DESC:Field of the invention

The present invention relates to a heat treatment process and more particularly, to a direct forge quenching apparatus and a method therefor.

Background of the invention

Currently, the most common heat treatment process applied to make forgings stronger and tougher is hardening and tempering. The products like wheel hubs, connecting rods and track links are a common example of parts which undergo this type of heat treatment process.

In the hardening and tempering process, the raw materials are first cut into pieces / billets then heated to the forging temperature and forged. After forging, the parts are cooled to room temperature in an open air, put into a furnace, fuelled by gas, electricity or fuel oil, where the temperature is raised above the austenitization temperature, then quenched in oil, polymer or water based on the material and the required properties and finally tempered at temperatures of 450-600 0C to obtain the desired toughness. This is an energy intensive process and consumes huge amounts of fuel resulting in higher costs and excess carbon dioxide emission. A recent development has been for the treatment of microalloyed steels where hardening and tempering heat treatment is replaced by a controlled cooling. However, the presence of microalloying elements like Vanadium as raw materials increases the cost of the process. Further, these steels have very low impact toughness that makes the parts susceptible to failure under Indian road conditions.
Developments have been made in a sheet metal industry to utilise rolling heat of steel plates by using direct quenching systems to replace offline hardening and tempering heat treatment processes. Attempts to develop similar systems for continuous production have also been made in the past for the forging industry, but they are not fully functional. Many of these systems try to make small batches of five or more pieces and feed them into the furnace to equalize the temperature of the parts which results in undesirable heat loss, part to part variation in temperature and thus variation in final properties. Another important development in the forging industry has been the introduction of induction heating technology for preheating of cut billets before forging. This has helped the forgers ensure a precise heating of the billets but within a temperature range of 50 0C.

Accordingly, there is a need of a direct forge quenching apparatus and a method therefor that overcomes the above mentioned drawbacks of the prior art.

Objects of the invention

An object of the present invention is to provide a cost effective heat treatment of forgings.

Another object of the present invention is to provide heat treatment of the forgings with minimum emission of carbon dioxide.

Yet another object of the present invention is to provide uniformity and repeatability of a heat treatment process.

Still another object of the present invention is to reduce the process time of the heat treatment process.
Summary of the invention

Accordingly, the present invention, in one aspect, provides a direct forge quenching apparatus. The direct forge quenching apparatus comprises a first conveyer, an equalization zone, a temperature sensitive accept-reject zone, a slider, a quenching tank and a second conveyer.

The first conveyer is adapted for carrying jobs from a trim press. The equalization zone is connected to the first conveyer for receiving the jobs there through. The equalization zone includes an insulated zone and a blower. The temperature equalization of the jobs is carried out using any one of the insulated zone and the blower depending on the temperature of the jobs. The job having a temperature higher than 950 0C is cooled by using forced air from the blower. The job is passed through the insulated zone to equalize temperature when a temperature difference between two parts of the job is greater than 50 0C.

The temperature sensitive accept-reject zone is connected to the equalization zone to allow jobs having temperature in a predefined/ desired temperature range to pass there through. The temperature sensitive accept-reject zone includes a pyrometer and a hydraulic rejection mechanism. The pyrometer is adapted to measure the temperature of the jobs. The hydraulic rejection mechanism is adapted to reject the jobs having temperature outside the predefined temperature range.

The slider is inclined on a base of the temperature sensitive accept-reject zone for carrying the jobs having temperature within the predefined temperature range. The quenching tank is connected to the slider to receive the jobs there from for cooling thereof at a controlled rate using quenchant for example water, oil and polymer.
The quenching tank includes a level sensor, a temperature sensor, a heat exchanger and an agitation system configured therein. The level sensor and the temperature sensor such as a thermocouple are adapted for detecting a level and a temperature of the quenchant in the quenching tank. The heat exchanger is adapted for cooling the quenchant in response to a high temperature detected by the temperature sensor. The agitation system includes at least three nozzles selected from a completely open nozzle, a half open nozzle and a quarter open/ completely closed nozzle adapted for circulating the quenchant in the quenching tank at a controlled to achieve three different levels of agitation intensities while the job is moving in the quenching tank.

The second conveyer is fitted on a base of the quenching tank for moving the cooled jobs therefrom into any of a box and a continuous belt type tempering furnace for a tempering step.

In another aspect, the present invention provides a method for direct forge quenching.

Brief description of the drawings

The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,

Figure 1 shows a schematic diagram of a direct forge quenching apparatus, in accordance with the present invention;

Figures 2a shows a cross sectional side view of an agitation system of the direct forge quenching apparatus of figure 1;

Figures 2b shows a cross sectional top view of the agitation system of figure 2a; and

Figures 2c shows a cross sectional view of nozzles in the agitation system of figure 2a illustrating hole geometry.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a direct forge quenching apparatus and a method therefor. The direct forge quenching apparatus and the method allow an online continuous process wherein residual heat of hot forgings is utilised to perform heat treatment thereby reducing cost and carbon dioxide emission. The direct forge quenching apparatus and the method also allow a single process flow thereby improving uniformity and repeatability of the heat treatment. The method allows for a continuous flow of materials hence reducing the processing time for the heat treatment.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

Referring now to figures 1-2c, in one aspect, a direct forge quenching apparatus (100) (herein after ‘the apparatus (100)’) in accordance with the present invention is shown. Specifically, the apparatus (100) is used for direct quenching of forgings/ jobs (herein after ‘the jobs’) made from any suitable material of any shapes, weighing between 500 Gms to 10 Kgs. The apparatus (100) comprises a first conveyer (not shown), an equalization zone (20), a temperature sensitive accept-reject zone (30), a slider (40), a quenching tank (50) and a second conveyer (60). The above mentioned parts can be made up of any suitable material and are connected by any suitable means known in the art.

The first conveyer is adapted for carrying jobs from a trim press (200). Specifically, the jobs immediately after undergoing a final step of forging and trimming in the trim press (200) are placed on the first conveyer. In an embodiment, the jobs after undergoing the final step of forging and trimming in the trim press (200) having a temperature ranging between 860-1050 0C can be placed on the first conveyer by any of a manual means or an automatic means such as a motor (not shown). The first conveyer is connected between the trim press (200) and the equalization zone (20). The first conveyer is adapted to carry hot jobs from the trim press (200) to the equalization zone (20) at a controlled temperature.

The equalization zone (20) is connected to the first conveyer for receiving the jobs there through. The equalization zone (20) includes a pre-heated/ insulated zone (18) (herein after ‘the insulated zone (18)’) and a blower/ fan (16). The temperature equalization of the jobs is carried out in any one of the insulated zone (18) and by using the blower (16) depending on the temperature of the hot jobs. The hot jobs having a temperature higher than 950 0C are cooled to 850-950 0C by using forced air from the blower (16). When a temperature difference between two parts of the hot job is greater than 50 0C, the hot job is passed through the insulated zone (18) to equalize temperature for 5-10 minutes and achieve a temperature equivalence within + 15 0C within the job and a minimum temperature of 850 0C. The rate of cooling of the jobs is controlled based on the required properties and final forging finish temperature. The equalization zone (20) is connected to the temperature sensitive accept-reject zone (30).

The temperature sensitive accept-reject zone (30) is connected to the equalization zone (20) to allow the jobs having temperature in a predefined/ desired temperature range (between 850-950 0C, depending on the part) to pass there through while the jobs having a temperature lower or higher than the predefined temperature range are rejected. The temperature sensitive accept-reject zone (30) includes a pyrometer (25) and a hydraulic rejection mechanism (26) positioned therein. The pyrometer (25) is adapted to measure the temperature of the jobs. The hydraulic rejection mechanism (26) is adapted to reject the jobs having temperature outside the predefined temperature range as measured by the pyrometer (25). In an embodiment, the jobs with the predefined temperature pass through the temperature sensitive accept-reject zone (30) in 8 - 10 seconds.

The slider (40) is inclined on a base (not numbered) of the temperature sensitive accept-reject zone (30). The slider (40) is adapted to carry or drop the jobs having temperature within the predefined temperature range into the quenching tank (50).

The quenching tank (50) is connected to the slider (40) to receive the jobs there from for cooling thereof at a controlled rate using quenchant such as water, oil, polymer and the like. In an embodiment, the jobs are cooled to a temperature less than 80 0C in 10-30 minutes. The quenchant is supplied to the quenching tank (50) from a reservoir (not shown) connected thereto depending on space and operational requirements. The quenching tank (50) includes a level sensor (42), a temperature sensor (43), a heat exchanger (44) and an agitation system (46) configured therein.

The level sensor (42) is adapted to detect a level of the quenchant in the quenching tank (50). If the level of the quenchant goes below a required level, then a signal is generated and sent to draw in more quenchant from the reservoir for cooling of the jobs. The temperature sensor (43) is a thermocouple adapted to detect the temperature of the quenchant. If the temperature of the quenchant is higher than a desired temperature, then the temperature sensor (43) sends a signal to pumps (41) that cause the quenchant to flow through the heat exchanger (44). The heat exchanger (44) is adapted for cooling the hot quenchant in response to a high temperature detected by the temperature sensor (43). In an embodiment, a coolant, such as water is continuously circulated in and out through the heat exchanger (41) using the pumps (41) to cool the hot quenchant.

The agitation system (46) is configured in the quenching tank (50) for proper circulation of the quenchant therein by controlling the rate of cooling of the jobs at various stages of quenching using a pump (46A). In an embodiment, the agitation system (46) is a spray agitation system that includes at least three nozzles / valves (45A, 45B and 45C). The nozzle (45A) is kept completely open, the nozzle (45B) is kept half open and the nozzle (45C) is quarter open or completely closed to achieve three different levels of agitation intensities of the quenchant while the job is moving in the quenching tank (50). The agitation intensity is controlled by controlling quenchant flow through the at least three nozzles (46A, 46B and 46C). This way, maximum agitation is ensured in the initial stage of cooling, helping in preventing the nose of the cooling curve. While, comparatively slower cooling rate in the later stage ensures lesser distortion and reduced chances of cracking.

The quenching tank (50) includes the second conveyer (60) fitted on a base (not numbered) thereof such that the agitation system (46) runs beneath a top layer (not numbered) of the second conveyer (60). Specifically, the second conveyer (60) is a continuously moving honeycomb conveyor having a plurality of perpendicular slats (61) configured thereon to progressively take the cooled jobs out of the quenching tank (50) with the help of a motor (not shown) and drop the cooled jobs into a box (70) for subjecting them to a tempering step. In an alternate embodiment, the cooled jobs are moved from the conveyor (60) to a continuous belt type tempering furnace (not shown) thereby making the entire process continuous.

Referring again to figures 1-2c, in another aspect, the present invention provides a method for direct forge quenching in accordance with the present invention. Specifically, the method is illustrated in conjunction with the apparatus (100). The method involves a step of placing the hot jobs from the trim press (200) on the first conveyer. Further, the method involves carrying the jobs from the trim press (200) to the equalization zone (20) by the first conveyer.

Furthermore, the method involves equalizing the jobs by using any of the insulated zone (18) and the blower (16) of the equalization zone (20) depending on the temperature of the hot jobs. The job having a temperature higher than 950 0C is cooled by using forced air from the blower (16) and the job having a temperature difference between two parts thereof greater than 50 0C is passed through the insulated zone (18) for temperature equalization.

Further, the method involves passing the jobs from the equalization zone (20) through the temperature sensitive accept-reject zone (30), measuring the temperature of the jobs by the pyrometer (25) of the temperature sensitive accept-reject zone (30) and rejecting the jobs having temperature outside the desired temperature range by the hydraulic rejection mechanism (26) of the temperature sensitive accept-reject zone (30) thereby allowing the jobs having temperature within the desired temperature range to pass there through.
Further, the method involves carrying the jobs having temperature within the desired temperature range from the temperature sensitive accept-reject zone (30) to the quenching tank (50) through the slider (40).

Furthermore, the method involves cooling the jobs at a controlled rate in the quenching tank (50) using quenchant selected from water, oil and polymer. In an embodiment, the quenchant is supplied to the quenching tank (50) from the reservoir connected thereto depending on space and operational requirements. The level and the temperature of the quenchant in the quenching tank (50) are detected by the level sensor (42) and the temperature sensor (43), respectively.

The quenchant is circulated in the quenching tank (50) at three different levels of agitation intensities by the at least three nozzles (45A, 45B and 45C) of the agitation system (46). The at least three nozzles (45A, 45B and 45C) are selected from the completely open nozzle (45A), the half open nozzle (45B) and the quarter open/ completely closed nozzle (45C) to achieve three different levels of agitation intensities while the job is moving in the quenching tank (50). Further, the method involves carrying the cooled jobs through from the quenching tank (50) into any of the box (70) and the continuous belt type tempering furnace by the second conveyer (60) for the tempering step.

Advantages of the invention

1. The apparatus (100) allows an online continuous process wherein the residual heat of the hot jobs is utilised to perform the heat treatment, thus reducing costs and carbon dioxide emission.
2. The apparatus (100) allows a single process flow thus improving uniformity and repeatability of the heat treatment.
3. The jobs being subjected to three different levels of agitation intensities in the apparatus (100) are less prone to breakage and distortion.
4. The process time for heat treatment operation is drastically reduced.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.
,CLAIMS:We claim:

1. A direct forge quenching apparatus (100) comprising:
• a first conveyer adapted for carrying jobs from a trim press (200);
• an equalization zone (20) connected to the first conveyer for receiving the
jobs there through, the equalization zone (20) having an insulated zone (18) and a blower (16), wherein temperature equalization of the jobs is carried out using any one of the insulated zone (18) and the blower (16) depending on the temperature of the jobs;
• a temperature sensitive accept-reject zone (30) connected to the
equalization zone (20) to allow jobs having temperature in a predefined/ desired temperature range to pass there through, the temperature sensitive accept-reject zone (30) having,
a pyrometer (25) adapted to measure the temperature of the jobs, and
a hydraulic rejection mechanism (26) adapted to reject the jobs having
temperature outside the predefined temperature range;
• a slider (40) inclined on a base of the temperature sensitive accept-reject
zone (30) for carrying the jobs having temperature within the predefined temperature range;
• a quenching tank (50) connected to the slider (40) to receive the jobs there
from for cooling thereof at a controlled rate using quenchant, the quenching tank (50) having,
a level sensor (42) configured therein for detecting a level of the
quenchant,
a temperature sensor (43) configured therein for detecting the
temperature of the quenchant,
a heat exchanger (44) configured therein for cooling the quenchant in
response to a high temperature detected by the temperature sensor (43), and
an agitation system (46) configured therein for circulating the
quenchant in the quenching tank (50), the agitation system (46) having at least three nozzles selected from a completely open nozzle (45A), a half open nozzle (45B) and a quarter open/ completely closed nozzle (45C) to achieve three different levels of agitation intensities while the job is moving in the quenching tank (50); and
• a second conveyer (60) fitted on a base of the quenching tank (50) for
moving the cooled jobs therefrom into any of a box (70) and a continuous belt type tempering furnace for a tempering step.

2. The direct forge quenching apparatus (100) as claimed in claim 1, wherein the
job having a temperature higher than 950 0C is cooled by using forced air from the blower (16).

3. The direct forge quenching apparatus (100) as claimed in claim 1, wherein the
job is passed through the insulated zone (18) to equalize temperature when a temperature difference between two parts of the job is greater than 50 0C.

4. The direct forge quenching apparatus (100) as claimed in claim 1, wherein the
quenchant is selected from water, oil and polymer.

5. The direct forge quenching apparatus (100) as claimed in claim 1, wherein the
temperature sensor (43) is a thermocouple.

6. A method for direct forge quenching, the method comprising the steps of:
• placing jobs from a trim press (200) on a first conveyer;
• carrying the jobs from the trim press (200) to an equalization zone (20) by
the first conveyer;
• equalizing the jobs by using any of an insulated zone (18) and a blower
(16) of the equalization zone (20) depending on the temperature of the jobs, wherein the job having a temperature higher than 950 0C is cooled by using forced air from the blower (16) and the job having a temperature difference between two parts thereof greater than 50 0C is passed through the insulated zone (18) for temperature equalization;
• passing the jobs through a temperature sensitive accept-reject zone (30);
• measuring the temperature of the jobs by a pyrometer (25) of the
temperature sensitive accept-reject zone (30);
• rejecting the jobs having temperature outside a desired temperature range
by a hydraulic rejection mechanism (26) of the temperature sensitive accept-reject zone (30) thereby allowing the jobs having temperature within the desired temperature range to pass there through;
• carrying the jobs having temperature within the desired temperature range
from the temperature sensitive accept-reject zone (30) to a quenching tank (50) through a slider (40), the quenching tank (50) having a level sensor (42) for detecting a level of the quenchant, a temperature sensor (43) for detecting the temperature of the quenchant, a heat exchanger (44) and an agitation system (46);
• cooling the jobs at a controlled rate in the quenching tank (50) using
quenchant circulated therein at three different levels of agitation intensities by the agitation system (46), wherein the agitation system (46) includes at least three nozzles selected from a completely open nozzle (45A), a half open nozzle (45B) and a quarter open/ completely closed nozzle (45C) to achieve three different levels of agitation intensities while the job is moving in the quenching tank (50); and
• carrying the cooled jobs through a second conveyer (60) into any of a box
(70) and a continuous belt type tempering furnace for a tempering step.

7. The method as claimed in claim 6, wherein the heat exchanger (44) is adapted
to cool the quenchant in response to a high temperature detected by the temperature sensor (43).

8. The method as claimed in claim 6, wherein the temperature sensor (43) is a
thermocouple.

9. The method as claimed in claim 6, wherein the quenchant is selected from
water, oil and polymer.