DE2624299A1 - Wear resistant alumina refractory - with negligible shrinkage on sintering suitable for sliding stoppers used for molten steel (NL061276) - Google Patents

Abstract

Hydraulically setting refractory concrete is used to make wear-resisting parts which come into contact with molten metals. The concrete has a high alumina content, and the dried green product has a cold compression strength (CCS) of >=400 kp/cm2 which, after sintering at 1400 degrees C attains a CCS of >=700 kp/cm2 with a dimensional stability at 1400 degrees C better than plus-or-minus 0.2%. The pref. concrete contains corundum and active alumina, plus an alumina cement contg. less than 22% CaO, and possible a liquefier, the resulting analysis being 96% min. Al2O3, 3% max. CaO and 0.5% max. SiO2. Up to 5% of the alumina additions can be replaced by a substance forming a spinel, pref. MgO, or by soot, pitch or graphite; and >=7% chromium oxide may be included. Used to make stopper plugs or bushes, and esp. the moving or stationary plates in sliding stoppers used on vessels holding molten steel, where the molten jet of steel is up to 120 mm dia.

Description

"Wearing Parts for Containers Containing Molten Metal" The invention refers to wearing parts that come into contact with metallic melt, such as stoppers, sleeves, in particular closure plates for slide valve closures on molten steel containing containers.

Wear parts are generally parts that after reaching a Wear limit must always be renewed or replaced in order to achieve the Not to endanger the safety of the units operated with them. They are mostly exposed to high thermal, chemical and possibly erosive attacks and In some cases, considerable strength loads must also be applied withstand. This is the case, for example, with closure plates for slide locks Prerequisite that the slide plate despite changes in shape, which the refractory Plate material is exposed to unavoidable temperature differences, with more reliable Sealing remains perfectly movable and the pair of plates with regard to the thermal, chemical and erosive attacks of the flowing melt with controllable Pouring stream cross-section withstands at least one emptying of the container.

To date, wear parts have been used for such and similar loads Made of high quality dry, semi-dry and plastic refractory fabric compositions in relatively complex tamping, shaking and pressing processes with more or less expensive post-treatment. Wear parts with appropriate training must be precisely adhered to with regard to temperature and time after expiry of Heat treatment process in addition to a careful metal-cutting deformation. For example, on panels of slide gate valves, the surfaces are that with others Surfaces should work together to form a seal with ease of adjustment, extremely to grind. But also holes, grooves or the like. Are often by cutting Deformation provided, so that primarily a fitting, mechanical processing Required wearing parts cause considerable production costs.

The present invention has set itself the goal of producing To simplify refractory wear parts using certain conditions fulfilling refractory concretes, which at the same time are new, and are not easily understood by experts Risks should be made accessible to areas of application avoided.

For this it can be assumed that the experts use it of concrete moldings, for example as fireproof sealing plates on the spout of a The container used to pour off steel was considered hopeless, especially with regard to the extraordinary caused by the outflowing melt Stresses consisting of sudden and severe temperature shocks erosive wash-off effects of the pouring stream up to 120 mm thick.

The object set is achieved according to the invention through the use of a hydraulically setting high-alumina refractory refractory concrete with an am cold compressive strength of at least 400 Kp / cm² measured on the dried scented product. which is at least 700 kp / cm2 after fire at 1400 ° C and a dimensional stability at 14000 C of at least + 0.2ob for those in contact with molten metal Wear parts, in particular for the slide and / or base plate of slide locks on containers containing molten steel.

In this way, the production of plate pairs in particular can be carried out for slide closures, since concrete is poured into a mold adapts to the shape of the surface exactly and smooth, clean surfaces of the shape are also smooth, Provide clean mating surfaces on the molded body. Consequently, it is possible to use the sliding surfaces of slide plates with great accuracy already during of shaping of the plates, so that tedious mechanical reworking is no longer necessary. Likewise, the flow openings can be molded directly and so the plates in finished State.

The high-alumina concretes with the prescribed physical Properties ensure the operational safety of wear bodies made from them also against high stresses due to thermal stresses as well as chemical and erosive attacks. It is of great advantage if the refractory concrete is corundum and has active alumina as aggregates and has less than 15% alumina cement Does not contain more than 22 lime, if necessary a liquefier added and the analysis is preferably at least 96 A1203, less than 3% Ca0 and less contains than 0.5% SiO. The high proportion of A1203 has a beneficial effect on the resistance to temperature changes of the concrete molding. In addition, there is also one for resistance to temperature changes favorable total porosity between 23 and 27 VolVo an exclusively for example open pores that are ideally suited for tar watering.

In the case of the aggregates corundum and active alumina, the proportion is the clay expediently between 5 and 15%, according to a further feature of the invention may be particularly useful for certain applications 1 to 5% of the aggregates through a spinel-forming substance, preferably MgO or MgO-supplying compounds. The magnesia contained in concrete reacts at around 10,000 ° C with those formed after the binder has been dehydrated Decomposition products to spinel, MgO.Al203. This makes the structure of the concrete stronger and more dense and consequently more resistant to infiltration of molten steel and against slag attacks, when they occur in the steel bath, spinel formation already occurs is done. Instead of MgO, NiO, CoO and ZnO as well as compounds, which form these oxides, use.

If there is a further increase in the slag resistance of the molding if desired, this can be done by adding up to 50/0 carbon black or graphite happen.

In some cases it is advisable to use up to 7% of the aggregate To replace chromium oxide in order to wetting the molded body by liquid melt and counteract slag. Also lie. expedient the aggregates below C, 5 mm in round grains, which is additional for the strength of the moldings brings a positive effect.

The manufacture of a refractory wear part is below on the basis of a mixture, grain size and property values of five within the framework of the Invention lying refractory concretes containing table described.

In a shape corresponding to the shape of a slide plate, a Pour concrete according to items 1 to 5 and vibrates. That subsequent setting and hardening took 12 hours. Remained after molding the plate stand for 48 hours at room temperature, then one of the manufacturing process to be subjected to final drying at 1100 C.

To test the strength values at higher temperatures, the Plate initially heat-treated at 6000 C and cold compressive strength after cooling measured The process was repeated at 14,000 ° C.

The burning shrinkage given in the table after the fire at 14,000 C in% is identical to the dimensional stability of the refractory concrete required according to the invention.

Notes on the usability of refractory concrete for wear parts The peeling test is particularly useful for the pair of sliding plates.

The following conditions are linked to this: A 100 x 100 piece of plate mm with a smooth (ground) surface is applied to a zone of approx. 30 mm in diameter using an autogenous sheet suitable for burning through 20 to 30 mm thick sheet metal Welding torch heated.

The oxygen pressure is 2.5 atmospheres, the pressure of the acetylene gas 0.5 atm. The distance from the nozzle of the torch, held by a tripod, to the plate is 50 mm and the test time is 1 5 sec.

If there is no chipping, then the material is very suitable for Manufacture of pairs of plates for slide closures. The material can be used if particles are detached when the test specimen is subsequently scratched, but useless as soon as chips occur during the test.

Example 1 2 3 4 5 Sintered corundum with 99% Al2O3 3.15 - 6 mm 17.50 17.50 17.50 17.50 17.50 1 - 3.15 mm 22.50 22.50 22.50 22.50 22.50 0.5 - 1 mm 7.50 7.50 7.50 7.50 7.50 0.09 - 0.5 mm 12.50 12.50 12.50 12.50 12.50 Chromium oxide> 0.09 mm 21.00 16.00 21.00 15.00 16.00 active alumina> 0.09 mm - 5.00 - - - Alumina cement with 80% gt 0.09 mm 9.00 9.00 5.00 11.00 9.00 Al2O3 and 19% CaO - mm 9.95 9.95 9.95 13.95 9.95 Liquefier for high alumina cement (polyelectrolyte) - 0.05 9.95 Mg0 gt 0.09 mm - 0.05 0.05 0.05 0.05 graphite flour - - 4.00 - -water addition (1/100 kg % 100.00 100.00 100.00 100.00 100.00 dry water) Cold drying strength (Kp / cm²) 1000 8.0 6.0 6.0 5.0 6.0 after drying at 110 ° V 1000 720 550 550 1200 630 after heat treatment at 600 ° C 1000 720 550 550 1200 560 * after firing at 1400 ° C 810 1200 1200 1200 1080 * total porosity after heat treatment at 600 ° C, (Vel. -%) 24 22 23 23 27 * Burning shrinkage after the fire at 1400 ° C, (%) +0.1 +0.2 +02 -0.1 +0.1 * * = reduced fire

Claims (8)

Claims 1. Use of a hydraulically setting high alumina refractory concrete with a cold compressive strength measured on the dried raw product of at least 400 kp / cm2, which after fire at 1400 ° C is at least 700 kp / cm2 and a dimensional stability at 14000C of at least + 0.2% for with molten metal wearing parts coming into contact. 2. Use of a refractory concrete with corundum and active clay as Aggregates, an alumina cement containing less than 22% lime and, if applicable a liquefying agent and an analysis of at least 96% Al 2 O 3, less than 3% CaO and less than 0.5% SiO2 for the purpose of claim 1. 3. Use of refractory concrete according to claim 2, d a d u r c h g e k It is noted that up to 5% of the aggregates are formed by a spinel Substance preferably MgO or MgO-supplying compounds are replaced. 4. Use of refractory concrete according to claim 2, d a d u r c h g e k It is noted that up to 5% of the aggregates are caused by soot, pitch or graphite are replaced. 5. Use of refractory concrete according to claim 2, d a d u r c h g e k It is noted that up to 7% of the aggregates have been replaced by chromium oxide. 6. Use of refractory concrete according to claims 1 to 5, d a d u Noted that the aggregates are less than 0.5 mm round Grains are present. 7. Use of refractory concrete according to claims 1 to 6 for the slide and / or base plate of slide closures on containers containing molten steel. 8. Use of refractory concrete according to claims 1 to 7, d a d u Noted that the molded wear parts are soaked with tar are.