METHOD OF PRODUCING A SURFACE,SUITABLE FOR SPECTRAL ANALYSIS,BY MEANS OF CUTTING WORK IN A METAL TEST PIECE

Abstract: Method of producing a surface suitable for spectral analysis of the material in the test piece by means of cutting work in a metal test piece (10). The invention is characterised in that an opposing member (11) is adjusted against one lateral surface of the clamped test piece (10) after which a grinding wheel (13) is fed through the surface material of the test piece which bears against the opposing member.

Description: METHOD OF PRODUCING A SURFACE, SUITABLE FOR SPECTRAL ANALYSIS,. BY MEANS OF CUTTING WORK IN A METAL TEST PIECE The present invention relates to a method of pro¬ ducing a surface, suitable for spectral analysis of the material in the test piece, by means of cutting work in a metal test piece. Before steel furnaces are tapped, it is absolute- ly essential that the composition of the molten metal, particularly with regard to carbon content and any alloying substances which may occur, should be kept within predetermined close limits. It is therefore necessary to take continuous samples of the melt which samples must be quickly analysed since a continuous alteration in the composition of the steel melt takes place so long as the melt is in the steel furnace. In recent times, computerized spectral analysis appar¬ atuses have been increasingly used to determine the composition of the melt. Such apparatuses provide rapid information about the composition of the melt but they require a test piece of homogeneous material from the melt to be available. A part of this test piece is melted in a protective atmosphere, for example by means of laser beams, and only after this the spectral ana¬ lysis can take place. The time which passes from taking the sample out of the steel furnace until a homogeneous portion of the sample can be melted for spectral ana¬ lysis, is still unsatisfactorily long. Since certain alloying substances which are used in steel production are volatile and therefore disappear relatively quickly from the melt in the furnace, it is desirable that this time should be further shortened. In order to obtain a homogeneous material which can be melted to carry out the spectral analysis, the test piece is machined, for example by grinding or mil¬ ling the material, since it is necessary to remove the outer layer of the material which is not representative of the composition of the melt. For harder material there is, today, only one conventional method of grind¬ ing, with which cooling water must be used to prevent the machined surface from being tempered or undergoing metallurgical change during the machining. This method takes about 30 seconds which is regarded as being too long a time. It is also known to mill metal samples of softer material but this involves problems for the laboratories because cutting data must be calculated in order that a -correct cutting work may take place without risk of the surface of the workpiece obtained undergoing change. Furthermore, it is absolutely essential that no residues of the cooling medium should remain when the "clean" surface of the workpiece thus obtained is melted, since the protective atmosphere in which the melting takes place would then be destroyed, as a result of which there is a risk that the result of the spectral analysis will be unreliable. Since all metal materials can be cut and the sur¬ face of the material thus obtained is satisfactory for analysis without further machining, experiments have been carried out in which a bakel ite-bound cutting wheel cuts the whole cutting depth in one passage with a high speed of feed. This cannot be done without problems, however, because the test piece which is to be machined often consists of a cylindrical body with a diameter of about 35 mm and a thickness varying between 8 and 15 mm and because a homogeneous "pure" material in this body is found about 1.5 mm above the "bottom surface" of the test body. This means that the cutting must not leave behind a tempered surface or a surface the material of which has undergone a metallurgical change. In order that a cutting machine may be able to be used in this connecti ' on, this must have adequate rigidity, which means that the machine becomes large and expensive while at the same time suitable cutting wheels must be developed which permit the necessary sharpening so that the shape of the cutting wheel can be retained. The object of the present invention is to provide a method which permits cutting of a metal test piece in one passage by means of a conventional grinding wheel, while at the same time the problems given above are substantially eliminated. This object is achieved according to the present invention by the fact that the method has the features given in claim 1. As a result of the fact that an opposing member is adjusted against one lateral surface of the test piece which is to be machined and the grinding wheel is then fed through the material in said lateral surface, the grinding wheel is prevented from being inclined or be¬ ing fed obliquely through the material. This in turn means that comparatively thin grinding wheels can be utilized for the necessary machining of the test piece. It is advisable to allow the grinding wheel to cut material both in the test piece and in the opposing mem¬ ber and the method according to the present invention can be used to advantage when the material in a plural¬ ity of test pieces has to be analysed and the opposing member also consists of a metal sample, the composition of which is to be analysed. For example, a grinding wheel with a thickness of 3 mm can be fed through the test pieces and cause a cutting work of 1.5 mm in each test piece. The invention is explained in more detail below with reference to the accompanying drawing in which FIG 1 shows, diagrammatical-ly, one variant of the method according to the invention, FIG 2 shows another variant, and FIG 3 shows a third variant. Reference is first made to FIG 1. Before cutting takes place in a test piece 10, this is clamped, after which an opposing member 11 is adjusted and located against the "bottom surface" of the test piece. After this, a grinding wheel 12 can be fed effectively and quickly through the test piece cutting away the region 13 marked by a chain line in the test piece. The machined surface thus obtained displays an insignificant rise in temperature immediately after the machining. This applies, of course, provided that the composition of the grinding wheel and the speed of feed through the material are selected in a suitable manner. It is a prerequisite, however, that the feed effect through the material should be sufficiently great and that the abras¬ ive grains in the grinding wheel cause a correct cutting action in the material. For test pieces of hard metal material this can mean that a comparatively "loose" grinding wheel is used, that is to say the grinding wheel is worn comparatively quickly during the machining. In order that the wear of the grinding wheel may be uniform, when the grinding wheel is fed through the test piece, the grinding wheel can cut both through the test piece and the opposing member in which case it is appropriate to use as an opposing member a test piece which was machined in a previous grinding operation, naturally on condition that the cooperating surfaces between the test piece and the opposing member have the same cross-sectional shape. This is shown in FIG 2 in which the opposing member 11 is also assumed to be a test piece and the region 13 cut away by the grinding wheel 12 is situated partly in the test piece 10 and partly in the opposing member/test piece 11, for example to an equal extent in each. According to the present invention, it is also possible - as shown in FIG 3 - to use an opposing mem- ber in the form of a bar 14 which is the subject of cutting when the test piece is machined. The bar is displaced after each cutting to be adjusted against the following test piece. By this means it is possible to control the wear of the grinding wheel on one side, which in many cases may be adequate to avoid a continu¬ ous sharpening of the grinding wheel before each cutting operation through the test piece. For certain metal materials, however, it may be necessary to sharpen or trim the effective surface of the grinding wheel before the grinding wheel is fed through the test piece and the material of the opposing member. The method according to the present invention can also be used to advantage for machining rectangular test pieces for example, which for certain qualities of steel are kept by the manufacturer for up to five years after delivery of the material from which the sample was taken. The opposing member, which can be shaped like another test piece, thus has the same shape as the first test piece and is adjusted against the whole surface which is to be machined in the first test piece. The various clamping means, feed devices, etc which are necessary for carrying out the method according to the invention can easily be produced by one skilled in the art and do not constitute part of the present inven¬ tion, for which reason they are not described in detail here.

Claims: CLAIMS 1. , A method of producing a surface suitable for spectral analysis by means of cutting work in a metal test piece, c h a r a c t e r i s e d in that an opposing member (11) is adjusted against one lateral surface of the clamped test piece (10) after which a grinding wheel (12) is fed through the surface material (13) of the test piece which bears against the opposing member. 2. A method as claimed in claim ^ c h a r a c ¬ t e r i s e d in that apart from the cutting machining of the test piece, cutting machining of the opposing member (11) is effected at the same time by means of the grinding wheel (FIG 2). 3. A method as claimed in claim 2, c h a r a c ¬ t e r i s e d in that the opposing member (11) also consists of a test piece. 4. A method as claimed in claim 2, c h a r a c ¬ t e r i s e d in that a test piece which was exposed to cutting work in a preceding grinding operation is used as an opposing member (11), a uniform wear and/or self-sharpening of the grinding wheel (12) being achieved. 5. A method as claimed in claim 2, c h a r a c - t e r i s e d in that a bar material (14) is used as an opposing member which is successively used up during machining of the test pieces (10) (FIG 3). 6. A method as claimed in one of the preceding claims, c h a r a c t e r i s e d in that the cutting takes place in one passage, the feed of the grinding wheel (13) through the material being effected with such a speed that the frictional heat generated during the cutting is low and/or is substantially carried away by the material cut away and/or abrasive particles eroded from the grinding wheel. 7. A method as claimed in one of the preceding claims, c h a r a c t e r i s e d in that a cutting away of 1 - 2 mm takes place. 8. A method as claimed in one or more of the claims 2 - 7, c h a r a c t e r i s e d in that the grinding wheel (13) is sharpened before being fed through the test piece (10) and opposing member (11), respective¬ ly.

Inventors: PERSSON A
Applicants: MASSAB MASKIN OCH SMIDE AB, PERSSON A
Application year: 1981
Main classification: G01N1
IPC codes: G01N1, G01N33