Steel Alloy, Use of Such a Steel Alloy, and Component

Abstract

The invention relates to a steel alloy comprising, in percent by mass:—0.17 to 0.23 carbon;—1.40 to 1.60 silicon;—0.50 to 0.60 manganese;—up to 0.020 phosphor;—up to 0.020 sulfur;—up to 0.30 chrome;—up to 0.12 molybdenum;—up to 0.80 nickel;—up to 0.30 copper;—up to 0.03 vanadium; the remainder being iron and incidental impurities.

Claims

1. A steel alloy comprising, in percent by mass: 0.17 to 0.23 carbon; 1.40 to 1.60 silicon; 0.50 to 0.60 manganese; up to 0.020 phosphor; up to 0.020 sulfur; up to 0.30 chrome; up to 0.12 molybdenum; up to 0.80 nickel; up to 0.30 copper; up to 0.03 vanadium; the remainder being iron and incidental impurities.

2. The steel alloy according to claim 1, wherein the steel alloy is a steel cast alloy.

3. The steel alloy according to claim 2, wherein the steel alloy as cast has a Brinell hardness of at least 190 HBW 5/750 and/or a yield point of at least 300 megapascal.

4. A method of manufacturing an article, the method comprising casting the steel alloy according to claim 1 to form the article.

5. The method of claim 4, further comprising subjecting the article to a heat treatment after casting.

6. The method of claim 5, wherein the heat treatment comprises a normalizing of the article.

7. The method of claim 6, wherein the normalizing is carried out in a temperature range extending from 900 degrees centigrade to 980 degrees centigrade.

8. The method of claim 5, wherein after the heat treatment the steel alloy has a tensile strength of at least 560 megapascal and/or a yield point of at least 370 megapsacal and/or an elongation at break of at least 20% and/or a Vickers hardness of at least 180 HV10 and/or a tensile ductility of at least 27 joule.

9. The method of claim 5, wherein the heat treatment creates a homogeneous perlitic-ferritic structure and during the heat treatment a carbonization and a decarbonization of the article are omitted.

10. A component of a vehicle, the component cast from a steel alloy according to claim 1.

11. The component of claim 10, wherein the component is a body component for a body in white or an integral body of a vehicle.

12. The component of claim 11, wherein the body component is a dome.

Description

[0018] Further details of the invention derive from the following description of preferred embodiments as well as from the drawings. The drawings show in:

[0019] FIG. 1 part of a schematic and perspective view of a component according to the present invention;

[0020] FIG. 2 part of a further schematic and perspective view of the component; and

[0021] FIG. 3 a flow diagram illustrating a method for manufacturing the component.

[0022] In the figures the same elements or elements having the same functions are indicated by the same reference signs.

[0023] FIGS. 1 and 2 show a component 1 for a vehicle such as a car or an automobile. In particular, said vehicle is a passenger vehicle having, in its completely assembled state, a body in white which is also referred to as a body, an integral body, a self-supporting body, a bodywork or a shell. In this regard, the component 1 is a body component of the body in white. Particularly, the component 1 is a dome in a form of a suspension-strut dome of the body in white. The component 1 has a particularly low wall thickness. Moreover, the component 1 has a rib structure 2 stiffening the component 1. Moreover, preferably, the component 1 is formed in one piece. In other words, the component is integrally formed. As can be seen from FIGS. 1 and 2, the component 1 has a recess 3 which is, preferably, a through opening. For example, a spring and/or damper element such as a suspension-strut can be supported on the component 1 in the vertical direction of the vehicle upwardly. Alternatively or additionally, the spring and/or damper element can be arranged partially in the recess 3.

[0024] In order to manufacture the component 1 in a particular easy and time- and cost-efficient way the component 1 is made from a steel alloy by casting, i.e. by a casting method. Said steel alloy is a steel cast alloy which can be processed by casting in a particularly easy and time- and cost-efficient way. Said steel alloy comprises at least the following substances, given in mass fractions in the unit %: [0025] 0.17 to 0.23 carbon (C) [0026] 1.40 to 1.60 silicon (Si) [0027] 0.50 to 0.60 manganese (Mn) [0028] up to 0.020 phosphor (P) [0029] up to 0.020 sulphur (S) [0030] up to 0.30 chrome (Cr) [0031] up to 0.12 molybdenum (Mo) [0032] up to 0.80 nickel (Ni) [0033] up to 0.30 copper (Cu) [0034] up to 0.03 vanadium (V) [0035] the remainder or balance being iron (Fe) and incidental, unavoidable or inevitable impurities.

[0036] This means the steel alloy comprises the afore-mentioned substances, in percent by mass or percentage by mass. In particular, due to the mass fractions of silicon and manganese respectively, the steel alloy can be processed very well, in particular by casting.

[0037] Preferably, after casting the component 1, the component 1 is subjected to a heat treatment, which is, preferably, a normalizing of the component 1. The normalizing is also referred to as a normalization and should be performed in a temperature range of 900 to 980 degrees centigrade. For example, the component 1 is normalized in an oven. A temperature and an atmosphere in the oven during the normalizing should be chosen in a way that a homogeneous perlitic-ferritic grain structure of the component 1 is accomplished and neither carbonisation nor decarbonisation of the component 1 or the steel alloy respectively occurs. This can be proven by means of a grain structure analysis.

[0038] Preferably, in a state or condition after the heat treatment and before an optional or possible further heat treatment to which the component 1 is possibly subjected, the component 1 or the steel alloy has a tensile strength (TS) of at least 560 megapascal and/or a yield point or yield strength (YS) of at least 370 megapascal and/or an elongation at break or a fracture elongation (A.sub.5.65) of at least 20 percent and/or a tensile ductility or toughness (KV) of at least 27 joule and/or a Vickers hardness of at least 180 HV10. A measurement to determine said toughness is preferably carried out according to ISO 148-1:2016 which, preferably, is or has been valid on Jun. 29, 2017. Alternatively or additionally, a measurement for determining said hardness is carried out according to DIN EN ISO 6507-1. Said tensile strength, said yield strength, said fracture elongation, said toughness and said Vickers hardness are mechanical properties or mechanical characteristics in normalized condition of the component 1, i.e. after said normalizing.

[0039] Preferably, after the casting and after the heat treatment the component 1 is cleaned, preferably by centrifugal blasting. Preferably, the component 1 is cleaned by means of airless blast cleaning after the casting and after the heat treatment.

[0040] FIG. 3 shows a flow diagram illustrating a process or process sequence which is carried out after the casting and after the heat treatment and, preferably, after said cleaning of the component 1. The process sequence shown in FIG. 3 is carried out in order to realize a particularly high quality of a surface of the, in particular completely manufactured, component 1.

[0041] In a first step S1 of the process sequence, the component 1 is degreased, preferably by means of an alkaline fluid. In a second step S2 the component 1 is subjected to a first purging in which, preferably, the component 1 is purged by means of deionised water. Preferably, the second step S2 is carried out after the first step S1. In a third step S3 of the process sequence the component 1 is subjected to an ultrasonically cleaning in which, preferably, the component 1 is cleaned by means of the deionised water. Preferably, the third step S3 is carried out after the second step S2. In a fourth step S4 of the process sequence the component 1 is subjected to a first chemical polishing which is preferably carried out after the third step S3. In the fourth step S4 at least or exactly one layer having a thickness of 10 to 15 micrometres is abased from the component 1.

[0042] In a fifth step S5 the component 1 is subjected to a second chemical polishing. The fifth step S5 is an alternative to the fourth step S4 so that either the fourth step S4 or the fifth step S5 is carried out. In the fifth step S5 at least or exactly one layer having a thickness of 25 to 30 micrometres is abased from the component 1. Preferably, the fourth or fifth step respectively is carried out after the third step.

[0043] In a sixth step S6 which is preferably carried out after the fourth step S4 or the fifth step S5 respectively, the component 1 is subjected to a second purging in which the component 1 is purged by deionised water. In a seventh step S7 of the process sequence the component 1 is subjected to an ultrasonically cleaning, wherein, preferably, the seventh step S7 is carried out after the sixth step S6. In the seventh step S7, the component 1 is ultrasonically cleaned by means of deionised water. In an eighth step S8 of the process sequence the component 1 is subjected to a pickling which is also referred to as a pickeling. Preferably, by means of the pickling the component 1 is cleaned. Preferably, the eighth step S8 is carried out after the seventh step S7.

[0044] In a ninth step S9 of the process sequence the component 1 is subjected to a galvanising process in which the component 1 is galvanised. Preferably, the ninth step S9 is carried out after the eighth step S8. In the ninth step S9, the component 1 is furnished or provided with at least one layer by means of galvanising. Said layer is made of zinc (Zn) in order to protect the component 1 from corrosion. Since the galvanising in the ninth step S9 is carried out after the pickling carried out in the eighth step S8, the layer adheres particularly advantageously or strongly to the surface of the component 1. In other words, by means of the pickling carried out in the eighth step a particularly advantageous surface of the component 1 can be realized, wherein the layer created in the galvanising process carried out in the ninth step S9 can adhere very advantageously and strongly to said surface created by the pickling.

[0045] In a tenth step S10 of the process sequence the component 1 is provided with a corrosion protection oil, in particular by spraying. In other words, in particular and preferably, said corrosion protection oil is sprayed on said zinc layer and, thus, on a surface formed by said layer which is a zinc layer. Preferably, the tenth step S10 is carried out after the ninth step S9.

[0046] Preferably, the component 1, in particular in its completely manufactured state, has a surface having a surface roughness fulfilling the following demands: Ra max. 10 micrometres, Rz max. 50 micrometres and Rt max. 75 micrometres. Preferably, said surface roughness is determined or measured according to DIN EN ISO 4288:1997.

[0047] The ninth step S9 is a coating or coating process which is also referred to as a galvanic zinc coating or galvanic zinc coating process, said layer being a zinc layer is a coat or a zinc coat. The zinc coat is also referred to as a sink coating which is, preferably, at every position of the component 1 and, thus, completely closed. Preferably, the layer has a thickness of 7 to 15 micrometres.

LIST OF REFERENCE SIGNS

[0048] 1 component [0049] 2 rip structure [0050] 3 recess [0051] S1 first step [0052] S2 second step [0053] S3 third step [0054] S4 fourth step [0055] S5 fifth step [0056] S6 sixth step [0057] S7 seventh step [0058] S8 eighth step [0059] S9 ninth step [0060] S10 tenth step