How to Review an MTR (Mill Test Report)

Whether manufacturing a subsea pipeline or a small skid package, using the correct material as determined in engineering for each component is critical. The Certified Mill Test Report is a tool used to ensure that received raw material matches the engineering and purchase order requirements. Think of the MTR as the DNA, this is one part of creating the birth certificate for your project or manufactured product.

A Certified Mill Test Report (CMTR) is a quality assurance document generated by the raw material manufacturer and provided with the material to intermediate suppliers and ultimately to a finished goods manufacturer. Whether it’s called a CMTR, Mill Test Report (MTR), Mill Certification, Metallurgical Test Report, or similar name, this document provides the end user of the raw material verification that the material received matches the requirements of their order. MTR’s are also used to maintain traceability of the material from its initial inception to its inclusion in a finished part.

MTR Review Process

At most manufactures or fabricators, it is the Receiving Department’s responsibility to match received goods to supporting MTRs and forward that information to the Project Engineer. The Project Engineer is responsible for review of the MTR to ensure it meets the engineering and order requirements. Below we have summarized what our engineers are reviewing, so that only the correct materials are issued to the shop for manufacturing. This being another way we support our promise to Reduce Project Risk and achieve the lowest total cost of ownership for our customers

MTR Example

CMTR Field Explanation

1- Material Heat Number

Material manufacturers can identify raw material in different ways, using lot, coil or other identifying numbers, but ultimately all MTRs will identify the material with a Heat Number. The heat number is used to maintain traceability of the material. When matching an MTR to its raw material all accompanying paper work and in many cases markings on the raw material itself must match the heat number on the MTR.

02 - Material Grade

Metal materials are produced in various grades. The MTR identifies the grade of the material. CMTR’s certify that the raw material meets the appropriate American Society for Testing and Materials (ASTM) or American Society of Mechanical Engineers (ASME) material product specification. ASME material specifications are required when fabricating Pressure or Vacuum Vessels to the ASME Boiler and Pressure Vessel Code. ASTM specifications are prefixed by an “A”, e.g. A240, while ASME specifications are prefixed by a “SA”, e.g. SA240. Often but not always the ASTM and ASME specification are identical. The product specifications that the raw material meets are listed on the CMTR.

03 - Material Description

The MTR identifies the applicable dimensions of the raw material. In the case of plate material this would be the thickness, round bar the diameter, or flat bar the thickness and width. This information must match the order requirements.

04 – Mechanical Test

There exists a large number of tests, many of which are standardized, to determine the various mechanical properties of materials. Some of the most common of the testing methods is tensile testing, which is used to obtain the stress-strain curve for a material and from there, properties such as Young Modulus, yield stress, tensile stress, and % elongation to failure. Hardness testing tests is used to determine hardness of a material to deformation. And Charpy testing is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's notch toughness and acts as a tool to study temperature-dependent ductile-brittle transition. This is a major factor in determining the weldability of materials.

05 - Chemical Analysis

The product specification lists the detailed requirements that the raw material must meet to be certified to that product specification and grade. The actual measured properties of the raw material are recorded on the CMTR for the identified heat number. The values listed on the CMTR must fall within the range or limits of the product specification for the raw material to be accepted for use.

06 - Heat Treatment

Depending on the raw material, there may be other requirements in the product specification. For example, 300 series stainless steels require a specific heat treatment which must be recorded on the CMTR. The reviewer must identify all special processes in the product specification and confirm they are properly recorded on the CMTR.

Finally the CMTR must be certified with the signature of a responsible employee of the foundry or mill producing the raw material. 

MTR’s (Mill Test Reports) provide a record of traceability and properties of a raw material, ensuring that the material will perform in the way it was designed to. Deviations from product specification values can have large consequences, even causing a component failure. The ability to effectively review a Certified Mill Test Report to avoid such consequences is just one-way to reduces project risk.