Home > News > Industry News > Heat Treatment —— Tempering
Browse Categories
The Last Day of Fastener Fair Global Stuttgart 2025 Trade Show
Industry News
Company News
Certifications
Contact Us
Harbin Rainbow Technology Co., Ltd.Address:C2-02 Handi Building,Songbei Distr.,Harbin,ChinaPostal Code:150028Web site address:http://www.fastenerequip... Contact Now
News

Difference between hot dip zinc and hot dip galvanising

Hot-dip zincing and hot-dip galvanising are two different processes for corrosion protection of metals, with hot-dip zincing usually providing better ...

What is Cold Forging – Cold Forging Process, Materials, Uses, Advantages & Disadvantages

Analysis of the principle and function of spring washers

In all kinds of mechanical connections, the anti-loosening of bolts is a very important link, and there are many ways to prevent loosening of bolts in...

High speed installation cold forging machine bolts and nuts making machine for screw

Working principle of nut tapping machine

Nut tapping machine is a kind of machining equipment that processes internal threads, screws or teeth buckles on the inner side of the holes of variou...

Max diameter one key molding nut drilling machine 2 spindle nut tapping machine

Nut tapping machine is a kind of mechanical processing equipment that processes internal threads, screws or teeth in the inner side of the holes of th...

Hot popular Cold Forging machine bolt forming machine with inveter for good design

Harbin Rainbow Technology Co.,Ltd is one of the biggest fastener equipment dealer and manufacturer in China. We have invested one Cold former factory(...

What's self-tapping screw?

Self-tapping screws: similar to machine screws, but the threads on the screw for special self-tapping screws with threads. Used to fasten the connecti...

China factory price and Advanced Automatic Screw Maker Thread Rolling Machine

Product Descriptionview more >>Frequently bought togetherHigh Speed Thread Rolling Machine Factory Price Thread Roller Hot Sale Thread Machine$4,800.0...

hot forging furnace induction heating machine ipsen furnace mesh belt

Harbin Rainbow Technology Co.,Ltd is one of the biggest fastener equipment dealer and manufacturer in China. We have invested one Cold former factory(...

Browse Categories

Heat Treatment —— Tempering

Doris Wang 2025-04-27 13:57:33

Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product. For instance, very hard tools are often tempered at low temperatures, while springs are tempered at much higher temperatures.

Introduction

Photomicrograph of martensite, a very hard microstructure formed when steel is quenched. Tempering reduces the hardness in the martensite by transforming it into various forms of tempered martensite.

Tempering is a heat treatment technique applied to ferrous alloys, such as steel or cast iron, to achieve greater toughness by decreasing the hardness of the alloy. The reduction in hardness is usually accompanied by an increase in ductility, thereby decreasing the brittleness of the metal. Tempering is usually performed after quenching, which is rapid cooling of the metal to put it in its hardest state. Tempering is accomplished by controlled heating of the quenched workpiece to a temperature below its "lower critical temperature". This is also called the lower transformation temperature or lower arrest (A1) temperature: the temperature at which the crystalline phases of the alloy, called ferrite and cementite, begin combining to form a single-phase solid solution referred to as austenite. Heating above this temperature is avoided, so as not to destroy the very-hard, quenched microstructure, called martensite.

Precise control of time and temperature during the tempering process is crucial to achieve the desired balance of physical properties. Low tempering temperatures may only relieve the internal stresses, decreasing brittleness while maintaining a majority of the hardness. Higher tempering temperatures tend to produce a greater reduction in the hardness, sacrificing some yield strength and tensile strength for an increase in elasticity and plasticity. However, in some low alloy steels, containing other elements like chromium and molybdenum, tempering at low temperatures may produce an increase in hardness, while at higher temperatures the hardness will decrease. Many steels with high concentrations of these alloying elements behave like precipitation hardening alloys, which produces the opposite effects under the conditions found in quenching and tempering, and are referred to as maraging steels.

In carbon steels, tempering alters the size and distribution of carbides in the martensite, forming a microstructure called "tempered martensite". Tempering is also performed on normalized steels and cast irons, to increase ductility, machinability, and impact strength. Steel is usually tempered evenly, called "through tempering," producing a nearly uniform hardness, but it is sometimes heated unevenly, referred to as "differential tempering," producing a variation in hardness.