How much does the induction heating quenching transition layer need to be reasonable

(1) The depth of the hardened layer after induction hardening is measured by metallographic method, due to the different pretreatment structures of medium carbon steel, the normalized structure is + p, and the transition layer area is thicker after induction hardening The quenching and tempering structure is sorbite, and the transition layer area after induction hardening is often thinner. (2) Hardness method ISO375-1976 stipulates that the depth of the effective hardening layer refers to the distance from the surface of the part to the limit hardness value. Limit hardness value (HV) = lower limit of surface hardness (HV).

In the Japanese JIS G 0559 standard, the limit hardness value of the effective hardened layer of steel with different carbon content is specified (for example, the limit hardness value of 45 steel is 450HV). Different hardness measures the depth of the effective hardened layer, and of course the transition layer area after induction hardening. (3) In general, there does not seem to be a requirement for a transitional layer, and it is all agreed upon by the parties concerned.

4) Someone once asked how the induction hardening curve is normal, and the heating time is too long and too short, which made me think about the impact of the depth of the transition layer after induction hardening on the quality of the part, and put forward a discussion and discussion.

If the original heat treatment of 45 steel is annealed, it is best to spheroidize annealing process If the ordinary annealing process is adopted, the induction heat treatment is a bit difficult.

In JB T5617-2005, it is stipulated that "the hardness of parts after induction hardening or flame hardening shall be less than the limit hardness minus 100 at three times the DS from the surface." In case of dispute, the higher ultimate hardness value can be used to determine the effective hardening layer depth after consultation between the parties". There are a few questions to ask you:

1. What is the actual function of ultimate hardness? How to use the ultimate hardness value to determine the effective hardening layer depth? 2. The function of stipulating that "the hardness at three times the DS from the surface should be lower than the limit hardness minus 100" is to limit the hardness of the matrix or the upper limit of the hardness of the heat-affected zone?

The frequency determines the hardened layer, and the cooling method and time determine the transition layer. [

1. There is really no relevant technical data or standard for the transition layer and heat-affected zone. I wonder if there is one? 2. Generally, only the depth of the hardened layer and the metallographic structure of the surface layer are tested.

What is the impact of this transition layer and the heat affected zone on performance? Under the condition that the hardening depth is required, the deeper the heating depth, the larger the transition layer and the heat-affected zone, but the excessively large transition layer and heat-affected zone not only waste electrical energy, but also reduce the performance of the substrate (mainly for the pretreated parts). Therefore, I personally think that on the premise of ensuring the depth of the hardened layer, the heating depth should be reduced as much as possible, that is, the transition layer and the heat-affected zone should be reduced accordingly.

The heating rate has a great influence on the quenching heating temperature, and there is a certain quenching heating temperature range for each steel grade, and only by heating and quenching in this temperature range can we obtain satisfactory structure and performance.

In production practice, if the optimal quenching temperature range for a certain steel grade is determined, but because the heating rate (i.e., the specific power of the part when heated) is greater or less than the corresponding heating rate, an unreasonable or undesirable quenching structure will also occur.

If the heating rate is less than the corresponding heating rate, the workpiece is heated to a certain quenching temperature, and the superheated structure will be obtained after quenching; If the heating rate is greater than the corresponding heating rate, when the workpiece is heated to the determined quenching temperature, the quenching structure with insufficient heating will be obtained after quenching.

Therefore, when selecting the quenching temperature for induction heating, it is necessary to consider not only the composition and original structure of the material, but also the influence of heating speed. The heating temperature selection of induction hardening is customarily about 50-100 degrees higher than that of the furnace heating and quenching temperature of the material.

A copy of the quenching temperature of certain steel grades at different heating speeds for the user's reference:

Answer: Hello, the quenching heating temperature is mainly determined according to the phase transition point of the steel, because for sub-eutectic steel, if the heating temperature is lower than AC3, the heating state is composed of austenite and ferrite two phases, and the ferrite is preserved after quenching and cooling, so that the hardness of the parts after quenching is uneven, and the strength and hardness are reduced. 30-50 higher than AC3 is to ensure that the core of the workpiece reaches a temperature above AC3 within the specified heating time, and the ferrite can be completely dissolved in the austenite, the austenite composition is relatively uniform, and the austenite grains are not coarse.

For eutectic steel, the quenching heating temperature is between AC1 and AC3, and the heating state is fine austenite grains and undissolved carbides, and cryptocrystalline martensite and uniformly distributed spherical carbides are obtained after quenching. This kind of structure not only has high strength and hardness and high wear resistance, but also has good toughness. If the quenching heating temperature is too high, the carbide will dissolve, the austenite grains will grow, and the flake martensite will be obtained after quenching, and its microcracks will increase, the brittleness will increase, and the quenching cracking tendency will also increase.

Induction heating quenching is the use of electromagnetic induction heating process to quench heating heating method, because the heat is emitted from the metal itself, so there is no flame, the oxide layer on the surface will also be reduced due to rapid heating. How to confirm the parameters of induction heating quenching? Here are a few things to look at:

Working power supply. Operating power range.

Output power. Oscillation frequency.

Output current. Cooling water.

However, one thing that can be determined is that the lower the frequency, the deeper the heating depth.

The purpose of surface quenching is to obtain a surface with high hardness and high wear resistance, while the core still retains the original good toughness, and is often used in machine tool spindles, gears, engine crankshafts, etc. Surface quenching is a local quenching method that hardens the surface layer of steel to a certain depth, while the core part remains in an unquenched state. During surface quenching, the surface of the steel parts is quickly heated to the quenching temperature, and the heat does not have time to penetrate the core of the workpiece, so as to achieve local quenching.

Induction heating quenching structure has hardening layer depth, transition layer, surface layer, induction heating quenching is according to different process materials, depth and other cooling conditions are also different, what is the material of the workpiece you quench, depth and area.