Composite roll

Details Composite roll Composite roll

1991-12-12

1993-12-14

Yee, Deborah

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

428685, B32B 1500

Patent

active

052701247

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a composite roll having a metal core and a hardface formed from a steel composition, the steel composition per se, and a method of heat treatment of the composite roll after the composite roll has been formed by welding a layer of the steel composition to the metal core.
The present invention relates particularly, although by no means exclusively, to rolls used in the production of rails and structural steel.
The main requirements for such rolls are wear resistance and toughness. The rolls are usually chill cast from steel-based or iron-based materials. However, the cast rolls tend to be susceptible to damage, particularly chipping, and often require replacement before the maximum life of the cast rolls has been reached. In this regard, cast rolls cannot be repaired and thus once damaged must be replaced.
It is an object of the present invention to provide an improved roll which alleviates the disadvantages of conventional chill cast rolls described in the preceding paragraph.
The present invention is based on the realisation that an improved roll can be formed as a composite roll comprising a metal core and a wear resistant and tough hardface of a particular steel composition, as described below.
According to the present invention there is provided a steel composition suitable for use to form a hardface of a composite roll comprising a metal core and the hardface, the steel composition comprising the elements carbon, manganese, silicon, chromium, molybdenum, niobium and vanadium in the amounts specified below, in wt.%:


______________________________________ C: 0.35 to 1.2 Mn: 0.3 to 3.0 Si: 0.3 to 2.0 Cr 5.0 to 11.5 Mo: 0.3 to 5.0 Nb: 0.4 to 5.0 V: 0.3 to 3.0 ______________________________________
The preferred amount in wt.% of the elements carbon, manganese, silicon, chromium, molybdenum, niobium and vanadium in the steel composition is as follows:


______________________________________ C: 0.45 to 0.90 Mn: 1.8 to 2.2 Si: 0.8 to 1.1 Cr: 5.6 to 6.5 Mo: 1.5 to 2.0 Nb: 1.7 to 2.2 V: 0.7 to 1.0 ______________________________________
It is preferred that the composition further comprises 1.0 to 3.0 wt.% tungsten. It is particularly preferred that the composition comprises 1.3 to 1.5 wt.% tungsten.
It is preferred that the amount of carbon in the steel composition is in the range 0.45 to 0.65 wt. %. It is preferred particularly that the amount of carbon is in the range 0.55 to 0.57 wt.%.
The incidental impurities may comprise titanium, phosphorus, sulphur, nickel and copper in the amounts specified below in wt.%:


______________________________________ Ti: 0.05 max. P: 0.03 max. S: 0.02 max. Ni: 0.05 max. Cu: 0.03 max. Al: 0.05 max. Ta: 0.05 max. ______________________________________
The steel composition may include the elements nickel, tantalum, and titanium in the amounts specified below in wt.%.


______________________________________ Ni: up to 3 Ta: 0.01 to 0.2 Ti: 0.01 to 0.2 ______________________________________
It is believed, although it has not been established with certainty at this stage, that the important elements in the steel composition from the viewpoint of wear resistance and toughness are niobium and vanadium. It has been found unexpectedly that the inclusion of vanadium in the amounts specified above disperses the niobium carbides into a plurality of small discrete grains and, as a consequence, the steel composition has improved wear resistance and toughness. It has also been found that the inclusion of the niobium and vanadium in the amounts specified above is synergistic in that the improvement in the wear resistance and toughness is greater than would normally be expected.
According to the present invention there is also provided a composite roll comprising, a metal core and a hardface formed from the steel composition described above.
It is preferred that the metal core is formed from a plain carbon steel composition comprising the elements carbon and manganese in the amounts set out below,

REFERENCES:
patent: 4110514 (1978-08-01), Nicholson

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