Is it better to quench steel with oil or water cooling?

The quenching of steel is a heat treatment process in which the steel is heated to a temperature above the critical temperature AC3 (sub-eutectic steel) or AC1 (super-eutectic steel), kept warm for a period of time to make it fully or partially austenitized, and then cooled to below ms (or isothermal near ms) at a cooling rate greater than the critical cooling rate for martensite (or bainite) transformation. Solution treatment of materials such as aluminum alloys, copper alloys, titanium alloys, tempered glass, etc., or heat treatment processes with a rapid cooling process are usually referred to as quenching.

There are four basic processes for steel heat treatment: annealing, normalizing, quenching and tempering.

Anneal. The workpiece is heated to the appropriate temperature, different holding times are used depending on the material and the size of the workpiece, and then slowly cooled (the slowest cooling rate) in order to bring the internal structure of the metal to or near equilibrium, to obtain good process performance and service performance, or to prepare the structure for further quenching.

Normalizing. The workpiece is heated to a suitable temperature and cooled in the air, and the effect of normalizing is similar to that of annealing, but the resulting structure is finer, which is often used to improve the cutting performance of the material, and is sometimes used as the final heat treatment for some parts that are not very demanding.

Tempering. In order to reduce the brittleness of the steel, the quenched steel is kept warm for a long time at an appropriate temperature above room temperature and below 710, and then cooled, this process is called tempering.

Quench. A heat treatment process in which the workpiece is heated and austeniticized and cooled in an appropriate way to obtain a martensite or bainite structure. The most common ones are water-cooled quenching, oil-cooled quenching, air-cooled quenching, etc.

Annealing, normalizing, quenching [2] and tempering are the "four fires" in the overall heat treatment, in which quenching and tempering are closely related, and are often used together, all of which are indispensable.

Objective. The purpose of quenching is to make the supercooled austenite undergo martensite or bainite transformation to obtain martensite or bainite structure, and then cooperate with tempering at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel, so as to meet the different requirements of various mechanical parts and tools. It can also meet the special physical and chemical properties of some special steels such as ferromagnetism and corrosion resistance through quenching.

A metal heat treatment process in which a metal workpiece is heated to an appropriate temperature and held for a period of time, followed by a rapid cooling by immersion in a quenching medium. Commonly used quenching media are brine, water, mineral oil, air, etc. Quenching can improve the hardness and wear resistance of metal workpieces, so it is widely used in various tools, molds, measuring tools and parts that require surface wear resistance (such as gears, rolls, carburizing parts, etc.).

Through quenching and tempering at different temperatures, the strength, toughness and fatigue strength of the metal can be greatly improved, and the combination between these properties (comprehensive mechanical properties) can be obtained to meet different use requirements.

Different materials are used differently.

Mainly according to the hardenability of the material.

Oil cooling is mainly for some metals with strong hardenability, such as 40cr and so on. Water-cooled is a tool for metals with weak hardenability, such as mild steel in general.

If the hardenable metal is cooled with water, the quenched parts are prone to cracking and other undesirable symptoms during the quenching process.

1. Cooling time: Because the cooling rate of oil is slower than that of water, the cooling time of oil cooling is longer than that of water cooling.

2. Quenching hardness: high water cooling, low oil cooling.

3. Quenching deformation: large water cooling, small oil cooling.

4. Quenching cracking tendency: large water cooling, small oil cooling.

5. The depth of the hardened layer: the water is deep and the oil is shallow.

6. Environmental pollution: water is basically not polluted, waste oil is polluted and oil smoke is also polluted, and there are potential safety hazards of combustion.

Medium and low configuration computers generally use air cooling, in the case of high configuration will choose water cooling or oil cooling, it is very easy to choose these two cooling methods, they are different media, just a conductor that transmits heat, in fact, water cooling is not necessarily pure water, understand the properties of different media, and then look at what situation or what configuration you use to choose!

The cooling rate of water cooling is very large in the range of 650 400 degrees, which is very beneficial to the carbon steel with less austenite stability, but in the range of 300 200 degrees, the cooling rate of water cooling is still very large, which will produce great structural stress, and it is easy to seriously deform the workpiece and even crack. The cooling rate of oil cooling in the range of 300 200 degrees is much less than that of water cooling, which is beneficial to reduce the deformation and cracking of quenched workpieces. However, its cooling rate in the range of 650 400 degrees is much smaller than that of water cooling, so it cannot be used for carbon steel, but can only be used for quenching alloy steels with high supercooled austenite stability.

Refer to Engineering Materials Higher Education Press.

Difference Between Water Quenching and Oil Quenching:

1. Water quenching cools quickly, but the stress is large, and the deformation and cracking tendency are large, and it is generally used for carbon steel with poor hardenability. Water quenching is to put a high-temperature object into water, then burn it red-hot, and then put it into water, and so on, can improve rigidity. Quenching with water as a quenching agent is called water quenching.

2. The cooling effect of oil quenching is mild, and it is generally used for alloy steel with good hardenability. The quenching process is usually cooled by water, oil or a low-temperature salt bath, but sometimes the same purpose can be achieved by using a fan to accelerate air cooling. Among them, the use of oak and bright song oil to cool Liang Zheng is called oil quenching.

Generally speaking, water-cooled engines are better, oil-cooled engines are prone to overheating, and the radiators are relatively large.

The specific capacity of oil is too small, and water has the largest specific heat capacity in nature, that is, the water temperature rises by 1 degree to absorb more heat than oil. Oil cooling is usually used in deserts and other places where water is scarce, and cooling oil is relatively expensive and troublesome to maintain. The advantage is that the boiling point of the oil is relatively high, the loss is less, and the thermal conductivity is good.

Generally, it is better to run or tremble pants with water, and the maintenance cost is less;

The function of the engine cooling system is to force the heat absorbed by the parts in contact with the hot gas to dissipate in time, and keep their temperature within the appropriate range to create normal working conditions of the engine;

Water cooling is the use of water as an endothermic medium to cool high-temperature parts, and then transfer heat to the outside air, so as to keep the engine working at the most suitable temperature.