Quick normalizing heat treatment method for Q345R steel

A kind of normalizing heat treatment and rapid technology, applied in heat treatment furnaces, heat treatment equipment, furnaces and other directions, can solve the problems affecting the production efficiency of heat treatment furnaces, excess heat treatment process capacity, long heat treatment cycles, etc., to shorten the heating time and holding time, improve The effect of shortening heat treatment capacity and heating time

Active Publication Date: 2011-08-03
NANJING IRON & STEEL CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the existing normalizing process can guarantee the qualified rate of products, the heat treatment process has excess capacity an

Method used

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  • Quick normalizing heat treatment method for Q345R steel
  • Quick normalizing heat treatment method for Q345R steel
  • Quick normalizing heat treatment method for Q345R steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] For a 38mm thick Q345R steel plate, the normalizing temperature is 910°C, the steel plate enters the furnace at a temperature of 750°C from room temperature, the heating time is 38min (ie 1.0min / mm), heated to the target temperature of 910°C, and the holding time is 32.3min (ie 0.85min / mm), and then air-cooled to room temperature. After normalizing, the microstructure is still ferrite-pearlite banded structure, but the size of ferrite grains and pearlite clusters is significantly smaller than that before normalizing, and the uniformity of the structure is also significantly improved, with a grain size of 9.5 Grade, (according to Chinese national standard GB / T6394-2002 "Measurement method of average grain size of metal"), see attached figure 1 . The various performance indicators are shown in Table 1, all of which meet the requirements of GB713-2008 "Steel Plates for Boilers and Pressure Vessels". The heating time of the slab in the furnace was successfully shortened b...

Embodiment 2

[0020] For the 38mm thick Q345R steel plate, the steel plate enters the furnace at a furnace temperature of 750°C from room temperature, the heating time is 34.2min (ie 0.9min / mm), heated to the target temperature of 910°C, and the holding time is 32.3min (ie 0.85min / mm ), and then air-cooled to room temperature. After normalizing, the microstructure is still ferrite-pearlite banded structure, but the size of ferrite grains and pearlite clusters is significantly smaller than that before normalizing, and the uniformity of the structure is also significantly improved, with a grain size of 9.5 Grade (Using Chinese National Standard GB / T6394-2002 "Measurement Method for Average Grain Size of Metal"), see attached drawing 2. The various performance indicators are shown in Table 1, all of which meet the requirements of GB713-2008 "Steel Plates for Boilers and Pressure Vessels". The heating time of the slab in the furnace was successfully shortened by 28.6%, so as to achieve rapid n...

Embodiment 3

[0022] For the 38mm thick Q345R steel plate, the normalizing temperature is 910°C, the steel plate directly enters the furnace at a temperature of 910°C from room temperature, the heating time is 32.3min (ie 0.85min / mm), and the holding time is 30.4min (ie 0.8min / mm ), and then air-cooled to room temperature. After normalizing, the microstructure is still ferrite-pearlite banded structure, but the size of ferrite grains and pearlite clusters is significantly smaller than that before normalizing, and the uniformity of the structure is also significantly improved, with a grain size of 9.5 Grade (Using Chinese National Standard GB / T6394-2002 "Measurement Method for Average Grain Size of Metal"), see attached drawing 2. Various performance indicators are shown in Table 1, all of which meet the requirements of GB713-2008 "Steel Plates for Boiler and Pressure Vessels". The heating time of the slab in the furnace has been successfully shortened by 32.7%, so as to achieve rapid normal...

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Abstract

The invention relates to a steel tempering process, in particular to a quick normalizing heat treatment method for Q345R steel, which comprises the following steps of: heating: making a steel plate enter a furnace with the temperature of 750 DEG C from a room temperature state, calculating the heating time according to unit thickness temperature equilibrium time of 0.8-1.1 min/mm, and segmentally heating to the target temperature of 910 DEG C, or uniformly setting temperature control areas of a scale-free roller-type heat treating furnace as 910 DEG C and making the steel plate directly enters the furnace with the temperature of 910 DEG C; keeping the temperature: after the steel plate is heated to 910 DEG C, and calculating the holding time according to unit thickness temperature equilibrium time of 0.8-0.9 min/mm for keeping the temperature; and cooling: cooling to room temperature. On the premise of ensuring that various properties meet requirements, the heating time and the holding time are shortened, the heat treatment capacity is improved, and problems that normalizing warmup time is too long so as to make various mechanical properties of steel meet requirements and ferrite-pearlite zonal textures refined, the capacity is lower and the like in the prior art are solved.

Description

[0001] technical field [0002] The invention belongs to the field of metal heat treatment, and relates to a steel tempering process, in particular to a quick normalizing heat treatment method for Q345R steel. Background technique [0003] Q345R steel is the main material for the production of pressure vessels. This steel has high strength, high toughness, good corrosion resistance, good welding performance and cold forming ability. It is widely used in pressure gas tanks, gas cylinders, reactors, heat exchangers, etc. Manufacture of equipment, etc. [0004] During the hot rolling process of Q345R steel, ferrite-pearlite band structure will appear, which has a great influence on the performance of the steel. A steel mill adopts LOI non-oxidizing roller hearth heat treatment furnace to carry out normalizing heat treatment on hot-rolled Q345R steel. This kind of heat treatment furnace uses the self-preheating burner installed in the radiant tube to heat under the nitrogen pr...

Claims

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Application Information

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IPC IPC(8): C21D1/28C21D9/46
Inventor 王道远黄贞益吴俊平王伟姜辉王萍郭怀兵章小峰王发仓
Owner NANJING IRON & STEEL CO LTD
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