A kind of all-ferrite enamel steel for heat exchanger and its production method

Abstract

The invention relates to a full-ferrite enamel steel for a heat exchanger. The full-ferrite enamel steel comprises the following chemical components in percentages by weight: less than or equal to 0.0050% of C, 0.10-0.50% of Mn, less than or equal to 0.010% of Si, less than or equal to 0.020% of P, 0.015-0.045% of S, less than or equal to 0.010% of Als, 0.010-0.055% of Nb, less than or equal to 0.0030% of B and 0.010-0.050% of O; the production method comprises the following steps of pretreating molten iron, smelting, refining and continuously casting by virtue of a converter; heating the cast blank; carrying out hot rolling; coiling and acid pickling; carrying out cold rolling; annealing; finishing for later use. The microstructure of the enamel steel disclosed by the invention is full ferrite, the grain size of ferrite reaches Grade 11, the main inclusions are long-wire-shaped MnS and granular Mn / Nb composite oxides, the precipitated phases are fine NbC / N and BN particles, Rel is 180-240MPa, the tensile strength is 280-360MPa, the elongation is 36-46%, the hydrogen permeation time of the steel plate is equal to or greater than 25min / mm<2>, no scute burst is caused after enamelling, enamel adhesion strength is greater than A1 level and the pinhole rate is less than 10 / m<2>.

Description

technical field [0001] The invention relates to an enamelled steel and a production method thereof, in particular to an enamelled steel for a heat exchanger and a production method thereof, in particular to an all-ferrite enameled steel for a heat exchanger and a production method thereof. Background technique [0002] The heat exchanger corrugated plate is the main component of the heat exchange element in the heat exchanger. It is in direct contact with the flue gas. It needs to have excellent acid and alkali resistance and corrosion resistance. At present, it is mainly made of enamel steel plate. The enamel corrugated plate is formed by rolling cold-rolled steel plate, then coated with a layer of enamel powder, and finally sintered at high temperature. In order to meet the harsh operating environment of the heat exchanger, the enamelling quality of the corrugated plate must be guaranteed, which requires that the steel plate used must have good scale explosion resistance, ...

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Problems solved by technology

The adhesion of the steel plate of this invention is between A1 and A2, which cannot meet the requirements of products whose adhesion is better than A1. At the same time, the optimal range of yield strength suitable for processing corrugated plates of heat exchangers is 200~220MPa, while the invention The yield strength of the steel plate is 148~220MPa, the fluctuation range is wide, and the processing adaptability is poor

[0006] The Chinese patent application number is CN201310486400.3, which discloses an enamelled steel with scale explosion resistance, which is made of the following components and weight percentages: C: 0.0020-0.0050%, Mn: 0.30-0.50%, Si: 0.0050~0.0100%, P: 0.010~0.015%, S: 0.011~0.020%, Als: 0~0.010%, O: 0.011~0.020%, and the balance is Fe and other unavoidable impurities. Less, low production cost, steel plate formability, scale resistance and enamelling adhesion performance meet the requirements for one-time enamelling, but the grain is relatively coarse, which makes the steel plate strength low, high temperature deformation resistance is poor, and cannot meet higher requirements heat exchanger needs

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