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Multi-cycle quenching-partitioning-tempering (M Q-P-T) technique

A multi-cycle, process technology, applied in the direction of process efficiency improvement, manufacturing tools, heat treatment equipment, etc., can solve the problems of quenching cracking, plasticity, deficiency, etc.

Active Publication Date: 2012-02-01
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the Q&T process is applied to the direct quenching of workpieces such as section steel or steel plate, it is found that there are problems of quenching cracking and insufficient plasticity.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0014] 42CrMo shaft parts with a diameter of 150mm are processed by M Q-P-T process. It is required that the mechanical properties at 1 / 2R (R is the radius of the axis) from the surface after quenching and high temperature tempering are higher than a certain index. In the MQ-P-T process, water is used as the medium for fast cooling, and air is used for slow cooling.

[0015] According to the isothermal transformation cooling curve (TTT curve) of the workpiece material and the interface heat transfer coefficient and other parameters, the temperature field, tissue field and stress / strain field of the workpiece during the cooling process are numerically simulated. -20mm layer, 20-30mm layer, 30-35mm layer M Q-P-T process of Q-P-T transformation, that is, the first water quenching time is 180s, the first air cooling time is 20s, the second water quenching time is 120s, and the second time The air cooling time is 15s, the third water quenching time is 80s, and the third air co...

Embodiment 2

[0017] The 50mm thick micro-alloyed steel rolling plate is processed by the M Q-P-T process, and the M Q-P-T process is arranged after the rolling mill. It is required that the tensile strength and yield of the material from the surface to the thickness of 1 / 4 section thickness after the MQ-P-T process are determined to be higher than a certain index (that is, the structure mainly composed of tempered martensite is required), and the elongation and Low-temperature impact toughness is required. If the traditional rapid cooling method with one water spray will cause cracks on the surface of the rolled plate if the cooling time is too long, and the performance indicators will not meet the requirements if the cooling time is too short.

[0018] This embodiment solves this problem by using the MQ-P-T process. The medium used to achieve rapid cooling is water, and the medium used to achieve slow cooling is air. Rapid cooling is to arrange several sections of strong cooling zones...

Embodiment 3

[0021] The H13 mandrel with a diameter of 300mm is treated by the M Q-P-T process, and the mechanical properties of the material at 1 / 2R (R is the radius of the axis) from the surface after the M Q-P-T process are required to be higher than a certain value, and the polymer water-soluble medium is used to combine The M Q-P-T process handles the product.

[0022] First, according to the isothermal transformation cooling curve (TTT curve) of the workpiece material and the interface heat transfer coefficient and other parameters, the temperature field, tissue field and stress / strain field of the workpiece during the cooling process are numerically simulated. M Q-P-T process in which Q-P-T transformation occurs on the 0-20mm layer, 20-55mm layer, 55-65mm layer, and 65-75mm layer on the surface, that is, the first water quenching time is 300s, the first air cooling time is 120s, and the second water quenching time is 300s. The quenching time is 600s, the second air cooling time ...

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Abstract

The invention discloses a multi-cycle quenching-partitioning-tempering (M Q-P-T) technique, belonging to the field of thermal processing technologies. The technique disclosed by the invention comprises the following steps of: dividing a workpiece with a large section into a plurality of regions from the surface to the centre part along the section, and making an MQ-P-T technique for the workpiecein combination with an isothermal cooling transformation curve of the workpiece; through alternately cooling the workpiece in a medium capable of quickly cooling and a medium capable of slowly cooling for many times, realizing a Q-P-T technique process in each alternate cooling of quick cooling and slow cooling; and gradually finishing martensitic transformation and carbon-rich retained austenitegeneration from the surface layer to the internal layer in the technique. The technique can be used for quenching and cooling processes of various types of mechanical structure members, thick plates directly quenched after rolling and various types of large-size profile steels which are made of microalloyed steels or alloy steels containing various types of components. According to the application of the technique disclosed by the invention, the purpose of obviously improving strength and toughness of large-size workpieces is achieved on the premise of avoiding cracking.

Description

technical field [0001] The invention relates to a heat treatment process for quenching and cooling of various mechanical structural parts, thick plates directly quenched after rolling and various large-size steels, specifically a multi-cycle "quenching-distribution-tempering" process. Background technique [0002] Quenching and tempering (hereinafter referred to as Q&T) is a traditional process, which heats the workpiece to the austenite zone, then quenches it to room temperature to obtain the martensite structure, and then tempers at a suitable temperature for a period of time to obtain Tempered martensite and carbide structure, this process is widely used in the heat treatment of workpieces that require high strength and certain plasticity and toughness. The application of Q&T process in direct quenching after rolling of workpieces such as section steel or steel plate has found that there are problems of quenching cracking and insufficient plasticity. After searching the ...

Claims

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Application Information

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IPC IPC(8): C21D1/78C21D11/00C21D9/00
CPCY02P10/20
Inventor 戎咏华陈乃录
Owner SHANGHAI JIAO TONG UNIV
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