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"Wear It's At"

Volume 2, Issue 2

Friday, February 11, 2000

 

In This Issue

1. Welcome
2. Internet Impact
3. Interpass Temperatures
4. Future Topics
5. Business Humor

1. Welcome

It's very nice to report that our newsletter is growing and I want to extend a warm welcome to all those newcomers.  Hope you find this periodical interesting and informative.  I welcome anyone who would like to contribute an article or noteworthy item.  It can be a new product, an unusual application or an anecdote.  

2. Internet Impact

The Internet is certainly having it's impact on our lives.  I have attached a recent file that was sent to me via http://www.iconocast.com.  The details are very eye opening.  The Web is expanding exponentially.  There are many that say that it really doesn't affect the welding business or the hardfacing business, but I assure you that it does.  The mere fact that you are receiving this newsletter attests to the fact that the Web is changing the way we do business.  One might argue that the newsletter could be sent out via the Post Office, and that is certainly true.  But many of our members are International, making newsletters via the Post Office a little cumbersome.  Animation is coming to the Web, which will change we view pages, and interact with the Web Site.  While E-Commerce in terms of  welding products doesn't rival Amazon.com,, there are a number of sites where you can buy welding products Online. This is just the beginning  Within the next year, we will all probably be amazed at what's available Online.

3. Interpass Temperatures

This topic is sometimes misunderstood when it comes to hardfacing.  In joining applications, it is done mostly to prevent rapid cooling and prevent hydrogen entrapment.  While the same is true in hardfacing, it does have additional implications.  In hardfacing we are dealing with the SURFACE characteristics of the weld metal to a much greater extent than we are in joining, so our focus has to be shifted a little bit.  This is especially true in a rebuilding procedure, where base materials can be pretty hard and contain hefty amounts of alloy and carbon.  Knowing the base metal chemistry as well as the hardfacing material is an essential part in determining the proper preheat and interpass temperatures to employ.  This is particularly true in dealing with Martensitic alloys as the hardfacing product.  Those hardfacing alloys such as High Chromium Irons or Chromium Carbide alloys do not fall into this category because their hardness is derived through the formation of very hard particles in a soft matrix and are not dependent upon quenching.  Martensitic alloys derive their hardness and also their wear resistance through quenching from high temperatures or the Interpass Temperature.  Thus it is essential to understand the ramifications of following the preheat and interpass requirements. 

There is an old formula, or should I say, a number of formulas that attempt to predict preheat and interpass temperatures by means of chemical compositions.  A Carbon Equivalent is calculated and then related to the temperature requirements.  Below is an example.

Carbon  Equivalent = Carbon + (Manganese/20) + (Nickel/15) + ((Chromium + Moly + Vanadium)/10)

Carbon Equivalent Preheat Temperature
0.80 350ºC  662ºF
0.50 250ºC   482ºF
0.30 150ºC   302ºF
0.20 100ºC   212ºF

* These temperatures are for thick materials and will vary downwards for thinner materials.

This method can be helpful, but a good rule of thumb is:

Interpass Temperature (Fahrenheit)  = (Carbon x 100) + 100(If alloys are present)

For example:  For a straight 1040 carbon steel, whose Carbon is 0.40, the Interpass temperature would be 400ºF.  But for a 4140 alloy steel, whose Carbon is also 0.40 and has additional alloy, the Interpass temperature would be (400 + 100) = 500ºF.  Of course it is always best to consult the manufacturer for the recommended temperatures, but this will suffice as a ballpark figure.  

Maintaining this temperature throughout the hardfacing procedure is essential.  If for any reason the temperature drops below the Interpass temperature before the hardfacing procedure is complete, hardening will start and increase in volume, depending  upon how far it drops.  While this doesn't appear to be too damaging, because we do want a hard surface, the danger comes when additional passes or layers are applied.  The additional heat from these passes and layers will soften the hardened material and leave the underlying layers prone to excessive wear.  The very top layer will be hard enough, but the layers underneath it will be soft and undesirable.  The whole idea when hardfacing with these alloys is to maintain the Interpass temperature and allow the whole deposit to quench to room temperature, or some intermediate temperature, all at the same time, thereby insuring that all the layers will be sufficiently hard. 

4. Future Topics

I have recently been approached to address the topic of "Carbon and Carbides" and their rolls in hardfacing.  So, over the next few issues we will explore this fascinating topic.  I promise not to get too technical ... it is an occupational hazard, I know.  We will keep it simple and straight forward.  Please feel free to comment and contribute. 

5. Business Humor

I would like to depart with a little humor.  I will be looking forward to visiting again with you all very soon.

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An American businessman was at a pier in a Mexican village when a small boat with just one fisherman docked. Inside the small boat were several large tuna. The American complimented the man on the quality of his fish and asked how long it took to catch them.

The man replied, “Only a little while.”

“Why don’t you stay out longer and catch more fish?” asked the American.

The Mexican shrugged. “I have enough for my family’s needs.”

“But what do you do with the rest of your time?” asked the American.

“Well,” replied the Mexican, “I sleep late, fish a little, play with my children, take siesta with my wife Maria, and stroll into the village each evening where I sip wine and play guitar with my amigos. I have a full and busy life, señor.”

The American scoffed, “I am a Harvard MBA and could help you. You should spend more time fishing and, with the proceeds, buy a bigger boat. With the proceeds from the bigger boat, you could buy several boats. Eventually you would have a fleet of fishing boats. Instead of selling your catch to a middleman you would sell directly to the processor, eventually opening your own cannery. You would control the product, processing, and distribution. You would need to leave this small coastal fishing village and move to Mexico City, then LA, and eventually New York where you will run your expanding enterprise.”

The astonished Mexican fisherman asked, “Señor, how long will this all take?”

“15-20 years,” answered the American.

“But what then, Señor?”

The American laughed: “That’s the best part! When the time is right, you will announce an IPO and sell your company stock to the public and become very rich. You would make millions.”

“Millions, Señor? Then what?” asked the incredulous Mexican.

“Then,” beamed the American, “You would retire. Move to a small coastal fishing village where you would sleep late, fish a little, play with your kids, take siesta with your wife, and stroll to the village in the evenings where you could sip wine and play your guitar with your amigos.”



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