Low-cost, safe and environment-friendly core rod heat treatment method

Abstract

The invention relates to a low-cost, safe and environment-friendly core rod heat treatment method. The treatment method comprises the following steps: quenching heating: the charging temperature is less than or equal to 350 DEG C, the speed limit is less than or equal to 50 DEG C / h, the temperature is increased to 670-690 DEG C, the temperature is kept for 2-4 hours, the temperature is increased to 1020-1040 DEG C at full power, the temperature is kept for 4-6 hours, the temperature is reduced to 960-1000 DEG C along with a furnace, the temperature is kept for 1-3 hours, and the core rod is discharged out of the furnace; quenching cooling is conducted, specifically, air cooling is conducted for 250-300 S; secondly, inorganic water-based liquid cooling is conducted for 10-15 min, the initial liquid temperature is 30-50 DEG C, and the concentration is 30-40% Thirdly, air cooling is conducted for 70-90 S; fourthly, inorganic water-based liquid cooling is carried out for 20-25 min; the charging temperature is smaller than or equal to 350 DEG C, the temperature is increased to 340-360 DEG C, heat preservation is conducted for 2 h, the speed limit is smaller than or equal to 50 DEG C / h, the temperature is increased to 600-630 DEG C, heat preservation is conducted for 11-15 h, and discharging and air cooling are conducted to the room temperature; the charging temperature is smaller than or equal to 350 DEG C, the speed limit is smaller than or equal to 80 DEG C / h, the temperature is increased to 560-590 DEG C, heat preservation is conducted for 11-15 h, and discharging and air cooling are conducted to the room temperature; the purposes of low cost, safety and environmental protection can be achieved while excellent comprehensive mechanical properties of the core rod are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of metal materials, and in particular relates to a low-cost, safe and environmentally friendly core rod heat treatment method. Background Art

[0002] At present, in the production of core rod heat treatment, heat treatment quenching cooling mainly uses two cooling media: oil or water-based quenching liquid. When oil quenching is used, when the workpiece enters the horizontal quenching tank at a temperature of 1030°C, the liquid surface instantly catches fire, which poses a great safety risk. Fire extinguishers must be equipped to be ready for fire extinguishing at any time, and the surrounding ground and equipment are seriously polluted. When water-based quenching liquid is used for quenching and cooling, in addition to strictly controlling the concentration of the quenching liquid, daily maintenance must also be done. Daily circulation stirring and regular addition of bactericides and PH regulators must be done in place, otherwise aging and odorization are likely to occur, which will affect product quality and the environment, and the maintenance cost and loss cost are high. Therefore, there is an urgent need for a low-cost, safe and environmentally friendly core rod heat treatment production method. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a kind of mandrel that can achieve excellent comprehensive mechanical properties. A low-cost, safe and environmentally friendly mandrel heat treatment method that achieves the goals of low cost, safety and environmental protection at the same time. During the quenching and heating process, thermal stress is reduced by controlling the furnace entry temperature, speed-limited heating and preheating; through step heating and heat preservation, while ensuring the internal structure and composition of the forgings are uniform, the quenching cooling intensity is reduced to reduce the risk of workpiece cracking and prepare for quenching cooling; through the quenching and cooling method of air-inorganic water-based liquid-air-inorganic water-based liquid, while achieving the designed quenching and cooling effect, the production loss and maintenance cost caused by the original water-based liquid cooling are greatly reduced, and the consumption per ton of steel is reduced from 4Kg to 1Kg. No maintenance is required during use, and there is no maintenance cost, and the safety and environmental risks brought by oil cooling can be avoided; thereby effectively eliminating internal stress, improving the plastic toughness of the workpiece, and obtaining good comprehensive mechanical properties.

[0004] In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solution: a low-cost, safe and environmentally friendly mandrel heat treatment method, wherein the treatment method is specifically implemented according to the following steps: Step 1), quenching heating: furnace temperature ≤ 350℃, speed limit ≤ 50℃ / h, heating to 670-690℃, keep warm for 2-4h, heating to 1020-1040℃ at full power, keep warm for 4-6h, cool down to 960-1000℃ with the furnace, keep warm for 1-3h before leaving the furnace; Step 2), quenching cooling: first, air cooling for 250-300 seconds; second, inorganic water-based liquid cooling for 10-15 minutes, with an initial liquid temperature of 30-50°C and a concentration of 30-40%; third, air cooling for 70-90 seconds; fourth, inorganic water-based liquid cooling for 20-25 minutes; Step 3), first tempering heating: furnace temperature ≤350℃, heat to 340~360℃, keep warm for 2h, speed limit ≤50℃ / h, heat to 600~630℃, keep warm for 11~15h, then air cool to room temperature; Step 4), second tempering heating: furnace temperature ≤350℃, speed limit ≤80℃ / h, heat to 560~590℃, keep warm for 11~15h, and air cool to room temperature.

[0005] Due to the adoption of the above technical solution, the present invention has the following advantages: The positive effects of a low-cost, safe and environmentally friendly core rod heat treatment method according to the present invention are as follows: 1. During the quenching and heating process, thermal stress is reduced by controlling the furnace temperature, speed-limited heating, and preheating; through step heating and insulation, while ensuring the homogenization of the internal structure and composition of the forging, the quenching cooling intensity is reduced to reduce the risk of workpiece cracking and prepare for quenching cooling.

[0006] 2. Through the design of air-inorganic water-based liquid-air-inorganic water-based liquid quenching and cooling, while achieving the designed quenching and cooling effect, the production loss and maintenance cost caused by the use of original water-based liquid cooling can be greatly reduced, and the consumption per ton of steel can be reduced from 4Kg to 1Kg. No maintenance is required during use, and there is no maintenance cost. It can also avoid the safety and environmental risks caused by the use of oil cooling.

[0007] 3. Perform high temperature tempering at 600-630℃ to effectively eliminate internal stress, improve the plasticity and toughness of the workpiece, and obtain good comprehensive mechanical properties.

[0008] 4. After tempering, air cool to room temperature and perform high-temperature tempering again at 560-590°C to reduce the amount of residual austenite and improve the organizational and dimensional stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Conventional mandrel heat treatment method using oil or water based fluid as quenching medium.

[0010] Figure 2 The invention discloses a low-cost, safe and environmentally friendly core rod heat treatment method. DETAILED DESCRIPTION

[0011] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0012] Example 1: Taking H13 forgings with an outer diameter of φ260mm as an example, the heat treatment process steps are as follows: Step 1), quenching heating: furnace temperature ≤ 350℃, speed limit ≤ 50℃ / h, heating to 670~690℃, keep warm for 3h, heating to 1030±10℃ at full power, keep warm for 5h, cool down to 990±10℃ with the furnace, keep warm for 2h before leaving the furnace; Step 2), quenching cooling: 1) air cooling 270±10S; 2) inorganic water-based liquid cooling 13±1min, initial liquid temperature 30~50℃, concentration 30~40%; 3) air cooling 80±10S; 4) inorganic water-based liquid cooling 22±1min; Step 3), first tempering heating: furnace temperature ≤350℃, heat to 340~360℃, keep warm for 2h, speed limit ≤50℃ / h, heat to 610±10℃, keep warm for 13h, then air cool to room temperature; Step 4), second tempering heating: furnace temperature ≤350℃, speed limit ≤80℃ / h, heat to 570±10℃, keep warm for 13h, and air cool to room temperature.

[0013] Comparison example: A low-cost, safe and environmentally friendly mandrel heat treatment method compared to a conventional mandrel heat treatment method using oil or water-based fluid as the quenching medium: The technical characteristics and product test data of the embodiment and the control example are compared, and the results are shown in Table 1 below.

[0014] Table 1 Mechanical properties test data of the products of the embodiments and the control examples Specifications / Characteristics Rp0.2(MPa) Rm (MPa) A(%) Z(%) AKV(J) Ultrasonic flaw detection Risk of quenching cracking Production costs Security Risks Environmental pollution Example 960 1157 14.5 52 24 / 20 / 22 qualified Large, controllable through process design Slightly higher none none Control Example (Water-Based Fluid) 980 1160 15 52 21 / 20 / 23 qualified In the process design, it is controllable high none middle Control Example (Oil) 935 1146 15 54 19 / 22 / 21 qualified Small Low big big After the core rod heat treatment production technology of the present invention is used for production with low cost, safety and environmental protection, various test results of the product meet the technical requirements of users, and the purpose of low cost, safety and environmental protection is achieved while obtaining excellent comprehensive mechanical properties.

Claims

1. A low-cost, safe and environmentally friendly mandrel heat treatment method, characterized in that: The processing method is implemented in the following steps: Step 1), quenching heating: furnace temperature ≤ 350℃, speed limit ≤ 50℃ / h, heating to 670-690℃, keep warm for 2-4h, heating to 1020-1040℃ at full power, keep warm for 4-6h, cool down to 960-1000℃ with the furnace, keep warm for 1-3h before leaving the furnace; Step 2), quenching cooling: first, air cooling for 250-300 seconds; second, inorganic water-based liquid cooling for 10-15 minutes, with an initial liquid temperature of 30-50°C and a concentration of 30-40%; third, air cooling for 70-90 seconds; fourth, inorganic water-based liquid cooling for 20-25 minutes; Step 3), first tempering heating: furnace temperature ≤350℃, heat to 340~360℃, keep warm for 2h, speed limit ≤50℃ / h, heat to 600~630℃, keep warm for 11~15h, then air cool to room temperature; Step 4), second tempering heating: furnace temperature ≤350℃, speed limit ≤80℃ / h, heat to 560~590℃, keep warm for 11~15h, and air cool to room temperature.

Images