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In document Metallography (Paper & Discussion) (Page 48-62)


The PRESIDENT, in moving the vote of thanks recorded in the

"Proceedings," said before they entered upon any discussion he felt the first thing members desired him to do was to express on their behalf their gratitude to Major Law for his excellent contribution. He moved that a hearty vote of thanks be accorded to Major Law. He thought the author was to be congratulated, not only upon the able manner in which he had presented the subject, but also for the long, and arduous, and patient research, which had preceded it. It had been a surprise to him that it had been left to this late date for the subject to come before the professional circles in Victoria. It was quite 14 or 15 years ago since Professor Ewing made his first com- munication to the Royal Society, and since then men like Arnold Stead, Rosenhain, and others ha•d followed it up. It was use- less to attempt a discussion of such a highly technical paper at that meeting, but they could not refrain from expressing their thanks to Major Law. He would like to have that supported by members and visitors.

Mr. J. A. SMITH said he had great pleasure in supporting the President. Looking through one of his old letter-books, he had come upon a letter to Major Law, dated just seven years ago, asking for the . very paper they had heard that night. The President and Mr. Clements had been able to bring further friendly pressure to bear upon Major Law, and they had had the paper, and would profit by it. It would be seen that the material which had been placed before them was not a casual compilation, but that it represented the digested material that Major Law had been collecting not only for seven years, but for longer. Discussion would be inopportune at that stage, and he would therefore content himself with supporting the vote of thanks.

Professor HENRY PAYNE said it was with very great pleasure he supported the vote of thanks to Major Law. The paper had touched upon a subject that was now becoming the province of the engineer. They were doing a certain amount of that work at the University. Mr. Higgin had the work in hand, and next year they would have special courses in Metallography for the students. The work Major Law had contributed that evening was most interesting and fascinating, and he would like to add his personal tribute to Major Law for what he had done.


Mr. J. SHEPHERD concurred in the appreciation that had been expressed. He had dabbled in the matter for many years, and he also had practical dealings with metals in various ways. It gave one rather a fearsome feeling to know what things had been happening at various times. As Major Law had said, a great deal of rule of thumb went on in practical manufacture to-day.

There would have to be some educating influence at work upon those who were employed as well as upon themselves. He believed the day would come when special education would be a necessity in ordinary manufacture, just as it was a necessity in the exact work that was performed at the laboratory. He had had great pleasure in listening to Major Law, and he well deserved the thanks of the Institute for his lecture.

Mr. R. J. FI-ETCHER said he wished to take the opportunity of thanking members for the courtesy extended to the Society of Chemical Industry, in giving them the opportunity of hearing such an intensely interesting paper. The subject was one that could not be discussed at a moment's notice. There was so much matter in it that required very serious and prolonged thought. But the Society which he represented had one object in common, that was to draw together those who were of one vocation, and have meetings where they could exchange ideas and discuss matters of great scientific interest. And in that respect he thought chemistry and engineering joined hands.

Although the matter Major Law had placed before them touched the province both of chemistry and physics, it was the chemical aspect which most concerned and interested him. He occa- sionally studied the properties of metals, and the composition of alloys. Last month they had interesting papers on the corrosion of iron, and the preservation of iron. At their next meeting they were to have a paper on the physical structure of iron and steel, a subject which, perhaps, might interest some members of the Institute of Engineers. He could assure the members of that Institute of a very cordial welcome to the meetings of the Society of Chemical Industry. He thanked the Institute for the great pleasure which had been afforded him in giving him an opportunity of hearing such an interesting 'paper, and heartily supported the vote of thanks.

Mr. ANKETELL HENDERSON, on behalf of the Photographic Association, thanked the Institute for the kind invitation to

DISCUSSION—METALLOGRAPHY. I07 attend the meeting. Major Law was an old member of their society, and it was very nice to see him again, doing such good and useful work. They had all enjoyed themselves, and would look forward to reading the paper, which the President had kindly promised to send to visitors.

Mr. WM. CHAS. ROWE supported the motion. He thanked Major Law for having given him personally a very pleasant evening. He had touched on the outermost fringe of the sub- ject, and Major Law had whetted his interest. The lecturer had shown a number of slides in which he pointed out where the metals had separated from the alloys. He took it that a true alloy was equivalent to a saturated solution ; when they got beyond saturation, they had separation. Having obtained a pure alloy, had it anything of the character of the metal they were dealing with? Take gun-metal, for example. When they examined it under the microscope, they found that the excess metal had separated out. If it were possible to treat that so that there was no separation, would it then be gun-metal? Was not one of the most important points of the alloys due to the separation out of excess metal?

Mr. D. AVERY said, in connection with the invitation the President of the Society of Chemical Industry had given to attend the next meeting of their society, he thought it was his duty, after hearing Major Law's paper, to inform them that he was only an amateur in the profession, in which Major Law was an expert. He proposed to traverse a good deal of the same ground that Major Law had taken. He wished to express his appreciation of the paper. Having discovered some of the difficulties of the work, he could appreciate the success that had been attained.

MAJOR LAW, in responding, thanked those present for the patient hearing they had given him. He was only too con- scious of his shortcomings in the matter. It was a very large subject, and a difficult subject to deal with in an hour and a half. There were so many facts which were new when they turned their attention to certain fields, which had to be driven


home again before they tried to build up. He had done his best to do that, and if he had succeeded in any way he was more than satisfied. He was looking forward to hearing Mr. Avery's paper on "Iron. and Steel" at the meeting of the Society of Chemical Industry. Mr. Shepherd had said it made one almost afraid as to what the results would be. MetallographY was not as common as football, but Mr. Shepherd would find that some of the men in his works could tell him what won the Hurdles 5o years ago. However, if some of those men had encouragement to follow up their work with something to exec' vise their brains it would be found that they would be quite equal to the task.

As to Mr. Rowe's question, the simplest alloy, probably, was gold and silver. In any proportions of gold and silver one could not get any separation. What was an alloy? One could not say that an alloy was a chemical compound or a mixture, or merely a mechanical mixture. It was a mixture of two metals for commercial purposes. Take the case of an ordinary bear- ing in an engine. One first of all got a plastic base, in which some harder constituent had separated, and which would give to the bearing its wearing surface, whilst the plastic portion would allow for irregularities of pressure. 'The question with regard to bronze was rather complicated. If they removed the copper and tin compound from the bronze the alloy would lose its characteristics ; the alloy they must look upon as being a mix- ture of metals, with properties differing from the components, and valuable from .a commercial aspect. One could not make any definite statement that an alloy was a chemical compound or mixture that would be applicable in every case. He did not know whether the reply satisfactorily met Mr. Rowe's question.

Mr. ROWS said he thought Major Law agreed with him in the opinion that it was purely a commercial combination.

The PRESIDENT said a number of scientific bodies in England formed a committee called the Alloys Research Committee, which embarked upon a complete investigation. He had had the pri- vilege of hearing a series of lectures at the Royal Institute when the question of the alloys of aluminium and zinc was discussed.

When the proportions of the two ingredients were nearly alike' when they approached 5o per cent., say 40 per cent. of one and 6o per cent. of the other, in the majority of cases the alloys were

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industrially useless. They were only useful when there was a small percentage of one and a large percentage of the other.

That was very marked in the case of those particular alloys, and it was stated as a general proposition that if the two materials Were almost in the same proportions, they were industrially use- less from the point of view of having valuable physical proper- ties, such as strength, hardness, tensile resistance, and so on.

On behalf of the Institute he cordially thanked Mr. Fletcher for the invitation to attend the meetings of the Society of Che- mical Industry.

Discussion adjourned.

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Discussion closed.

DISCUSSION—METALLOGRAPHY. 123 far unequally check the rate of progress of floods, that a simul- taneous rainfall over the whole watershed would fail to give syn- chronising effects on the main stream.

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The PRESIDENT declared the discussion on Major R. Law's paper on "Metallography" open, and invited visitors to take part therein.

Mr. A. J. HIGGIN said that Major Law had explained the sub- ject of MetalIography in an admirable manner. It was a very large subject, but Major Law had contrived to touch upon all the important points in a short space of time.

Without wishing in any way to detract from the value of the microscopic examination of metals, he would_ like to point out that there were limitations to its usefulness. There were, for instance, certain cases in which steel failed in the mechanical tests, but when examined under the microscope revealed no flaws.

This seemed to be very mysterious, but it could be explained.

When a mass of molten steel solidified it crystallized, and the divi- sions between the crystal grains could be seen under the micro- scope. The crystals would adhere, providing that nothing was


interposed between them. Unfortunately, this was not always.

the case. In the manufacture of steel by the "open hearth pro- cess" substances such as silica and magnetic oxide of iron were formed. These substances would remain suspended in the molten steel, just as an insoluble powder would remain suspended in water, with the difference, however, that the steel would not wet the substances. When a mass of steel containing these sus- pended impurities solidified they collected between the crystal grains and caused unsoundness. Sometimes the impurities were so finely divided that they could not be detected under high magni- fication. The method of removing these substances was to add manganese in the form of ferromanganese, to the molten steel.

Silica and magnetic oxide of iron would not combine with one another. The manganese reduced the magnetic oxide of iron to the state of ferrous oxide, and in that form the iron would combine with the silica'to form a slag.

It was necessary to allow a certain time for the slag to rise to the surface of the molten steel. In the "acid open hearth pro- cess" the ferromanganese was added to the steel while it was in the furnace, and plenty, of time could be allowed for the slag to rise to the surface of the metal before tapping. In the basic

"open hearth process" however, the ferromanganese had to be.

added to the steel after pouring into the casting ladle, otherwise phosphorus would be reduced from the slag and enter the steel again. There was not sufficient time for the slag formed after the addition of the ferromanganese to rise to the surface of the metal, before it was necessary to pour the steel into the ingot moulds. Hence steel made by the "basic" process was more liable to contain slag inclusions than that made by the acid pro- cess.

Mr. JAS. ALEX. SMITH said tnat further perusal of Major Law's paper had strengthened the recognition of its reliability and value, especially to those approaching the subject for the first time.

Whilst the microscope was of the very greatest value, alone it was not conclusive. Also, whilst it was of the utmost importance toi have an exact knowledge of the unit areas of a surface, to be obtained only by the use of microscopic methods, it was not of less importance to have an equally definite knowledge of the general arrangement of the structure of the whole surface of large sec-


DISCUSSION-METALLOGRAPHY. 12 5 tions. This did not require any microscopic apparatus more powerful than a hand magnifier.

Such structures must be considered as forms resulting from the flow of the material, either in the mould, or whilst passing through the rolls. It was essential to know, for instance, whe- ther the lines of flow were free from abrupt flexures, whether the individual lamina were disposed so as best to resist shear, bend- ing, or attrition, whether there was an absence of inert, unworked metal—metal "eddies," he might call them.

[The speaker showed by blackboard diagrams that in structural sections, the static condition was that to be chiefly considered, whilst in a rail there was necessity to provide an arrangement most permanently effective in the several parts of the rail under conditions of resistance to bending, in various planes, to shear, and to attrition and lamination in the head.]

Such large sections could be prepared in the workshop by any of the ordinary workship methods—machining, filing, emery cloth polishing, etc. Freed from grease by, lime or chalk powder, they could be etched lightly by any suitable medium—for instance, nitro-hydrochloric acid for iron or ammonia for copper alloys, for the former extract of liquorice was effective.

He noted that the author depended for revelation of structure upon methods which ultimately were based upon the chemical change of the components. But often the engineer required to know, not the resistance to chemical reagents, but the relative.

hardness of the component elements of a section. In such a case attrition was a solution, and a sand blast, or its equivalent, a mode. For instance a stream of fine carborundum, or emery powder falling upon a polished micro. specimen would give a re- sult showing differences of hardness of the component parts.

He also noted that in referring to crucible work in the labora- tory, mention had not been made of the electric furnace. This,

for this use, had very great advantages. By varying the resist- ance the temperature could also be varied, exactly, from the lowest to that comparable with the electric arc. Also, by the inter- position of suitable chrono-mechanism, the temperature could be automatically varied through any time period, and between these thermal extremes. Any predetermined heating or cooling curve could thus be accurately conformed to.


He would _ again emphasise the great advantage in bringing the ordinary routine of their lives under the analysis of_ the . me- thods of exact science. To the earlier engineer the metallic matter he used was unchanged and unchangeable, except in direct and immediate response to intense external force. Now we knew that such matter was not dead and inert in the sense that it was unchanging. We now knew that the mass responded in a most complex way—for instance, there might be catalysis—to ever) external stimulus, that to attain equilibrium, after such stimulus had ceased, might extend over years, and that the uli- mate condition might be profoundly different from the initial state. For instance, a steel alloy might be rolled into a rail, satisfactory to-day, but deteriorating, even in store, into an unreli- able material in the course of years. Chemical and microscopical analysis would go far towards detecting such tendencies.

The speaker illustrated on the blackboard an electric furnace consisting of a carbon tube cut into a spiral, with water-cooled terminals, with the crucible within the tube, and with carborun- dum or "kryptol" and magnesia thermal insulation.]

The PRESIDENT said that in entering upon a discussion of Major Law's paper, one's first reflection was one of sincere congratulation to the author, for the very fine contribution with which he had favoured them. The clearness, the consecutiveness, and the simple yet pregnant illustrations with which the subject had been put before them, all stamped the author as a master of his subject. Because of the fact that the results of the author's re- searches had been thus ably and clearly compressed in the small space of some twenty pages, it was really very difficult for them to properly estimate the amount of patient experiment which had been necessary to bring the research to the stage of completeness in which the author had given it to them.

The subject was one of the greatest complexity, and scientists were now only on the very threshold of the enquiry as to the. phenomena and conditions which determined the micro-structure of the industrial metals. They were only now in the stage of developing methods, procedures, and appliances, and the body of evidence collected, large as it was, was not yet sufficiently exten- sive for sound_ deductions and generalizations as to the characters istics of metals and their alloys.

In document Metallography (Paper & Discussion) (Page 48-62)

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