CN104278209A

CN104278209A - Steel alloy for chain and chain assembly, and chain/chain assembly

Info

Publication number: CN104278209A
Application number: CN201410315858.7A
Authority: CN
Inventors: A.哈顿
Original assignee: Theile JD GmbH and Co KG
Current assignee: Theile JD GmbH and Co KG
Priority date: 2013-07-03
Filing date: 2014-07-03
Publication date: 2015-01-14
Anticipated expiration: 2034-07-03
Also published as: PL408716A1; CN104278209B; DE102013106990A1; RU2679813C2; DE102013106990B4; RU2014120771A; PL226741B1; DE202013012601U1

Abstract

The invention relates to the steel alloy applied as the manufacturing material for a chain and a chain assembly in mining applications, which contains the following components by weight: 0.17-0.25% C, 0.8-1.4% Mn, 0.4-1.5% Cr, 0.3-1.0% Mo, 0.9-1.3% Ni, 0.1-0.5% W, 0.015-0.05% Al, at most 1.5% Si, at most 0.25% Cu, at most 0.015% P, at most 0.015% S, at least one selected from the group consisting of Ta, Nb, V, Hf, Zr and Ti and with the total content thereof 0.005-0.1%, and a balance of iron, along with inevitable impurities.

Description

Use of alloy steel for chains and chain assemblies, and chain link or chain assembly

Technical Field

The invention relates to the use of an alloy steel for chains (ketten) and chain assemblies (kettenbauteile) for mining applications, and to chain links (kettenglied) produced from said alloy steel.

Technical Field

Steel chains are put to different uses in the mining industry, in particular underground mining industry. Steel chains are used, for example, in transport devices, in digging equipment and the like. These chains must be able to carry particularly high static and dynamic loads. In addition, they must have good corrosion resistance due to the sometimes corrosive atmosphere in the use environment. In addition to these requirements arising from the operation and use of chains, there is also a demand for steel materials arising from the manufacturing method of such link chains or flat link chains. Therefore, the link chains (Gliederketten) made of such steel must not only meet the specific requirements of the above-mentioned applications, but must also be ductile (and thus producible from chain links by forging or bending), quality-processable and the alloy steel must meet the requirements for good welding properties.

Steels meeting such requirements are known from DE 4337148C 1. Chains made from these steels can meet the high stresses in mining applications.

Particularly for mining applications, chains with excellent properties are always required. The performance of such a link chain is even more excellent when high loads can be carried by means of such a chain. In principle, the improvement in performance can be achieved by optimizing the geometry of the links to reduce the material required to form the links, by using a material with a higher tensile strength and/or by increasing the wire diameter (Drahtdurchmesser) of the links.

A link chain is known from DE 10348491C 1, in which at least the vertical links are optimized with respect to their geometry in order to improve the performance of the chain. According to the link geometry first disclosed by this prior art, the cross-sectional area in the region of the journals (Schenkel) is reduced by 15 to 45% in relation to the cross-sectional area in the region of the arc. The result is considerable material savings and the disadvantage in terms of breaking strength does not have to be borne. Thus, with such a link chain, higher tonnages can be loaded, in case a drive is used which is provided for a standard link chain having the same nominal diameter. However, efforts to improve chain performance by changing the geometry of the links have been limited. The same is true for a suitable optimization of the alloy steels used for manufacturing such chains. Chains used in mining are made of alloy steel, using as a typical material a chromium nickel molybdenum (CrNiMo) steel of the type 1.6758 in accordance with the DIN17115 standard. The steel has a high Cr content and a high Ni content, wherein the Cr content is 0.4 to 0.6 wt% and the Ni content is 0.9 to 1.1 wt%.

The steel disclosed in DE 4337148C 1 has achieved an improvement in properties over such steels. However, when the steel material meets the above requirements, further improvement in steel strength is limited. In this case, further improvement of the link chain performance can only be achieved by increasing the diameter of the material used to form the links. In this respect, the use of the central region of the arc-shaped region to determine and specify the nominal diameter of the wire as a link is independent of whether the link is a link bent from a wire or a link forged from a forging. However, there is a limit to the improvement of the properties by increasing the diameter of the links, that is, by the heat treatment process for adjusting the hardness. Such a tempering process comprises quench hardening and subsequent tempering of the semifinished product. The links are heated to the austenitizing temperature during quenching and then rapidly cooled (quenched). Such heat treatment is carried out so as to form a martensitic structure inside the workpiece (herein referred to as chain links). Such a link meets the load requirement only if it has a martensitic structure over its entire cross-section and thus has sufficient hardness. The coils provided by the steel can then be optimally used. However, the martensite structure can be produced by cooling only when the cooling is performed fast enough. Since cooling by extracting heat from such chain links can only take place on the outer shell surface, the cooling process becomes longer with increasing distance to the outer shell surface of the chain link. This results in that, in the case of larger chain link diameters, for cooling in the core region of the cross section, since the cooling is slower or delayed there, a complete transformation of the austenitic structure into the martensitic structure can no longer be ensured, and other, in particular softer structures, such as bainite structures, can form. The lower hardness of the other structure the link has a significantly lower load capacity in a cross section where no martensitic structure is present. Such inhomogeneities in the metallographic structure cannot be corrected by subsequent tempering. As a result, the load capacity of such a link is for this reason much lower than would be expected for the link. Materials and processing techniques are limited to optimizing the cooling process for rapid heat dissipation. This is due on the one hand to the relatively large mass to be cooled of the links of the nominal diameter and on the other hand to the heat transfer capacity of the material used, by means of which heat has to be transferred through such links from the inside outwards, i.e. from the core region to the link shell surface forming the cooling surface.

In JP 2008266721 a high-strength component produced by press hardening is described. The component is a structural component of a motor vehicle body. The thin sheet subjected to press quenching has only a very small thickness of about 1.4 mm. The alloy steel used for manufacturing the sheet has the following composition in weight percent: 0.1-0.55% of C, 0.1-3% of Mn, 21% of Si, 20.03% of S, 20.1% of P, 20.01% of F and the balance of iron.

Against the background of the prior art discussed above, it is desirable to have a chain or chain assembly, particularly for mining applications, which always has a martensitic structure in the case of large workpiece diameters.

Disclosure of Invention

The object of the invention is to provide a solution by means of which, despite the above-mentioned limitations, it is possible to produce a joint chain (Gliederketten) and its components with high performance.

The technical problem stated in the present invention is solved by the use of a steel alloy as a material for the manufacture of chains and chain components, mainly for mining applications, said steel alloy having:

0.17 to 0.25 wt% of C,

0.8 to 1.4 wt% of Mn,

0.4 to 1.5 wt% of Cr,

0.3 to 1.0 wt% of Mo,

0.9 to 1.3 wt% of Ni,

0.1 to 0.5% by weight of W,

0.015 to 0.05 wt% of Al,

up to 1.5% by weight of Si,

at most 0.25% by weight of Cu,

at most 0.015% by weight of P,

at most 0.015% by weight of S,

at least one element selected from the group consisting of Ta, Nb, V, Hf, Zr and Ti in a total content of 0.005 to 0.1% by weight, and the balance of iron together with unavoidable impurities. .

The steel alloys used according to the invention are less sensitive to cooling and quenching than conventional steel alloys and, surprisingly, also than the steel alloys disclosed in DE 4337148C 1. It is hypothesized that the insensitivity to quenching and thus the improved hardenability are due to the particular setting of the alloy in the composition of its alloy constituents and in particular to the combination of the element tungsten and at least one element selected from the elements tantalum, niobium, vanadium, hafnium, zirconium and titanium. At the same time, the alloy steel not only meets the requirements for form, processability and weldability, but also meets the requirements for bearing static and dynamic high loads in mining applications. The special combination of the alloy components with their specific contents results in a longer time-dependent shift of the transformation behavior to the bainite structure during the quenching process. This results in that the desired martensitic structure remains unchanged when the cooling time is longer in duration, which is often the case for the core region in links with larger diameters. Using the specific steel alloys described above, it is possible to produce links with nominal diameters significantly exceeding 52mm, in particular exceeding 58mm, and which, using the usual cooling methods, have a martensitic structure over their entire cross section. Thus, no other, in particular more complicated, cooling methods need to be employed to achieve the desired hardenability. After the cooling process, the semifinished product is tempered in a conventional manner in order to adjust the other properties required.

Surprisingly, the claimed steel alloys are in fact less sensitive to cooling than conventional steel alloys. The reason for this is that thermodynamic simulations carried out prior to the present invention do not show such a delayed transformation to bainite in the case of the use of the claimed alloy composition. In this respect, the thermodynamic simulation using the alloy to be protected does not differ from that performed in parallel using previously known alloy steels.

Further improvements in the above hardenability can be achieved when the alloy steel has the above-mentioned alloy composition with the following narrow range of contents:

0.19 to 0.23 wt% of C,

0.9 to 1.1 wt% of Mn,

0.7 to 1.0 wt% of Cr,

0.6 to 0.9 wt% of Mo,

1.0 to 1.25 wt% of Ni,

0.15 to 0.35 wt% of W,

0.015 to 0.05 wt% of Al,

up to 0.3% by weight of Si,

at most 0.15% by weight of Cu,

at most 0.015% by weight of P,

at most 0.015% by weight of S,

at least one element selected from the group consisting of Ta, Nb, V, Hf, Zr and Ti in a total content of 0.02 to 0.08 wt%, and the balance of iron together with unavoidable impurities.

Although in principle at least one element selected from Ta, Nb, V, Hf, Zr and Ti with the above-mentioned contents participates in the composition of the alloy, it is preferred to select the element Ta and/or Nb as the alloying element selected from them. The total content of elements from the group of elements participating in the composition of the alloy does not exceed 0.1% by weight, which could otherwise have an adverse effect on one or more other requirements imposed on the material and the products made therefrom.

Of particular importance for achieving a particular hardenability of semifinished products made of said steel alloys, such as chain links provided for mining applications, is the interaction between the element tungsten (W) and one or more of the elements concerned, selected from the group consisting of Ta, Nb, V, Hf, Zr and Ti. If the alloying elements tungsten and one or more other microalloying elements selected from the group consisting of the elements Ta, Nb, V, Hf, Zr and Ti comply with the following formula with each other, particularly good results are obtained in relation to the hardenability of products made of said steel alloys, in compliance with other requirements set on the manufacturability and workability of the steel alloys or on semi-finished products and products made therefrom:

wherein,

k is the coefficient of one or more microalloying elements: for Ta, Nb, Hf and Zr, k is 1; for V and Ti, k is 0.3:

C_MAis the content of one or more microalloying elements in weight percent;

C_Wis the content of tungsten, in% by weight;

m_Tais the atomic weight of tantalum (in u, Ta-180.95 u)

m_MAIs the atomic weight (in u) of one or more microalloying elements,

and the result E is between 0.06 and 0.9. Very good hardenability results have been achieved over this entire range. When the result E of the formula is between 0.08 and 0.5, a further improved result can be achieved. Thus, the tantalum equivalent is referred to in the above relationship. Tantalum and niobium of the above-mentioned microalloying element group are preferably selected as the main microalloying elements participating in the alloy composition.

The participation of silicon in the alloy is not critical. The invention is advantageous not only when the Si content does not exceed 1.5% by weight, but also when the content is only below 0.3% by weight. Preferably, the silicon content in the alloy is in the interval 0.08 to 0.2 wt.%.

Drawings

Fig. 1 is a graph showing the results of an end-quench test (Jominy test) performed on the end faces of the samples tested.

FIG. 2 is a graph showing the results of thermodynamic simulations performed on samples VL-1, VL-2 and LS-3.

FIG. 3 is a graph comparing the tensile strength of the inventive alloys LS-3 and LS-4 with the tensile strength of the control alloys VL-1 and VL-2 with respect to tempering temperature.

Fig. 4 is a graph depicting the toughness of each alloy.

FIG. 5 is a bar graph comparing the corrosion resistance of the alloy LS-3 of the present invention with the corrosion resistance of sample pieces made from the control alloys VL-1 and VL-2

Detailed Description

The examples and the experiments thereof will be described in more detail below, i.e. in comparison with the above-mentioned prior art steel alloys according to the types DE 4337148C 1 and 1.6758.

The chemical compositions of two experimental alloys LS-3 and LS-4 according to the invention are given again below:

the compositions of the two inventive alloy samples LS-3 and LS-4 were essentially identical. The two alloys are decisively distinguished by the composition of the microalloying elements. Tantalum forms the decisive microalloying element in alloy LS-3, while niobium is the decisive microalloying element in LS-4.

Cylindrical steel samples having a diameter of 25mm and a length of 100mm were made from these alloy steels. These samples were subjected to a Jominy test whereby they were heated to the austenitizing temperature and their ends were cooled as specified in the test. Therefore, this experiment is also called an end quench test. The test was carried out in accordance with DIN EN ISO 642. After the grinding of the longitudinally extending portion of the sample piece, the surface hardness of the underlying cylindrical sleeve portion was measured in accordance with the rockwell (HRC) standard at intervals on the ground surface, starting from the quenched end side of the sample.

In addition to the alloy steel samples of the present invention, control samples were also tested in the same manner. The first control sample of the same size as the sample piece made of the steel according to the invention (hereinafter: control alloy VL-1) consists of chain steel with material number 1.6758 in accordance with DIN 17115. Another control sample (hereinafter: control alloy VL-2) was made of an alloy steel known from DE 4337148C 1 and they were also tested in the same way. The compositions of the control alloys VL-1 and VL-2 are listed in the following table:

fig. 1 is a graph showing the results of an end-quench test (Jominy test) performed on the end faces of the samples tested. Fig. 1 shows the hardness data measured on the sample piece according to the end-quench test, in which no tempering has been carried out after the quenching process.

Samples LS-3 and LS-4 made using the steel alloys according to the present invention showed very clearly no significant hardness reduction at a first distance of about 25mm from the quench end face, compared to the control samples VL-1 and VL-2. However, in the test sample, a decrease in hardness was recognized to some extent in the interval from 25mm to 30mm from the quenched end face of the sample. However, Rockwell Hardness (HRC) of greater than 40 was still found relatively far from the quenched end face of the sample. It can be seen that the sample pieces made from the alloys LS-3 and LS-4 according to the invention still have a significantly higher hardness at a relatively large distance from the quenched end faces than the control samples VL-1 and VL-2. The fact that the sample piece according to the invention still has a high hardness at a distance of 30mm demonstrates that with this alloy it is possible to manufacture links with a nominal diameter of 60mm or more without having to worry about the hardening process, the core region of which no longer has a martensitic structure. These alloys are therefore particularly suitable for the production of objects with large material diameters, in particular chain links. Sample pieces made with the alloy according to the invention exhibited greater hardness at distances from the quenched end face of the sample relative to control sample VL-2, from about 15mm from the quenched end face, and even from 10mm relative to control sample VL-1.

FIG. 2 is a graph showing the results of thermodynamic simulations performed on samples VL-1, VL-2 and LS-3. The simulated time-temperature profiles (ZTU plots) of these samples show nearly identical cooling behavior. In particular, there was no difference between the simulated sample LS-3 according to the present invention and that of the control alloy VL-2. The results of these simulations are interesting because alloy development can be performed periodically on the basis of the simulations. Accordingly, it is expected that in practice the alloys of the present invention will not exhibit significantly improved hardenability as demonstrated in FIG. 1. The ZTU profile of sample LS-4 in relation to the present invention is largely identical to that of sample LS-3.

FIG. 3 shows a graph comparing the tensile strength of the inventive alloys LS-3 and LS-4 with the tensile strength of the control alloys VL-1 and VL-2 with respect to tempering temperature. It is clear that the alloys LS-3 and LS-4 according to the invention and the control alloy VL-2 have a better tensile strength than the samples made from the control alloy VL-1. This aspect shows that the alloy according to the invention meets the requirements made for tensile strength even better than the control alloy VL-2, which is generally used to meet particularly high requirements.

Another important attribute for chains, particularly those required in mining applications, is toughness. Fig. 4 shows a graph depicting the toughness of the respective alloys. It can clearly be seen that alloy sample LS-3 according to the invention is at least inferior in its toughness to the alloy steels according to VL-2 which were tested in mining applications. However, the toughness of the alloy sample LS-4 of the present invention, which corresponds to the toughness of the sample LS-3 shown in FIG. 4, is not shown in this figure.

Interestingly and unexpectedly, the alloy according to the invention also exhibits a particularly high corrosion resistance. In the conventional, extreme hydrogen embrittlement thereofIn a particularly functional stress corrosion test, control alloys VL-1 and VL-2 had fragmented after about 20 or 35 hours, whereas control samples made from alloy steel LS-3 of the present invention survived the test without fracture. The test was terminated after 250 hours. Tests have shown that the steel alloys according to the invention are particularly suitable for the manufacture of chain links or other components for mining applications. The variation of the alloy composition with respect to that of the control sample VL-2, the steel of which has proved to be particularly effective only for mining applications for the manufacture of chains for conveyors, indicates that no losses have to be accepted.

In particular for the use of products made of steel in mining, the corrosion resistance plays a considerable role, since these products are partially immersed in corrosive solutions. FIG. 5 shows a bar graph comparing the corrosion resistance of the alloy LS-3 of the present invention with the corrosion resistance of sample pieces made from the control alloys VL-1 and VL-2. In this graph, the corrosion resistance of the alloy LS-4 according to the invention is also not shown. A photograph of a sample made of alloy LS-3 according to the invention after the fracture test is shown beside the figure. According to NACE TM 0177-₂The S solution was subjected to a test relating to corrosion resistance at a pressure of 0.1 MPa. The above experiments show impressively that the samples made from the alloy according to the invention are significantly superior with respect to this property to the control sample made from the control alloy VL-2, which is considered to be particularly resistant.

The particular quenching insensitivity, while maintaining the requirements for conveyor chains, for example for mining applications, allows for the first time the production of links (keytenglied) with a nominal diameter of more than 58mm, which then makes it possible to meet the higher requirements set for their thicker nominal diameter. Finally, for mining applications, the diameter of the links is not simply increased, but the cross-sectional area is also used optimally. Accordingly, higher loads can be transported using chains formed from such links. Chains with a nominal diameter of 60mm or more are nowadays achievable.

Claims

1. Use of a steel alloy as a material for the manufacture of chain and chain components, primarily in mining applications, said steel alloy having:

0.17 to 0.25 wt% of C,

0.8 to 1.4 wt% of Mn,

0.4 to 1.5 wt% of Cr,

0.3 to 1.0 wt% of Mo,

0.9 to 1.3 wt% of Ni,

0.1 to 0.5% by weight of W,

0.015 to 0.05 wt% of Al,

up to 1.5% by weight of Si,

at most 0.25% by weight of Cu,

at most 0.015% by weight of P,

at most 0.015% by weight of S,

at least one element selected from the group consisting of Ta, Nb, V, Hf, Zr and Ti in a total content of 0.005 to 0.1% by weight, and the balance of iron together with unavoidable impurities.

2. Use according to claim 1, characterized in that the steel alloy comprises the following composition:

0.19 to 0.23 wt% of C,

0.9 to 1.1 wt% of Mn,

0.7 to 1.0 wt% of Cr,

0.6 to 0.9 wt% of Mo,

1.0 to 1.25 wt% of Ni,

0.15 to 0.35 wt% of W,

0.015 to 0.035% by weight of Al,

up to 0.3% by weight of Si,

at most 0.15% by weight of Cu,

at most 0.015% by weight of P,

at most 0.015% by weight of S,

3. Use according to claim 1 or 2, characterized in that in the alloy steel the following relationship exists for the elemental tungsten and one or more elements selected from the group of elements Ta, Nb, V, Hf, Zr and Ti in terms of their contents:

wherein,

k is the coefficient of one or more microalloying elements: for Ta, Nb, Hf and Zr, k is 1; for V and Ti, k is 0.3;

C_MAis the content of one or more microalloying elements in weight percent;

C_Wis the content of tungsten, in% by weight;

m_Tais the atomic weight of tantalum (in u, Ta-180.95 u);

m_MAis the atomic weight (in u) of one or more microalloying elements,

and the result E is between 0.06 and 0.9.

4. Use according to claim 3, wherein the result E is in the range of 0.08 to 0.5.

5. A link or chain assembly made of the steel alloy according to one of claims 1 to 4, characterized in that it is quenched and then tempered starting from its austenitizing temperature by cooling positively supported using conventional methods.

6. A chain link according to claim 5, characterized in that the chain link has a nominal diameter of more than 50mm, in particular more than 58 mm.

7. A product according to claim 6, wherein a plurality of said links are assembled to form a linked chain.