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Industry Headlines

CIRCOR Announces Availability of Historical Segment Information

6 HOURS AGO

CIRCOR International announced the availability of certain historical segment information reflecting its previously announced organizational realignment beginning in the fourth quarter of 2016.

The new “Energy” segment, including the recent acquisition of Critical Flow Solutions, will prima...

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Curtiss-Wright, Clarke Industrial Engineering Sign Licensing Agreement

7 HOURS AGO

Clarke Industrial Engineering has entered into a licensing agreement with Curtiss-Wright Corporation, whereby Clarke’s patented and proprietary Shutter Valve technology will be exclusively available to Curtiss-Wright for the worldwide naval defense market, the U.S. maritime homeland security mar...

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New Investments Spur Permian Oil Production Increase

12 HOURS AGO

The Department of Energy (DOE) said on Tuesday that oil production in the Permian Basin could increase by 53,000 bpd by next month. According to the Energy Information Administration (EIA), that is the largest monthly increase in the region in a year.

“The EIA’s first shale oil forecast o...

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Why is Oil & Gas Slow to Adopt Cloud Technology?

1 DAY AGO

“There are endless benefits to implementing a cloud-based system, many of which center around less waste and less hassle, but due to operational characteristics, oil & gas companies stand to benefit more than most.”

“Yet, while being among the sectors that stand to gain most fro...

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Industrial Production Sees Largest Rise in More Than Two Years

11 HOURS AGO

Industrial production rose 0.8% in December, the largest increase since November 2014, after falling 0.7% the previous month. For the fourth quarter as a whole, the index slipped 0.6% at an annual rate.

Manufacturing output moved up 0.2% in December, as an increase in durable manufacturing outweighed d...

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IMF Raises U.S. Economic Growth Forecast

1 DAY AGO

After a lackluster outturn in 2016, economic activity is projected to pick up pace in 2017 and 2018, especially in emerging market and developing economies. However, the International Monetary Fund (IMF) noted in its new World Economic Outlook, there is a wide dispersion of possible outcomes around ...

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Checking Metal Materials With a Magnet

materials_q_and_a_graphicQ: I’ve seen people checking metal materials with a magnet. Is this a useful method of sorting materials, and if so, how does it work?

A: Valve companies deal with a large number of pure metals and alloys due to the variety of applications in the process industry. Occasionally, alloy identification must be performed on parts due to customer inquiries, mix-ups in bar stock, questionable machining characteristics or for some other reason. Although positive material identification (PMI) has become quite common, a PMI tester is not always available in a timely manner. One common identification/sorting technique that is often overlooked—and sometimes misapplied—is magnetic inspection. Magnetic inspection can save a lot of time by quickly proving a material is not what it is supposed to be.

Categorizing Materials by Magnetic Attraction

Magnetic inspection refers to categorization of a material by observation of its magnetic attraction force. Various alloy groups behave differently when exposed to a magnet. However, virtually all alloys fall into one of four behavior categories:

  • F - Fully magnetic:Materials such as carbon steels, alloy steels.
  • N - Never magnetic: Materials such as aluminum alloys, copper alloys, most nickel-base alloys, some stainless steels, etc. These materials exhibit no perceptible attraction to a magnet.
  • P - Partly magnetic: Materials such as some stainless-steel castings and wrought products. These materials exhibit some attraction to a magnet, but less than the fully magnetic materials.
  • V - Varying:Materials such as some stainless steels, nickel-copper alloys, etc. These materials may or may not be attracted to a magnet, and when attracted to a magnet, the attraction strength may vary significantly, depending upon the exact composition and processing history.

Information on magnetic characteristics can usually be found in material product literature.

An unknown material’s magnetic characteristic is determined by placing a magnet against the material and observing whether it is attracted or not. If there is no perceptible attraction, the material falls into category “N”. If there is attraction, decide whether it is full or partial. This is best done by placing the magnet against the unknown material and then bringing a piece of carbon steel into contact with the opposite end of the magnet. If the carbon steel easily removes the magnet from the unknown material, then the unknown falls into category “P”. If the magnet is attracted with approximately equivalent force by both materials, then the unknown falls into category “F”. In performing this comparative test, it is important that the surface contour and finish of the unknown piece and the carbon steel piece be the same (preferably flat). It is also important that both parts are more massive than the magnet or, in the case of sheet materials, that both parts have approximately the same thickness.

Limitations of Magnetic Inspection

The most important thing to keep in mind regarding magnetic inspection is that, although it can prove that a part is not a particular material, it cannot prove that a part is a particular material.

Here are some example applications of magnetic inspection:

  • Example 1: Records have been lost for a valve shaft that has been stored for several years. It is assumed the shaft is probably either S17400 or S20910, since these are the standard materials of construction for this part. Magnetic inspection determines that the shaft is fully magnetic. S17400 is fully magnetic, whereas S20910 is never magnetic. Therefore, the shaft is not S20910, and may be S17400. It could also be some other fully magnetic material.
  • Example 2: A customer orders a “316” valve body, but upon receipt of the body finds that it is slightly magnetic. The customer calls and complains that he did not receive a “316” body as ordered, because he knows that 316 stainless steel is never supposed to be magnetic. The problem with this logic is that the body is not 316, but rather is a CF8M casting, the equivalent of 316 wrought material. The chemistry of the cast material is adjusted to intentionally produce a small percentage of “ferrite,” which is a magnetic phase. This renders the casting partly magnetic, and often leads to this type of confusion. This highlights the importance of accuracy in material designation and product form (cast, wrought, etc.) when using magnetic inspection.
  • Example 3: A casting is sent to inspection for a material check because the machine operator noticed its machining characteristics were unusual. The casting is supposed to be CW2M. Magnetic inspection may save a great deal of time vs. performing a PMI. The casting is found to be partly magnetic. This proves that the casting is not CW2M, which is never magnetic.
  • Example 4: Same situation as example 3. This time, the material is found to be non-magnetic. This does not mean that the material is CW2M. This is one of the most important limitations in magnetic inspection. Magnetic inspection can prove that a part is not a particular material, but it cannot prove that a part is a particular material. In this case the casting should be further evaluated by PMI or some other method to determine if it is CW2M or some other non-magnetic material.

Remember that magnetic inspection can be a valuable, time-saving technique, but if used improperly it can produce erroneous identification of materials.

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