Business Segments - Schedule of results of operation, depreciation and amortization, capital expenditures and total assets by reportable segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Jun. 30, 2021
Net Sales:
Consolidated net sales	$ 489.0	$ 351.9	$ 1,272.6	$ 1,054.0
Operating Income (Loss):
Consolidated operating income (loss)	1.1	(40.0)	(49.5)	(177.8)
Depreciation and Amortization:
Consolidated depreciation and amortization	33.2	32.0	98.5	91.6
Capital Expenditures:
Consolidated capital expenditures	25.1	18.6	58.5	78.5
Total Assets:
Consolidated total assets	3,230.2		3,230.2		$ 2,971.2
Operating | Specialty Alloys Operations
Net Sales:
Consolidated net sales	418.0	299.6	1,080.7	900.8
Operating Income (Loss):
Consolidated operating income (loss)	5.8	(9.9)	(20.4)	(40.1)
Depreciation and Amortization:
Consolidated depreciation and amortization	27.9	26.5	82.4	73.1
Capital Expenditures:
Consolidated capital expenditures	21.8	13.4	50.5	50.8
Total Assets:
Consolidated total assets	2,268.1		2,268.1		2,150.1
Operating | Performance Engineered Products
Net Sales:
Consolidated net sales	88.4	65.7	248.7	182.3
Operating Income (Loss):
Consolidated operating income (loss)	4.2	(3.3)	7.8	(14.2)
Depreciation and Amortization:
Consolidated depreciation and amortization	3.9	4.1	11.8	14.4
Capital Expenditures:
Consolidated capital expenditures	2.8	1.2	6.0	4.4
Total Assets:
Consolidated total assets	430.2		430.2		418.5
Corporate
Operating Income (Loss):
Consolidated operating income (loss)	(8.6)	(26.3)	(37.3)	(123.4)
Depreciation and Amortization:
Consolidated depreciation and amortization	1.4	1.4	4.3	4.1
Capital Expenditures:
Consolidated capital expenditures	0.5	4.0	2.0	23.3
Total Assets:
Consolidated total assets	528.8		528.8		402.2
Intersegment
Net Sales:
Consolidated net sales	(17.4)	(13.4)	(56.8)	(29.1)
Operating Income (Loss):
Consolidated operating income (loss)	(0.3)	$ (0.5)	0.4	$ (0.1)
Total Assets:
Consolidated total assets	$ 3.1		$ 3.1		$ 0.4