DE10027049B4 - Use a chrome steel alloy - Google Patents

Abstract

Use a chrome steel alloy
0.4 to 0.75% carbon,
0.4 to 0.8% manganese,
14 to 19% chromium,
up to 0.1% nickel,
up to 0.4% silicon,
0.5 to 1.5% molybdenum,
0.05 to 0.2% vanadium, titanium and / or niobium
0.025 to 0.15% sulfur,
up to 0.1% nitrogen,
up to 0.008% boron,
Rest of iron including melting-related impurities as a material for industrial needles.

Description

Recent developments in sewing machines also have the requirement profile of industrial (sewing) needles decisively changed. So far, industrial needles for sewing machines made from a carbon steel with about 0.8 to 1.1% carbon. Such needles tend to form rust spots in moist air, which limits their use very much. To improve the corrosion resistance and to avoid rusting, the needles are therefore galvanized coated, e.g. in rotating drums. As a coating Nikkel and / or chrome deposited cathodically. The fall Layer thicknesses often vary greatly, with critical ones Places, e.g. in the area of the eye, the tip or thread groove, often only very thinly coated can be. It is precisely in these areas that increased wear and tear occurs during operation. Also abrasion of the coating is undesirable since it is known that nickel itself is a very allergenic metal in very small concentrations.

Another disadvantage of galvanic Coating is that when cathodic metal deposition in electroplating baths hydrogen in the needle material can be installed. This hydrogen causes the brittleness increases very sharply, causing the dreaded needle breaks potential consequential damages triggered on the machine become.

For an economical manufacture of the needles has the machinability of central importance. This is especially true for the manufacture of thin needles. The previously used carbon steels with up to 1.1% carbon can just meet these conditions, being, in the annealed condition with carbon contents over 1%, Difficulties in processing the thread groove and the eye may already occur. With these carbon steels is after a special heat treatment a hardship from a maximum of 800 to 840 HV1.

The temperature stability, so maintaining hardness after warming up however, is insufficient. Already when heated to 300 ° C. on decline the hardness possible by more than 200 HV1 units (10 HRC units). at full of hardness there is also a large one Sensitivity to absorption of hydrogen, e.g. during galvanic coating. Even small amounts of hydrogen can only do this through carbon stabilized martensitic structure go brittle and an increased Trigger risk of breakage. With thin This is particularly critical for needles. The advantages of higher alloys steels So far, due to difficulties in micro and Finishing of the eye and the thread groove and an insufficient coordination of the alloy elements not be used.

The requirements for new needle materials are primarily determined by the performance increases in sewing machines. The developments go in the direction of increasing the cost-effectiveness of seam production with simultaneous ease of use and a longer service life of the sewing machines. The following measures serve this goal:
Increase in sewing speed,
Improvement of thread guidance,
Optimization of the presser foot pressure,
continuous adjustment of the stitch width,
the highest possible piercing force of the needles with the lowest possible friction.

The desire for higher sewing speeds becomes alone through economic constraints triggered to reduce costs and increase production. So be currently industrial sewing machines already driven at more than 7000 rpm. The high sewing speeds (or the high number of stitches) lead to special loads on the needles and require an adjustment of the Materials as well as the material properties.

The high sewing speeds and the associated special loads on the needles improved material properties. These concern the heat resistance the needle tip, the wear resistance as a sum property of corrosion and abrasion resistance, the Hardness, the rigidity, the maximum bending force and the maximum deflection.

Recent studies have shown that at Sewing thick fabrics at high sewing speeds Temperatures of up to 300 ° C occur at the tip of the needle. Under these conditions will also wear resistance already deteriorated after a short period of use, which also inadequate protection through galvanic coatings to be led back can.

A big disadvantage with needles Carbon steel lies particularly in the drop in core hardness and in the insufficient mechanical properties under extreme loads. The matrix, which is only stabilized by carbon, can withstand higher temperatures often do not resist deformation. The service life of the needle is greatly reduced. The deformation in turn the risk of damage to the sewing machine significantly increased.

An industrial needle is said to be high core hardness and have a high heat resistance, preferably above 300 ° C.

The wear resistance as a sum property of abrasion resistance and corrosion resistance is said to be good and should not be worsened by exposure to air and moisture or by contact with fabric and fiber abrasion (avitage, dyes, chemicals, bleach residues and other substances).

The danger of a needle break should be even when sewing of different materials, especially when sewing in the transition area various fabrics as well as inlays and reinforcements be small.

The numerical value for the stiffness S, expressed as the quotient F _max / S _max (maximum bending force / maximum deflection) should be high and have as little scatter as possible. The deflection of a needle until it breaks should be between 1.5 and 2.5 mm and not exceed 3.0 mm.

The production of needles was inexpensive and environmentally friendly and be simple. The shaping and the heat treatment should be conventional Investments possible his. For hard metal needles (German Offenlegungsschrift 38 19 481) this condition is not met, because diamond grinding tools are used for shaping are necessary and the eye must be manufactured by means of spark erosion.

Needles for medium sewing speeds are made of wire, which is a simple alloy structure has and is easy to edit. The inexpensive manufacture is a crucial aspect for the choice of materials. common are carbon steels with about 0.8 to 1.1% carbon, corresponding to about a steel the material number 1.1545. For High demands are currently being placed on needles from the upper carbon range used. Here, however, the limits of workability already occur.

For making an industrial needle a wire is mainly processed using non-cutting shaping. Doing so first the shaft and the needle neck are machined and extruded using presses as well as the eye flattened and shaped. Then the needles are straightened and the thread groove by means of roller embossing brought in. Fine machining follows as further processing stages of the eye and grinding the needle tip.

This is followed by hardening with subsequent tempering treatment, sometimes in combination with freezing. The sewing needles then reach a hardness of approx. 60 HRC. This is followed by a fine sanding of the needle tips, cleaning and electroplating with nickel and / or chrome. The galvanic coating takes place in rotating plastic containers with the supply of direct current, the negative current lead being introduced into the interior of the plastic container and contacting the needles there. The acidic solution of a chromate (Cr ⁶⁺ ) salt is often used as the electrolyte. From this, a thin layer of chrome or hard chrome is deposited on a previously deposited nickel layer.

When coating can be very easy Diffuse hydrogen into the lattice of the needle material, causing the hardened Carbon steel can become very brittle. This in turn leads to an elevated Break sensitivity of the needle and increases the risk of failure at high Sewing speeds.

The disadvantage of hydrogen embrittlement can be overcome through the use of a physical coating process, For example, avoid the PVD (Physical Vapor Deposition) process. These processes mainly work in vacuum or under vacuum and need Temperatures from 300 to 500 ° C. The relatively high temperatures have the consequence that the needles - due to their low content of alloy metals - thermally overwhelmed become and a decrease in the substrate hardness (core hardness) occurs. This will the compressive strength of the tip deteriorates.

In order to achieve the greatest possible compressive strength and hardness, beats German patent application 38 19 481, the needle shaft and to manufacture the tip of a machine needle from a fine-grain carbide. This high-strength needle shaft is to be used with the needle piston using cold extrusion are connected, with an eroding to form the thread groove and the eye takes place. The high costs of this complex design and the size Time required for erosive processing does not meet the criteria of one economic mass production and therefore have not enforced.

It has also been tried, known Stainless steels with additives of molybdenum and other alloying elements for the manufacture of industrial needles to use. This should especially corrosion resistance be improved. These needles made from conventional stainless toughen let themselves be difficult to machine, however, and did not achieve the necessary surface hardness. Compared to the known carbon steels especially the lower rigidity with a high one plastic deformation is a major disadvantage.

Therefore, to increase the surface hardness German Offenlegungsschrift 2 054 671 before, machine needles made of stainless steel and exposed to wear Subsequent parts by nitriding to harden.

This version was also unsuccessful, since warping occurs due to the high nitriding temperatures and the layer, which is only a few μm thick, did not improve the compressive strength. Correction of the warpage by straightening is generally difficult to carry out, as this will result in tears in the Layer and thus the formation of fractures.

Known. is from the "STAHL-EISEN-LISTE", 1977, pages 86 and 87 also a range of stainless molybdenum containing toughen with less than 2% nickel, which is a material for knives and surgical instruments suitable. So is from the "STEEL IRON LIST" under the material number 1.4109 a knife steel with 0.60 to 0.75% carbon, up to 1.0% Silicon, up to 1.0% manganese, up to 0.045% phosphorus, up to 0.030% sulfur and 13.0 to 15.0% chromium and 0.50 to 0.60% molybdenum, the rest Known iron. Another knife steel with the material number 1.4118 contains 0.60 to 0.65% carbon, up to 1.0% silicon, up to 1.0% manganese, up to 0.03% phosphorus, up to 0.015% sulfur, 13.0 to 15.0% chromium, 1.0 up to 1.5% molybdenum, 0.2 to 0.5% vanadium and 1.2 to 1.7% cobalt, balance iron. Another Knife steel with material number 1.4126 contains 1.05 to 1.15% carbon, up to 1.0% silicon, up to 1.0% manganese, up to 0.045% phosphorus, up to 0.030% Sulfur, 17 to 18% chromium and 0.80 to 1.0% molybdenum, balance Iron.

Finally, the "STEEL IRON LIST" describes one under material number 1.4117 as material for surgical instruments suitable steel with 0.35 to 0.40% carbon, 0.30 to 0.50% silicon, 0.20 to 0.40% manganese, up to 0.045% phosphorus, to 0.030% sulfur, 14 to 15% chromium, 0.40 to 0.60% molybdenum and 0.10 up to 0.15% vanadium.

From German patent specification 739 958 is also a steel alloy with 0.60 to 2.50% carbon, 8 to 22% chromium, 0.05 to 0.25% nitrogen and 0.20 to 6% molybdenum, balance Known iron, which is a material for by rolling or the like Process manufactured corrosion-resistant hardened cutting tools, for example Razor blades and surgical instruments.

The aim of the invention is a nickel-free or low-nickel alloy for the production of stainless and wear-resistant Industrial needles to propose.

To achieve this goal, the invention proposes the use of a chrome steel alloy:
0.4 to 0.75% carbon,
0.4 to 1.6% manganese,
12 to 19% chromium,
up to 0.2% nickel,
up to 0.7% silicon,
0.5 to 1.5% molybdenum,
up to 1.5% tungsten,
0.05 to 0.3% vanadium, titanium and / or niobium
0.02 to 0.15% sulfur,
up to 0.1% nitrogen,
up to 0.008% boron
Remainder iron and melting-related impurities.

The alloy has an improved Workability, one in hardened and heat treated Condition improved stiffness, improved heat resistance as well as an excellent Abrasion resistance and corrosion resistance.

A preferred embodiment includes:
0.6 to 0.7% carbon
17 to 19% chromium,
0.03 to 0.1% silicon,
0.5 to 0.8% manganese,
up to 0.1% nickel,
1 to 1.5% molybdenum
up to 1.5% tungsten
0.05 to 0.3% vanadium, titanium and / or niobium
0.02 to 0.15% sulfur
up to 0.1% nitrogen
up to 0.008% boron

It is also an advantage if the alloy - individually or side by side - each at least 0.10% silicon, 0.05% tungsten, 0.01% titanium and each a total of 0.05% vanadium and titanium and / or 0.05% vanadium and niobium contains.

The alloy is preferably characterized by the ratio: K 1 = 30 × (% C +% N) / (% Cr +% Mo) = 0.9 to 1.25.

Another identification of the alloy can be the coordination of the sulfide formers manganese, titanium Be sulfur, carbon and nitrogen. Particularly advantageous properties exist within the following limits: K 2 = 10 ×% S / (% C +% N) = 0.35 to 1.50 and or K 3 = (% Mn +% Ti) /% S = 5 to 30.

These relationships characterize the Interaction of the sulfur depending on the total content Carbon and nitrogen as well as manganese and titanium.

• – Gute Verarbeitbarkeit mit Umformwerkzeugen, insbesondere mittels Präge- und Stanzwerkzeugen.
• – Hohe Korrosionsfestigkeit durch die Legierungselemente Chrom und Molybdän. Die hohe Korrosionsfestigkeit ermöglicht den Verzicht auf teure und umweltbelastende galvanische Beschichtungsverfahren (Verchromung).
• – Wegfall der beim galvanischen Beschichten möglichen Wasserstoffversprödung. Bei der Aufnahme von Wasserstoff können die Nadeln unterschiedlich stark verspröden, wodurch sich die Bruchgefahr stark erhöht.
• – Hohe Verschleiß- und Abriebfestigkeit sowie Härte nach einer üblichen Wärmebehandlung (Härten). Die gute Verschleißfestigkeit und die notwendige Härte werden durch eine hohe Festigkeit der Matrix sowie darin fein verteilte Karbide und/oder Karbonitride erzielt. Die mechanischen Eigenschaften der Matrix werden vorwiegend durch den Anteil an gelösten Legierungselementen bestimmt und können über eine spezielle Abstimmung der Gehalte an Chrom, Molybdän, Kohlenstoff und Stickstoff vorzugsweise bei einem Nickel-Gehalt unter 0,1% eingestellt werden.
• – Geringe plastische Verformbarkeit der gehärteten Nadel bei gleichzeitig geringer Streuung der Biegekraft, der Durchbiegung und der Nadelsteifigkeit. Die Nadelsteifigkeit kennzeichnet das Verhältnis der maximalen Biegekraft zur maximalen Durchbiegung. Diese Werte werden durch das Verhältniss der Legierungselemente Mangan und Titan zu Schwefel sowie von Kohlenstoff und Stickstoff zu Chrom und Molybdän bestimmt.
• – Geringe Streuung der Werte der maximalen Durchbiegung, der maximalen Biegekraft sowie der Nadelsteifigkeit.

The following properties of the alloy are particularly advantageous:

• - Good processability with forming tools, especially using embossing and punching tools.
• - High corrosion resistance thanks to the alloy elements chrome and molybdenum. The high corrosion resistance makes it possible to dispense with expensive and environmentally harmful galvanic coating processes (chrome plating).
• - Elimination of the hydrogen embrittlement that is possible with galvanic coating. When absorbing hydrogen, the needles can become brittle to different extents, which greatly increases the risk of breakage.
• - High wear and abrasion resistance as well as hardness after a usual heat treatment (hardening). The good wear resistance and the necessary hardness are achieved through a high strength of the matrix as well as finely distributed carbides and / or carbonitrides. The mechanical properties of the matrix are mainly determined by the proportion of dissolved alloy elements and can be adjusted by a special adjustment of the chromium, molybdenum, carbon and nitrogen contents, preferably with a nickel content below 0.1%.
• - Low plastic deformability of the hardened needle with at the same time little variation in the bending force, the deflection and the needle stiffness. The needle stiffness characterizes the ratio of the maximum bending force to the maximum deflection. These values are determined by the ratio of the alloying elements manganese and titanium to sulfur as well as carbon and nitrogen to chromium and molybdenum.
• - Low scatter of the values of the maximum deflection, the maximum bending force and the needle stiffness.

The alloy is nickel free or - poor and is therefore characterized by a particularly low allergy potential out.

The invention is described below of embodiments of the nearer explained.

In Table I are conventional Alloys A1 to A3 and C1 to C3 six alloys according to the invention E1 to E6 compared.

With these test alloys Experiments to determine the total wear resistance in a humid atmosphere the KFW test according to DIN 50017 with a subsequent one 30- or 60-minute Abrasion test carried out in a rotating container. As Samples served in the usual way Way hardened and ground wire pins with a diameter of 1 mm and Industrial needles with a galvanic nickel coating. The KFW test served to the corrosion resistance of the samples in a condensation water alternating climate of a climatic chamber determine. The samples were 8 hours at 40 ° C and 100% rel. Moisture stored in air. After that, the samples slowly cooled to room temperature over the course of 16 hours and the rust attack was found. In the subsequent abrasion test became the change the sample surface optically assessed and the mass loss determined.

The bending behavior of the samples was determined using an F 33 testing machine from Shimatazu at a bending speed of 2.5 mm / min. The stiffness S, F _max and S _{max were} taken or calculated from the corresponding force / bending diagrams.

The data of the experiments are in the Tables III and IV below.

The data in the two tables show that itself the alloys according to the invention E1 to E6 due to high stiffness S with good processability distinguished.

The graphic representation shows the maximum bending force depending from the deflection, where the alloys E1 to E6 according to the invention in Compared to the conventional ones Test alloys B1 to B3 and C1 to C3 as well as known hard metals tough and tough Area are arranged.

The scope of the invention is designated E. It is characterized in that the needles are present in the tough and hard area after hardening. B denotes the results of tests with a steel with 0.88% to> 1% carbon. B1 denotes the area of embrittlement due to hydrogen. In this brittle area, the maximum possible bending force and the deflection are greatly reduced changed values.

Area C, however, affects that Behavior of known stainless steels with a strong plastic Deformation component. With these steels there is a risk that at high sewing speeds a permanent bending of the needle severe damage on the sewing machine occur.

Area D describes this in comparison the behavior of carbide. However, this material is for practical Uses as needle material too brittle.

Like the diagram of the 1 shows (see also Table III), the bending behavior is advantageously kept within narrow limits in the alloy according to the invention. The advantageous alloy according to the invention for industrial needles (E in 1 ) is characterized by a high alloy content of the matrix, which is advantageously also coordinated with the content of carbides, nitrides and carbonitrides. This coordination is particularly defined by the ratio numbers K1, K2 and K3.

The results of wear resistance Table II shows. It has a particularly unfavorable effect on overall wear high humidity with abrasion. By this double stress can trigger increased needle wear. Such conditions are particularly common in tropical countries. Galvanic layers offer insufficient protection under these conditions, since there is increased corrosion after removal of the layer comes.

The test alloys E1 according to the invention to E6, however, only show one under the selected conditions minimal wear. This is due to the fact that in addition to the coordination of the alloy contents also the criteria regarding of the factors K1, K2 and K3 fulfilled and the matrix is very wear-resistant.

Claims (6)

Use a chrome steel alloy 0.4 up to 0.75% carbon, 0.4 to 0.8% manganese, 14 to 19 %Chrome, up to 0.1% nickel, up to 0.4% silicon, 0.5 to 1.5% molybdenum, 0.05 up to 0.2% vanadium, titanium and / or niobium 0.025 to 0.15% sulfur, to 0.1% nitrogen, up to 0.008% boron, Remainder iron including melting related Impurities as a material for Industrial needles. Use of a chrome steel alloy according to claim 1, however 0.6 to 0.7% carbon, 17 to 19% chromium, 0.03 up to 0.1% silicon contains. Use of a chrome steel alloy according to claim 1 or 2, but the condition K 1 = 30 × (% C +% N) / (% Cr +% Mo) = 0.9 to 1.25 enough. Use of a chrome steel alloy according to any one of claims 1 to 3, but the condition K 2 = 10 × S / (% C +% N) = 0.35 to 1.50 enough. Use of a chrome steel alloy according to any one of claims 1 to 4, but with the condition K 3 = (% Mn +% Ti) / S = 5 to 30 enough. Use of a chrome steel alloy after a of claims 1 to 5 in hardened Condition for the Purpose according to claim 1.