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Carpenter matched tool and die steels.

Choices. Everyone wants them, but too many can be as bad as too few. Golfers, for example, don't carry a large, random selection of clubs. They rely on a carefully matched set: One club for every situation, each one picking up where the other leaves off. It's the only way a golfer can switch from club to club with predictable results.

Too many choices can be just as undesirable for users of tool and die steels. Manufacturing engineers setting out to choose the best material for a new tool or die are confronted with not less than 80 basic types of steels. This makes it difficult to know where to start, and even more difficult to predict what will happen when switching from one grade to another.

To help make the choices reasonable and results predictable, Carpenter Technology Corp, Reading, PA, has just revised their guide for selecting the best grade for any given application. It's called the "Carpenter Matched Tool and Die Steels."

"Our matched set isn't new," remarks Walter Burd, specialist--bar product metallurgy at Carpenter. "Only three of the original nine grades remain in today's 12-grade set; however, the original purpose remains unchanged. The guide serves as a practical selection tool for manufacturing engineers who must specify materials for various tool and die applications."

The two most important features of the 156-pg book are the matched set with its diamond selection diagram (see illustration), and the tool-steel selector section.

The tool-steel selector section offers 182 typical tool listings, each with its own suggested steels (first choice and possible alternatives) for a given combination of properties. Serving as a complement to the matched set, the selector is the compiled best judgment of many people who know both tools and materials.

The specific data section provides complete information about each of the matched set's 12 steels, including type analysis, description, size change in hardening, machinability, wear resistance, typical applications, thermal processing, and mechanical and physical properties. Also, there are data for tool steels not in the matched set.

Tables provide information for hardness conversions, temperature conversions, decimal equivalents, and weight. New for this edition are comparative machinability and wear-resistance tables for the matched-set steels.

The diamond diagram relating the matched-set grades has three important changes:

* The three-grade water-hardening set is dropped.

* Thermowear steel replaces T-K steel in the red-hard set.

* A new set of Pyrotool grades is added for applications needing strength at high temperatures.

"All changes are based on current trends and the latest alloys," emphasizes Burd. "For example, the water-hardening grades were dropped because of their decline in popularity. At one time, they were the most used, but as service requirements became more critical, there was a significant shift to oil-hardening and air-hardening grades to minimize distortion after heat treating." Although water-hardening grades are no longer part of the diagram, they still are available from Carpenter.

A map through the

tool-steel jungle

The diamond diagram matrix contains grades that dovetail so accurately that users can know in advance what to expect when switching from one to the next. "The starting point is Stentor," notes Burd, "an oil-hardening steel for general purpose toolroom work such as blanking dies, forming dies, laminating dies, molding dies, trimming dies, master tools, etc.

"To use the diagram, ask the question: 'Can I use Stentor for this application?' If the answer is yes, then obviously there's no need to go further. If the answer is no, however, then ask: 'Why can't I?' There are essentially only four possible answers, each relating to a property used as a selection criterion:

* Greater wear resistance is needed for the job.

* More toughness is needed.

* The job requires greater hardening accuracy and safety.

* The tool will get so hot in service the steel will lose its temper, i.e., more red-hardness is needed.

"Moving up the diagram results in greater wear resistance. Moving down yields greater toughness. It follows, of course, that greater wear resistance means giving up some toughness and vice versa. Moving left always results in greater hardening accuracy and safety. Greater red-hardness results from moving right."

Notice that each diamond contains a second name. Stentor steel, for example, also is referred to by its generic name, oil-hard.

The entire middle row has the word "hard" in the generic names: air-hard, oil-hard, red-hard, and hot-hard. Likewise, all grades in the top row have "wear" in the name, and all in the bottom row have the word "tough."

Now look at the vertical columns. The column on the left contains steel names beginning with "air," signifying they are air-hardening grades. The second column contains oil-hardening grades. Both columns contain steels for cold-work tools and dies.

The third column contains names beginning with "red," which are hot-work die steels. The last column contains names beginning with "hot," which provide greater strength at higher temperatures than the "red" grades for applications such as aluminum and brass hot-extrusion dies.

Sometimes a job might demand both good wear resistance and hardening accuracy. First, ask the question: "Can I use oil-hard steel?" The answer is no, because greater wear resistance and maximum hardening accuracy and safety is needed. For this job, move up one diamond for wear resistance and left one for hardening accuracy. The position is No 610 steel, an air-hardening grade.

Another application might require maximum red-hardness and wear resistance. In this case, move up for wear resistance and right for red-hardness, arriving at red-wear steel.

The book's introduction gives complete instructions for using the matched set and the diamond diagram, cites advantages of using the matched set, offers notes on ordering tool steel, provides heat-treating information, and explains Carpenter's DCF (DeCarb-Free) finish and ESR (ElectroSlag Remelting), the process used to make the firm's tool steels.

For a free copy of this valuable reference piece, circle 544.
COPYRIGHT 1985 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Article Type:Book Review
Date:Oct 1, 1985
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