The Company has defined contribution retirement plans or defined benefit pension plans covering substantially all employees. Company contributions to defined contribution retirement plans are generally based on a percentage of eligible pay or based on hours worked. Benefits under the defined benefit pension plans are generally based on years of service and/or final average pay. The Company funds the U.S. pension plans in accordance with the Employee Retirement Income Security Act of 1974, as amended, and the Internal Revenue Code.

The Company also sponsors several postretirement plans covering certain collectively-bargained salaried and hourly employees. The plans provide health care and life insurance benefits for eligible retirees. In most retiree health care plans, Company contributions towards premiums are capped based on the cost as of a certain date, thereby creating a defined contribution.

For the three month periods ended June 30, 2018 and 2017, the components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following (in millions):



	Pension Benefits						Other Postretirement Benefits
	Three months ended June 30,						Three months ended June 30,
	2018			2017			2018			2017
Service cost - benefits earned during the year	$	4.0		$	3.5		$	0.6		$	0.6
Interest cost on benefits earned in prior years	26.3			29.2			3.2			3.6
Expected return on plan assets	(39.5		)	(36.7		)	—			—
Amortization of prior service cost (credit)	0.1			0.3			(0.7		)	(0.7		)
Amortization of net actuarial loss	16.5			15.7			2.6			2.3
Curtailment loss	0.4			—			—			—
Total retirement benefit expense	$	7.8		$	12.0		$	5.7		$	5.8

For the six month periods ended June 30, 2018 and 2017, the components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following (in millions):



	Pension Benefits						Other Postretirement Benefits
	Six months ended June 30,						Six months ended June 30,
	2018			2017			2018			2017
Service cost - benefits earned during the year	$	8.2		$	7.0		$	1.2		$	1.2
Interest cost on benefits earned in prior years	52.4			58.4			6.3			7.3
Expected return on plan assets	(79.0		)	(73.4		)	—			—
Amortization of prior service cost (credit)	0.2			0.6			(1.4		)	(1.4		)
Amortization of net actuarial loss	33.0			31.3			5.3			4.5
Curtailment loss	0.4			—			—			—
Total retirement benefit expense	$	15.2		$	23.9		$	11.4		$	11.6

On June 1, 2018, a new four-year collective bargaining agreement (CBA) was ratified by USW-represented employees of the Company’s Specialty Alloys & Components (SAC) operations in Millersburg, OR. The new SAC CBA resulted in changes to retirement benefit programs, including a freeze to new entrants to the U.S. defined benefit pension plan and to postretirement health care benefits, and a hard freeze for most current pension plan participants covered by the SAC CBA, effective July 31, 2018. New hires covered by the CBA, and pension plan participants who are subject to the hard freeze, will receive Company contributions to a defined contribution retirement plan. The CBA also included pension benefit increases for all current pension plan participants affecting both prior and future service. The Company recognized a $0.4 million pension curtailment charge in the second quarter 2018 for the prior service cost of these pension benefit increases in connection with employees being hard frozen in the pension plan.

The Company has now completely closed its U.S. defined benefit pension plan to new entrants.