Hardness and Metallographic Analysis of Common Steel Materials for Mechanical Blades

Introduction

Mechanical blades are common tools in industrial production and daily life, and different materials of blades need to be selected in different application fields. The performance of blades is closely related to the hardness and metallographic structure of the selected materials. This article will introduce the hardness and metallographic analysis of commonly used steel materials for blades, helping readers understand the characteristics of blade materials and their impacts.

1. Overview of Common Steel Materials for Mechanical Blades

1.1 Principle Of Blade Material Selection

Mechanical blades play a crucial role in various processing scenarios in industrial production and daily life. Choosing suitable blade materials can directly affect the performance and service life of blades. Therefore, the selection of mechanical blade materials needs to follow the following principles:

• Hardness and wear resistance: Blade materials need to have sufficient hardness and wear resistance to ensure that the blades are not easily worn or deformed during processing, thereby maintaining cutting performance and processing accuracy.
• Toughness and fracture resistance: Although hardness is an important indicator, blade materials also need to have certain toughness and fracture resistance to prevent unexpected fractures during processing, thereby protecting processing equipment and operators’ safety.
• Cutting performance: Blade materials need to have good cutting performance, that is, they can effectively remove workpiece materials and produce clear cutting surfaces during cutting processes, improving processing efficiency and quality.
• Thermal stability: Under high temperature and high-speed cutting conditions, blade materials need to have good thermal stability to prevent problems such as softening, oxidation, or shedding of materials due to high temperatures.
• Economy: Under the premise of meeting performance requirements, selecting economically reasonable blade materials to reduce production costs and improve processing efficiency.

1.2 Overview of Common Steel Materials for Mechanical Blades

• High-speed steel (HSS): High-speed steel is an alloy steel containing a high proportion of tungsten (W), molybdenum (Mo), cobalt (Co), and other elements. It has high hardness, wear resistance, and thermal stability, suitable for high-speed cutting and machining.
• Hard alloy (carbide): Hard alloy is a composite material composed of tungsten carbide (WC) particles and a binder phase (usually cobalt). It has extremely high hardness and wear resistance, suitable for cutting hard materials such as steel, cast iron, stainless steel, etc.
• Tool steel: Tool steel is a type of high carbon alloy steel suitable for manufacturing cold and hot molds and cutting blades. It has high hardness, toughness, and wear resistance, suitable for various blade and cutter manufacturing.

1.3 Introduction to the Application Scenarios of Different Steel Materials

• High-speed steel (HSS): Suitable for various high-speed cutting blades such as milling cutters, drills, blades, etc., widely used in automotive, aerospace, machinery manufacturing, and other fields.
• Hard alloy (carbide): Suitable for cutting hard materials such as steel, cast iron, alloy steel, stainless steel, etc., widely used in CNC lathes, CNC milling machines, turning blades, etc.
• Tool steel: Suitable for the manufacture of various molds and cutting blades, such as stamping dies, extrusion dies, cold heading dies, cutting blades, etc., widely used in industries such as automotive, aerospace, electronics, etc.

2. Hardness Analysis

Hardness is one of the important factors affecting the performance of blades. Suitable hardness can improve the wear resistance, fatigue resistance, and cutting performance of blades, thereby improving the service life and processing efficiency of knives.

2.1 Definition

Hardness refers to the material’s resistance to external forces invading or scratching. In knife materials, hardness is an important performance indicator that directly affects the wear resistance, cutting performance, etc., of knives.

2.2 Measurement Methods

In the engineering field, common hardness testing methods include Rockwell hardness, Brinell hardness, and Vickers hardness.

• Rockwell Hardness: Rockwell hardness testing determines the hardness of materials by measuring the depth of indentation formed on the material surface during loading and unloading under a certain load. Rockwell hardness is divided into three different test methods: A, B, and C, which are used for different types of materials. Their hardness values are usually represented by “HRA”, “HRB”, or “HRC”.
• Brinell Hardness: Brinell hardness testing determines the hardness of materials by measuring the diameter of the indentation formed on the material surface by applying a certain load with a spherical indenter. Its hardness value is usually represented by “HB”.
• Vickers Hardness: Vickers hardness testing determines the hardness of materials by measuring the diagonal length of the indentation formed on the material surface by applying a certain load with a diamond indenter. Its hardness value is usually represented by “HV”.

There are certain conversion relationships between these hardness testing methods, and their hardness values can be converted through corresponding conversion formulas to meet different engineering requirements.

2.3 Hardness Comparison Analysis of Common Steel Materials for Knives

The hardness of commonly used tool steels depends on factors such as their composition and processing technology. Generally, hard alloy (carbide) has the highest hardness, followed by high-speed steel (HSS), and tool steel has relatively lower hardness.

For example, the hardness of hard alloy is usually between 90-94 HRA, and the hardness of high-speed steel is about 62-67 HRC.

2.4 Relationship between Hardness and Knife Performance

Hardness is an important performance indicator of knife materials, directly affecting the wear resistance, fatigue resistance, and cutting performance of knives, etc.

• Wear resistance: Higher hardness usually means better wear resistance. Knives are less prone to wear during operation, thereby extending the knife’s service life.
• Fatigue resistance: Suitable hardness can improve the knife’s fatigue resistance, making it less prone to fracture and deformation during prolonged operation.
• Cutting performance: There is a certain balance between the cutting performance of knives and hardness. Excessive hardness may cause the cutting edge to break easily, while insufficient hardness may cause the cutting edge to wear easily. Therefore, selecting the appropriate hardness is key to ensuring good cutting performance of knives.

3. Metallographic Analysis

Metallographic analysis is an important method to understand the organizational structure and properties of knife materials. By analyzing the metallographic structure, the selection and processing of knife materials can be optimized, and the performance and life of knives can be improved.

3.1 Definition

Metallographic analysis observes the microscopic structure of knife materials through a metallographic microscope. By magnifying the microscopic structure of materials, the shape, size, distribution of grains, and the content and distribution of various phases can be observed to understand the types and characteristics of materials.

3.2 Significance and Applications of Metallographic Analysis

Metallographic analysis has important significance and wide applications:

• Understanding the type of material organization: Metallographic analysis can determine the grain structure and phase composition of knife materials, including austenite, ferrite, carbides, etc., to understand the basic organizational types and characteristics of materials.
• Evaluation of processing effects: Metallographic analysis can be used to evaluate the effects of processing technology on the organizational structure of knife materials, judge the rationality of processing technology, and optimize the processing accuracy and performance of knives.
• Quality control and defect analysis: Metallographic analysis can be used to detect defects and non-uniformities in knife materials, help solve quality problems during production, and improve product stability.

3.3 Tools Used for Metallographic Analysis

Metallographic analysis typically uses metallographic microscopes and corresponding sample preparation equipment.

• Metallographic microscope: A metallographic microscope is a special type of microscope with high magnification and excellent resolution, which can observe the microscopic structure of materials. Through a metallographic microscope, the grain morphology, size, and distribution, as well as the content and distribution of various phases, can be observed.
• Sample preparation equipment: In the process of metallographic analysis, knife materials need to be prepared into samples, usually including cutting, grinding, corrosion, etc., to observe the internal structure of materials. Common sample preparation equipment includes metallographic sample cutting machine, grinding wheel grinder, corrosion tank, etc.

3.4 Interpretation of Metallographic Analysis Results of Common Steel Materials for Knives

Metallographic analysis provides information about the microscopic structure of commonly used knife steel materials, such as grain size, morphology, phase content, and distribution. Different tool steel materials have different metallographic structure characteristics, influenced by factors such as material composition and heat treatment processes.

For example, high-speed steel (HSS) usually has fine austenite grains and dispersed carbide phases, while hard alloy (carbide) mainly consists of uniformly distributed carbide particles and a binder phase.

3.5 Relationship between Metallographic Structure and Knife Performance

The metallographic structure has a significant impact on the performance of knives, with factors such as grain size and phase content being important factors affecting knife performance.

• Grain size: Finer grains usually indicate higher hardness and strength of materials, while also having good toughness and fatigue resistance, which are beneficial for improving the wear resistance and cutting performance of knives.
• Phase content: Different phases in knives also have important effects on knife performance. For example, appropriate carbide phase content can improve the hardness and wear resistance of knives, but excessive carbide content may increase knife brittleness, affecting the impact resistance and toughness of knives.

4. Case Analysis and Case Sharing

To deeply understand the performance characteristics of different commonly used tool steel materials, we selected several common tool steel materials for hardness and metallographic analysis, and interpreted the analysis results.

4.1 High-speed steel (HSS):

• Hardness analysis: According to Rockwell hardness testing, the hardness of HSS is about 62-67 HRC.
• Metallographic analysis: Through observation with a metallographic microscope, the structure of HSS usually consists of fine austenite grains and dispersed carbide phases.

4.2 Hard alloy (carbide):

• Hardness analysis: The hardness of hard alloy usually reaches 90-94 HRA.
• Metallographic analysis: The metallographic structure of hard alloy mainly consists of uniformly distributed carbide particles and a binder phase.

4.3 Tool steel:

• Hardness analysis: The hardness of tool steel varies depending on specific compositions but is generally slightly lower than hard alloy.
• Metallographic analysis: The metallographic structure of tool steel is more complex, typically including austenite, ferrite, etc.

4.4 Case Sharing

In practical engineering applications, optimizing knife material selection and processes through hardness and metallographic analysis can significantly improve knife performance and service life.

For example, in a mechanical processing plant, they found that knives made of ordinary knife steel were prone to wear and fracture when processing high-hardness materials, affecting production efficiency and product quality. Through hardness and metallographic analysis, they found that hard alloy has higher hardness and a more uniform metallographic structure, suitable for cutting high-hardness materials. Therefore, they decided to use hard alloy as the knife material and optimized the processing technology, including knife shape design, knife coatings, etc. After improvement, the service life of the knives was significantly extended, and production efficiency was improved.

Through the above cases, we can see that optimizing knife material selection and processes through hardness and metallographic analysis is of great significance for improving knife performance and service life, effectively solving problems encountered in actual production, and improving processing efficiency and product quality.

5. Conclusion

In this article, we have delved into the hardness and metallographic analysis of commonly used knife steel materials and provided a comprehensive explanation of their importance.

Hardness and metallographic analysis are important means to evaluate the performance of knife materials. Hardness analysis can objectively reflect the material’s resistance to external forces, while metallographic analysis reveals the microscopic structure of the material, thereby understanding its performance characteristics. Through these two analysis methods, we can comprehensively evaluate the advantages and disadvantages of knife materials, providing important references for the selection, design, and application of knife materials.

Choosing the right knife material has a significant impact on knife performance. Different knife materials have different characteristics such as hardness, toughness, wear resistance, etc., suitable for different processing scenarios and workpiece materials. Therefore, when choosing knife materials, it is necessary to comprehensively consider factors such as processing requirements, workpiece characteristics, and material properties to ensure that the knives have good processing performance and long-term stable use.

With the continuous development of science and technology, knife material analysis technology is also continuously improving. In the future, we can expect the following development trends:

Development of multidimensional analysis methods: With the advancement of materials science and engineering technology, multidimensional analysis methods will be more widely used, including mechanical property testing, chemical composition analysis, surface morphology observation, etc., to comprehensively evaluate the performance of knife materials.

• Application of intelligent analysis technology: With the development of artificial intelligence and big data technology, intelligent analysis technology will gradually be applied to the field of knife material analysis, improving analysis efficiency and accuracy, and providing more reliable technical support for the optimization design and processing of knife materials.
• Realization of customized material design: Based on advanced material simulation and calculation technology, more customized knife material designs will be realized in the future, designing knife materials more suitable for specific scenarios according to specific processing requirements and workpiece characteristics, further improving knife performance and processing efficiency.

The continuous development and improvement of knife material analysis technology will bring new opportunities and challenges to the knife industry, promote the innovation and application of knife materials, and drive the progress and development of industrial manufacturing.

6. About METAL Industrial

Nanjing Metal Industrial CO., Limited is a manufacturer of mechanical blades from China, producing blades and accessories for industries including metalworking, converting, food, and more. We have more than 15 years of experience in the manufacture and sales of industrial machine blades, machine parts, and regrinding services. We invite you to experience the superior quality of production