What's the difference between soft tooth surface reducer and hard tooth surface reducer

What's the difference between soft tooth surface reducer and hard tooth surface reducer
Hard gear reducer and soft gear reducer are two popular gear reducer. But what are the differences between them, and how should they be used?
In general, gear using special steel, after carburizing and quenching after the surface hardness of the gear up to 45HRC above the gear reducer can become a hard tooth surface reducer. And the gear of soft tooth surface reducer is mostly cut and polished by the whole piece of steel, the gear hardness is lower. Because the machine of decelerate of hard tooth flank gear of high hardness, can bear the load, torque is much bigger, and wear resistance, good life than soft gear tooth surface, so if it is used in the working condition is bad, load a lot of devices, such as cranes, mining crusher, large cement mixers, sewage treatment equipment and so on must be used machine of decelerate of hard tooth flank was able to meet the use. As the gear hardness is not high, the reducer with soft tooth surface can bear a lower load, so it is generally used in equipment with relatively small motor power. The maximum motor power of reducer with soft tooth surface is generally no more than 3.7kw, mostly used in special chicken raising machines, food packaging machinery, electric rolling gates and assembly lines. So hard tooth surface reducer gear so good, why not all use hard tooth surface reducer good? Because of machine of decelerate of hard tooth flank gear machining needs certain period to use, production cycle need 15-20 working days, delivery time is very long, and although soft tooth surface reducer gear hardness is not high, but is more than enough to cope with small load conditions, the production cycle need only 1-3 working days to deliver the goods, but also relative to the cost of machine of decelerate of hard tooth flank is much lower.