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Large -molding gear axis real vacuum carbonate quenching

1 Requirements for the requirements of the big mold Gear vacuum carbonic quenching

In order to ensure abrasion resistance, the heat treatment is generally adopted by vacuum carburizing quenching process in order to ensure wear resistance. Its carburizing surface hardness generally requires 56 ~ 60HRC. From the perspective of contact fatigue performance, the large forging parts bear contact stress and bending stress in relative exercise. Under a certain circulation contact stress (mainly orthogonal transformation stress), the shear stress on the surface is 0.786bmm from the surface of the surface 0.786bmm At the point (B is half of the width of the two contact surfaces) is the cutting stress peak, and then the shear stress to the heart will gradually decrease, and this reduced gradient will increase with the radius of the contact surface curvature and become slow and flat. When the cutting strength of the entire carbure layer from the surface is not enough to compete with foreign shear stress, fatigue cracks are beginning to form. Only by pushing the hard -quenching area to the heart can T/σt <0.55 do not become a dangerous danger zone. Therefore, the depth of the carburizing layer of the large forging parts must be deepened. For example, the depth of the effective hardening layer of the large -loading gear on the rolling machine often requires greater than 5 mm.

Comprehensively consider the speciality of heavy -duty large -molding gears (including gear shafts), and summarize the quality requirements of large -scale digital gear carburizing quenching in the following aspects:

(1) Surface hardness, requires high wear resistance;

(2) The depth of the carburizing layer is sufficient to ensure the depth of the effective hardening layer;

(3) The form, quantity and distribution of carburizing layers on the surface;

(4) The gold phase tissue of the carburizing layer, that is, the Matselin level;

(5) the hardness and mechanical performance of the heart;

(6) Railing layer gradient;

(7) grain size.

2 17CR2NI2MO large model number gear axis technical requirements

17CR2NI2MO Materials Big Model of Materials Figne Shafts is shown in Table 1. The basic size of the workpiece is shown in Figure 1, and the number of method is 24, the number of teeth is 20.17Cr2NI2MO material production processes are steelmaking → forging Carbon → Removing grinding amount of fine processing → quenching recovery → grinding. After carburizing and quenching, the technical requirement of the tooth surface hardness is 56 ~ 60HRC, the effect is 3.2mm ~ 4.0 mm, and the heart hardness is 310 ~ 350HBS.

3 17CR2NI2MO Materials Big Model Fiton Shaft Vacuum Carburization and Vacuum Study Craft

17CR2NI2MO Materials Big Model The Gear Shaft uses the SIMUWU vacuum carburizing furnace for carburizing treatment. After carburizing, the heat treatment furnace of 2.5 mx4.06 m Taiwan car is high -temperature recovery, quenching, and recovery.

4 17CR2NI2MO Materials Big Model Gar Rightshaft Crystal Carburization and Quenching Process

Optimized the large -mold gear axis vacuum carburizing and vacuum quenching process.

First increase the procedures for the fire before the vacuum carburizing, and refine the grain tissue. See the figure below.

Secondly, the hot oil is cooled during vacuum quenching, and a sufficient circulation is stirred. The martensite of the 17CR2NI2MO material began to change temperature at about 300 ° C. The starting temperature of the transition of the carbon -carbon layer high carbon mace is around 120 ° C, and the quenching and cooling to the surface is 120 ~ 300 ° C. After the body was fully transformed, after forming a hard matewars, the mart -. Because the transformation of the surface of the surface causes the volume expansion, it can cause strong surface compression stress, improve the surface hardness of the gear shaft, and reduce the tissue stress and thermal stress.

The fully circulating mixing during cooling keeps the large forging uniformly cooling and does not cause fire risk.

Third, the temperature is cooled to 180 ° C (surface temperature). You can put the quenching parts in an equivalent furnace for a long time insulation (about 4 h), or it can be placed in the air to heat it up to maintain the surface temperature.

After carburizing and quenching above, the hardness of the carburizing layer of the gear shaft is 56 ~ 57HRC. After the gold phase inspection, the carburizing layer was tissue to the firewood of the macwardinnia + the bellnium + the residual Aolinite (30%). Best. The hardness of the core is about 335HBS.

5 Conclusion

17CR2NI2MO Large Model Gear Shaft Deep Carbarium Crystation To get a satisfactory carburizing quality, it should be used to refine the grain tissue before carburizing, and then the ballization treatment is performed again after carburizing and cooling. The particles are evenly distributed. Cool oil during vacuum quenching, and mixes sufficient circulation. Cooling to about 180 ° C (surface temperature) for equal temperature.