8 Methods for Testing the Composition of Metal Materials

Metal materials include pure metals, alloys, special metals, etc., which can be widely used in various fields, including aviation, machinery, computer hardware and other fields.

With the increasing demand for metal materials in various industries, some complex materials came into being.

The composition of metals is the main factor that determines the properties of materials. Understanding the composition and properties of metals can better apply materials to products.

In production activities, we often have to face two problems, one is what is the material of metal, and the other is whether a metal material meets the desired material requirements.

By analyzing the composition of metal materials, we can understand the composition of materials, so as to monitor the product quality, analyze the products with problems, and analyze the causes to eliminate hidden dangers.

Knowledge of metal material analysis

There are about 70 kinds of metals in nature, including iron, copper, aluminum, tin, nickel, gold, silver, lead, zinc, etc.

And alloy refers to two or more kinds of metal or metal combined with non-metal, which has metal characteristics.

Common alloys such as steel alloys composed of iron and carbon;

Stainless steel composed of iron, chromium and nickel;

Brass formed by copper and zinc, etc.

Metal materials are usually divided into ferrous metals, non-ferrous metals and special metal materials.

Ferrous metals, also known as iron and steel materials, include pure iron, cast iron with 2% – 4% carbon, carbon steel with less than 2% carbon, as well as structural steel, stainless steel, heat-resistant steel, tool steel, superalloy, precision alloy, etc. for various purposes.

Ferrous metals in a broad sense also include chromium, manganese and their alloys.

Iron is the most abundant and inexpensive metal element on the earth, and it is an indispensable basic material for almost all industries.

It is full of refrigerators, kitchenware, washing machines, cars, railways, trams, iron bridges, ships, electric towers, buildings, factories and machinery.

Nonferrous Metals refer to all metals and their alloys except iron, chromium and manganese, which are usually divided into light metals, heavy metals, precious metals, semi metals, rare metals and rare earth metals.

The strength and hardness of the alloy are generally higher than that of pure metal, and the resistance is large and the resistance temperature coefficient is small, so it has good comprehensive mechanical properties.

Common non-ferrous alloys include aluminum alloy, copper alloy, magnesium alloy, nickel alloy, tin alloy, titanium alloy, zinc alloy, etc.

As structural and functional materials, they are widely used in machinery manufacturing, construction, electronic industry, aerospace, nuclear energy utilization and other fields.

Methods of analysis and test for metallic materials

The composition analysis and testing methods of metal materials are constantly developing, from the traditional titration and spectrophotometry to new testing methods, such as plasma emission spectrometry, spark direct reading spectrometry, etc. from the traditional element by element testing, to now, multiple elements can be tested at the same time, and the efficiency and accuracy are continuously improved.

The principles and characteristics of different test methods are as follows:

1. Spectrophotometry

Spectrophotometry is an analytical method for quantitative analysis of metal elements.

By measuring the absorbance and luminous intensity within a specific wavelength range of the substance to be measured, the qualitative and quantitative analysis of the substance is carried out.

It has the characteristics of wide application, high sensitivity, good selectivity, high accuracy and low analysis cost.

The disadvantage is that only one element can be analyzed at a time.

The detection instruments include ultraviolet spectrophotometer, visible spectrophotometer and infrared spectrophotometer.


2. Titration

Titration is to test the metal components contained in the solution with a standard concentration of test reagent.

After the metal components fully react with the reagent, it can reach the final titration end point.

This method is applicable to the test of various substances with a content of more than 1%.

The main disadvantage of this method is low efficiency.


3. Atomic spectrometry

Atomic absorption spectrometry can be divided into atomic absorption spectrometry and atomic emission spectrometry.

It is a traditional technology for analyzing the composition of metal materials.

The principle of atomic absorption spectrometry is to quantitatively analyze the content of the measured elements through the absorption intensity of the outer electrons of the ground state atoms in the gaseous state to the corresponding atomic resonance radiation line of visible light and ultraviolet light.

This method is especially suitable for gaseous atomic absorption radiation, and has the advantages of high sensitivity, strong anti-interference ability, strong selectivity, wide analysis range and high precision.

However, there are also defects, such as the inability to analyze multiple elements at the same time, the low sensitivity in the determination of insoluble elements, and the poor effect in the measurement of some complex samples.

The principle of atomic emission spectrometry is that each element ion or atom has the characteristics of emitting special electromagnetic radiation under electrical or thermal excitation.

This method uses emitters for qualitative and quantitative analysis of elements, which can test multiple elements at the same time, consume less samples to achieve the purpose of measurement, and can also get the results quickly.

Generally, this method is used to detect the whole batch of samples, but poor accuracy is its fatal disadvantage, and it can only analyze the components of metal materials, and there is nothing to do with most non-metallic components.

Atomic spectrometry

4. X-ray fluorescence spectrometry

X-ray fluorescence spectrometry is mostly used to determine metal elements, and it is also a common method to determine the composition of metal materials.

The test principle is: the atoms in the ground state will be in the low-energy state when they are not excited, but once they are excited by the radiation line of a certain frequency, they will become the high-energy state.

In the high-energy state, they will emit fluorescence.

The wavelength of this fluorescence is very special.

Measuring the wavelength of these X-ray fluorescence spectral lines can determine the type of elements in the sample.

Taking the spectral line intensity of the standard sample as a reference, the content of elements can be measured by comparing the spectral lines of the measured samples.

This method is a qualitative and semi quantitative method, which is mainly used to determine the approximate content in metal composition analysis.

X-ray fluorescence spectrometry

5. Inductively coupled plasma spectrometry

Inductively coupled plasma atomic emission spectrometry is the most widely used method at present.

Its principle is to use the excitation of metal elements to produce electronic transition, which will show a certain intensity on the spectral line to determine the elements and content.

The test range is wide, the sensitivity is high, the analysis speed is fast, and the accuracy is high.

It can test a batch of samples under one marking line, and test multiple elements at the same time.

Inductively coupled plasma spectrometry

6. Spark Direct Reading Spectrometry

Spark direct reading spectrometer uses the high temperature of electric arc (or spark) to directly vaporize and excite the elements in the sample from the solid state and emit the characteristic wavelengths of the elements.

After light splitting with a grating, it becomes a “spectrum” arranged according to the wavelength. The characteristic spectral lines of these elements pass through the exit slit and enter their respective photomultiplier tubes.

The optical signal becomes an electrical signal, which is integrated by the instrument’s control and measurement system and converted to analog / digital.

Then it is processed by computer and the percentage content of each element is tested.

This method has high accuracy and can be used for simultaneous analysis of multiple elements. Qualitative and quantitative analysis results of dozens of elements can be obtained at the same time in one excitation and analysis.

It is easy and fast to analyze. It can simultaneously measure the content of dozens of elements in alloy steel or non-ferrous alloy in 20 seconds for real-time analysis.

It does not consume expensive chemical reagents or special excipients.

Solid samples can be tested directly.

The disadvantage is that there are certain requirements for the shape and size of the sample.

8 Methods for Testing the Composition of Metal Materials 1

Eight methods for testing the composition of metal materials

7. Carbon and sulfur analysis

In metal materials, especially steel metals, carbon and sulfur are the main test elements, and the above methods can not directly quantify carbon and sulfur accurately.

Therefore, carbon and sulfur elements need to be tested by carbon sulfur analyzer.

The carbon and sulfur in the sample are oxidized into carbon dioxide and sulfur dioxide after high temperature heating under oxygen enriched conditions.

After treatment, the gas enters the corresponding absorption pool to absorb the corresponding infrared radiation, which is transmitted by the detector as a signal, and the computer processes and outputs the results.

This method is accurate, rapid and sensitive, and can be used for both high and low carbon and sulfur content.

Carbon and sulfur analysis

8. Oxygen and nitrogen analysis

The oxygen and nitrogen analyzer decomposes the sample by pulse heating under inert atmosphere through the oxygen and nitrogen analyzer, and the content of oxygen and nitrogen in various steel, non-ferrous metals and new materials are measured by infrared detector and thermal conductivity detector respectively.

It has the characteristics of high accuracy and low detection limit.

Oxygen and nitrogen analysis

Introduction to test items

Metal category


Iron and steel

Element analysis

Grade identification

(to identify whether it conforms to a standard or a grade)


Coating composition analysis (test coating composition and element

Element content)

Copper alloy / high purity copper

Lead free solder / lead solder

Aluminium alloy

Magnesium alloy


Titanium alloy

Precious metals (gold, silver, palladium, platinum)

High pure metal

Brazing filler metal

Powder metallurgy

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