GB2155035A - Steel ring - Google Patents

Abstract

The present invention relates to steel rings, mainly for use in manufacturing casing couplings, connectors and other ring formed products produced from a steel with the following analysis, in %: C 0.10-0.40 Si 0.10-0.50 Mn 1.0 -2.0 Cr 0 -0.50 Ni 0 -0.50 Mo 0.20-0.60 V 0 -0.15 Cu 0 -0.50 Ti 0 -0.05 Nb 0 -0.05 B 0 -0.010 either of Ca, Se, REM 0 -0.010 S 0 -0.05 Al 0.01-0.08 and normal concentrations of impurities, and the carbon equivalent factor Ec being max 0.65.

Description

SPECIFICATION Steel ring The present invention concerns steel rings, and more specifically steel rings for use as blanks fo the manufacture of casing couplings, connectors and other ring formed components.

The demands for such steel rings are great and to a certain extend contradictory material characteristics are requested, such as - the material in the steel ring must show a good hardenability in dimensions up to 75mm wall thickness - the yield stress should be at least 700 MPa -the ultimate tensile stress should be at least 830 MPa - good impact properties in transverse direction (KV at least 30 J at - 55"C) - good weldability - good machinability - low alloying Previously the steels En 24 and SAE 4140 were used for the manufacture of the above mentioned steel rings, but these steel rings no longer satisfy the demands listed above, since some of them are new.Besides, the weldability of the steel rings manufactured up till now is not very good.

The purpose of the present invention is to achieve steel rings, which exhibit better characteristics than those steel rings previously having been used for the manufacturing of casing couplings, connectors and other ring formed componenets.

This purpose is, most surprisingly, achieved by steel rings being manufactured from a steel having the following analysis (in %): C 0.10-0.40 Si 0.10-0.50 Mn 1.0-2.0 Cr 0-0.50 Ni 0-0.50 Mo 0.20-0.60 V 0-0.15 Cu 0-0.50 Ti 0---0.05 Nb 0-0.05 B e--0.010 either of Ca, Se, REM 0--0.010 S 0--0.05 Al 0.01-0.08 ad normal concentrations of impurities, and the carbon equivalent factor Ec being max 0.65.

According to an embodiment of the invention the analysis (in %) is the following: C 0.15-0.35 Si 0.10-0.50 Mn 1.0-2.0 Cr 0---0.50 Mo 0.10-0.40 V 0.0-0.15 Cu 0---0.50 Nb e--0.05 B 0.0014.006 Ca 0-0.005 S 0-0.05 Al 0.01-0.08 ad normal concentrations of impurities, and the carbon equivalent factor Ec being max 0.65.

According to another embodiment of the invention the S content is 0-0.012%.

According to the present invention a good impact strength is achieved by manufacturing a steel with low sulphur contents or with rounded sulphide slags, which are produced by the addition of Ca. Thereby alloying compounds like Mn, B, Cr, Cu could be used in order to obtain a better hardenability.

Further, the steel is preferably killed by Al, and will thus also exhibit a small Al-content. The killing by Al also implies a fine-grain treatment. The relatively high Al content gives full effect to the boron addition.

The carbon equivalent Ec is a measure of the weldability of the steel, the lower the value is the better, and it is determined by the formula below, based on the percentage of the comprised alloying components: Mn Cr+V+Mo Cu+Ni Ec = C + - 6 5 15 Therefore, the content of alloying components must not be too high, since then the weldability will be too poor. The material of the steel ring according to the invention is therefore limited so that Ec is not allowed to exceed 0.65.

As a comparative example it could be mentioned that the steel En 24 has a value Ec of 0.89.

All of the alloying components used in said steel ring material having a bearing on the characteristics, see below: boron has a very strong positive effect on the harden ability but has very little effect on the weldability. Boron is used in very small amounts.

- Titanium is added because of its high affinity to nitrogen and binds nitrogen dissolved in the steel and prevents the boron content from being inactivated.

- Aluminium is added, when used, for killing the steel and perform a finegrain treatment and can in excess amounts substitute titanium.

- Calcium is added to achieve rounded sulphide slags, which most easily is achieved when the sulphide concentration is low, that is lower than 0.01 2% S.

- In fact, rounded sulphide slags can be achieved in other ways, for example by the addition of Se or REM (Rare Earth Metals). These give stronger effect than Ca and thus higher sulphide concentrations could be allowed. However, the use of these elements gives rise to other disadvantages such as higher oxide slag concentrations and when possible, the use of these elements should therefore be avoided.

- Vanadium in concentrations up to 0. 15% has a positive effect on the hardenability, however, in steel rings of smaller dimensions vandium can be dispensed with.

The steel used in the steel rings according to the invention contains no or relatively low concentrations of nickel. Nickel has a positive effect on the impact strength of the steel ring, but it decreases weldability and it is very expensive compared to other alloying elements.

In order to illustrate the invention further a test production of steel rings and a testing thereof are related in the examples below: Example 1 Analysis of the steel (%) C 0.17 Si 0.23 Mn 1.40 P 0.013 S 0.005 Cr 0.27 Ni 0.02 Mo 0.51 Cu 0.01 V 0.03 Al 0.068 Ti 0.003 B 0.0019 Nb 0.03 Ec= 0.55 The wall thickness of these rings was 54 mm.

Mechanical characteristics in transverse direction in quenched and tempered state: ReL = 880 MPa (yield stress) Rm = 920 MPa (tensile stress) As = 18 % (elongation) KV = 93 J at - 55"C (impact strength) The carbon equivalent indicates a good weldability.

Example 2 Analysis of the steel (%) C 0.19 Si 0.22 Mn 1.37 P 0.017 S 0.003 Cr 0.28 Ni 0.06 Mo 0.51 Cu 0.02 V 0.01 Nb 0.04 Al 0.073 Ti 0.005 B 0.0024 Ec= 0.58 The wall thickness of these rings was 60 mm: Mechanical characteristics in transverse direction in quenched and tempered state: ReL = 900 MPa (yield stress) RM = 940 MPa (tensile stress) A5 = 17 % (elongation) KV = 39 J at - 60"C (impact strength) The carbon equivalent indicates a good weldability.

CLAIMS 1. A steel ring, produced from a steel with the following analysis, in %: C 0.10 -0.40 Si 0.10 -0.50 Mn 1.0 -2.0 Cr 0 -0.50 Ni 0 -0.50 Mo 0.20 -0.60 V O -0.15 Cu O -0.50 Ti 0 -0.05 Nb 0 -0.05 B 0 -0.010 either of Ca, Se, REM 0 -0.010 S 0 -0.05 Al 0.01 -0.08 ad normal concentrations of impurities, and the carbon equivalent factor Ec being max 0.65.

2. A steel ring according to claim 1, the composition of the steel being: C 0.10 -0.30 Si 0.10 -0.50 Mn 1.0 -2.0 Cr O -0.50 Mo 0.20 -0.60 V O -0.15 Cu O -0.50 Nb 0 -0.05 B 0.001-0.006 Ca 0 -0.005 S 0 -0.05 Al 0.01 -0.08 ad normal concentrations of impurities, and with a carbon equivalent factor Ec of max 0.65.

3. A steel ring according to claim 1, wherein the S content is 0-0.012 %.

4. A steel ring according to any one of claims 1 to 3, when used for casing couplings, connectors and other annular components.

5. A steel ring substantially as hereinbefore described with reference to Example 1 or Example 2.

Claims (4)

CLAIMS New claims or amendments to claims filed on 1 3 Feb 1 985 Superseded claims 1-5

1. A steel ring for casing couplings and connectors, produced from a steel with the following analysis, in %: C 0.10 -0.40 Si 0.10 -0.50 Mn 1.0 -2.0 Cr 0 -0.50 Ni 0 -0.50 Mo 0.20 -0.60 V O -0.15 Cu 0 -0.50 Ti 0 -0.05 Nb 0 -0.05 B 0 -0.010 either of Ca, Se, REM 0 -0.010 S 0 -0.05 Al 0.01 -0.08 ad normal concentrations of impurities, and the carbon equivalent factor Ec being max 0.65.

2. A steel ring according to claim 1, the composition of the steel being: C 0.10 -0.30 Si O.iO -0.50 Mn 1.0 -2.0 Cr 0 -0.50 Mo 0.20 -0.60 V O -0.15 Cu 0 -0.50 Nb 0 -0.05 B 0.001 -0.006 Ca 0 -0.005 S 0 -0.05 Al 0.01 -0.08 ad normal concentrations of impurities, and with a carbon equivalent factor Ec of max 0.65.

3. A steel ring according to claim 1, wherein the S content is 0-0.012 %.

4. A steel ring substantially as hereinbefore described with reference to Example 1 or Example 2.