January 1975

Microscopic and Macroscopic Test for the image orderedCarbide Distribution of High Speed Steels

STEEL-IRON-Test Sheet

16152. Edition

1. Basis and Purpose of the Test:

The distribution of carbides in the high speed steels may be important for the usage properties of such tools.Therefore, the carbide distribution should be subject to proper marking in order to achieve an equal determination.The easiest way to do this is to compare a present steel structure with a picture serial.

In this test sheet/page, such picture orders/series are displayed (1). These will assist in understanding theevaluation of structure pictures. Picture series show the carbide distribution of molybdenum-wolfram andmolybdenum high speed steels in technical manufacture: The picture series should carefully be used in more than%8 of high speed steels containing wolfram, because equal diameters of carbides and their distribution may beharmful.

One of the picture series in your test sheets shows the carbide distribution followed in the microscopic observationof high speed steels. In microscopic evaluation, there is a disadvantage of just evaluation the small parts of thesteel, so the other picture series in this test sheet allows the macroscopic evaluation carbide distributions. It ispossible to be informed about the development of carbides and blocks along the transverse section of the rod bymacroscopic evaluation.

2. Generation of carbide net structures and carbide cells in high speed steel

Technical possibilities which affect the carbide distribution should be considered in order to make a reasonableevaluation in the carbide distribution in steel. So, only carbide net structure and generation of carbide cells shall bedescribed in this part.Carbides of high speed steels which are manufactured of current concrete blocks such as ledeburitic steels showan unequal distribution. The hardening of the steel within the block causes the remaining enamel to a fast meltingchange as carbide and austenite. This carbide, changing as an easy solution, is always like a net. The hangerwidth of the carbide net structure depends on the hardening speed. Speed reduces from block surface to its kernel.Therefore, larger hanger width sets in the kernel of a block or modified rod, so there is an unequal distributioncompared to the surface of the block. Because of the same reason, larger blocks required in the thickerpunch/blacksmith parts have a bigger net structure compared the small blocks. Therefore, the usage of biggerblocks is limited.

The carbide net structure are stretched and extended as required and for proper shape when blocks aretransferred to rod shape. The extending of the carbide net structure strikes depending on the increasing shaperating; therefore the carbides are seen in line form although they have no similarity with the previous net structure.

Macroscopic examination allows the evaluation of distribution of carbides of the entire transverse section on theprocesses material. Other than the block leakages shown in the picture series, periodic leakages and shadowstrips are rarely seen. Bu if these are significantly seen in the macroscopic image of limited structure, then it willhave adverse effects of the usage of steels.

3. Select in pictures in the correct picture series

Picture series of microscopic norm series are classified for 9 ratings and 3 groups from various modification ratingsof concrete (unmodified net) to power modification ratings (significant line order) according to technicalmanufacture processes and possibilities. Small and power modified rods have lines not just with information for netstructure. When the modification rating id small the lines are wider and the connection between the previous netstructures is more significant.

-----------1) These two picture series of the STEEL-IRON test may be requested from Verlag Stahleisen GmbH, Postfach 10 51 64, 40042Dsseldorf

Premises Technical Boars, Technical request sub commission, Tribotechnique operation link

Large rods are generally are connected to the carbide net structure in the casting state because of the limitedpossibility of modification and limited usage of raw material blocks. Modifications possible in bigger dimensions areso small that casting structure may sometimes be the same. The density of net structure, in other words, thepenetration of net structure by carbides, are not just affected by production conditions but also it is associated withthe steels alloy amount.Picture series of microscopic norm series are classified for 6 ratings and 3 groups (2). These show the granulatingcarbide and block leakages alongside with the transverse section in the increasing diameter.Ratings for the dimension ratings and modification degrees are proper in microscopic norm process.

4. Microscopic test of carbide distribution

4.1 Samples and sample preparation

A disk plate is taken from the hot and soft rod which is examined. This rod is sliced lengthways as seen in Picture 1in order to connect the cut surface with the rods axis. Constituting a sub group for bigger dimensions may beproper in grinding process. (See picture 1). The cut surface is grinded and burnished in conventional ways and thecarbides are etched until they are in front of the dark main body of the light colored steel in a 90 cm alcohol and10 cm concentrate saltpeter acid solution.

Picture 1: Example of the Allocation of samples and position of examined parts

4.2 Experiment application and evaluation

Grinded/etched parts are maximized up to 100 times under the microscope and the structures of examined areasare paired with structure pictures of microscopic picture series. The following should be cared: Because the carbidearrangement develops from the corner to the kernel, the carbide development evaluation should always be madefrom the same point of the transverse section of the rod. The picture series in this test sheet , is prepared as theexamined section is between the corner area and the kernel, so the diameter of the examined area should bewithin .

5. Macroscopic test of carbide development

5.1 Samples and sample preparation

A disk plate is taken from the hot and soft rod which is examined. This rod is sliced lengthways as seen in Picture1 in order to connect the cut surface with the rods axis. Constituting a sub group for bigger dimensions may beproper in grinding process. (See picture 1). The cut surface is grinded and burnished in conventional ways and thecarbides are etched until they are in front of the dark main body of the light colored steel in a 90 cm alcohol and10 cm concentrate saltpeter acid solution. For bigger dimensions, the disk plate is properly divided.

5.2 Experiment application and evaluation

Etched samples are paired and compared with the pictures of microscopic picture series.

-----------2) Based on the General Motors Co. und Latrobe Steel Co. norm series