Patent Application
20120325372
In general, a gas carburizing process would require an atmospheric heat treating furnace herein called heat treating furnace along with a gas generator for conventional carburizing. However there are existing designs that use heat treating furnaces for carburizing without a gas generator. Example of this is a drip feed type furnace with Methanol for direct carburizing.
Prior art and problem to be solved: In the conventional method, the carburization starts from the time heat treating furnace attains the temperature of 930° C. to begin the process, but in the present invention the carburization starts from 800° C., 850° C., 900° C. to 930° C. In the conventional method the process of quenching takes place with low agitation quenching & oil velocity (rpm), wherein in the present invention the agitation varies from 1200-1500 rpm with high velocity rate of quenching.
This cooling apparatus of the present invention is a significant innovative step as compared to conventional cooling apparatus.
The present invention reduces the total cycle time during carburization and diffusion in the carburizing process, and to lower the production cost of the carburization processing. The present invention allows carburization on a part to start from 800° C. by adding LPG or propane along with methanol during heating and during the withholding duration. The other object of the invention is to begin carburizing much earlier than what it would have achieved after beginning of carburizing at 930° C.
Further object of the invention is after the process of completing carburizing process; the parts need to be quenched. The Quenching apparatus in this invention has made significant changes as compared to conventional quenching apparatus which is about 0.25 in−1. The further object of the invention is to enhance the severity of quench apparatus by surpassing the conventional severity of quench by 0.43-0.8 in−1.
The present invention provides a process for reduction of time in gas-carburizing process and cooling apparatus to perform carburization by step heating of a part during carburizing heating from 800° C., 850° C., 900° C. onwards to a carburization temperature of 930° C. with the part being held at each mentioned temperature for 10 minutes by adding LPG or propane along with methanol in the furnace for activation/diffusion, the holding time is thereby reduced for carburization, thereafter the carburized parts are quenched in the invented apparatus to discharge high severity of quenching. A quenching oil flow rate of about 1.6 meters per second is critical to the process.
Other features and advantages of the instant invention will become apparent from the following description of the invention which refers to the accompanying drawings.
In the following detailed description of the invention, reference is made to the drawings in which reference numerals refer to like elements, and which are intended to show by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and that structural changes may be made without departing from the scope and spirit of the invention.
Carburization on a part starts from 800° C. by adding LPG or propane along with a methanol gas in the furnace. This begins the carburizing process. During this period the temperatures are maintained at 800° C., 850° C. and 900° C. for a duration of 10 minutes. With the rise of temperatures from 800° C., 850° C., 900° C. and 930° C. the carburization takes place by the presence of LPG and propane along with methanol inside the furnace. To allow penetration of saturated carbon content to the surface of the part is done by altering the carbon potential at each set temperature (as above). The apparatus required to operate in manual or automatic mode a certain quantity of LPG or propane along with methanol to reach the required carbon potential at the set temperature. As shown in
As shown in
This cooling apparatus has two characteristics (1) introduce homogeneous cooling: (2) Improve the severity of quench. The severity of quench is 0.80 in−1 at 1500 rpm in the new process. The severity quench is 0.25 in−1 in the conventional process. This illustrates the innovative capability of the quenching mechanism. This produces a critical flow rate of around 1.6 meters per second with the quenching oil temperature of around 60 degrees Centigrade. This increased flow rate over the prior art produces a more uniform faster cooling of the selected steel part and thereby enhances the quench severity which cools the part faster. This results in a more uniformly distributed martensitic structure which in turn enhances the effective case depth. Only by utilizing the instant's invention's flow rate will the above hardening characteristics be realized. Additionally, the increased flow rates result in reduced processing time as discussed above.
The function of the cooling apparatus shown in
The quenching oil starts flowing through quench oil circulation pipe 7 and it is jetted through perforated grid by the churning effect of propeller 3. Work basket 5 comes down to the quenching oil and the work (job) is quenched into the cooling oil.
Scope/Ambit of Invention:
The result of CO, C02 and Carbon Potential.
This invention: Heating from 800° C. to 930° C.: 100 min.
Carburizing: 4 hour, Diffusing: 2 hour total: 7.67 hour.
Conventional: Heating 70 min.
Carburizing: 5 hour, Diffusing: 3 hour total: 9.12 hour.
Reduction: 16%
This invention: Heating from 800° C. to 930° C.: 85 min.
Carburizing: 3 hour, Diffusing: 1 hour total: 5.42 hour.
Conventional: Heating 55 min.
Carburizing: 5.5 hour, Diffusing: 2 hour total: 8.42 hour.
Reduction: 36%
This invention clearly reduces the cycle time.
The revolutions per minute of the motor is changed as shown in
The number of revolutions of the motor revealed that the severity of quench became 0.80−1 at the time of 1,500 rpm.
In addition, distortion level is examined after the heat-treatment by the Navy test specimen. We noted the severity of the quench in the range from 0.43−1 to 0.8−1 did not offer any significant difference in a level of risk of 5% in a range from 0.43−1 to 0.8−1.
The test made on the part, showed the quantity of carbon at pre-determined positions which showed an effective case depth (Hv550)0.28% from 0.4% (conventional law) by improving severity of quench to 0.43−1.
The above statement illustrates a very unique advantage of the quenching apparatus.
Although the instant invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.
This application is a continuation in part of U.S. patent application Ser. No. 12/970,986, filed Dec. 17, 2010, the entire contents of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12970986 | Dec 2010 | US |
| Child | 13603256 | US |
