What is the difference between an MTR and CofC?

Posted by Nucor Grating on Jun 3, 2019 11:21:22 AM



MTR – An Overview

When ordering bar grating, sometimes it is necessary to know the origin and path of your materials. In these cases, buyers will occasionally request an MTR, or Mill Test Report. This report traces a specific metal back to its origin, and provides detailed information about processes, makeup and testing history for that metal.


An MTR can go by a number of different names, including material test report, inspection certificate, or certificate of test. Whatever its name, if MTRs are required for your project, it is important that we know at bid time so we can plan accordingly. This ensures that we do not combine multiple heats or other materials from the mill throughout the process of your order.


If the grating manufacturer is given the adequate time to know an MTR is needed, they can ensure that the lot in question is separated and tracked throughout the process to maintain a clean traceability chain from start to finish.


The Four Main Areas of Information on an MTR are:

  • Product: This part specifies the metal’s specific characteristics, including its alloy, temper, thickness, width, and finish. Also included, if required, would be ASTM (American Society for Testing and Materials) and AMS reports. While there may be some range limits to the specificity of characteristics such as thickness and width, there is little leeway to ensure that the materials are the same and provide an accurate reading for the finished product.

  • Heat Number or Lot: The heat number is a code to provide verification of a metal product's origin. It can be used to trace the origin and verify quality. This is often the main way to trace the metal’s origin and is stamped on the side of the finished product. In the MTR, a specific heat number for that product must match across all paperwork.

  • Properties: The strength, ductility, hardness, and elasticity of steel products. This will ensure the material meets the structural standards of the end use.

  • Chemical Makeup:  Most of the time, these will include the material’s chemical properties. Depending on what alloy you are buying, the chemical composition will need to meet certain requirements.


All of these categories are vital to ensuring that the finished material and its accompanying MTR provides a complete and thorough picture of the material’s manufacturing journey and end result. When reading an MTR, be sure the basic information on the report matches with that of the finished product, especially the heat number. Any discrepancies could invalidate the results and muddy the waters of authenticity.


What is a Certificate of Compliance (CofC)?

If a project includes bar grating but does not require a full MTR, just verification that the grating meets industry standards, then a Certificate of Compliance, or CofC, may be the more relevant option. This report provides additional information than what is normally presented, but adds less time and additional cost to the overall project.


A Certificate of Compliance is the manufacturer’s documented guarantee that the material is verified to meet the NAAMM Standard, the bar grating industry standard set forth by the National Association of Architectural Metal Manufacturers.


There are certain metal types typical to grating manufacturing specified by the NAAMM, which include:

  • Metal Bar Grating (ASTM): A1011/A1011M Commercial Steel (CS Type 2) as per MBG 531-00 of the bar grating manual.

  • Heavy Duty Metal Bar Grating (ASTM): A1011/A1011M Commercial Steel (CS Type 2) as per MBG 532-00 of the bar grating manual.

  • Aluminum Grating (ASTM): B221 (B221M) as per MBG 531-00 of the bar grating manual.

  • Stainless Grating (ASTM): A666 as per MBG 531-00 of the bar grating manual.


The Certificate also states if the materials used for the job are domestic to the project, but is often only included if specifically requested by the customer. It will also list the different grating types that the finished product will align.


When to ask for an MTR versus CofC?

It depends on the project. For some projects, an MTR is required but it is imperative that the grating manufacturer knows before bidding as the MTR process is very involved. For other projects just seeking verification of industry standards, a CofC should be requested. Certificate of Compliances are much less involved and response time for the buyer is much quicker.  Note, all material shipped from Nucor Grating stock complies with the CofC’s we offer.