How does the quenching heating temperature of steel change as the carbon content in it increases5

The main thing is what kind of crystals you want to obtain, such as martensitic, austenite, etc., as well as your tempering temperature, cooling method, other alloy composition and content, etc.

It is recommended to refer to the Concise Heat Treatment Handbook

There are more detailed instructions and explanations in it.

It cannot be generalized, even a steel quenching heating temperature will have several. For different purposes, the quenching temperature is different, and the high-temperature solution quenching temperature of the tool and die steel is several different from the ordinary quenching temperature; At the same time, the quenching effect is also related to the cooling method and holding time.

The quenching temperature will affect the austenitic carbon content, alloy content, carbide solubility, and then the paralympic content and the remaining carbide content, and finally affect the strength, hardness, dimensional stability, etc. Quenching usually heats the steel to a certain temperature above the critical temperature AC3 (sub-eutectic steel) or AC1 (super-eutectic steel), which is affected by the type and content of alloying elements. In carbon steel, the AC3 of sub-eutectic steel decreases with the increase of carbon content, and the quenching temperature should be reduced. The AC1 of the eutectic steel did not change much, and the AC3 increased with the increase of carbon content, and the quenching temperature could be increased appropriately. However, various alloying elements will have complex effects on phase transition points, austenite homogenization, grain growth tendency, etc., and the quenching temperature must be determined according to field tests.

Different heating temperature, cooling rate, tempering temperature, the metallographic structure produced is different, and the mechanical properties of steel with different structures are definitely different.

Cooling with furnace: the obtained microstructure has low hardness and good plasticity and toughness;

Cooling in air: the hardness of the microstructure is slightly higher than that of cooling with the furnace, but the plastic toughness is slightly worse;

Rapid cooling: that is, quenching, cooling in liquid, to obtain martensitic structure, high hardness and poor plastic toughness;

Take iron as an example: not the higher the temperature, the better, if the temperature is too high, the iron will quickly oxidize when it comes out of the furnace, resulting in the outer layer becoming a layer of ferric oxide in a non-dense hole filled with oxide, which is more likely to rust or cause mechanical damage.

Take iron, for example.

The higher the heating temperature, the more carbon in the iron is oxidized into CO2 overflow to create a low carbon steel, increasing the hardness of rigidity, but not the higher the temperature, the better, if the temperature is too high, the iron will be rapidly oxidized when it comes out of the furnace, resulting in the outer layer becoming a layer of ferric oxide in the non-dense holes filled with oxide, which is more prone to rust or mechanical damage.

The rapid cooling process is also called quenching.

In general, reducing the cooling time can effectively improve the hardness of iron, because when cooling rapidly, the thermal expansion and contraction of iron atoms (although the amplitude is small, but imagine that n multi-iron atoms are cooled and contracted at the same time) will make the surface, at least the surface, form a dense form of iron, which effectively improves the hardness and mechanical strength of the surface.

1. Improve the mechanical properties of metal materials, give full play to the potential of materials, save materials and prolong the service life of parts. 2. Eliminate the residual stress of the material and improve the cutting performance of the metal, heating temperature, holding time and cooling method are the three most important basic process factors for heat treatment.

Solid phase transformation of metal, that is, below the melting point temperature, different temperatures, different cooling rates will obtain different structures, common stainless steel heating into austenite structure, cooling and quenching to obtain martensitic structure. For detailed explanations, refer to Metallurgy & Heat Treatment, and find solid phase transitions in the catalog, and microstructure transitions when steel is cooled.

Answer]: False flushing in the eutectic steel of the Huai calendar, and the heating temperature of the quenching is in accm

Above, the higher the carbon content, the lower the hardness of the quenched steel.

Hello, the main basis for determining the quenching heating temperature of carbon steel is the iron-carbon phase diagram, I hope mine is satisfied with you.

The main basis for determining the quenching heating temperature of carbon steel is the Fe-Fe3C phase diagram.

When tempering steel, the general trend of mechanical property changes is that with the increase of tempering temperature, ()aThe balance of the strength and hard section increases, and the plasticity and toughness decrease.

b.The hardness of the strength grip is reduced, and the plasticity and toughness are increased;

c.The strength and hardness increase, and the plasticity and toughness increase.

d.Strength and hardness are reduced, plasticity and toughness are reduced.

Correct answer: The hardness of the attack Hu decreases, and the plasticity and toughness increase;

The carbon content is between, with the increase of carbon content, the quenching hardness gradually increases, and when the carbon content reaches about the left, the hardness increases very slowly with the increase of carbon content. When the carbon content reaches the above level, the hardness will even decrease, mainly due to the increase of residual austenite.

Classified by high and low carbon content:

1. Low carbon steel: the carbon content is generally lower than the mass fraction);

2. Medium carbon steel: carbon content is generally mass fraction);

3. High-carbon steel: the carbon content is generally higher than the mass fraction).

It is a very professional question, which should be combined with phase diagram analysis. The simple relationship is that within a certain range, the higher the C content, the higher the hardness after quenching. This is because of the action of quenching martensite.

Selection of quenching heating temperature: AC3+30 50° for sub-eutectic steel, AC1+20 40° for eutectic steel and per-eutectic steel.

If the quenching temperature is high, the austenite grains will be coarse, and the plasticity and toughness will be seriously affected and reduced after quenching, and if the quenching temperature is low, the austenitization will be incomplete, and there will be ferrite after quenching, resulting in insufficient quenching hardness and reduced strength.

For eutectic steel and eutectic steel, the quenching temperature is high, the same austenite grains will be coarse, and at the same time, the carbide dissolves into the austenite too much, and it is easy to deform and crack after quenching, and at the same time seriously reduces the hardness and strength, if the temperature is low, the carbide dissolves into the austenite too little, most of the carbides are retained, and it is easy to deform and crack after quenching, and the carbon content of austenite after austenitization is too low, resulting in quenching of martensite hardness is not enough, and the strength is reduced.

In the case of the same carbon content, except for alloy steels containing Ni and Mn, the heat treatment heating temperature of most alloy steels is higher than that of carbon steel, which is mainly due to the addition of alloying elements that change the diffusion rate of carbon in steel. Non-carbide forming elements such as Ni and CO can reduce the diffusion activation energy of carbon in austenite and increase the rate of austenite formation. On the contrary, strong carbide forming elements such as V, TI, W, MO, etc., have a greater affinity with carbon, increase the diffusion activation energy of carbon in austenite, strongly slow down the diffusion of carbon in steel, and greatly slow down the process of austeniticization.

After the formation of austenite, the stability of the various types of carbides that have not yet been solidified varies. For carbides with high stability, in order to completely decompose and dissolve in austenite, it is necessary to further increase the heating temperature, and these alloying elements will increase the austenitization time.

The austenitization process in alloy steels also includes the process of homogenization. Not only does it require diffusion of carbon, but it also requires diffusion of alloying elements. However, the diffusion rate of alloying elements is very slow, even at a high temperature of 1000 meters, it is only a few ten-thousandths or a few dry fractions of the carbon diffusion rate.

As a result, the homogenization of the austenite composition of alloy steels is slower than that of carbon steels. In order to ensure that the alloying elements are dissolved into the austenite and homogenized, so as to give full play to the role of the alloying elements.

The main reason for this is that the addition of alloying elements changes the diffusion rate of carbon in steel. Ni and Mn expand the austenite region, so that the AC3 point moves downward, and other elements shrink the austenite region AC3 and move up, so the austenitization temperature of alloy steel heat treatment except Ni and Mn is higher than that of carbon steel.