Segment Information, Geographic and Product Data - Schedule of Results of Operation, Depreciation and Amortization, Capital Expenditures and Total Assets by Reportable Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Consolidated net sales	$ 2,877.1	$ 2,759.7	$ 2,550.3
Consolidated operating income	521.8	323.1	133.1
Consolidated depreciation and amortization	139.2	134.6	131.0
Consolidated capital expenditures	154.3	96.6	82.3
Consolidated total assets	3,486.8	3,291.7
Operating
Segment Reporting Information [Line Items]
Consolidated net sales	2,969.0	2,854.8	2,647.3
Consolidated operating income	625.6	444.5	210.9
Consolidated total assets	3,062.8	2,973.7
Corporate
Segment Reporting Information [Line Items]
Consolidated operating income	(102.9)	(123.0)	(75.5)
Consolidated depreciation and amortization	5.4	5.0	5.4
Consolidated capital expenditures	3.4	3.4	2.0
Consolidated total assets	433.2	334.8
Intersegment
Segment Reporting Information [Line Items]
Consolidated net sales	(91.9)	(95.1)	(97.0)
Consolidated operating income	(0.9)	1.6	(2.3)
Consolidated total assets	(9.2)	(16.8)
Specialty Alloys Operations
Segment Reporting Information [Line Items]
Consolidated net sales	2,548.7	2,432.8	2,201.5
Specialty Alloys Operations | Operating
Segment Reporting Information [Line Items]
Consolidated net sales	2,563.6	2,443.8	2,213.6
Consolidated operating income	588.6	408.5	179.1
Consolidated depreciation and amortization	117.3	113.3	110.0
Consolidated capital expenditures	135.9	80.0	70.2
Consolidated total assets	2,649.3	2,542.2
Specialty Alloys Operations | Intersegment
Segment Reporting Information [Line Items]
Consolidated net sales	(14.9)	(11.0)	(12.1)
Performance Engineered Products
Segment Reporting Information [Line Items]
Consolidated net sales	328.4	326.9	348.8
Performance Engineered Products | Operating
Segment Reporting Information [Line Items]
Consolidated net sales	405.4	411.0	433.7
Consolidated operating income	37.0	36.0	31.8
Consolidated depreciation and amortization	16.5	16.3	15.6
Consolidated capital expenditures	15.0	13.2	10.1
Consolidated total assets	413.5	431.5
Performance Engineered Products | Intersegment
Segment Reporting Information [Line Items]
Consolidated net sales	$ (77.0)	$ (84.1)	$ (84.9)