| Project Overview

Due to the wide variety of types and specifications, as well as the diverse properties and uses of metallic materials, they are widely used in many fields such as metallurgy, manufacturing, machinery, chemical engineering, and construction. Conducting grade identification of metallic materials is a necessary part of quality supervision. It helps enterprises fully understand the properties and usage conditions of products, making manufacturing enterprises more trustworthy and users more confident.

| Test Objective

By analyzing the elements and components of metals, the analyzed data is compared with the standard chemical composition of the grade to determine which metal grade it belongs to. The grade can reflect the type, chemical composition, or mechanical properties of the material, and it plays a crucial role in the quality control of products for enterprises:

① It is beneficial to understand the cause of the properties of metallic materials; 

② It is beneficial to reasonably select the processing methods, heat treatment methods, and equipment for metallic materials; 

③ It is beneficial to economically, safely, and reasonably apply metallic materials, avoiding the occurrence of huge losses caused by using non-standard materials.

| Differences between different grades

(1) Different countries, continents, and international organizations have their own independent metallic and alloy grade systems. These grade systems generally use numbers or letters to indicate a metal.

① In some cases, these letters and numbers can directly indicate the chemical composition and mechanical properties of the metal. For example, for a spring steel with an average content of carbon, silicon, and manganese of 0.60%, 1.75%, and 0.75% respectively, its grade is represented as "60Si2Mn". For high-quality spring steel, the symbol "A" is added at the end of the grade, and its grade is represented as "60Si2MnA".

② In other cases, letters and numbers are simply arranged in a certain order and do not directly reflect the specific composition or properties of the metal. Details of their composition and properties need to be understood indirectly according to the corresponding standards. For example: ADC6, ADC12, A380.1 (all are cast aluminum), TA4, TB4, TC4 (all are titanium alloys).

| How to distinguish metals of different grades?

Under the same system, different grades of metals or alloy materials mean differences in the elements and compositions they contain, and their reflected properties also vary.

Taking stainless steel as an example, 304 and 202 are both American standard grades. The differences between the two are as follows:

① 304 is a general-purpose stainless steel. Common marking methods in the market include 06Cr19Ni10 and SUS304. Among them, 06Cr19Ni10 generally indicates production according to the national standard, 304 generally indicates production according to the American standard, and SUS 304 indicates production according to the Japanese standard.

② 202 stainless steel is one of the 200-series stainless steels. Its national standard grade is 1Cr18Mn8Ni5N, and its Japanese standard grade is SUS202.

③ They both belong to austenitic stainless steels. In 202, part of the nickel is replaced by Mn and N, thus obtaining good mechanical properties and corrosion resistance. It is a new type of nickel-saving stainless steel. The room-temperature strength of 202 is higher than that of 304, and it has good oxidation resistance and medium-temperature strength below 800°C.

Experienced practitioners on-site can use quick identification methods to observe the sparks, color codes, fractures, sounds, etc. of the material to judge the grade of the metal. However, this method is only limited to simple judgments. To truly distinguish the quality of the material and identify which grade the material belongs to, it is necessary to conduct a composition analysis of the material to obtain the content of each element.

| What are the common methods for representing grades of metal materials?

① Common naming rules for national standard grades

② Grades of other common alloy materials

| Differences in metals/alloys under the same grade

(1) Different ways of indicating the grades of metal materials under the same grade represent differences in their compositions or properties.

For example: The same grade of Q345 steel is divided into Q345A, Q345B, Q345C, Q345D, and Q345E according to the quality grade. It represents different impact temperatures of different grades of steel.

(2) There will also be differences in different batches of metal materials with the same grade and the same level. The composition of the same grade is only a range, not a fixed value. Therefore, the fluctuation of the composition will inevitably cause differences in the distribution of the second phase, and the hardness will also inevitably vary. However, if the same batch of materials is used and the same part is taken, the quality is roughly the same.

| Standards for metal grade identification

GB - National standard; GB/T - Recommended national standard; ISO - International Organization for Standardization

EN - European Standard; ASTM - American Society for Testing and Materials; JIS - Japanese Industrial Standards  

① Direct-reading standards:

Stainless steel: GB/T 11170-2008  

Medium and low alloy steels: GB/T 4336-2016

Cast iron: GB/T 24234-2009 

Copper alloys: YS/T 482-2005

Aluminum alloys: GB/T 7999-2015

Magnesium alloys: GB/T 13748.21-2009 

Zinc alloys: GB/T 26042-2010

Titanium alloys: ASTM E2994-2016

Solder (lead-containing/lead-free): JSA JIS Z3910-2017 Analytical methods for solders

② The following are all ICP-OES and CS test standards:

Low-alloy steel: GB/T20125-2006, GB/T20123-2006 

Stainless steel: GB/T20123-2006, SN/T 2718-2010, SN/T 3343-2012

Other steels: EPA 6010D-2014, GB/T20123-2006 

Copper alloy: GB/T 5121.1-2008, GB/T 5121.4-2008, GB/T 5121.27-2008

Aluminum alloy: GB/T 20975.25-2008

Zinc alloy: GB/T 12689.12-2004, EPA 6010D-2014

Magnesium alloy: GB/T 13748.20-2009, EPA 6010D-2014

Nickel alloy: EPA 6010D-2014, GB/T14265-2017

Titanium alloy: EPA 6010D-2014, GB/T14265-2017, HB 7716.13-2002

③ Standards for other precious metal materials/Standards for other high-purity metal materials

High-purity metals (including precious metals): Refer to the corresponding product standards and use ICP-OES or ICP-MS to test the impurity content.

Precious metals: For silver alloys, use the titration method for silver and ICP-OES to test impurities;

For gold alloys, use the gravimetric method for gold and ICP-OES to test impurities;

For other precious metal alloys, use the ICP-OES internal standard method to test precious metals and ICP-OES to test impurities.

| Metal grade identification/Recommended test methods

MTT has a professional engineer team and has introduced instruments such as inductively coupled plasma atomic emission spectrometry (ICP-OES), spark direct-reading spectrometer (Spark-OES), X-ray fluorescence spectrometer (XRF), carbon-sulfur analyzer, scanning electron microscope and energy-dispersive spectrometer (SEM+EDS). It conducts the following tests on metal materials according to American standards, ISO international standards, national standards, European standards, German standards, Japanese standards, etc.:

I. Component analysis (qualitative analysis)

II. Component content (quantitative analysis)

Through the above two steps, the grade of this metal material can be known. For unknown metal materials, the detection can also be carried out according to the above test steps, and the grade of the unknown metal material can be determined by referring to the corresponding national or industrial standards.

| Identification of common metal/alloy grades

Common identifications of metal/alloy grades include:

① Composition analysis of stainless steel and identification of stainless steel grades.

Such as analysis of stainless steels like 304, 304L, 316, 316L, 201, 202, 420, 430, etc.;

Determination of elements such as carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), nickel (Ni), chromium (Cr), molybdenum (Mo), copper (Cu), etc.

② Composition analysis of other iron-based alloys.

Cast iron, carbon steel, structural steel, spring steel, tool steel, bearing steel, die steel, galvanized sheet, free-cutting steel, etc.

③ Full composition analysis and grade identification of non-ferrous metal alloys.

Copper-based alloys (pure copper, brass, cupronickel, bronze, etc.)

Aluminum-based alloys (wrought aluminum, cast aluminum, pure aluminum, etc.)

Magnesium-based alloys (magnesium-aluminum-zinc, magnesium-aluminum-silicon, etc.)

Nickel-based alloys (superalloys, precision alloys, etc.)

Titanium-based alloys (pure titanium, TA1, TB2, TC4, etc.)

Tin-based alloys (pure tin, lead-tin alloys 6337/6040, lead-free solders SAC0307/SAC305, etc.)

Zinc-based alloys (pure zinc, zinc-aluminum alloys, etc.)

④ Other alloy materials

Cemented carbides (tungsten-based, tungsten carbide-based, cobalt-based, etc.)

Contact materials (silver-tungsten, copper-tungsten, silver-tungsten carbide, etc.)

| Precautions?

① When an enterprise entrusts a third-party testing agency to conduct grade identification of metal/alloy materials, it needs to provide the chemical composition limits of the standard grade and other standard contents (or the standard number corresponding to the grade) to avoid errors.

② If an enterprise does not have relevant standards, the engineers of MTT Laboratory can recommend the most suitable grade for testing based on their professional experience.

③ For unknown metal materials, the technical engineers of MTT can also conduct a series of tests on the elemental composition content of the metal materials. Then, according to national standards or international standards, the grade can be determined through matching. If the metal material does not meet the limit range requirements of the standard grade, its composition can be analyzed, and the product process can be improved to enhance the product quality.

MTT specializes in the grade identification service of metal/alloy materials. With precise instruments and equipment and an expert technical team with rich testing experience, it can help enterprises

① compare whether two (or more) metal/alloy materials are of the same kind;

② determine whether the metal/alloy material is of the specified grade (including national and foreign standard grades);

③ recommend suitable grades for metal/alloy materials with unknown grades (national and foreign standard grades can be recommended as required).

| Official definition of metal grades

Actually, simply put, a metal grade is the name given to each specific metal material.

Each country, continent, and international organization has introduced its own independent metal grade system according to relevant standards, numbering different metal materials to distinguish them, thus making the production and use of metal/alloy materials more standardized and convenient.

For example, regarding cast iron grades: the Italian grade is designated as GG25, the Chinese grade as HT250, the Japanese grade as FC250, the American grade as NO.35, and the British grade as 250. However, they all refer to the same cast iron material, with only different designations used in different countries.