GB2086040A

GB2086040A - Molten metal sampler

Info

Publication number: GB2086040A
Application number: GB8033394A
Authority: GB
Original assignee: British Steel Corp; Land Pyrometers Ltd
Current assignee: British Steel Corp; Land Pyrometers Ltd
Priority date: 1980-10-16
Filing date: 1980-10-16
Publication date: 1982-05-06

Abstract

A molten metal sampler has a uniform bore silica tube (1) open at both ends and surrounded along its length by a sleeve of refractory material (2) to which it is sealed at one end. The sample is obtained by immersing this end together with the bulk of the tube into the melt for a period sufficient for the sample to freeze within the bore. <IMAGE>

Description

SPECIFICATION Improvements in molten metal samplers This invention relates to molten metal samplers, that is, devices for extracting a sample of molten metal e.g. steel, for analysis during melting, refining or processing. The invention is particularly concerned with obtaining samples suitable for hydrogen analysis.

Hydrogen analysis is conventionally effected by melting a short length of the sample and measuring the quantity of gas evolved. This most conveniently requires the sample to be in the form of a thin rod or 'pin' which is homogeneous throughout and without cavities or voids.

A variety of designs have hitherto been adopted to obtain such samples, incorporating tubular moulds from which the solidified pin samples can be extracted after quenching but difficulties have often ensued in obtaining a sufficiently clean sample suitable for hydrogen analysis. For example, the gases, casting powders etc., must be properly vented so as not to impede the consistency of the sample and the metal must solidify in the mould so as not to run out on withdrawal. The problem is made more acute when samples are extracted from the mould in a continuous casting machine since it is most important to avoid splashing metal over the inner surfaces of the continuous casting mould on immersion of the sample; 'outgassing' that is, exhaustion of gases from the sampler itself on immersion compounds this problem.A solution has been adopted by utilising a suction technique, but the use of such 'evacuated-space' devices in a steelworks melting shop/casting bay environment is fraught with difficulties.

It is an object of this invention to provide an improved molten metal sampler which mitigates this problem.

From one aspect, the present invention provides a molten metal sampler comprising a refractory tube of uniform bore, open at both ends and surrounded along its length with a heat insulating sleeve of refractory material to which it is sealed at one end, the sample being obtained by immersing said one end together with the bulk of the tube into the melt for a period sufficient for the metal sample to freeze within the bore.

The refractory tube may be made from silica or quartz and the sleeve may comprise a ceramic fibre, e.g. an alumino-silicate; this sleeve may be in contact with the tube along its whole length or only at its said one end and a refractory cement may be provided by which the fibre is positively secured to the tube mould, and more importantly, the exposed end sealed to it. The tube may depend from a holder, a cranked lance being inserted in the holder (or alternatively into the 'exposed' end of the refractory sleeve) in order to effect immersion.

In order that the invention may be fully understood, two embodiments thereof will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a longitudinal section through one design of sampler; and Figure 2 is a longitudinal section through another design.

Referring now to Figure 1 a thin-walled silica tube 1 has extending along its length an outer sleeve 2 of a ceramic fibre material, e.g. Triton Kaowool. The ends are sealed by a refractory cement 3, which additionally acts to secure the sleeve firmly to the tube, and around one end is wrapped paper 4 which enables the sleeve subassembly to be force-fitted into a cardboard tube 5 which acts as a holder. Finally a cement 6 is applied over the inner end of this cardboard tube to assist in securing it to the sub-assembly.

As mentioned, this design is particularly suited to obtain for hydrogen analysis metal samples from the mould of a continuous casting machine.

Thus, in operation the holder 5 is pushed on to a lance and the tube is immersed vertically into the molten metal in the mould -- which of course is very near the liquidus temperature -- to a level close to the end of the holder 5. The sampler is then withdrawn after 5 or 6 seconds carrying with it the pin of metal within the tube 1 , the design being such that this period of immersion is sufficient to ensure that the pin solidifies and does not discharge during removal. Following removal the sampler is water-quenched, and struck on a hard surface to break up and reveal the pin sample intact.

Typical dimensions of the sampler employed are: internal diameter of silica tube 1 - 7/9 mm; outer diameter of fibre sleeve 2 - 20 mm; length of sleeve/tube sub-assembly - 1 75 mm.

In Figure 2 an alternative, simpler, design is depicted comprising the silica tube 1 which is surrounded along its length by the sleeve 2 the forward end of this sleeve being crimped or closed up on to the tube end so as to secure it. The adherence may be improved by a cement layer 3 as before.

With this design it is possible to dispense with the cardboard tube, the lance being directly pushed on to the exposed end of the sleeve 2.

Typical dimensions are; internal diameter of silica tube 7/9 mm; outer diameter of fibre sleeve 35 mm and wall thickness 6 mm.

In practice it has been found that there is little or no outgassing when either design of sampler is plunged into the melt, there is no splashing over the mould and there is little or no adherence of metal over the outer surface of the sleeve enabling a clean sample to be obtained.

The invention is not restricted to the dimensional limitations given, of course, and further although the particular embodiments have been described with reference to sampling in a continuous casting mould, it is to be understood that sampling could alternatively be obtained from a ladle or ingot particularly if a consumable metal disc were to be placed over the leading end to withstand plunging through the slag layer.

Claims

1. A molten metal sampler comprising a refractory tube of uniform bore, open at both ends and surrounded along its length with a heat insulating sleeve of refractory material to which it is sealed at one end, the sample being obtained by immersing said one end together with the bulk of the tube into the melt for a period sufficient for the metal sample to freeze within the bore.

2. A sampler according to claim 1, in which the sleeve is substantially in contact with the tube along its whole length.

3. A sampler according to claim 2, in which a tube of cardboard or the like is force fitted over that end of the sleeve remote from the said one end.

4. A sampler according to claim 1, in which the sleeve is crimped on to the tube at the said one end and is in contact therewith only at said end.

5. A sampler according to any one of claims 1 to 4, in which the sleeve is positively secured to the tube at the said one, or at each, end by a cement.

6. A sampler according to any one of claims 1 to 5, in which the refractory tube is made from silica or quartz.

7. A sampler according to any one of claims 1 to 6, in which the sleeve is made from a ceramic fibre.

8. A sampler according to any one of claims 1 to 7, in which a consumable metal disc is placed over the sampler at the said one end.

9. A molten metal sampler substantially as herein described with reference to the accompanying drawings.