Revenue - Summary of Revenue by Geography (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Total net sales	$ 690.1	$ 489.0	$ 1,792.1	$ 1,272.6
Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	603.4	418.0	1,546.6	1,080.7
Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	115.1	88.4	315.1	248.7
Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	(28.4)	(17.4)	(69.6)	(56.8)
United States
Disaggregation of Revenue [Line Items]
Total net sales	419.6	312.7	1,093.0	813.7
United States | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	368.4	271.7	942.7	702.0
United States | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	61.5	48.9	178.1	136.1
United States | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	(10.3)	(7.9)	(27.8)	(24.4)
Europe
Disaggregation of Revenue [Line Items]
Total net sales	130.2	71.5	308.2	172.3
Europe | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	112.8	58.8	262.8	139.8
Europe | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	23.5	16.1	58.8	42.3
Europe | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	(6.1)	(3.4)	(13.4)	(9.8)
Asia Pacific
Disaggregation of Revenue [Line Items]
Total net sales	78.8	56.6	216.2	171.4
Asia Pacific | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	78.3	55.8	214.9	169.6
Asia Pacific | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	12.5	7.0	29.6	24.3
Asia Pacific | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	(12.0)	(6.2)	(28.3)	(22.5)
Mexico
Disaggregation of Revenue [Line Items]
Total net sales	25.1	24.2	90.3	61.6
Mexico | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	15.9	12.1	60.0	28.1
Mexico | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	9.2	12.1	30.3	33.5
Mexico | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	0.0	0.0	0.0	0.0
Canada
Disaggregation of Revenue [Line Items]
Total net sales	18.9	12.5	45.9	28.4
Canada | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	13.9	9.2	34.6	19.8
Canada | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	4.9	3.3	11.3	8.6
Canada | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	0.1	0.0	0.0	0.0
Other
Disaggregation of Revenue [Line Items]
Total net sales	17.5	11.5	38.5	25.2
Other | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Total net sales	14.1	10.4	31.6	21.4
Other | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Total net sales	3.5	1.0	7.0	3.9
Other | Intersegment
Disaggregation of Revenue [Line Items]
Total net sales	$ (0.1)	$ 0.1	$ (0.1)	$ (0.1)