CZ281654B6 - Knife for mincing machines - Google Patents

Abstract

The steel for the production of knives for the shredder and meat mixers consists of 0.7 to 0.9 wt. % of the slag, less than 1 wt. % silicon, less than 1 wt. % manganese, 0.5 to 1.5 wt. % molybdenum, 0.7 to 0.95 wt. % vanadium, 0.3 to 0.9 wt. % niobium, 12.1 to 13.9 wt. % of chromium, the remainder being iron, including impurities due to melting

Description

Knife for meat grinding and mixing machines

Technical field

The invention relates to martensitic chromium steel, which is high-strength, tough and corrosion-resistant, for the production of knives for meat mincing and mixing machines.

Such knives are used in particular for slicing meat. Steel suitable for such knives must have a certain spectrum of properties. Such a spectrum includes, in particular, corrosion resistance from the action of tissue fluids, essentially saline solutions that result from slicing meat, high hardness to ensure blade durability, high strength, resisting centrifugal forces at high rotation speeds of about 4,000 rpm, good abrasion resistance in order to achieve large time intervals between grinding, satisfactory toughness, so as to cut even harder, for example deep-frozen pieces, good polishability to ensure a good optical appearance, and finally to be manufactured at low cost as possible.

Background

It has long been known from DE-PS 1 59 794 to use martensitic stainless chromium steels with 0.2 to 2.5 wt. % carbon, 8 to 22 wt. % of chromium, as well as the usual contents of manganese of silicon, phosphorus, sulfur and nitrogen, as well as 0.2 to 6 wt. % molybdenum and / or tungsten. An example is steel with about 1 wt. % carbon, 0.5 wt. % manganese, 0.24 wt. % silicon, 13 wt. % chromium, 1 wt. % molybdenum and 0.14 wt. % nitrogen. Similarly, composite steels for cutting tools with additional carbide-forming elements, such as vanadium, titanium, tantalum, niobium and zirconium, in total amounts up to 2 wt. % are known from DE-AS 17 52 655. An example is steel with 0.6 wt. % carbon, 1 wt. % silicon, 0.36 wt. % manganese, 10.5 wt. % chromium and 1 wt. % molybdenum. This known steel contains at least 20 wt. % residual austenite.

For special applications for knives for meat mincing and mixing machines, DE-OS 33 39 904 discloses a three-layer steel in which either a hard middle layer between two tough layers is provided or a tough middle layer between two hard layers, these layers being interconnected by composite rolling. Steels with a relatively high chromium content, for example 14 or 18 wt. % chromium. The tough layer has a relatively low carbon content of about 0.1 wt. %. The carbon content of the hard layer has a value of about 1 wt. %. In addition to the usual silicon and manganese content below one weight percent, these steels may each contain 1 to 2 wt. % molybdenum and 1 to 2 wt. % vanadium.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to provide steel for knives for meat grinding and mixing machines which, in view of the above-mentioned spectrum of properties, have optimum values at favorable production costs.

-1GB 281654 B6

This object is achieved according to the invention by a martensitic steel consisting of

0.7 to 0.9 wt. % carbon, less than 1 wt. % silicon, less than 1 wt. % Manganese, 0.5 to 1.5 wt. % molybdenum, 0.7 to 0.95 wt . % vanadium, 0.3 to 0.9 wt. % niobium 12.1 to 13.9 wt. % chromium, whereas the rest is iron, including impurities,

conditional on melting.

Steel from this region with about 0.80 wt. % carbon, 0.50 wt. % silicon, 0.45 wt. % manganese, 13.0 wt. % chromium, 1.3 wt. % molybdenum, 0.90 wt. % vanadium and 0.70 wt. % niobium has proven particularly useful for such knives. The reason for this is that the steel used according to the invention has an excellent corrosion resistance compared to the steel used so far, the material number 1.4153 due to its higher molybdenum content and the grain-refinement effect of the niobium. In addition, the niobium primary carbides precipitated in fine form together with the secondary carbides eliminated during tempering provide high abrasion resistance.

DETAILED DESCRIPTION OF THE INVENTION

The steel is produced by a conventional melt metallurgical process. Hot and subsequently cold rolled strips are processed into knives. After austenitizing at 1050 to 1100 ° C to form a martensitic variable structure from the curing temperature, the blades are rapidly cooled and then tempered at temperatures of 460 to 560 ° C for optimum hardness, toughness and corrosion resistance.

The properties listed below are then achieved.

At roughly the same hardness according to the invention, the steel used, by virtue of its finer and more uniform carbide formation, achieves a 15 to 25% higher toughness, as shown in FIG. 1. In long-term experiments, a permanent fatigue limit of 50% higher which makes it possible to significantly increase the resistance of highly stressed knives of this type. In the salt spray test, the steel according to the invention produced a significantly less corrosion attack than the comparable steel, material number 1.4153.

Claims (2)

Knife for mincing and mixing machines for meat, made of martensitic chromium steel, characterized in that it consists of 0.7 to 0.9 wt. % carbon, less than 1 wt. % silicon, less than 1 wt. % manganese, 0.5 to 1.5 wt. % molybdenum, 0.7 to 0.95 wt. % vanadium, 0.3 to 0.9 wt. % niobium, 12.1 to 13.9 wt. % of the chromium, with the remainder being iron, including melt impurities. Knife according to claim 1, characterized in that it consists of 0.80 wt. % carbon, 0.50 wt. % silicon, 0.45 wt. % manganese, 13 wt. % by weight, 1.3 wt. % molybdenum, 0.90 wt. % vanadium and 0.70 wt. % niobium, the remainder being iron.