CS216230B2 - Steel for cold working - Google Patents

Abstract

Cold work steel comprising 0.45-1.5% C, 0.2-2% Mn, 0.2-1.8% Si, with opt. =1% Mo, =1% W, =2% Ni, 0.5% Cu and bal. Fe additionally contains 0.05-2.5% Nb. The steel has numerous uses as a cutting steel eg. saws, chisels, scissors, helicoidal drills etc.

Description

The invention relates to steel for cold working.

Cold working steels must, in accordance with their stress, have a very high abrasion resistance, which must be associated with minimal toughness. Especially in the case of highly stressed frame and circular saws, as well as in the case of band saw blades, as well as in the case of friction saws for woodworking, the toughness requirements of the steel are increasingly demanded. Tools for this purpose have so far been manufactured from steels containing 0.50 to 1.20% carbon.

In order to improve the quality, chromium, molybdenum, tungsten, vanadium and nickel are added to the usual manganese and silicon contents to these steels.

The working hardness of steels for cold working varies between 50 and 70 HRC depending on the application. On the one hand, maximum hardness is required with respect to abrasion, but on the other hand this requirement decreases the toughness of the materials used to such an extent that the tools can be damaged by slight impact, even when transported to the consumer. A reduction in tempering hardness results in increased toughness properties, but also leads to increased wear when used in service. The addition of chromium, molybdenum and tungsten alloying elements led to a slight improvement in toughness at elevated temperature only when the chromium, molybdenum and tungsten carbides were formed in the steel. These carbides were embedded in a low martensitic matrix and remained effective only as long as the matrix had maximum hardness. Tempering, i.e. a reduction in hardness and thus an increase in toughness, has led only to initial successes.

During further in-service stresses, the steel matrix was worn and carbides were machined. Heating above 100 ° C, caused by traffic, accelerated this process.

Another suggestion, namely to improve the durability of cold working tools, was to provide a particularly wear-resistant coating on the working edge of the tools. However, this had the disadvantage that after some time the surface layer was worn out and the entire tool had to be removed and re-treated to re-apply it.

The invention is based on the task of improving the durability of cold working tools while improving the natural brittleness of these tools at maximum hardness.

The addition of niobium significantly improves durability up to 500 ° C in low carbon steels. It is also known to add niobium to hot working steels and high speed steels. In all these cases, the hot strength of these steels increases. In austenitic chromium-nickel steels, the addition of niobium in amounts equal to 8 and 10 times the carbon content prevents grain breakdown due to the carbon-binding capacity of niobium.

In all cases, however, niobium is used as an alloying element in high-alloy steels in the presence of larger amounts of molybdenum, quarry, tungsten and nickel elements. The use of niobium in tool steels is thus limited, since niobium with carbon forms poorly soluble carbides, which lead both to depletion of the base material by carbon and, on the other hand, to the heat treatment of such steels due to the poor solubility of the deposited niobium carbide.

The invention is based on the discovery that additions of niobium to carbon-containing low-alloy cold steels unexpectedly lead to a significant improvement in abrasion resistance while at the same time optimum toughness and strength. These characteristics give extremely high durability in the manufacture of circular, chain and band saws as well as knives of any kind.

The invention therefore depends on the use of cold working steel consisting in a concentration by weight of 0.55 to 0.95% carbon, 0.25 to 0.50, preferably up to 1.8% silicon, 0.30 to 0.50% preferably up to 2.0% manganese, 0.1-0.2% chromium, 0.1-0.2% molybdenum, 0.1-0.2% tungsten, 0.05-0.1% vanadium 0.8 to 1.2% nickel, 0.25 to 0.35% ^! niobium, the rest of the iron and the necessary impurities for the production of band and chain saws.

Contrary to expectations, it has also been shown that the optimum action of niobium additives in cold working steels is particularly evident when the a ... *

when other alloying elements such as chromium, molybdenum, tungsten, nickel and vanadine lie in a concentration of 0.01 to 1% chromium, 0.01% molybdenum, 0.01 to 1% tungsten, 0.01 to 2 ° / d nickel and 0.01 to 0.5% vanadium.

For machine knives, hand chisels, butchers knives, bread knives, scissors knives, punching tools, punching tools, agricultural cutting tools and shears, steels with a weight concentration of 0.60 to

1.10 "/ o of carbon, from 0.25 to 0.50% silicon, 0.20 to 0.70% manganese, 0.15 to 0.25% molybdenum, 0.15 to 0.25 ^LB / drawbar chromium, 0.01 to 0.05 why, vanadium, 0.30 to 0.55% niobium, the rest iron and necessary impurities.

Thread cutting knives, twist drills, knives with special blade stability are preferably made of steel with a weight concentration of 0.95 to 1.35% carbon, 0.30 to 0.60% silicon, 0.80 to 1.20% of manganese, from 0.30 to 0.60%. chromium, 0.30-0.60% tungsten, 0.15-0.20% vanadium, 0.40-0.65% niobium, the remainder iron and necessary impurities.

For purposes where, in addition to abrasion resistance and toughness, increased flexibility is also required, it is recommended to add up to 1.8% / silicon to the steels of the invention.

Extreme requirements in terms of abrasion resistance, toughness and flexibility are imposed on pneumatic hammers. The steel according to the invention contains, in a concentration by weight of 0.45 to 0.60% carbon, 1.30 to 1.70% silicon, 0.60 to 1.00% manganese, 0.50 to 1.00% Chromium, 0.10 to 0.30% molybdenum, 0.30 to 0.80% nickel, 0.30 to 0.60% niobium, iron remnants and necessary impurities, met all the requirements for a drill drill steel during the trial operation.

In order to improve the hot formability, it may be expedient to add up to 2% of manganese to the steels according to the invention.

Claims (1)

OBJECT OF THE INVENTION Use of a cold working steel consisting in a concentration by weight of 0.55 to 0.95% carbon, 0.25 to 0.50, preferably up to 1.8% silicon, 0.30 to 0.50%, preferably up to 2.0% manganese, 0.1-0.2% chromium, 0.1-0.2% molybdenum, 0.1-0.2% tungsten, 0.05-0.1% vanadium, 8 to 1.2% nickel, 0.25 to 0.35% niobium, the remainder iron and the necessary impurities for the production of band and chain saws.