Application and development of aluminum alloy materials

Author: Chief Editor: Wang Chengbei
Publisher:
Publish Date: 2004-01-01
Features:
Introduction This book systematically and comprehensively elaborates on the development process, current status, and future trends of die steel, the alloying principles, key production processes, testing methods, selection and application of die steel, and the main performance data of commonly used die steel. It integrates the latest scientific research achievements and production application experiences from domestic and international fields. The book is divided into 10 parts, providing detailed discussions and introductions on plastic die steel, cold work die steel, hot work die steel, and special die steel. This book is suitable for science and technology personnel and technical workers engaged in die steel research, development, production, inspection, as well as die design, manufacturing, application, and maintenance. It can also be used as a reference for faculty and students of relevant majors in universities and colleges, as well as for professional training personnel.
Excerpt:
With the development of industrial production technology and the continuous emergence of new materials, the working conditions of dies have become increasingly severe, placing higher and newer demands on the performance, quality, and variety of die steel. To meet these requirements, countries around the world have actively developed new types of die steel with various characteristics to suit different needs in recent years. Significant efforts have been made in variety, quality, production processes, and production equipment, resulting in rapid progress. The following aspects are described in detail:
1.3.1 Development of Die Steel Types
Die steel is categorized into three types: plastic die steel, cold work die steel, and hot work die steel.
1.3.1.1 Plastic Die Steel
Since the 1950s, the world plastic industry has developed rapidly, and plastic has become an important industrial material. Most plastic products are formed through molding, and in many industrialized countries, the output value of plastic dies has ranked among the highest in the die industry [2]. Plastic die steel has gradually evolved into a specialized steel series. For example, the current ASTM A681 standard in the United States includes the P series for plastic die steel, comprising 7 steel grades [12]. Plastic die steel is generally classified into five categories:
(1) Non-alloy type: Primarily uses medium-carbon structural steel, such as Japan's S55C, which is equivalent to China's 55 steel.
(2) Pre-hardened type: Generally medium-carbon alloy steel, such as the P20 steel from the United States and China's 3Cr2Mo steel. These are supplied by steel plants after quenching and tempering (in a pre-hardened state), allowing users to directly machine them into dies.
(3) Age-hardening type: In low- and medium-carbon alloy steel, by adding elements such as Ni, Al, Ti, and Cu, the hardness after quenching is relatively low, making it easier to machine into dies. Subsequently, through a deformation-minimized aging hardening treatment, the die achieves the required hardness. This type of steel is further divided into low-alloy age-hardening steel and high-alloy martensitic age-hardening steel, generally recommended for manufacturing complex precision plastic dies [13].
(4) Carburizing type plastic die steel: Some low-carbon alloy steel with very low carbon content, due to their excellent plasticity, are suitable for forming dies using cold extrusion and imprinting methods, followed by carburizing and quenching for use [13].
(5) Through-hardening type plastic die steel: Generally uses high-quench-hardening cold work die steel (e.g., high-carbon high-chromium steel, air-hardening steel) or hot work die steel (e.g., chromium-based hot work die steel). Used for manufacturing high-wear-resistant plastic dies [13].
With the emergence of new plastics and the increasing demands for dimensional accuracy and surface roughness of plastic products, as well as the need to simplify die machining processes, some foreign countries have developed plastic die steel with special properties. The main types are as follows:
(1) Corrosion-resistant plastic die steel: Used for forming dies for corrosive plastics (e.g., polyvinyl chloride), often employing high-chromium steel with a chromium content of 13%–17%, such as 38CrMo15 in ISO 4957 [15].
(2) Mirror-finishing plastic die steel: Used for forming dies for plastic products requiring very low surface roughness, such as plastic products in optical instruments and household appliances, generally produced through electroslag remelting or vacuum arc remelting processes to achieve high purity and uniformity.
(3) Machinability-enhanced plastic die steel: To reduce die machining costs and extend tool life, foreign countries have developed a series of machinability-enhanced plastic die steel by adding elements such as S, Ca, and Pb.
(4) Non-tempered pre-hardened plastic die steel: By adding appropriate alloying elements, the die blank can directly obtain the required microstructure and hardness after forging or rolling and air cooling, eliminating the need for quenching and tempering treatment before machining into dies.
1.3.1.2 Cold Work Die Steel
Cold work dies are also widely used, and their output value has historically ranked first in the die manufacturing industry. In recent years, due to the rapid development of plastic dies, cold work dies have fallen to second place in some industrialized countries [2].