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About Us
Tianjin Xun'er Technology Co., Ltd
Date: 2025-03-13Read: 7
Annealing process in the steel industry is a heat treatment process mainly used to improve the internal structure and properties of metal materials.It involves heating the metal to a certain temperature, holding it for a period of time, and then slowly cooling it down.This process aims to achieve or approach the equilibrium state of the internal structure of the metal, thereby obtaining good processability and usabilityOr to prepare the structure for further heat treatment (such as quenching, tempering).
The purpose of annealing includes improving or eliminating the structural defects and residual stresses caused by metal during casting, forging, rolling, and welding processes, and preventing workpiece deformation or cracking;Soften the workpiece for cutting processing;Refine grain size and improve the mechanical properties of the workpiece;And prepare the organization for the final heat treatment.
The heating medium of the steel production annealing unit is generally coal gas or natural gas, and these combustion media have the risk of explosion. So how to safely and effectively use these energy media?
Process of using furnace mixer N2+H2
Special steel production continuous annealing furnace requires decarburization (partially or completely) for both intermediate annealing and finished annealing，Usually, finished steel requires a carbon content of ≤ 27ppm (1ppm equals one ten thousandth),The lower the better.
Annealing furnace protection gas and decarburization principle:
① Decarbonization mainly relies on the protection of gas through humidification (H2O): H2O+CFe=CO+H2;② Due to the simultaneous reaction between water and iron-based materials:Fe＋H2O=FeO＋H2；Si＋H2O=2H2＋SiO2， Oxidation of the steel plate is also not allowed, so the function of increasing moisture should not only decarburize but also prevent oxidation of the steel plate,It is necessary to strictly control the protective atmosphere, including the ratio of hydrogen and nitrogen (inlet amount), the amount of water vapor (and water temperature), the directional flow of protective gas in the furnace, the distribution of furnace pressure, and the magnitude of furnace pressure differenceOxidation conditions such as iron and silicon in the steel strip must also be avoided as much as possible, and the partial pressure ratio H2O%/H2% must be strictly controlled.
Xun'er on-site application case
A steelmaking enterprise in Hunan Province uses a mixture of H2+N2 gas as the protective atmosphere gas for the continuous annealing furnace of special steel. According to the process requirements, the proportion of hydrogen gas in the mixture concentration is 20%. In order to maintain positive pressure in the furnace and prevent air from entering the furnace, a certain amount of N2 needs to be introduced into the sealed chambers at the inlet and outlet of the furnace body and the nitrogen circulation injection cooling section. When the temperature inside the pipeline reaches a certain level, an additional amount of N2 is addedH2Insulation is required, so the flow rate should be relatively stable. The on-site pipelines of the enterprise are all DN25 caliber, with a working pressure of 50kPa.
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Accurate measurement of the ratio (flow rate) of hydrogen and nitrogen in the protective atmosphere;
2
Flow meters require stable performance;
3
Instruments need to ensure the safety of production;
The nitrogen measurement adopts the LWQ series gas turbine flowmeter with a precision of 1.5% to control the flow rate. Due to the vertical installation on site, no oil injection meter body is selected. The hydrogen measurement adopts the pipeline SFMT series thermal gas mass flowmeter.
The customer adopted Xun'er gas turbine flowmeter and thermal mass flowmeter for measuring oxygen and hydrogen gas in the protective atmosphere of special steel high-temperature annealing process in June 2023. As of today, all flowmeters are running stably and the measurement effect is accurate and reliable. The customer stated that precise control of gas flow is crucial in the high-temperature annealing process of special steel. These two flow meters from Xun'er can accurately measure the flow rates of oxygen and hydrogen, providing stable and reliable data support for the process, ensuring stable improvement in production efficiency and product quality.
Recommended on-site application products
Product Features:
Wide measurement range, complete product models, ranging from DN25-DN400 caliber;
High accuracy, up to level 1.0, with repeatability of up to 0.15% R;
The instrument has intrinsic safety and explosion-proof functions, with a protection level of IP65;
■ With real-time data storage function, it can prevent data loss in case of sudden power failure;
■ Detachable fully enclosed movement structure, strong anti impurity ability, high precision;
Imported precision bearings specifically designed for instruments have good wear resistance and high stability, while also increasing the lower sensitivity of the instrument and reducing the starting flow rate;
Equipped with pulse signal, 4-20mA signal output, and RS485 (MODBUS RTU protocol) communication output;
Product Features:
Measure gas mass flow rate without temperature or pressure compensation;
Large range ratio, measurement flow rate range: 0.1~100Nm/s, no pressure loss, suitable for any shape of pipeline with known cross-sectional area. Corrosion resistant sensor, suitable for measuring corrosive gases;
Plug in sensors can be installed and maintained online;
The expert algorithm for the full range ensures the accuracy of the measurement. Suitable for trade settlement or gas leak detection.