How much does normalizing and isothermal normalizing affect gears?

The gap between isothermal normalizing and ordinary normalizing in the processing cost of workpiece is large. For the material of 20crmnti, for general products, ordinary normalizing can meet the requirements, especially for products that require strict deformation, isothermal normalizing. For materials with high hardenability such as 22crmo and 22crnimo, ordinary normalizing can not meet the requirements of hardness uniformity, which seriously affects the service life of the processing tool, and the processing stress generated in the processing process is relatively large, which affects the deformation of the finished product heat treatment.

In addition, isothermal normalizing should pursue the uniformity of hardness of the workpiece, rather than the metallographic structure of the workpiece; In this regard, there is no corresponding standard in China, and the relevant standards in Germany can be referred to. [

Due to the influence of personnel, equipment and environment, it is difficult to control the cooling rate and uniformity of the workpiece, resulting in large hardness dispersion and uneven metallographic structure, which directly affects machining and final heat treatment: the thermal deformation is large and the quality of irregular parts cannot be controlled. The isothermal normalizing process can effectively change the disadvantages of ordinary normalizing, effectively reduce the heat treatment deformation, and make the product quality stable and reliable.

View the original post

According to the material used and the structural shape of the part, if normalizing can ensure the uniform structure and hardness of the blank, and the reproducibility is good, then the normalizing and isothermal normalizing results are the same, but as mentioned upstairs, if the materials used are treated with normalizing and are prone to abnormal structures such as shellfish, then normalizing and isothermal normalizing have a greater impact on subsequent processing. View the original post

Isothermal normalizing is relatively compared with ordinary normalizing, and isothermalizing is of course better than ordinary normalizing for the heat treatment quality of parts. For the processing cost of parts, isothermal normalizing is more expensive than ordinary normalizing. View the original post

Agree with the upstairs point of view, but the cost of isothermal normalizing is about 40% higher than that of ordinary normalizing View original post

Problems of quality and cost Normalizing time period Isothermal normalizing time is long View the original post

Isothermal normalizing: The use of isothermal normalizing process realizes the effective control of the quality of transmission gears and shaft parts, thereby improving the machinability and heat treatment deformation stability. The key to the formulation of the isothermal normalizing process is to reasonably control the speed and time of fast cooling, slow cooling and the temperature and time of isothermal treatment in the intermediate cooling stage according to the austenitic isothermal transition curve.

Compared with ordinary normalizing, isothermal normalizing can obtain the microstructure and hardness required for uniformity. Pretreatment of parts treated with isothermal treatment can reliably obtain good cutting performance and stable quenching deformation laws.

For forgings, the normalizing time has no effect on the parts themselves. It's nothing more than a little more oxide scale.

Isothermal annealing is generally used for rigid or non-transformable alloy steels with relatively high carbon content.

20CrNi3 alloy steel20CrNi3 Features:20CrNi3 steel is a kind of alloy carburizing structural steel, belonging to the Cr-Ni series of alloy structural steel, after quenching and tempering or quenching and low temperature tempering, it has good comprehensive mechanical properties, low temperature impact toughness is also good, 20CrNi3 steel has a tendency to be sensitive to white spots, and has a tendency to temper brittleness when tempering at high temperature. Quenched to semi-martensitic hardness, oil quenching can be hardened 50 70mm, good machinability, medium weldability.

20CrNi3 Executive Standard:gb/t 3077-2015

20CrNi3 Chemical Composition:Carbon C:;

Silicon SI:; Manganese mn:;

Sulfur S: permissible residual content;

Phosphorus P: permissible residual content;

Chromium cr:; Nickel Ni:;

Copper Cu: permissible residual content.

20CrNi3 heat treatment:Quenching heating temperature ( )830; Coolant: water, oil.

tempering heating temperature ( ) 480; Coolant: water, oil.

20CrNi3 Applications:It is mostly used in the manufacture of gears, shafts, worms and screws, stud bolts, pins, etc. working under high load conditions.

20CrNi3 Main Specifications:20CrNi3 round bar, 20CrNi3 forging bar, 20CrNi3 plate, 20CrNi3 flat bar, 20CrNi3 forging, 20CrNi3 forging ring, 20CrNi3 machining parts, 20CrNi3 pipe, 20CrNi3 forging cake.

20CrNi3 heat treatment:

Quenching heating temperature ( )830; Coolant: water, oil.

tempering heating temperature ( ) 480; Coolant: water, oil.

20CrNi3 alloy structural steel.

20CrNi3 is a grade of alloy structural steel specified in the Chinese national standard.

Unified numeric code: A42202.

Chemical Composition: C:

si：mn：

cr：ni：

Mechanical Properties] Tensile Strength ( b MPa): 930

Yield point ( s mpa): 735

Elongation after fracture (δ5%)11

Section shrinkage (55

Work of impact absorption (aku2 j): 78

Brinell hardness (HBS100 3000) (annealed or tempered at high temperature): 241 Main characteristics. It has good comprehensive mechanical properties after quenching and tempering at low temperature, and the impact toughness at low temperature is also good.

This steel has a tendency to be sensitive to white spots, and high-temperature tempering has a tendency to temper brittleness. Quenched to semi-martensitic hardness, oil quenched can be quenched 50 70mm. Good machinability and medium weldability.

Application examples: It is mostly used in the manufacture of gears, shafts, worms and screws, stud bolts, pins, etc. working under high load conditions.

According to DIN17210BG is the German standard, there is no 20CrNi3 material in it. However, it can be normalized or isothermal normalized according to the requirements of 160 200HB to meet the requirements of subsequent machining.

isothermal normalizing isothermal normalizing. isothermal annealing isothermal annealing (recrystallization annealing). Isothermal quenching.

After heating to 940 950 degrees of austenitization, air cooling to 560 600 degrees of isotherm and then air cooling.

Heat to about 860 to keep warm, fast cool to 680 to keep warm, and then bake.

I haven't heard of normalizing and isothermic, normalizing needs to be kept warm, is it that normalizing cools to a certain temperature, keeps warm for a period of time and then continues to air cool? What's the final organization?

1 As a gear blank, it is generally normalized, but there are indeed many manufacturers who do not normalize the seepage and guess the processing. There may be two reasons for this: one is that the size of the blank is too small, and it is difficult to normalize (the amount of furnace loading and the quality of normalizing contradict each other); The second is that the requirements for deformation are not strict, which saves costs.

2 I understand that there are not many good isothermal normalizing of gear blanks at present, the main reason is that the contradiction between furnace loading volume and cooling effect is difficult to solve. Ipsen, Aixielin and other warm fire lines have not been used, but FAW Jiaxin, Changchun Fengdong and other warm Zhengcong socks fire lines are not good, and the actual production is not ideal; But after all, it's a little better than an ordinary normalization. 3. The hardness of normalizing is different for different enterprises, different modules and processing methods.

In the forum, there is often a lot of discussion about the performance after normalizing, grain refinement and other purposes, and there is less discussion on processing performance. However, at present, the normalization of gears is mainly to solve the machining performance, reduce tool loss and improve efficiency, and at the same time reduce the tooth shape and tooth deformation after carburizing and quenching. 4 Generally speaking:

Large modulus (MN = gear hardness 160-175HB high-speed hobbing effect is good; Small module gear: 170-185HB high-speed rolling effect is good; 175-190HB CNC milling effect is good. In addition to the soft tooth surface gear, it seems that there are few normalized hardness requirements of 220-240HB, if the hardness is so high, it is estimated that the life of the hobbing and shaving tools is very low, and there is no actual production significance.

I have done this material of gear before, incoming materials refer to the blank has been normalized, in the machining process only to eliminate the judgment found a lot of blank hardness, the knife, and then their own normalizing processing, air-cooled bridge family!

I think it should be normalized, so that the hardness of the machining can be adjusted by the bang, and it can also prepare for carburizing. The hard front handicap can be adjusted by talking about normal normalizing, and then adjusting the cooling rate after normalizing.

20grmo material is used as pinion, which is normalized before finishing, which is conducive to tooth shape stability, reducing tool consumption and sometimes even normalizing before rough machining, and then normalizing after rough machining. It is better to use isothermal normalization. In order to achieve the hardness of HRB220-240, the normalizing process, low isothermal temperature or the general normalizing process, after the furnace, the wind is used to guess the cold, but the hardness range of the rental filial piety is a bit narrow, and the normalizing process spike row is more difficult to do, but it can be quenched and tempered after normalizing.

Generally, it is not the use of raw materials normalized treatment is wide, and the finishing key is brightened, and we generally use stress relief treatment of 600-650 degrees, after all, the chain does too much normalized oxide scale.