selection of mesh belt material for mesh belt quenching furnace

1, preface

the operating temperature of mesh belt quenching furnace is 8 l5 & mdash; 1 150 ℃, generally used between 840 ￠ 920 ℃. Because the workpiece runs at a uniform speed in the furnace, there is no phase movement between the workpiece and the conveyor belt, which has the advantages of small deformation and uniform heating. It is widely used to deal with various medium and small parts. Introduced since the 30s. Domestic has reached hundreds of units. However, due to its structural characteristics, its heat-resistant steel consumption is large and its maintenance cost is high. As one of its three-day parts, the same belt is known to have an effective service life of each [z 0 00O 1 40 0ooh & ldquo; The effective service life of imported mesh belt is about 6,000 h, which does not include premature damage caused by abnormal reasons}. We through research and understanding of the family. After the mesh belt manufacturer found that the mesh belt materials currently used and customized by various users are basically expensive Cr20Ni80. There are occasional children who try 1Cr25Ni20SI2 materials, which reflect that the oxidation problem cannot be solved in use and have to still use Cr20Nis0 materials.

2, the use effect of 1Cr25Ni20Si2 steel belt

the original mesh belt material of our factory mesh belt furnace is Cr20Hi 8 o,_perplexed with diameter blue 1.1ram; I of furnace with temperature at 800 "￠ 900 ℃ is directly quenched and cracked by methanol as protective gas; Medium. The mesh belt has been used for more than 3,000 hours (including scrapping after repeated pressing until it cannot be used). Analysis of oxidation resistance and carburizing resistance of alloy elements in Cr20Ni80 and 1Cr25Ni205 ￣ 2 materials; Cr is the main addition element for oxidation resistance in steel (gold). when 950 C, 2O j Si is required as the auxiliary additive chong. generally, 2 1 3 are added. Ni is mainly used to form austenite in steel to stabilize the matrix structure and has no obvious effect on oxidation resistance. N10 ・ can only be formed when the addition amount is large. Cr., However, cr and si, which have good oxidation resistance, can reduce the absorption of c by steel (Taiwan gold) and the j dispersion speed of c, where Sj plays a role {l! The alliance J and Ni seem to have reduced the absorption of C, but it has accelerated the expansion of C is respect & ldquo; & rdquo;. For 1.1mm static filaments, although the Nj-based lcr 0Ni O gold matrix is stable and has good oxidation resistance, the matrix is easily infiltrated by C and embrittled after the reducing atmosphere is over. At the same time, chromium carbide is generated to make the matrix poor in chromium, thus reducing the oxidation resistance of the matrix. When the furnace is not supplied with protective gas, the oxygen entering the quenching furnace and the residual oxygen in the furnace gas quickly make the matrix, especially the grain boundary, be oxidized first and then embrittled and fractured. ICr25Ni20Si 2 it has good oxidation resistance, and impermeability c is better than Cr20Ni80. So we chose 1Cr25Ni20Si2 material to make mesh belt, and the price of each belt was reduced from I 6,000 yuan to 8 800 yuan, reducing the cost by 45. After I}}j half a year, the effective use time is more than 2,000 h, the mesh belt is intact, and the yarn does not produce brittleness. Originally made of Cr20Ni80 material, the weft heading head was used for more than l 000 h, and the weft heading head fell off sporadically due to corrosion in the reducing atmosphere, causing the stopper at the edge of the mesh belt to fall off, resulting in stress concentration on the same edge on the mesh: the warp wire, knowing that the belt was broken and deformed and damaged {but after making the mesh belt with 1Cr25NiSI2, the weft heading head fell off was found, and the mesh belt stopper was all intact, thereby, it is advantageous to further improve the lifetime of the subband. However, in use, we found that when the mesh belt made of-IC ￠ 25Ni20Si 2 material is not used at rest, the drying surface of the two belts and the part that is sealed in the water of the mesh belt return channel will produce hoop color corrosion. The longer the time, the more serious the corrosion will be, and the part that is immersed in the sealed water surface will be oxidized most seriously. In this way, the surface oxide film of the steel wire is seriously damaged, so that after the mesh belt is used at commercial temperature, the 1 gears of the mesh belt are all embrittled and broken one after another, and the nearby gears are also embrittled quickly. The dry part on the surface of the same belt must be replaced in time without rust spots. We analyzed that this is because the mesh belt material is iron-based metal, and the cut belt wire works in a reducing atmosphere for a long time, and the continuity of the surface oxide film is destroyed by C infiltration. Therefore, once water adheres to the surface, a galvanic cell will be formed to cause oxygen absorption corrosion 2Fe & mdash;te = 2Fei 2H 2O + O + 4e:40H & rsquo; Iron as a negative electrode loses electrons and is oxidized: on the positive electrode of ￣ jFe, oxygen dissolves in dry water to obtain electrons and is reduced. Near the surface of the dense router, the mesh belt is more serious due to the large amount of water and oxygen provided. The mesh belt made of Cr20Ni80 materials is also F than Ban G. The high & plusmn;& rsquo;: friction is seriously deteriorated due to the destruction of the oxide film on the surface.Due to this phenomenon, a layer of green oxidized spider spots will be generated on the wet surface of porridge when the month I is not used, except that NiO and Cr:0 are combined into NiO ・Cr O is indeed resistant to oxidation and dry {and prevents fL from deepening the oxidation corrosion layer. This iron-based 1Cr25Ni20Si 2 material is used to prevent premature damage caused by oxidation: when the mesh belt stops at different J (tuo is not used for a long time), the sealing water at the entrance of the return channel of the belt is completely dissipated. And dry the residual moisture on the net to keep the net belt yuan surface dry. Note that when rescuing the sealed water, if the explosive reducing atmosphere used in the furnace is explosive, the furnace temperature should be lowered to below the gas ignition point, and the water should be drained to prevent the air from being sucked into the furnace from being mixed with the residual furnace gas and exploding, and the heat from being sprayed out to hurt people.

3, other iron-based heat-resistant furnaces

mesh belt furnaces generally have a straight beam of only 1.1ram, so the material matrix is required to be stable in structure, not easy to embrittle after aging, has good oxidation resistance and good thermal fatigue resistance. Generally, the atmosphere in the furnace is mostly carbon-containing & infin; It is also spicy and exhausting, so it is also required that the crucible} material has good impermeability and C- resistance. Jin-based gold Cr20Nis0 has good high-temperature performance, but it is expensive and not suitable for use in a reducing atmosphere. From our trial, it is feasible to use iron-based heat-resistant alloys as long as they are selected and maintained well. The chemical composition of heat-resistant steel (alloy) materials required for making mesh belts is shown in the following table. Among them, 3Cr24Ni7SiNRE is a high-quality low-Ni heat-resistant steel developed in recent years, which has the high temperature performance of excellent fish. The steel has low Ni content, is relatively stable in reducing atmosphere containing C, etc., is not easy to produce intergranular corrosion that often occurs in high-Ni steel, and the cost is lower than 1Cr25Ni20Si2. Due to the addition of rare earth elements, the phenomenon that the grain boundary of superalloy is first oxygen billion at high temperature is effectively prevented, make its high temperature performance has greatly improved & ldquo;. In the case of heat treatment, smelting, controllable non-uniform heating, etc., many problems related to the electromagnetic force of the inductor performance life and energy consumption are gradually exposed, which are worthy of serious solution. At the same time, modern design and control methods have provided conditions for solving these complex dynamic exposition problems. It is important to fully understand the physical characteristics of the material to be heated and its changes and amplitudes in some typical heating processes, as well as its influence on the quality of electromagnetic tillage, so as to more accurately grasp that induction heating is completely reliable for proper maintenance. If necessary, local trial can be taken on a strip to summarize the effect and meet the requirements before popularization and use, only in this way can we truly realize the localization of the attached furnace mesh belt, reduce the use cost of the mesh belt furnace and expand the scope of application.

4, conclusion

at present, the materials of mesh belt used in mesh belt furnaces in our country are basically finished. Full reference to the introduction of equipment models, are used Cr20Nigo, which is not consistent with China is Ni resource-poor national conditions, in the economy is a great waste. I think each user should choose a cheap iron-based heat-resistant disc-containing action belt suitable for their own use according to the use temperature and the atmosphere in the furnace. As long as it is properly used and maintained, it is completely reliable. When necessary, partial trial can be carried out on a strip, the effect can be summarized, and the use can be promoted after meeting the requirements. Only in this way can the localization of the attached furnace mesh belt be truly realized, reduce the use of mesh belt furnace cost and expand the scope of application.