The reducer gear damage cause analysis
First understand the manufacturing process of the next gear, and then gradually analysis.
Gear manufacturing process:
Allocations → forging the blank → normalizing (low temperature annealing) → rough turning → mill hole semi-finish turning → → hobbing teeth Chamfer → → high frequency quenching finishing plug keyway (B → face grinding face grinding C → → → grinding teeth → deburring) → test
Second, the gear materials and heat treatment
People usually divided into two categories, namely, hardened gear and soft tooth surface gear gear. Usually a pair of meshing gear tooth surface hardness are greater than 350HBS, called hardened gear, otherwise is known as a soft tooth surface gear. According to the size of the tooth surface hardness, people usually teeth
The wheel drive is divided into two categories, namely, hardened gear and soft tooth surface gear. Choose the kind of gear drive according to the design requirements of the two gear drive their pros and cons, but because of the the hard gear transmission load, long service life, prepared a wide range of applications.
Hardened lot of gear materials and heat treatment method, such as several:
(1) 40Cr. 45 # .45 Mn2 steel, can be used with high-frequency tempering final heat treatment or a nitriding treatment,
(2) 20Cr.20CrMnTi.20CrMnVB.20CrNiH carburizing and quenching can be employed,
(3) 38CrMnAl can be achieved with a nitriding process a high hardness, to use a special method of heat treatment of some special materials.
The gear manufacturing materials and heat treatment process of carrying capacity and the size of the gear weight have a great impact. 1950s, gear Carbon Steel, the 1960s to switch alloy steel, hardening steel used in the 1970s. Soft tooth surface and hardened by the hardness of the tooth surface can be divided into two
Species.
Soft tooth surface of the gear carrying capacity of (A) is low, but relatively easy to manufacture, running-good transmission size and weight, and more for no strict limitation, and the small scale production of general machinery. Paired gear, a heavier burden on the ferry, so the size of the life of gear and generally
Equal, small tooth surface hardness than the big wheel high.
(B) the carrying capacity of the hardened gear, it is in gear after fine cut, and then quenching, surface quenching or carburizing to improve the hardness. However, in the heat treatment, the gear will inevitably be deformed, therefore, after the heat treatment required for grinding, polishing or fine cut
To eliminate errors generated due to distortion and improve the accuracy of the gear.
Third, the form of gear damage, broken teeth cause analysis
A. gear damage in the form
The reducer gear damage fault broken teeth, gear wear. According to the of Weigao transmission engineer many years of experience in analysis: the gear damage form in addition to the non-normal wear and tear of the broken tooth and gear (here referred to as non-normal wear and tear is more appropriate because the gear is normal wear and tear can not be considered a failure. Abnormal grinding
Loss gears premature wear, wear life up to less than the gear should have), there is damage to the tooth surface pitting and flaking form. The tooth surface pitting and spalling occurred in the middle of the tooth height above the top of the bit.
B. broken tooth cause analysis
(1) reducer gear teeth broken part of the reason is due to manufacturing quality defects.
(B1) manufacturing caused by the quality of the gear teeth broken reasons: steel did not choose the right gear casting quality is not good, low quenching hardness, hardness gear not pliable enough tooth wear, the ball ink technology is not enough, use long alternating stress impact will fatigue damage, etc. ...
(B2) gear precision of broken teeth. Despite the gear meshing accuracy to a certain extent broken teeth, broken teeth is not. Not enough, because the gear engagement accuracy of the contact surface of the gear, increased contact stress will occur, the load
Uneven phenomenon, but this is not the main reason for broken teeth.
(B3) broken teeth, there is a reason to load Japanese tooth root defects, not enough due to the bending strength of the tooth. (The main factors affecting the bending strength is the magnitude of the force acting on the load on wheel tooth and the tooth root of the defect levels gear engagement accuracy difference, and does not change the force load on the tooth
The size and the tooth root of the defect level only increases the contact stress of the tooth).
(B4) gear wear except for the reducer poor manufacturing quality, some issues, such as: reducer in oil, semifluid lubricant use.
(B5) normal wear manufacturing quality factors:
① gear materials do not meet the requirements, resulting in non-normal wear and tear;
The ② gear trachoma, porosity and loose ball ink of inadequate defect exists;
(3) heat treatment hardness is not enough or no heat treatment;
The ④ gear precision motion accuracy below standard;
⑤ arc gear very center distance error sensitivity, especially center distance forward error not only reduces the bending strength of the tooth, but also increase the sliding wear.
(2) speed reducer lack of oil for non-normal wear great influence. Reducer lubricant oil spill, the management failed to timely detection, continues to operate reducer reducer is also lack of oil in the state continue to work until the ground addendum Marquise been discovered, open the cover of the reducer see
Xiangdi heap with a layer of metal powder, this lack of oil for non-normal wear great influence.
(3) the metal particles increases the wear of the gear. Adsorption magnetic metal particles. Reducer semifluid lubricant fluid, gear wear out, fine metal particles are mixed in the lubricating fluid, exacerbated by the wear of the gears. Recommended in the tank to increase several magnetic body using magnetic adsorption lubrication
Fine metal particles in the liquid can be reduced to the metal fine particle content of the lubricating fluid.
Fourth, the gear teeth wear causes and prevention:
1, quenching hardness is low, 40Cr recommends HRC48-55 / motor shaft, large gear required low (large gear and pinion hardness area with, will produce excessive wear and tear);
2, hardened deep enough, you need at least ensure that the tooth root down 1mm hardenability;
3, microstructure abnormalities, such as coarse microstructure, etc., requires fine needle-like martensite with a small amount of pearlite ferrite - metallographic analysis;
4 If the appliance is demanding, you can try the temperature cyanide or carburizing quenching
How to improve the strength of the gear
Mainly to improve the strength of the gear bending strength and tooth contact strength, the following methods:
1, if the structure can choose a larger modulus, but not as the only recommended program.
2, select the appropriate modification coefficient, designed to gear (positive displacement) can increase tooth thickness, improve the flexural strength of the tooth, but not as the only recommended program.
3, in the manufacturing process, increase the tooth root fillet, improved surface quality, can also improve the strength of the gear.
4, suggested reasonable selection of materials (such as 40Cr, 45 #, 45Mn2 steel; 0Cr.20CrMnTi.20CrMnVB.20CrNiH) and heat treatment (quenching, carburizing, high-frequency hardening), to improve the surface hardness of the tooth, the tooth surface can be increased contact fatigue strength.
Sixth, to improve the contact strength of gear:
Contact strength and modulus, modulus and flexural strength of the contact strength and tooth surface hardness about you can:
1. The gear machining of precision (high precision will improve meshing performance, thus improving the contact strength)
Treatment (generally high-frequency hardening of medium carbon steel, quenched and tempered surface increased hardness; carburizing quenching of low speed and high load gear low-carbon alloy steel, the hardness increases contact strength improve)
Tooth surface modification (particularly important aspect same meshing performance can be improved, to avoid an impact)
4 the lubrication center distance and the number of teeth with the contact strength has nothing to do, say, you need to drive have been identified, the number of teeth and the center distance, how can casually change it?
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