{"id":21050,"date":"2023-03-24T17:25:24","date_gmt":"2023-03-24T15:25:24","guid":{"rendered":"https:\/\/fractory.com\/?p=21050"},"modified":"2024-01-26T13:17:54","modified_gmt":"2024-01-26T11:17:54","slug":"quenching-explained","status":"publish","type":"post","link":"https:\/\/fractory.com\/quenching-explained\/","title":{"rendered":"Quenching Explained \u2013 Definition, Process, Benefits and More"},"content":{"rendered":"

Heat treatment processes<\/a> are crucial to obtain desired properties from different metals and make them suitable for various applications.<\/u> Through heat treating, many mechanical properties can be altered without changing a metal’s chemical composition.<\/p>\n

There are many different processes in heat treatment. One of the most commonly used among these is the process of quenching. Let us discuss what it is.<\/p>\n

What Is Quenching?<\/h2>\n

Quenching is a rapid cooling process that alters specific properties of materials by manipulating the cooling rate. The material is heated above the recrystallisation temperature\u00a0but below the melting point to allow grain restructuring followed by controlled cooling to a predetermined temperature.<\/p>\n

The temperatures to which carbon steels are heated during quench hardening can be determined from the iron-carbon phase diagram<\/a>. For hypoeutectic steels (0,2…0,8% C) it is 30-50\u00b0C over Ac3 and for hypereutectic steels (C > 0,8%) over 30-50\u00b0C over Ac1.<\/p>\n

\"ferrite<\/p>\n

The intention of quenching is to transform the austenitic phase into martensite, which is an exceptionally hard phase of steel. To achieve this, the material is exposed to a cooling media and the cooling time is reduces.<\/p>\n

When heating hypoeutectic steels over Ac1 and not Ac3, some ferrite will still remain in the structure after quenching, this reducess hardness. For hypereutectic steels, it is optimal to heat the steel to a temperature between the Ac1 and Acm phase limits and thus, secondary cementite will remain in the structure next to martensite. When going over Acm, there is the risk of the formation of a coarse-grained structure after quenching which makes the steel very brittle.<\/p>\n

Overall, the quenching process leads to increased hardness and reduced ductility of the material. But the brittleness also increases and thus, to avoid unwanted side effects such as cracking and distortion, choosing a suitable cooling rate is essential.<\/p>\n

Quenching and tempering processes<\/a> are often used in sequence to restore some of the lost ductility and reduce hardness to suitable levels. Tempering also reduces brittleness.<\/p>\n

Annealing<\/a> is also occasionally performed to reduce the hardness of quenched steel.<\/p>\n

When Is Quenching Used?<\/h3>\n

Quenching is used when increased hardness is a requirement. Many applications such as construction, mining, heavy machinery, military, etc. require metals with a hard surface. One that can resist abrasion, scratches and take impacts. The increased hardness from quenching is capable of providing these qualities.<\/p>\n

Quenching can be done for a wide range of materials but steel is the most commonly quenched metal. Quenched steel shows extreme hardness.<\/p>\n

Quenching Process<\/h2>\n

\"quenching<\/p>\n

The quenching process may happen in one of two ways: spray quenching or bath quenching.<\/p>\n

In the spray quenching process, the metal’s hot surface cools by the impinging effect of a quenchant sprayed upon the metal. This method has a higher heat transfer rate than bath quenching.<\/p>\n

The bath quenching process is, however, more common. In bath quenching, the material to be cooled is placed in a bath of liquid or gas. As the quenchant surrounds the material, it is rapidly cooled.<\/p>\n

But even this rapid cooling occurs at different rates from the time quenching begins until it ends. Let us look at these different stages in the next section.<\/p>\n

Quenching Stages<\/h3>\n

During the bath quenching process, the material undergoes three distinct cooling stages. These stages are:<\/p>\n