Alloys or metallic compositions – Ferrous – Chromium containing – but less than 9 percent
Patent
1998-11-30
2000-04-11
Yee, Deborah
Alloys or metallic compositions
Ferrous
Chromium containing, but less than 9 percent
420113, 148333, 148335, C22C 3844
Patent
active
060484918
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a steel alloy having a certain chemical composition, a steel product made of the steel alloy, and use of the steel product. The invention particularly relates to the use of the steel product for the manufacturing of plastic moulding tools.
BACKGROUND OF THE INVENTION
A number of demands, which are difficult to combine, are raised on materials for the manufacturing of plastic forming tools. Among these demands, in the first place the following ones should be mentioned: dimensions of the product, a feature which is particular important because the mould cavity usually has to be engraved out of the core of the piece of steel. dimensions. plastic moulds often are provided with cooling channels in order to cool the tool between the shots in order to increase the production capacity. machinability (EDM). surface nitridability, such as ability to be surface hardened through ion nitriding.
It is also desired to simplify the heat treatment and, if possible, to completely eliminate hardening and tempering which substantially influence the total production costs and which also can cause cracks or other defects in the material.
The material which so far has been regarded to be the material which has satisfied the above requirements best is the material which since decades is known under its tradename IMPAX.RTM. SUPREME and which has the following nominal composition: 0.37C, 0.3 Si, 1.4 Mn, 2.0 Cr, 1.0 Ni, 0.2 Mo, 0.008 S, balance iron and unavoidable impurities and accessory elements. This material is tough hardened to 290-330 HB in its delivery condition. Successively, however, demands have been established upon plastic moulding tools having better performance than what IMPAX.RTM. SUPREME can offer. Above all a better hardenability, a higher and more even hardness independent on dimensions, a better weldabilty and electrical discharge machinabilty, and a better toughness are desired.
It has also been suggested in the past that a steel having the nominal composition 0.05 C, 0.3 Si, 2.0 Mn, 3.0 Cr, 1.5 Ni, 0.3 Mo, balance iron and unavoidable impurities, intended i.a. for tubes and for chains, particularly for anchor chains, should be useful also for plastic moulding tools. This steel, however, has not been able to satisfy the above specification of features and has, as far as is known to the applicant, never been used as a plastic moulding steel.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to provide a steel alloy and a steel product which satisfy the above mentioned combination of features. The invention also aims at providing a material which can be manufactured in a more rational mode than the above mentioned IMPAX.RTM. SUPREME as well as other conventional plastic moulding tool steels. Particularly, the invention aims at providing a steel which need not be hardened and tempered but can be used with the structure which the steel obtains after cooling after finished hot working through forging and/or rolling to the shape of blocks, rods, or plates. These and other objectives can be achieved therein that the steel has the composition which is stated in the appending claims, wherein the steel after finished hot working and cooling to room temperature obtains a homogenous structure through the whole piece of steel independent of its physical dimensions, said structure consisting of a so called low carbon lath martensite having a hardness which typically lies in the range 350-380 HB.
In the following, the importance of the individual elements and their interaction with each other shall be explained. All percentages relating to the chemical composition of the steel refer to weight-% unless something else is stated.
Carbon shall exist in the steel in an amount of at least 0.075%, preferably at least 0.08%, and suitably at least 0.09% in order that the steel shall achieve a desired hardness and strength. The C content must not exceed 0.15%. If the C content is higher, the steel will be too hard and brittle and difficult to work after cooling from the hot
REFERENCES:
patent: 4428781 (1984-01-01), Norstrom
Jesperson Henrik
Norstrom Lars-.ANG.ke
Uddeholm Tooling Aktiebolag
Yee Deborah
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