A process for the co-forging and co-quenching of a crank forging

Abstract

The present application relates to a kind of curved handle forgings's joint forging joint quenching process, the heat treatment process of the curved handle forgings of weight and volume is relatively large is scientifically designed.First in the process of forging, the forming forging ratio and final forging ratio of forging are set, and the final forging temperature of forging is set, to ensure that the forging has the condition of heat treatment, after the end of forging process, directly quenching and heat treatment is carried out, specific heat treatment process is set, to ensure the quality of heat treatment of the forgings, and improve production efficiency and save production cost.

Description

Technical Field

[0001] This invention relates to a crank forging and heat treatment process, and particularly to a combined forging and quenching process for large crank forgings, belonging to the field of metal hot working technology. Background Technology

[0002] The crankshaft is the component in an engine that converts reciprocating motion into rotary motion. Large crankshafts are subjected to large and complex forces, thus requiring crankshaft forgings to have sufficient rigidity, strength, and the ability to withstand impact loads. Traditional metal forging and post-forging heat treatment processes are mostly carried out separately, requiring repeated heating and cooling to complete. Traditional post-forging heat treatment processes for forgings are quite complex, involving post-forging cooling, reheating, recooling, and tempering. This not only involves many steps and high processing costs but also results in a significant amount of energy waste. Especially during the forging process, the temperature of the forged part is still relatively high after forging, with a large amount of heat available for utilization. Therefore, it is necessary to improve existing forging and quenching processes. Summary of the Invention

[0003] In response to the problems pointed out in the background art, the present invention provides a combined forging and quenching process for crank forgings. By setting the forging ratio and final forging temperature of the forging, adopting a specific quenching process, and utilizing residual heat for tempering, the present invention achieves the goal of good product quality and high production efficiency.

[0004] To achieve the above objectives, this invention proposes a combined forging and quenching process for crank forgings. The crank forgings comprise: medium carbon manganese steel, medium carbon chromium steel, medium carbon chromium-molybdenum steel, medium carbon chromium-nickel-molybdenum steel, and medium carbon chromium-nickel-manganese-molybdenum steel. The medium carbon steel contains 0.25-0.60% carbon; the medium carbon manganese steel contains 0.60-1.80% manganese; the medium carbon chromium steel contains 0.60-2.50% chromium; and the medium carbon chromium-molybdenum steel contains... The chromium and molybdenum contents are 0.60-2.50% and 0.15-0.55%, respectively. In the medium-carbon chromium-nickel-molybdenum steel, the chromium, nickel, and molybdenum contents are 0.60-2.50%, 0.60-1.80%, and 0.15-0.55%, respectively. In the medium-carbon chromium-nickel-manganese-molybdenum steel, the chromium, nickel, manganese, and molybdenum contents are 0.60-2.50%, 0.60-1.80%, 0.60-1.80%, and 0.15-0.50%, respectively.

[0005] The forging and quenching process of the large crank forging is as follows:

[0006] I. Forging process

[0007] Step 1: Select any one of the medium carbon alloy steels mentioned above as the billet;

[0008] Step 2: Place the billet selected in Step 1 in a heating furnace and heat it to 1200℃-1250℃, and keep it at that temperature for the set time.

[0009] Step 3: Forge the heated billet from Step 2 into the desired shape and size on a forging machine. Set the total forging ratio to ≥5, with the final forging stage forming ratio to ≥0.7. Set the final forging temperature for different types of medium-carbon alloy steel forgings. The final forging temperatures for different steel grades are shown in the table below:

[0010]

[0011] II. Quenching Process

[0012] Step 4: Slowly cool the forging obtained in Step 3 in air to the initial quenching temperature, with the range set as shown in the table below:

[0013]

[0014] Step 5: Place the forgings obtained in Step 4 in a water bath at 10–35℃ or an oil bath at 40–70℃ for liquid cooling, and alternate between liquid cooling and air cooling multiple times; the multi-stage cooling time settings for medium carbon alloy steel forgings of different thicknesses are shown in the table below (thickness unit is mm, time unit is min):

[0015]

[0016] Step 6: According to the technical requirements of different specifications and steel grades, the forgings quenched in Step 5 are put into the furnace for tempering and held at the set temperature for a set time before being taken out of the furnace to complete the process flow.

[0017] Preferably, the weight of the large crank forging is set between 10 and 50 tons.

[0018] This invention sets the forming forging ratio and final forging temperature for large medium carbon alloy steel crank forgings, enabling the forgings to be directly quenched using residual heat. Through a specific quenching process, the quality of the tempering treatment of the forgings is guaranteed, and production efficiency is improved and production costs are saved. Detailed Implementation

[0019] The invention will be further explained and illustrated below through three implementation examples:

[0020] Example 1: Large forgings made of 42CrMo alloy steel:

[0021] 15 tons of 42CrMo steel billet were selected and heated in a furnace to 1200-1220℃. The billet was held at this temperature for a set time to ensure uniform temperature throughout. The high-temperature billet was then rapidly forged into a 150mm thick "herringbone" shaped module. The final forging temperature was controlled between 850-800℃. The module was quickly transported to a water tank while simultaneously being cooled in air. Once the module temperature dropped to between 760-720℃, it underwent quenching in the following sequence: water cooling for 2.6 minutes, air cooling for 1 minute, and oil cooling for 15 minutes.

[0022] Implementation Case 2: Large Modules Made of 3Cr2NiMnMo Alloy Steel.

[0023] 25 tons of 3Cr2NiMnMo steel were selected and heated in a furnace to 1220-1240℃. The temperature was maintained for a set time to ensure that the temperature inside and outside of the billet was consistent. The high-temperature billet was then removed and forged quickly into a 300mm thick "herringbone" module. The final forging temperature was controlled between 850-800℃. The module was then quickly transported to a water tank while being cooled in the air. Once the module temperature dropped to between 750-710℃, it was quenched in the following sequence: water cooling for 9 minutes, air cooling for 2 minutes, water cooling for 4 minutes, air cooling for 2.5 minutes, and oil cooling for 28 minutes.

[0024] Example 3: Large module made of 3Cr2Mo alloy steel.

[0025] Twenty tons of 3Cr2Mo steel billet were selected and heated in a furnace to 1200-1220℃. The billet was held at this temperature for a set time to ensure that the internal and external temperatures were consistent. The high-temperature billet was then removed and forged rapidly into a 250mm thick "herringbone" module. The final forging temperature was controlled between 820-770℃. The module was then quickly transported to a water tank while being cooled in the air. Once the module temperature dropped to between 790-750℃, it was quenched in the following sequence: water cooling for 6 minutes, air cooling for 1.6 minutes, water cooling for 3 minutes, air cooling for 2.2 minutes, and oil cooling for 20 minutes.

[0026] The three types of steel forgings in the above cases were directly quenched after forging, and their grain size reached level 5 or above. Their mechanical properties were significantly improved compared with the existing conventional forging and heat treatment methods. Moreover, the quenching heating process was omitted, saving a lot of energy and improving efficiency.

Claims

1. A combined forging and quenching process for a crank forging, wherein the crank forging comprises: Medium carbon manganese steel, medium carbon chromium steel, medium carbon chromium-molybdenum steel, medium carbon chromium-nickel-molybdenum steel, and medium carbon chromium-nickel-manganese-molybdenum steel are included. The carbon content in the aforementioned medium carbon alloy steel is 0.25-0.60%. The manganese content in the medium carbon manganese steel is 0.60-1.80%, the chromium content in the medium carbon chromium steel is 0.60-2.50%, and the chromium and molybdenum contents in the medium carbon chromium-molybdenum steel are 0.60-2.50% and 0.15-0.55%, respectively. The nickel-molybdenum steel contains 0.60-2.50% chromium, 0.60-1.80% nickel, and 0.15-0.55% molybdenum, respectively. The medium-carbon chromium-nickel-manganese-molybdenum steel contains 0.60-2.50% chromium, 0.60-1.80% manganese, and 0.15-0.50% molybdenum, respectively. The crank forging is set to weigh between 10 and 50 tons, and the forging and quenching process for the crank forging is as follows: I. Forging process Step 1: Select any one of the medium carbon alloy steels mentioned above as the billet; Step 2: Place the billet selected in Step 1 in a heating furnace and heat it to 1200℃-1250℃, and keep it at that temperature for the set time. Step 3: Forge the heated billet from Step 2 into the desired shape and size on a forging machine. Set the total forging ratio to ≥5, with the final forging stage forming ratio to ≥0.

7. Set the final forging temperature for different types of medium-carbon alloy steel forgings. The final forging temperatures for different steel grades are shown in the table below: II. Quenching Process Step 4: Slowly cool the forging obtained in Step 3 in air to the initial quenching temperature, within the range shown in the table below: Step 5: Place the forgings obtained in Step 4 in a water bath at 10-35℃ or an oil bath at 40-70℃ for liquid cooling, and alternate between liquid cooling and air cooling multiple times; the multi-stage cooling time settings for medium carbon alloy steel forgings of different thicknesses are shown in the table below, with thickness in mm and time in min. Step 6: According to the technical requirements of different specifications and steel grades, the forgings quenched in Step 5 are put into the furnace for tempering and held at the set temperature for a set time before being taken out of the furnace to complete the process flow.

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