CS208068B1 - Method of making the steel belts for the furnaces dampers - Google Patents

Description

The invention relates to a method for processing cold-rolled steel strips for gates, in particular baking ovens and other food processing machines.

Hitherto known processes in cold rolling mills consist in that steel strips with a weight composition of 0.08%, magnesium 0.13%, manganese 0.53%, chromium 0.05%, nickel 0.08%, sulfur 0.022 %, phosphorus 0.014% are pickled, annealed, cold rolled, annealed, cold rolled, annealed, cut to the required width, quenched and tempered, both surfaces are sanded to remove the decarburized layer, and in the final phase they are laterally divided into the required length. Some rolling mills alternatively emit one annealing or, after quenching and tempering, include grinding of the strip edges in the coiled state (coils) to improve straightness values. The strips thus treated reach a tensile strength of 1300 to 1600 MPa, are resistant to temperatures up to 200 to 250 ° C only, are insufficiently resistant to the effects of flue gases and have low resistance to abrasion at temperatures of about 450 ° C.

The above-mentioned drawbacks are overcome by the method of manufacturing steel strips for the furnace damper according to the invention. The principle of the invention consists in that steel strips with a mass composition of traces up to 0.12% carbon, traces up to 2.0% manganese, traces up to 1.0% silicon, 17 to 22% chromium, 8 to 12.5% nickel and impurities such as phosphorus not more than 0.035% and sulfur not more than 0.030% are annealed austenitising at 1050 to 1200 ° C, after cooling to 20 ° C they are pickled in an acid or salt bath, then rolled with a deformation of 30 to 50%, again austenitizing, annealing, cooling to 15-20 ° C, and reduced by 30-50% by rolling to final thickness. In this way, austenitic: CrNi-based steel processing, ie by gradual rolling up to a degree of hardening φ 0.6, achieves a tensile strength of 1300 MPa and other adjustments to achieve other dimensional properties such as straightness, thickness and width tolerances, Resistance to flue gas and temperature 450 ° C.

A particular method of cold rolling of the strip from a starting thickness of 3 mm to a final thickness of 0.90 mm and a starting width of 310 mm to: a final width of 300 mm was carried out on steel containing max. 2%, silicon max. 1%, phosphorus max. 0.035%, sulfur max. 0.030%, chromium 17-22%, nickel 8-12.5%.

After continuous annealing at 1100 ° C with a min. 2 min. the strips were cooled with water to 20 ° C and then continuously pickled in a salt bath - sodium hydroxide, sodium nitrate, borax in the bath for 3 to 6 min. Continuous refilling, hydrocarbon + nitric acid -I- sulfuric acid + water bath, in bath 3 min. Continuous rinsing with hot water, brushing

208 088 insulating brushes. Rolling on a quartostable 0 work rolls 160 mm draws from a starting thickness of 3 mm to a thickness of 1.60 mm. Continuous annealing, 1100 ° C in a protective atmosphere of 75% hydrogen, 25% nitrogen with a temperature of 20 ° C. Rolling on a quarto table with a working roll diameter of 160 mm draws from a starting thickness of 160 mm to a thickness of 0.91 mm. Cutting to a width of 300 mm on the longitudinal dividing line by both sides cutting longitudinal edges of the strips. Rolling on a quarto table with a working roll diameter of 160 mm, the surface of rollers with a roughness of max R _a = 0.4 to a final contract thickness of 0.90 mm. Cutting and straightening with a roller straightener with transverse dividingip into contract lengths, stripes and contract flatness.

Further examples of the method of processing are conditioned by the required dimensions of the finished strip or strip and other necessary qualities of the waist or strip. >

They are also conditioned by the cold rolling mill production equipment. For example, it can be used for pickling other types of baths, other types of rolling mills with other diameters and shapes of working rolls and hence other spinning. Further other variability of the treatment method is possible, provided that the degree of hardening φ corresponding to the chemical composition of the austenitic steel used and the final other desired strength of the strip or strip is achieved in the final rolling.

The strips or strips treated in this way can be used for the manufacture of sliders of food, especially bakery ovens and other ovens, or in other facilities where a tensile strength of about 1300 MPa, a temperature resistance of 450 ° C or higher, resistance to chemical effects or flue gases are required. at this temperature and abrasion resistance.

Claims (1)

Method for producing steel strips for furnace gate, annealing steel strips, pickling them and cold rolling, characterized in that strips of steels with a weight composition of up to 0.12% carbon, traces of up to 2% of manganese, traces of up to 1% of silicon, up to 22% of chromium, 8 to 12.5% of nickel and impurities such as phosphorus not more than 0.035% and sulfur not more than 0.030% are annealed austenitizing at 1050 to 1200 ° C, after cooling to 20 ° C they are pickled in an acid or salt bath after which they are rolled with a deformation of 30 to 50%, re-annealed by austenitization, cooled to a temperature of 15 to 20 ° C and reduced by 30 to 50% by rolling to a final thickness.