bat that’s operating below that melting point. The salt the neutral salts will come off in the tempering salt, 当然, they’re not melted at the temperature of the tempering bath, 所以这些盐会出来, 它会以雪撬的形式沉淀出来. What you do is you cool that tempering bath down to if it’s a 275°F melt tempering bath, 把它冷却到350华氏度, 然后你进去, 然后舀出掉出来的污泥. It’s almost like snow falling; imagine your tempering salts in the atmosphere; the chloride salts the snow that falls down and accumulates at the bottom of the pot, 把它拿出来. 被拖进高温浴的污染物——比如工作不够干净，或者上面有很多沙砾、污垢或颗粒物质——也可能在中性浴中形成这些污泥, 高温中性浴, 结果是一样的. Say the salt bath has a melting point of a 1000°F, you’d cool it down to maybe 1075°F and then slowly and very carefully, 当然, go in and try to ladle out from the bottom of the salt bath the contaminates to get them out.
Does your company have the capability of performing analysis of the salt baths?
We routinely do salt bath analysis for customers. 在某些情况下, 它是付费的, 在某些情况下, 这不是, but we do have the capability to do both the high heat neutral salts and the tempering salts.
What are the differences and advantages of the several tempering salts you provide?
真的没有太大的区别. It really is all predicated on what temperature you want to operate at. With the exception of the salt that’s used on aluminum, that salt is very specific because you don’t want nitrites in a salt that’s used on aluminum. So, it really depends on the factors that come into play; 当然 the cost of the salt — sodium nitrite being the most expensive ingredient that’s typically in there — but it’s also the ingredient that gives you a lower melting point. I recommend a 275°F melt point; it’s a very precise melt point and it gives you an operating range of up to 1000°F. The salt could be used for a lot of applications; if you want a less expensive salt, you could go to a 300°F melt point salt and use that instead, 但是一般来说, 总之，回火盐的吸热和热传导特性并没有太大的区别.
我应该把样品送到哪里去测试?
We do the testing down in our Inman, South Carolina facility. 他们会被送到. Douglas Patton, and he does all the salt and salt analysis for us.
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